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Concord CXC -

Installation

CONTENTS

Air Supply. ........................................................................ 9

Boiler Assembly - exploded view. ............................... 10

Boiler Clearances. ........................................................... 6

Burner Assemblies - exploded views. .............................

CXC 48-70. ................................................................ 28
CXC 94-116. ............................................................... 29

Casing Assembly. .......................................................... 13

Commissioning. ............................................................. 18

Condensate Drain Connection ..................................... 12

Controls. ........................................................................... 5

Electrical Connections. ................................................. 15

Electrical Supply. ........................................................... 10

Fault Finding. ................................................................. 33

Flue System. ..................................................................... 9

Gas Connections. .......................................................... 13

Gas Safety Regulations ................................................... 3

Gas Supply. ..................................................................... 10

Hydraulic Resistance. ...................................................... 6

Initial Lighting. ................................................................ 18

Installation. ..................................................................... 10

Mandatory Requirements. ............................................... 9

Option Kits. ....................................................................... 5

Pump. ................................................................................ 7

Servicing. ........................................................................ 25

Short List of Parts. ......................................................... 36

Static Head Requirements. ............................................. 7

Ventilation. ........................................................................ 9

Water Circulation. ............................................................ 7

Water Connections. ......................................................... 5

Water Treatment. .............................................................. 8

Wiring Diagrams. ........................................................... 16

INTRODUCTION
CONSTRUCTION

BOILER BODY

The Concord CXC boiler consists of 2 basic parts; a conventional
Concord CXD boiler; plus an additional heat exchanger.

The Concord CXC boiler body is constructed from cast iron
sections, insulated by a foil backed fibre glass blanket. It is mounted
on a sheet steel combustion chamber.

An aluminiumised mild steel flue collector hood and stainless steel
condensate sump is fitted on top of this heat exchanger. The sump
supports the secondary heat exchanger which is constructed from
aluminium finned tubes between aluminium and cast iron headers.
This heat exchanger is also insulated by a foil backed fibre glass
blanket.

Above the primary heat exchanger an induced draught fan is fitted
- capable of overcoming the resistance of a 30m length of 6" flue
pipe. The boiler is supplied with header pipework between the
primary and secondary heat exchanger.

Within this pipework, a 'shunt' pump is provided to ensure an
adequate flow through the primary heat exchanger, independently
of the system pump. This also ensures that a sufficient temperature
is maintained in the primary heat exchanger to prevent corrosion.

CASING

The combined boiler bodies are enclosed in a white, stove
enamelled casing which incorporates a control panel fascia.

The casing is specially designed to ensure easy access for both
servicing and cleaning of both heat exchangers.

BURNERS

The 3 burners are of stainless steel construction.

Gas Safety (Installation and Use) Regulations, 1994,
amendments 1996 or rules in force.

It is the law that all gas appliances are installed and serviced by a
CORGI registered installer (identified by ) in accordance with
the above regulations. Failure to install appliances correctly could
lead to prosecution. It is in your own interest, and that of safety, to
ensure that the law is complied with.

The Concord CXC 48/116 range of boilers has been tested and
certified by British Gas to prEN656 for use with Natural gas only.

Note. The CXC 48 and CXC 70 boilers are intended for use as
COMMERCIAL BOILERS and are NOT certified for use in domestic
applications. A domestic installation is defined as an installation
where the boiler takes its combustion air from a living space or
from a room directly or indirectly connected with the living space.
It is important, therefore, that no external control devices - e.g.
flue dampers, economisers etc., are directly connected to this
appliance unless covered by these Installation and Servicing
Instructions or otherwise recommended by Caradon Plumbing
Limited in writing. If in doubt please enquire.

Any direct connection of a control device not approved by Caradon
Plumbing Limited could invalidate the British Gas Certification,
the normal appliance warranty and could also infringe the Gas
Safety Regulations. Table 1, Table 2 and the descriptive notes
which follow contain all the essential data likely to be required by
the installer.

Concord CXC 48-116 (Natural gas)

B.G. Certified - P.I. No. 87/AQ/340

Destination Countries: GB and IE

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Installation

Boiler

CXC 48

CXC 70

CXC 94

CXC 116

Number of sections

Flow tappings

Rc (in. BSP)

2 (2) - 1 at rear

Return tappings

Rc (in. BSP)

2 (2) - 1 at rear

Maximum static head

metres (feet)

45.7 (150)

Maximum pressure

bar (p.s.i.)

4.5 (65)

Gas inlet connection

Rc (in. BSP)

3/4 (3/4)

1 (1 )

Minimum dynamic gas

mbar gauge

15.0

16.2

15.0

pressure required at the boiler inlet in.w.g.

6.0

6.5

6.0

Electricity supply

230 Volts- single phase, 50 Hz, fuse 5 A

Power Consumption

Watts

Nominal flue size (to BS. 835)

mm (in.)

152 (6)

Diverter outlet socket

154

internal diameter

1/16

Length of burner bars (overall)

377

497

617

737

14.8

19.5

24.3

29.0

Approx. dry weight

298

350

442

494

658

771

974

1090

Water contentm

litre

gal

6.2

8.0

9.5

11.2

Gas type

G20 I

20 mbar

Boiler

CXC 48

CXC 70

CXC 94

CXC 116

Number of sections

Boiler output High Rate

48.83

69.84

93.65

116.25

Condensing

Btu/h x 1000

166 600

238 300

319 500

396 600

Boiler output High Rate

44.63

63.84

85.6

106.3

Non-Condensing

Btu/h x 1000

152 300

217 800

292 100

362 700

Boiler Input

Gross

31.5

45.06

60.42

Low Rate

Btu/h x 1000

107 500

153 700

206 200

255 900

Nett

28.4

40.6

54.44

67.58

Btu/h x 1000

96 900

138 500

185 800

230 600

Boiler Input

Gross

52.5

75.1

100.7

125

Btu/h x 1000

179 100

256 200

343 600

426 500

High Rate

Nett

47.3

67.67

90.73

112.6

Btu/h x 1000

161 400

230 900

309600

384 200

Gas rate

4.4

7.0

9.4

11.6

172

247

331

411

Approx. flue gas 8.0% CO

& 60°C. m

/sec

0.023

0.033

0.045

0.056

volume (non condensing)
High rate

8.0% CO

& 140°F.

ft.

119

Manifold setting pressure

mbar

3.9

3.8

4.1

Low Rate

in.w.g.

1.6

1.5

1.6

Manifold setting pressure

mbar

11.7

11.8

10.7

11.5

High Rate

in.w.g.

4.7

4.3

4.6

Seasonal efficiency (SEDBUK)*

[85.8]%

[85.5]%

[86.2]%

[85.7]%

Electricity supply

230V, 50Hz, fuse 5A

Ignition

5 attempts followed by nonvolatile lockout.

Gas valve

High/Low and Off

Gas safety time

Maximum of 10 secs with 5 attempts with one min. between attempts.

Safety check

The control de-energises every 4 hours to check internal control functions.

Pump

Pump overrun operates if the flow temperature is greater than 75

Boiler thermostat

The boiler thermostat hysteresis is a maximum of 3

Table 3 - Boiler Control specification Maximum Flow Temperature 85

Table 2 - General Data

GENERAL

Table 1- Performance Data

Note. To obtain gas consumption, divide gross heat input (kW) by a calorific value of 37.8 (MJ/m

)

*The value is used in the UK government's Standard Assessment Procedure (SAP) for energy rating of dwellings.
The test data from which it has been calculated have been certified by BGplc 0087.

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Boiler Size

Cold Feed

Open Vent

CXC 48 -70

3/4

CXC 94 -116

1/4

Sealed system filling point - refer to Frame 8

GENERAL

GAS CONTROLS

The gas controls consist of a high / low arrangement with direct
burner ignition.

ELECTRICAL CONTROLS

WARNING. The ON/STANDBY [1/0] button does NOT electrically
isolate the boiler.

The Concord CXC range incorporates an advanced
microprocessor based control system which operates all electrical
functions of the boiler including for operation, ignition, flame
detection, thermostatic control, and high/low operation. In addition,
the microprocessor has onboard servicing and commissioning
instructions and a fault diagnosis programme.

The illuminated LED display gives a continual read-out of the boiler
status and functions, but in the (unlikely) event of a fault condition,
will display the fault areas.

Combustion products are drawn through the boiler by a fan and
air flow is proved by a pressure switch.

The burner flame is ignited by a spark generator.

Blockage of the condensate drain is protected against by a float
switch situated in the sump.

OPTION KITS

Pressure Gauge Kit: A pressure gauge is available for the range
of boilers. Details for fitting are included with the pressure gauge.

Remote Indication Board (volt free): This provides the ability
for remote indication of lockout and overheat conditions.

Outside Sensor: This kit provides a sensor for temperature
compensation when the outside temperature changes. Each
boiler needs to be individually switched on therefore a sensor is
required per boiler.

DUTY

The range of boilers is suitable for: Combined indirect pumped
domestic hot water and central heating systems; Independent
indirect pumped domestic hot water or central heating systems.

Fully pumped systems may be open vented or sealed.

Flow and return connections are 2" BSP.

Safety Valve
A safety valve must be sized and fitted in accordance with BS.
6644 for every type of system. The valve should be set at 0.7
bar (10 lb/in.

) above the operating pressure in the boiler. The

maximum safety valve setting is 0.7 bar (10 lb/in.

) above the

maximum design operating pressure of 4.5 bar (65 lb/in.

Cold Feed/Open Vent
The independent cold feed and the open vent must comply
with BS. 6644 and be of the following minimum size.

WATER CONNECTIONS

The range of boilers is NOT suitable for:

1. Gravity DHW systems.
2. Gravity heating systems.
3. Direct domestic hot water supply.

SYSTEM DESIGN

The water efficiency of this range of boilers is higher than
conventional boilers, at any water temperature, because of the
increased heat exchanger area.

At return temperatures of 55 °C and below, the differences become
more marked because the water in the flue gases starts to
condense, releasing its latent heat. In general, the lower the return
temperature (down to its minimum temperature of 35 °C to protect
the primary heat exchanger) the better the boiler efficiency.

In new systems it is best to design for the lowest flow and return
temperatures that are practical (subject to the lower limit mentioned
above). Of course, the lower the mean water temperature the
greater must be the heating surface area.

PERFORMANCE

The efficiency of the Concord CXC range of boilers is related to
the return water temperature of the boiler. This graph shows that,
in order to achieve maximum efficiency at any given load, the
system controls should be used in a manner which maintains the
lowest return temperature commensurate with system performance

Graph 1 - Boiler efficiency

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GENERAL

Rear clearance: sufficient clearance should be given
at the rear of the boiler for connection of gas and
water pipework.

*Additional clearance is required for access at either
end of the installation.

POSITION OF BOILER

Minimum clearances required
from walls or other fixed
objects to allow for the free
access of combustion air are
shown in Table 4 above.

However, for maintenance
purposes we suggest a
minimum rear clearance of
200mm.

Any combustible material
adjacent to the boiler and its
flue system must be so placed
or shielded as to ensure that
its temperature does not
exceed 65

C (150

F).

MULTIPLE BOILER INSTALLATIONS

The minimum installation clearances must conform to the
dimensions given below:

CXC 48 & 70

Clearance between boilers = 50mm
Clearance at both ends of the multiple installation = 50mm*

CXC 94 & 116

Clearance between boilers = 100mm
Clearance at both ends of the multiple installation = 100mm*

CLEARANCES & DIMENSIONS

Boiler Size

CXC 48

CXC 70

CXC 94

CXC 116

Front clearance

mm (in)

750 (29 1/2)

Rear clearance

mm (in)

200 (8) see text

Side clearance

mm (in)

50 (2)

100 (4)

Dimension A

mm (in)

723(28

1/2

)

846(33

5/16

) 969(38

1/8

)

1092(43)

Table 4

Graph 2 - Heat Load/ Water Volume

Graph 3 - Hydraulic Resistance

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GENERAL

3 OPEN VENTED SYSTEMS - Minimum static head requirements

Note A.
This minimum height must be increased, if necessary, to
comply with the minimum head required by the pump
manufacturer in order to avoid cavitation.

Note B.
This diagram does not show safety valves, water flow
switches, etc., necessary for the safe operation of the
system.

Table 5 - Flow rates for fully pumped systems

Boiler

Minimum flow rates for a

temperature difference of 35

C (63

l/s

g.p.m.

CXC 48

0.33

4.4

CXC 70

0.48

5.3

CXC 94

0.64

8.5

CXC 116

0.79

10.4

Particular reference should be made to BS. 6644: Section 2;
Subsection 10 and Guidance note PM5 "Automatically controlled
steam and hot water boilers" published by the Health and Safety
Executive.

The information and guidance given below is not intended to override
any requirements of either of the above publications or the
requirements of the local authority, gas or water undertakings.

Other British Standards applicable are BS.5422 and BS.6700.

The information provided is based on the following assumptions:

1. An independent open vent/safety pipe connection is made to the

redundant boiler flow tapping or is positioned immediately after
the system flow pipe connection to the header, as shown (C).

2. An independent cold feed/expansion pipe connection is made to

the redundant boiler return tapping ("D"). Cold feed/expansion pipe
connections made to the pumped system return will result in an
increase in the static head requirement, caused by the additional
resistance of the distributor tube. Surging may also increase.

3. The maximum flow rate through the boiler is based on a

temperature difference of 11°C at full boiler output and the
circulating pump is positioned in the flow to the system.

4. The boiler is at the highest point of circulation in the system.

Systems designed to rise above the boiler flow tappings will
automatically require a minimum static head higher than that
shown.

5. The position of the open vent/safety pipe above the expansion

cistern water level is given as a guide only ("B"). The final position
will depend upon the particular characteristics of the system.
Pumping over of water into the expansion cistern must be avoided.

and cost. Graph 1 is based on a 20°C temperature difference
across the boiler.

WATER CIRCULATION SYSTEM

Due to the compact nature of the boiler the heat stored within the
castings at the point of shutdown of the burner must be dissipated
into the water circuit in order to avoid the overheat thermostat
tripping. In order to allow pump operation after burner shutdown
the boiler control box incorporates a pump overrun facility which
operates when the boiler switches off and until the flow temperature
is below 75

C and, in order to make use of this, the pump must be

wired to the appropriate terminal L

(pump) in the boiler control

box.

1. The minimum flow rate as given in Table 5 must be maintained

whenever the boiler is firing and during the pump overrun period.

2. During the period of pump overrun there must be an open circuit

of adequate water volume and/or load. The minimum size of
this circuit is given by the use of Graph 2.
Examples shown on Graph 2
a. For the CXC 116 the minimum circuit during pump overrun

could be a load of 6 kW with a volume of 31 litres or any
other combination given by the relevant line.

b. For the CXC 94 the minimum circuit during pump overrun

could be a load of 2 kW with a volume of 45 litres or any
other combination given by the relevant line.

The above circuit capacity during pump overrun may be
achieved either by provision of an adequate bypass circuit

or by ensuring that a zone of suitable size is open for
circulation during this period by relevant control of zone
valves or pumps.

The wiring diagrams in Frames 16, 17 and 18 illustrate
the control methods for achieving the above.

3. Pump selection should take account of the hydraulic

resistance given in Graph 3.

PUMP POSITIONS

Whenever practically possible the circulating pump(s) should be
positioned so that it pressurises the system being served. The
vertical distance between the pump(s) and any cold feed and
expansion cistern MUST comply with the pump manufacturers
requirements in order to avoid cavitation. These requirements
override the information given in Frame 3 if the static head required
for the pump(s) exceeds that required for the boiler.

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SEALED (PRESSURISED) SYSTEMS

automatic reset. In the event of shut down both visual and
audible alarms may be necessary.

Pressure vessels used must comply with BS. 4814 and must
be sized on the basis of the total system volume and initial
charge pressure.

Initial minimum charge pressure should not be less than 0.5
bar (7.2 psi) and must take account of static head and
specification of the pressurising equipment. The maximum
water temperatures permissible at the point of minimum
pressure in the system is specified in Guidance Note PM5.

When make up water is not provided automatically it will be
necessary to fit controls which shut down the plant in the event
of the maximum system pressure approaching to within 0.35
bar (5 psi) of safety valve setting.

Other British Standards applicable to commercial sealed
systems are:-

BS. 6880: Part 2.
BS. 1212
BS. 6281: Part 1
BS. 6282: Part 1
BS. 6283: Part 4

GENERAL

the cold feed pipe that system water expands into the tank when
the boiler passes heat into the system. Conversely, when the
system cools, water previously expelled is drawn back from the
tank into the system, together with a quantity of dissolved oxygen.

Even if leakage from the heating and hot water system is
eliminated there will be evaporation losses from the surface of
the tank which, depending upon ambient temperature, may be
high enough to evaporate a large portion of the system water
capacity over a full heating season.

There will always be corrosion within a heating or hot water system
to a greater or lesser degree, irrespective of water characteristics,
unless the initial fill water from the mains is treated. Even the
water in closed systems will promote corrosion unless treated.

Aluminium Heat Exchanger

The secondary heat exchanger of the Concord CXC is made of
aluminium finned tube and so any water treatment must be
suitable for systems containing aluminium.

Under no circumstances should the boiler be fired before
the system has been thoroughly flushed.

Caradon Plumbing Limited recommend only the use of Fernox
or Betz Dearborn water treatment products, which must be used
in accordance with the manufacturers instructions. For further
information contact :-

Fernox Manufacturing. Co. Ltd, Tandem House, Marlowe Way,
Croydon, Surrey CRO 4XS, Tel 0870 5601 5000

Betz Dearborn Ltd, Widnes, Cheshire, Tel. 0151 424 5351

IMPORTANT: Any other treatment for this product will render
the guarantee of Caradon Plumbing Limited INVALID.

Notes.
1. If an inhibitor is used, and in hard water areas where treatment

to prevent lime deposits is necessary, it is most important that
the water treatment MUST be maintained at the correct
concentrations recommended by the treatment manufacturer.

Persons responsible for the continued operation of this boiler
should be made aware of this requirement.

If the boiler is installed in an existing system then any unsuitable
water additives MUST be thoroughly drained.

MINIMUM FLOW OF WATER - Refer to Table 5

The system design must provide for an adequate flow rate through
the boiler at all times when the boiler is firing. The minimum flow
rate should correspond to a temperature difference across the
boiler flow and return of 35

C (63

F), assessed at catalogue

rating.

It is essential that the main pump and shunt pump both overrun
to dissipate the residual heat in the primary heat exchanger. This
is done automatically if:

a. An unswitched live supply is connected to the boiler control

box (for details see 'Electrical Connections').

b. The shunt pump (prewired) and main pump are connected to

the boiler control box (for details see 'Electrical Connections').

c. Part of the system is available to the main pump when the

call for heat by external controls is satisfied.

The boiler produces condensate when the system return water
temperature falls below 55 °C (the Dew Point of the combustion
products).

This condensate must be led away by a condensate drain
connected to the steel pipe at the rear of the boiler and installed
in accordance with IM22 (see 'Condensate Drain').

WATER TREATMENT FOR HOT WATER AND
HEATING BOILERS

There is a basic need to treat the water contained in all heating and
indirect water systems, particularly open vented systems. It is
assumed, incorrectly, that because boilers are operating in
conjunction with what is apparently a closed circuit an open vented
system will not, under normal circumstances, allow damage or loss
of efficiency due to hardness salts and corrosion once the initial
charge of water has been heated up a few times.

1mm of lime reduces the heat transfer from metal to water by 10%.

In practice the deposition of these salts is liable to cause noises
from the boiler body or even premature boiler failure. Corrosion and
the formation of black iron oxide sludge will ultimately result in
premature radiator failure.

Open vented systems are not completely sealed from the atmosphere
if proper venting and expansion of system water is to be achieved.
The same tank is used to fill the system with water and it is through

Working pressure 4.5 bar maximum.

Particular reference should be made to BS. 6644: Section 6
and Guidance note PM5 "Automatically controlled steam and
hot water boilers" published by the Health and Safety Executive.

The information and guidance given below is not intended to
override any requirements of either of the above publications or
the requirements of the local authority, gas or water undertakings.

In general, commercial closed pressurised systems are provided
with either manual or automatic water make up.

On both instances it will be necessary to fit automatic controls
intended to protect the boiler, circulating system and ancillary
equipment by shutting down the boiler plant if a potentially
hazardous situation should arise.

Examples of such situations are low water level and operating
pressure or excessive pressure within the system. Depending
on circumstances, controls will need to be either manual or

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GENERAL

capacity to support the weight of the boiler (when filled with water)
and any ancillary equipment.

If the boiler is mounted on a plinth then the dimensions must exceed
the plan area of the boiler by at least 75mm on each side.

VENTILATION

Safe, efficient and trouble-free operation of conventionally flued
gas boilers is vitally dependent on the provision of an adequate
supply of fresh air to the room in which the appliance is installed.
Ventilation by grilles communicating directly with the outside air is
required at both high and low levels. The minimum free areas of
these grilles must be according to the scale in Table 6.

Position ventilation grilles to avoid the risk of accidental obstruction
by blockage or flooding. If further guidance on ventilation is required
then consult BS.6644.

AIR SUPPLY BY MECHANICAL VENTILATION

The supply of air by mechanical means to a space housing the
boiler should be by mechanical inlet with natural or mechanical
extraction. Mechanical extract ventilation with natural inlet must
not be used.

Where a mechanical inlet and a mechanical extract system is
applied, the design ventilation flow rates should be as in Table 4 of
BS.6644.

The requirements for air supply by mechanical ventilation are given
in BS.6644.

Note. For mechanical ventilation systems an automatic control
should be provided to cause safety shutdown or lockout of the
boiler(s) in the event of failure of air flow in either inlet or extract
fans.

IMPORTANT. The use of an extractor fan in the same room as the
boiler (or in an adjacent, communicating room) can, in certain
conditions, adversely affect the safe operation of the boiler. Where
such a fan is already fitted (or if it is intended to fit an extractor fan
after installation of the appliance) the advice of the gas supplier
should be obtained.

FLUE SYSTEM DESIGN

The Concord CXC condensing boiler is supplied with an integral
fan which is fully matched to the boiler in each case to provide
correct combustion air flow.

The power of this fan is such that there is a large reserve of pressure
available to overcome a significant length of the flue without
affecting the combustion performance of the boiler. The pressure
available at the base of the flue to overcome flue resistance is
0.25 mbar (0.1 w.g.) This is sufficient to overcome the resistance
of approximately 30 metres of 150mm diameter smooth, straight
flue pipe.

Material

The type of flue pipe used should conform BS.715: Section 2
Stainless Steel or be of equivalent corrosion resistance. Advice
regarding the availability of proprietary types of flue system can
be obtained by contacting Caradon Plumbing Ltd. All joints or
connections in the flue system must be impervious to condensate
leakage and also any low points in the flue system should be
drained using pipe of material resistant to condensate corrosion.

Care should also be taken in the selection of flue terminals as
these tend to accentuate the formation of a plume.

Care should be taken to ensure the specification of the chimney is
suitable for the application by reference to the manufacturers
literature. Caradon Plumbing Ltd can offer advice on the design
of suitable chimney systems.

INSTALLATION REQUIREMENTS

The appliance must be installed by a CORGI registered installer,
identified by . The installation of the boiler must be in accordance
with the relevant requirements of the Gas Safety Regulations, current
IEE (BS.7671) Regulations, Model Water Bye-laws, local water
authority bye-laws and it should also comply with any relevant
requirements of the local gas supplier, local authority and the relevant
British Standard Codes of practice and building regulations.

Limitations of Intended Operating Environment
These appliances are NOT suitable for installation where they will
be exposed to the elements.

A boiler room shall be constructed or adapted to meet the
requirements of BS. 6644.

The maximum ambient temperature is 32° C at 1.5 metres from
the floor, with a maximum humidity of 90% RH.

FOR SMALL PIPE INSTALLATIONS:
BS. 6891:

Installation of low pressure pipework

FOR LARGE PIPE INSTALLATIONS

Gas Installations
IGE-UP-1:

Purging Procedures of Non-domestic Gas
Installations. Soundness Testing Procedures
for Industrial and Commercial.

IGE-UP-2:

Guidance notes on the Installation of Gas
Pipework, Boosters and Compressors in
Customer's Premises Equal to or Greater
than 25mm (Non-domestic).

IGE-UP-10:

Installation of Gas Appliances in Industrial and
Commercial Premises.

BS.6644:

Installation of Gas Fired Hot Water Boilers
70kW to 1.8MW (net).

BS 6880 Pt 1-3: Control Heating by Low Pressure Hot Water.
CP342:2:

Centralised Hot Water Supply.

Model Water Bye-laws
Manufacturers notes must not be taken, in any way, as
overriding statutory obligations.

The appliance must be installed in a room separated from living
rooms and provided with appropriate ventilation direct to the outside
- see Table 6.

2. Artificially softened water must not be used in the system, under

any circumstances.

3. In all systems the fitting of a filter to the return pipework, in order

to prevent debris reaching the heat exchanger, is essential.

FOUNDATION

The boiler must stand on a non-combustible floor (i.e. concrete
or brick) which must be flat, level and of a suitable load bearing

Table 6 - Ventilation Requirements
Required area (cm

) per kW of total rated input (net)

Boiler room

Enclosure

Low level (inlet)

High level (outlet)

Note: Where a boiler installation is to operate in summer
months (e.g. DHW) additional ventilation requirements
are stated, if operating for more than 50% of time (refer
to BS6644).

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CONDENSATE DRAIN

The Concord CXC boiler will produce condensate whenever
the temperature of the return water from the system is below
approximately 55

C (the Dew Point of the combustion products).

Natural gas condensate is mildly acidic with a pH value of about
4 and therefore corrosion resistant materials must be used in the
construction of the condensate drain. Standard PVC pipe is
suitable for this purpose and should be connected to the steel
drain fitted on the boiler.

GAS SUPPLY

If there is any doubt regarding the capacity of the gas meter, the
available gas pressure, the adequacy of existing service pipes
or the size required for new service pipes then the advice of the
gas supplier should be requested. Installation pipework should

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INSTALLATION

be fitted and tested for gas soundness in accordance with BS.
6891 for small installations or IGE-UP-1 and IGE-UP-2 for large
installations.

The local gas supplier must be consulted if it is necessary to employ
a gas pressure booster.

ELECTRICAL SUPPLY

WARNING. This appliance must be efficiently earthed.
A 230 V ~ 50 Hz mains supply is required, fused at 5 amps.
Wiring external to the appliance MUST be in accordance with the
I.E.E. (BS. 7671) Wiring Regulations and any local regulations
which apply.

For details of connections see Frame 14.

CONCORD CXC BOILER ASSEMBLY - Exploded view

6. Float switch
7. Shunt pump.
8. End section.

Legend
1. Collector hood
2. Cleanout cover
3. Fan
4. Secondary heat exchanger
5. Air pressure switch.

9. Middle section.
10. Tie rods.
11. Base plate.
12. Combustion chamber.
13. Section bolt.

14. Front plate.
15. NOx duct.
16. Drain cock.
17. Burner manifold assy.
18. Gas cock.
19. Flueway baffles.
20. Thermostat pocket.

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1. Remove the jacket carton and outer packaging frame.

2. Remove the jacket pack support frame.

3. Remove the controls package and installation pack.

4. Remove the 2" BSP steel handling bars from installation

pack.

5. Remove 4 base bolts holding the assembly to the

packaging base.

6. Remove the wood screws securing the front cross

member on the packaging base.

7. Remove the gas cock by unscrewing the union and screw

in the handling bars into the 2 front tappings. Protect the
exposed inlet gas union from ingress of dirt.

8. Knock out front spacing blocks from the packaging base,

ensuring that the boiler assembly is supported, using 2"
BSP handling bars.

9. Using the handling bars, manoeuvre boiler forwards on the

packaging base and slide over the collapsing base on to
the floor.

Note.
Before manoeuvring the boiler into its final position see
Frame 8.

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PACKAGING

The Concord CXC boiler is despatched from the factory fully
assembled except for the casing, controls and installation
packs which are packed separately within the same wooden
crate as the boiler.

JACKET PACK contains

Lower front panel ................. 1 off

Upper front panel ................ 1 off.

Lower LH side panel ........... 1 off.

Lower RH side panel ........... 1 off.

Upper LH side panel ........... 1 off.

Upper RH side panel ........... 1 off.

Lower top panel .................. 1 off.

Upper top panel .................. 1 off.

Infill panel ............................ 1 off.

Support bracket ................... 2 off.

Flue brush ........................... 1 off.

Jacket hardware pack ......... 1 off.

Lower rear panel ................. 1 off.

Upper rear panel ................. 1 off.

Upper middle rear panel ..... 1 off.

Lower middle rear panel ..... 1 off.

CONTROLS PACK contains

Controls box complete ....... 1 off

Controls installation pack ... 1 off

INSTALLATION PACK contains

R2 sq. hd. plug .................................... 3 off.

R2 installation pipe .............................. 2 off.

Installation & Servicing Instructions .... 1 off.

Users instructions ............................... 1 off.

System warning label ......................... 2 off.

PACKAGING AND BOILER REMOVAL

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Manoeuvring the boiler

1. Remove the gas cock to access the LHS tapping.

2. Screw the 2 handling bars (2" pipe supplied) into the 2

top tappings.

3. Screw in 2 bars (not supplied), 1 into the LH rear top

tapping and the second into the tee at the RH top
tapping.

4. Use these bars to manoeuvre the boiler into position.

5. Complete the system connections, using suitable

jointing compound, as follows:

a. The flow connection must be made to the upper

tapping on the primary heat exchanger.

10 FLUE CONNECTION

The 150mm (6") flue should conform to BS.715: Section 2
Stainless Steel or be of equivalent corrosion resistance.

The flue must be designed to have no greater resistance
than that of 30m of straight, smooth 150mm (6") pipe.

All joints must be impervious to condensate leakage.

The condensate drain must be 1

1/4

" diameter PVC pipe

from the pre-fitted drain at the rear of the boiler.

The condensate drain may be led directly into the normal
drainage system. The pipe should be installed with an
adequate slope (e.g. 1 in 50) and consideration should be
given to frost protection.

The drain should be in accordance with IM 22.

Connections to BS.5355 can be used directly, or
connections to BS.5354 may be used with a suitable
adaptor.

Note.
A condensate trap is built into the boiler sump therefore an
external trap is not necessary.

b. The return connection must be made to the upper

tapping on the secondary heat exchanger.

c. Complete the water connections by plugging the 2

front top and 1 rear top tappings with the 2" BSP
plugs provided. The remaining 1" lower tapping
should be plugged if not used for cold feed on an
open vent system or connection of a pressure
vessel, if on a sealed system.

3. Position the overheat thermostat phial into the LH side

thermostat pocket.

The illustration shows the rear of the boiler with the
flow and relative overheat thermostat position.

Ensure that the overheat thermostat phial is correctly
secured in the pocket. Refer to Frame 13.

BOILER ASSEMBLY AND SYSTEM CONNECTIONS

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CONDENSATE DRAIN CONNECTION

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11 GAS CONNECTION

1. Refit the gas cock.

2. Connect the gas supply to the gas pipe elbow.

The gas pipe should enter the boiler at the top LH side of
the boiler.

3. Table 2 gives details of the inlet connection size and the

minimum working pressures.

5. Fit clips to the top of each side panel.

6. Fit the spire clips to the side casing panels.

7. Hook on the control box to side panels.

8. Screw in self tapping screws at the bottom of the

control box to fix it to the side panels.
Push in the mains plug into the socket at the back
of the control box.

Unpack the control box from its carton and find the mains plug
strapped to the back of the box.

The boiler casing should now be fitted.

The jacket hardware pack contains all the screws required for assembly.
1. Fit support angles to the

collector hood and sump. The
angle with the hole for the
earth screw fits to the front.
Ensure the rear support angle
is fitted as shown.

2. Wire up the mains input cable

to the plug provided.
Run this cable along the lower
clips (using the cable ties in the hardware pack) of the LH side panel with
the plug placed at the front.

3. Slide bottom of lower side panels on to studs on base tray.
4. Screw lower side panel to support angles.

Repeat for other side.

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12 CASING ASSEMBLY

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10. Ensure that the Heyco bush is correctly located

and that the top of the bush is at the marked line.
Route the cables from the temperature probe, air
pressure switch and float switch through the clips
on the RH side panel.
Neatly coil up any excess length of cable and
push in the plug-in connector into the connection
box.

11. Hook the upper side panel into the keyhole slot.
12. Fix the upper side panel in position.

One screw into the lower side panel, one screw
into the upper support angle.
Repeat for the other side.

13. Clip in the upper top panel.

Fit the infill panel around the flue and secure
underneath top panel with the 2 self tapping
screws provided.

14. Fit earth leads as

shown.

9. Route the overheat thermostat capillary through the cable clips as

shown.
Ensure the phial is correctly seated in the correct pocket opposite
side to the flow connection - refer to Frame 8.
Secure with the split pin provided.

Complete the following after reaching Frame 32
15. Fit the lower top panel.

Fit the lower front panel.

16. The upper front panel has 2 hooks at the bottom.

Drop in these 2 hooks behind the back edge of the
lower top panel, push home onto the 4 catches and
secure with the top screw.

17. Fit rear panels in the sequence shown. Do NOT

tighten the screws until all panels are fitted.
Fit No.1 panel with the top 2 screws only.
Fit No.2 panel with the bottom 2 screws only.
Fit No.3 panel with the 4 screws engaging panels 1 and 2.
Fit No.4 panel with the 4 screws.

Align all panels and tighten all screws.

13 CASING ASSEMBLY - continued

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14 ELECTRICAL CONNECTIONS

WARNING.

This boiler must be efficiently earthed.

The internal wiring of the boiler control box is shown in Frame
15.

Connection must be made in a way that allows complete
isolation of the electrical supply - such as a double pole switch,
having a 3mm (1/8") contact separation in both poles, or a
plug and socket serving only the boiler and system controls.
The means of isolation must be accessible to the user after
installation.

This should serve only the boiler, together with its controls and
pumps. The supply must be wired direct to the boiler control
box and must not be interrupted by any system controls. The
pump(s) and any system controls must be wired back to the
boiler control box.

The control box incorporates a pump overrun device which is
necessary to dissipate residual heat after plant shutdown. It is
essential that the main pump is wired to the pump terminals
marked L2, N on the plug-in mains voltage connector shown
below and in Frame 15.

If no external controls are fitted it is essential that a link is
wired in place of one on the "Fan/pump plug-in connector".

The flow switch should be connected via volt-free contacts to
the 'Flow S' terminals. A link may be fitted in place of the flow
switch but the control will not be able to analyse the faulty flow
switch, if such a failure should occur. Either of the above must
be fitted or the boiler will not operate.

Any system controls should be connected, via volt free contacts,
to the terminals marked 'EXT C'. Do NOT connect an external
clock to these contacts or any mains voltage. If no external
controls are fitted a link must be fitted across EXT C.

The boiler provides frost protection via the boiler sensor. If an
external frost thermostat is required contact Caradon
Plumbing Limited.

Wiring should be PVC insulated cable, not less than 0.75mm

(24/0.2mm). All fuses must be ASTA approved to BS. 1362.

The length of the conductors between the cord anchorage
and the terminals must be such that the current conductors
become taut before the earthing conductor, if the cable or
cord slips out of the cord anchorage.

BOILER CONNECTIONS

Ensure the boiler is ELECTRICALLY ISOLATED.

The live supply cable should be fitted before assembly of the
jacket - see Frame 12 for details.

All wiring between entry at the rear of the boiler and the
connection box must be secured neatly under the cable
clips provided.
Wiring must never be allowed to come into contact with
any heated surfaces.

1. Check that the mains plug is pushed firmly into its socket.

2. Check that the temperature/float/air pressure plug-in

connector is fitted into the RH connection box.

3. Carefully route the electrical leads from the gas valve/

spark generator behind the LH panel return and secure
with the clip as shown.
Fit this plug-in connector into the bottom connection
box.

4. Route the fan and shunt pump cables through the clips

at the top of the LH side panel.

5. Wire the main system pump (L2 & N), flow switch and

external controls into the Fan/pump plug-in connector
(see below). The earth wires should be looped back
through the cable clamps and fixed to the earth post as
shown in Frame 13.
The earth connections MUST NEVER be omitted.

Fit the fan/pump plug-in connector into the mains voltage
connection box behind the control box.

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16 ZONES WITH BI-DIRECTIONAL MOTORISED VALVES

IMPORTANT

Terminal L2 may control the appropriate
pump(s) directly, provided that the total
running or starting current does not
exceed 6A (resistive or inductive): if this
rating would be exceeded, then
appropriate switchgear must be used to
control the pumps indirectly.

Three zones are illustrated but the
principles may be extended as required,
provided the above conditions are met.
Each relay will then require as many
contacts as there are zones.

Overrun

Since any zone may be the load during
overrun, all zones MUST individually be
able to satisfy the conditions in the
foregoing paragraph. If not all zones can
do this, then consider other means of
control detailed on other sheets.

Normal operation

When any thermostat is satisfied while
others are calling for heat, power is

15 INTERNAL WIRING

At the start of the next call for heat (or the next clock period)
valves on the zones not calling for heat will motor-shut.

Water circulation system - refer to page 7

LEGEND

v violet
pk pink

y/g yellow/green
or orange

y yellow
w white

br brown
r

red

b blue
bk black

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available via relay contacts to close the valve for that zone.
When all thermostats are satisfied (also when the clock period
ends) all relays will be off so the zone valves which were open
will remain open for the pump overrun period.

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IMPORTANT

Terminal L2 may control the appropriate
pump(s) directly, provided that the total
running or starting current does not exceed
6A (resistive or inductive): if this rating would
be exceeded then appropriate switchgear
must be used to control the pumps indirectly.

Three zones are illustrated but the principles
may be extended as required, provided the
above conditions are met. Only one relay is
required, irrespective of the number of zones.

Overrun
During overrun and dormant periods, Zone
Valve 1 is held open. This zone, therefore,
MUST satisfy the conditions in the foregoing
paragraphs and Graph 2.

Normal operation
During a call for heat on Zone 1 only, the
boiler is energised via Zone 1 thermostat and
the normally closed contacts of the relay.

During a call for heat on other zone(s), the
relay will be energised by the auxiliary switch
on the zone valves. This provides power to
energise the boiler. If, in addition, Zone 1 now
calls for heat, its thermostat will open Zone 1
valve via the normally open contacts of the
relay.

17 ZONES WITH INDIVIDUALLY PUMPED ZONES (3 zones shown)

IMPORTANT

Terminal L2 may control the appropriate
pump(s) directly, provided that the total running
or starting current does not exceed 6A (resistive
or inductive): if this rating would be exceeded
then appropriate switchgear must be used to
control the pumps indirectly.

Three zones are illustrated but the principles
may be extended as required, provided the
above conditions are met. For each zone
(except Zone 1) a relay with 2 C/O contacts is
required.

Overrun
During overrun periods, Zone 1 pump performs
the overrun facility; this zone, therefore, must
satisfy the conditions in the foregoing
paragraphs and Graph 2.

Normal operation
During a call for heat on Zone 1 only, Zone 1
thermostat energises the boiler, which in turn
energises Zone 1 pump from terminal L2.

During a call for heat on other zones, the
appropriate relay directs power to L1 to
energise the boiler, at the same time ensuring
that Zone 1 pump is controlled by Zone 1
thermostat.

Water circulation system - refer to page 7

When the clock period ends, Zone valve 1 will (stay) open via normally
closed relay contacts to achieve pump overrun.

Water circulation system - refer to page 7

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18 ZONES WITH SPRING-RETURN MOTORISED VALVES

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19 COMMISSIONING AND TESTING

GENERAL

Check that all drain cocks are closed, that any stop valves
fitted to the flow and return pipes are open and that the
system has been filled and properly vented. Ensure that the
caps on both secondary heat exchanger automatic air vents
are open.

Check that the shunt pump is set to maximum and that both
isolation valves are open.

PURGING

Check that the electricity supply is switched OFF.

Remove the jacket lower front panel.

Extinguish all naked lights and open all doors and windows.

The Concord CXC incorporates an advanced
microprocessor based control system which
operates all electrical functions of the boiler
including automatic ignition, flame detection,
thermostatic control, and high/low burner
operation. In addition, the microprocessor also
has onboard commissioning and servicing
instructions and a fault diagnosis programme.

The next section describes the minimum
procedure to light and commission the boiler. Full
operating instructions for the microprocessor
control and details of the high/low operation
system are included in Frames 27-30.

1. Check that the gas and electricity supplies to the boiler are

turned off.

2. Connect a gas pressure gauge to the inlet pressure test

point. (Frame 23 or 24).

3. Turn on the gas and electricity supplies. The display will

initially show a start-up code followed by;

4. Press the [1/0] button The display will change to:

then change every few seconds to indicate the boiler
status. The boiler will commence its ignition sequence.

5. The fan will start and the boiler should light, initially at low

rate, for a maximum period of 3 minutes, if less than 55°C,
before proceeding to maximum rate. If the boiler fails to
light, allow the controls to cycle until ignition is established.
If the boiler fails to light after 5 attempts, the display will
show "Detection Fault". In this case, the ignition sequence

should be reset by pressing the [COPY] button. Check that
the gas inlet pressure is at least the minimum value stated
in Table 2 when the boiler is firing at maximum rate (High).

6. Whilst the boiler is warming up, observe the display to

become familiar with its operation. The display changes
automatically between the:

Boiler status and flow temperature

Hours run

Temp set

Programmer status

Enter for menu

Day

Date and time

Note. As the boiler flow temperature approaches the
thermostat setting, the boiler is automatically reduced to low
rate.
This feature is designed to improve overall operating efficiency
and reduce short cycling under low load conditions. The
controls will automatically switch the boiler between high and
low upon demand.

21 LIGHTING INSTRUCTIONS

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20 INITIAL LIGHTING

DO NOT SMOKE. Check that the gas supply is turned ON at
the meter and open the main gas inlet cock. Loosen the union
and allow air to be purged from the gas line until gas is
smelled. Refer to BS 6891 or IGE-UP-1 for further details.
Retighten the union.

TESTING FOR GAS SOUNDNESS

Close the gas supply cock at the meter.

Remove the screw in the inlet pressure test point (Frames 23/
24) and connect a gas pressure gauge to the test point. Take
particular care to ensure a gastight connection. Open the gas
supply cock at the meter and the appliance gas cock; record
the static pressure. Next, close the gas supply cock at the
meter. Wait for 1 minute for temperature stabilisation then
observe the pressure gauge over a period of 2 minutes.

Any leaks must be cured.

Replace all pressure test point screws.

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22 CHECKING THE MANIFOLD PRESSURES

23 ADJUSTING THE MANIFOLD PRESSURES

5. Press the [0/1] button to turn the appliance off, then

disconnect the high/low solenoid connector plug (10)
from the gas valve. Turn the appliance on and repeat the
above sequence but using the low rate adjustment screw
(6) inside the spindle.

6. Turn the appliance off, reconnect the high/low solenoid

plug, refit the dust cover over the adjustment screws and
refit both pressure test point screws. Check for gas
soundness.

7. Press [EXIT] to leave the commissioning mode and

return to the main menu.

8. Press [EXIT] again to return to the status displays.

1. Press the [ENTER] button on the fascia panel, then press

either the [UP] or [DOWN] arrow button until the display
shows:

then press [ENTER]. The microprocessor is now in
commissioning mode. Failure to enter the Commissioning
mode will result in a fault condition being detected when
the following actions are carried out.

2. If desired, it is possible to use the onboard commissioning

instructions, using the [UP] / [DOWN] arrow buttons.
However the following paragraphs provide more detailed
instructions and are recommended until the installer is
familiar with the Concord CXC.

3. It is essential to adjust the maximum setting first.

4. Adjust the system controls to ensure that the boiler will

operate at high rate for a reasonable period, then remove
the dust cover and adjust the high rate burner pressure
setting, using a suitable spanner. Turn the maximum
adjuster (7) clockwise to increase, or anticlockwise to
decrease, the pressure. After setting to the indicated
pressure allow the boiler to operate for about 5 minutes to
stabilise then recheck the burner pressure.

CXC 48 & 70 ONLY

6. Screw - minimum adjuster.
7. Gas rate adjuster - maximum.
8. Burner setting pressure test

point.

9. Inlet pressure test point.
10. High/low solenoid connector.

LEGEND
1. Fascia panel display.
2. Overheat thermostat

reset button.

3. Main gas inlet cock.
4. Union.
5. Gas control valve.

Turn the boiler OFF by pressing the [0/1] button and allow the
flow temperature to cool to less than 50°C.

Connect a pressure gauge to the burner manifold test point
(Frame 23 or 24). Press the [0/1] button again to turn the boiler
ON.

The boiler will operate at low rate for approximately 3 minutes
before proceeding to high rate (this will only happen if the flow
temperature is below 55

C otherwise the boiler will proceed

immediately to high rate).

Observe the burner pressures and compare them to the
values given in Table 1. If either pressure differs by more than
10%, reset the pressures by following the procedure in Frame
23 or 24.

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24 ADJUSTING THE MANIFOLD PRESSURES

1. Press the [ENTER] button on the fascia panel, then press

either the up or down arrow button until the display shows:

then press [ENTER]. The microprocessor is now in
commissioning mode. Failure to enter the commissioning
mode will result in a fault condition being detected when
the following actions are carried out.

2. If desired, it is possible to use the onboard commissioning

instructions using the up/down arrow buttons. However the
following paragraphs provide more detailed instructions
and are recommended until the installer is familiar with the
Concord CXC.

3. It is ESSENTIAL to adjust the LOW setting first.

4. Press the [0/1] button to turn the appliance OFF, then

disconnect the power leads from the right hand (HIGH)
gas valve.

LEGEND
1. Fascia panel display.
2. Overheat thermostat reset button.
3. Main gas inlet cock.
4. Union.
5. Gas control valve low rate.
6. Gas control valve high rate.
7. Low rate adjusting screw.
8. High rate adjusting screw.
9. Burner setting pressure test point.
10. Inlet pressure test point.
11. RH (high) gas valve power

connector.

The Concord CXC features direct burner ignition, high/low
burner operation, and a microprocessor control system.

Upon a demand for heat, the controls start the fan, the air
pressure switch senses flow then the controls open the low
rate gas valve and provides a rapid spark at the ignition
electrode for up to 10 seconds.

The burner will light and remain at low rate for approximately 3
minutes before proceeding to high rate (when the
microprocessor opens the remaining gas valve).

If the boiler fails to light, the gas valve is closed and there will
be a delay of 1 minute before the cycle is repeated. If, after 5
attempts, the burner has failed to light, the boiler will go to
lockout and

will be displayed on the screen.

When the boiler flow temperature reaches the thermostat set
point, the controls will turn the burner to low rate. If the flow
temperature continues to rise, the burner and fan will be
turned off at 3

C above the set point.

If, however, the temperature falls below the set point whilst on
low fire, the controls will automatically turn the burner back up
to maximum rate.

This system has the advantages of ensuring that the boiler
accurately maintains the set temperature (without the large
temperature swings that can be associated with on/off
boilers), prevents rapid or short cycling, and provides more
efficient system operation.

CXC 94 & 116 ONLY

5. Press the [0/1] button again to light the burner. Allow the

burner to run at low rate for several minutes then check
that the low burner pressure is as shown in Table 1 for
the appropriate boiler size. If necessary, adjust the low
burner pressure adjusting screw (7).

6. Press the [0/1] button to turn the boiler off, reconnect the

power leads to the RH valve and press the [0/1] button
again to relight the boiler. Adjust the system controls to
allow the boiler to fire at high rate for several minutes,
then remove the dust cover and adjust the high burner
pressure adjusting screw (8). After setting to the indicated
pressure replace the dust cover and allow the boiler to
operate for about 5 minutes to stabilise then recheck the
burner pressure.
Note. If high rate pressure is not achievable as above
check that the gas restrictor in the low-rate valve is fitted
(see Frames 39 & 42).

7. Press the [0/1] button to turn the boiler off, then refit both

pressure test point screws. Check for gas soundness.

8. Press [EXIT] to leave the commissioning mode and

return to the main menu.

9. Press [EXIT] again to return to the status displays.

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25 OPERATING INSTRUCTIONS

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26 ADDITIONAL FEATURES OF THE CONTROL SYSTEM

FAULT DIAGNOSIS

In the unlikely event of a fault condition, the microprocessors
will identify the fault area and display a suitable message on
the display.

Further to these accessible features, there are other features
present in the system which the installer/service engineer
should be aware of.

HOURS RUN LOG

This feature enables the installer to determine the workload of
the boiler.

PUMP OVERRUN

If the flow temperature is above 75

C at the time of boiler

shutdown, the controls will maintain pump operation until the
residual heat within the appliance has been dispersed and the
flow temp is below 75

ANTI-CYCLE DEVICE

On any heating system, if the heating load is very low, there is
a tendency for the boiler to cycle on and off rapidly. This is
inefficient and can lead to shortened boiler life. The high/low
operating system of the Concord CXC minimises the risk of
this but, in addition, the controls prevent the boiler from short
cycling by preventing subsequent ignition within a period of 2
minutes. When active, the display will show:

ON / STANDBY [1/0] BUTTON

Turns the boiler ON and to STANDBY.

WARNING

STANDBY does NOT electrically isolate the boiler.

When this switch is in the STANDBY position the display will
show :-

On initial start up the boiler will indicate the hardware and
software code, the boiler type and indicate if the boiler is ON or
STANDBY. If the boiler is at STANDBY the rotating information
screens will not be in evidence.

An example of the display is as follows :-

MONDAY
14 : 10 19 / 09 / 95
ON HIGH 50

HOURS RUN 250
TEMP SET 82

PROGRAMMER ON
"ENTER" FOR MENU

To switch the boiler on press the On/Standby
[1/0] button. The display will show :-

This display will be retained for 5 seconds
before the information screens are displayed.

INFORMATION SCREENS

If the optional outside temperature kit, enabling
weather compensation, has been fitted the
display will indicate the compensated set point
temperature.

In addition to the operational characteristics described above,
the control system incorporates the following features
accessible to the user or service engineer:

ADJUSTABLE BOILER TEMPERATURE CONTROL

This is factory pre-set at 82

C but may be adjusted by the user

between 60

C and 85

C. Refer to Frame 30.

PROGRAMMER TIMER

A maximum of 3 time periods per day can be programmed in
to the boiler.

Note. This is a boiler timer only and does not replace a
conventional system programmer serving more than one
heating zone.

OUTSIDE SENSOR (optional extra)

If the optional outside sensor is fitted, the control system will
recognise this and automatically regulate the boiler flow
temperature with respect to changes in the external
temperature. If the sensor is fitted, an extra status information
screen will appear stating whether the device has been
activated or not (i.e. compensator on/off).

COMMISSIONING INSTRUCTIONS

These are provided to assist the installer to commission the
boiler.

SERVICING INSTRUCTIONS

These are provided to assist the service engineer.

27 DESCRIPTION AND OPERATION OF BOILER CONTROLS

INSTALLATION

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29 DESCRIPTION AND OPERATION OF BOILER CONTROLS - continued

MENU

To access the menu screen ensure that the information
screens are being displayed.
Any key, except the [1/0] button, may now be pressed to
access this feature but, as indicated on the information screen,
the [ENTER] button is the preferred means.

On entering this option the first screen displayed will be:-

The [DOWN] button can be pressed consecutively to access
the features required, which are as follows:-

If the weather compensation option is fitted then a further
screen will be displayed after commissioning.

The [UP] button will access the above options in reverse.
When the option required is displayed and the [ENTER] button
pressed another set of menus will be available as discussed
on the following pages.

PROGRAMMER TIMER

The programmer has 3 time zones per day for each day of the
week. Each day can be programmed for the requirements of
that day, giving 7 programmed days or, using the copy facility,
any number of days can be the same. If a particular time zone
is not required then the ON and OFF periods should be
programmed for the same time.

Each button has an auto repeat function.

The programmer is based on a 24 hour clock and the boiler
comes with a backup programme set for :-

All Day

The boiler will respond to this programme unless an alternative
is programmed in.

Using the [UP] or [DOWN] button select the "Programmer
Timer" from the menu and press [ENTER]. The following
menus will be available using the [UP] or [DOWN] buttons:-

To select any of the above use the [UP] or [DOWN] button until
the option required is displayed and press [ENTER].

STATUS

Enables the selection of programme hours, all day usage or 24
hour.

If the "Programme Hours" option is selected the boiler will go
on and off, subject to the times programmed.

If ALL DAY usage is selected the boiler will come on at the first
"ON" period selected and off on the last "OFF" period selected,
ignoring all other time settings. Based on the above backup
programme this means the boiler would run, subject to any
other external controls, from 07:30 to 22:00 hours.

If 24 HOUR is selected the programme times will be ignored
and the boiler will run subject to the external controls until one
of the other options is again selected.

SET TIME/DATE

Enables the correct time and date to be entered.

The display will show a flashing day of the week as follows :-

The correct day can be selected by use of the [UP] or [Down]
button and, when correct, the [ENTER] button should be
pressed. The time and date will now be displayed as follows:-

with first two digits, the hours, flashing.

By use of the [UP] or [DOWN] button the correct hour is
selected and the [ENTER] button pressed. The minutes will
now be flashing and, by use of the [UP] or [DOWN] button, the
correct minutes selected and the [ENTER] button pressed.

This method is repeated until the correct day, month and year
are selected. On selecting the correct year and pressing
[ENTER] the hours will flash. Then, if all the data is correct, the
[EXIT] button should be pressed for the control to accept this
information.

ADVANCE

Enables the programme to be advanced by one hour.

The following display will be available:-

If the [YES] button is pressed and the programmer is in an
OFF period the boiler will be brought on for one hour, subject
to external controls. If the boiler is on with less than one hour
to a programmed off period then the difference between this
time and one hour is the time of the extended on period. If the
boiler is in the 24 hour mode then this option will have no
effect.

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30 DESCRIPTION AND OPERATION OF BOILER CONTROLS - continued

SERVICING

The SERVICE option is intended as a memory aid to the more
comprehensive servicing instructions to be found in this manual.

Using the [UP] or [DOWN] button select "Service" from the menu
and press [ENTER]. The following display will be available:-

The 2 screens will alternate to display this whole message.

When using this option, arrow keys will be in evidence to indicate
if the [UP] or [DOWN] buttons should be used.

It is IMPORTANT that these instructions are carried out precisely
and in the order displayed.

COMMISSIONING

The "Commissioning" option is intended as a memory aid to
the more comprehensive commissioning instructions to be found
in this manual.

Using the [UP] or [Down] button select "Commissioning" from
the menu and press [ENTER]. The following display will be
available:-

The 2 screens will alternate to display this whole message.

When using this option arrow keys will be in evidence to indicate
if the [UP] or [DOWN] buttons should be used.

It is IMPORTANT that these instructions are carried out precisely
and in the order displayed.

FAULT DIAGNOSIS

In the unlikely event of a fault condition, the microprocessors
will identify the fault area and display a message indicating the
nature of the fault to assist a speedy and effective repair.

See "Fault Finding" section for more details.

If the Advance has been selected, then to cancel it the same
procedure should be followed but the [NO] button pressed.

PROGRAMME HOURS

Enables a user- timed programme to be entered.
The following display will be available:-

with the hours, 06, flashing

Using the [UP] or [DOWN] button select the correct hour and
press [ENTER]. The minutes will now flash and the correct
minutes should be selected, using the [UP] or [DOWN] button
followed by pressing [ENTER]. This will cause the hours to flash
and if the correct ON time has been entered the [EXIT] button
should be pressed. The display will now show the OFF for time
zone one.

This procedure should be repeated for all 3 time zones for
Monday.

After the last [EXIT] the display will ask if this day's programmes
require to be copied to Tuesday. If the [YES] button is pressed
Tuesday's programme will be the same as Monday. This action
can be repeated for all the days or as many as required,

If the [NO] button is pressed then all 3 time slots will need to be
programmed with the required times.

TEMPERATURE SET POINT

Enables the temperature at which the boiler is required to operate
to be set. It has a range of 60

C - 85

Using the [UP] or [DOWN] button select the "Temp set" from the
menu and press [ENTER]. The following will be displayed:-

with the temperature flashing

The [UP] and [DOWN] button should be pressed until the correct
temperature is selected and then the [ENTER] button should be
pressed and the temperature selected will become stationary.
Pressing the [EXIT] button will ensure that the control accepts
the new setting and return to the menu.

High / Low Operation
In the example above, when the boiler flow temperature is equal
to 82

C the high rate gas valve will close, allowing the boiler to

run at low rate. When the flow temperature exceeds the set
temperature by 3

C, in the example above 85

C, the low rate

gas valve will close and the boiler will be off. The information
screen will display

The boiler will remain OFF for a minimum of 3 minutes or until
the boiler flow temperature has dropped by 3

C, whichever is

the greater time.

If the boiler load is such that it cycles between high and low
operation the boiler will fall through 3

before the high rate gas

valve is energised.

INSTALLATION

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Delayed High Rate Gas valve Operation
When the boiler is started from cold the high rate gas valve will
be delayed for thirty seconds and then energised. If the boiler
flow temperature is equal to or greater than 55

C then this delay

will NOT occur.

Notes.
1. If a fault occurs with the boiler thermostat the fault display

screen will show "C/H Sensor Fault".

2. When the low rate gas valve is de-energised as the

temperature required has been obtained the boiler will go
into an anticycle route for 2 minutes. The display will indicate
anticycle and the current flow temperature.

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34 HANDING OVER

ROUTINE OPERATION

Full instructions covering routine lighting and operation of the boiler are
given on the Lighting and Operation Instruction Label located on the inside
of the casing door.
Draw the attention of the boiler owner or his representative to the Lighting
and Operating Instruction Label on the inside of the casing door. Give a
practical demonstration of the lighting and shutting down of the boiler.

Describe the function of the boiler and system controls and show how they
are adjusted and used.
Hand over these and the User's Instructions to the customer and request
him to keep them in a safe place for ready reference.

IMPORTANT. Point out to the owner that the boiler must have regular
maintenance and cleaning, at least annually, in order to ensure reliable
and efficient operation. Regular attention will also prolong the life of the
boiler and should preferably be performed at the end of the heating
season.
Recommend that a contract for this work should be made with a CORGI
registered installer.

Caradon Plumbing Limited do not accept any liability
resulting from the use of unauthorised parts or the repair
and servicing of appliances not carried out in accordance
with the Company's recommendations and specifications.

A comprehensive service should be carried out at least
once a year. The User is advised to make a contract with
a CORGI registered engineer.

WARNING.
ALWAYS turn OFF the gas supply at the gas cock and
switch OFF and disconnect the electricity supply to the
appliance BEFORE servicing or replacing any
components.

CLEANING THE BOILER

Pull and lift off the lower front panel.

Remove the screw from the top of upper front panel. Pull
the panel forward and lift the bottom hooks clear of the
lower top panel.

32 TESTING

33 ADJUSTMENT OF WATER

FLOW RATE THROUGH THE
BOILER

When commissioning the heating/
domestic hot water system the shunt
pump must be adjusted to give the
minimum flow rate given in Table 5, when
that part of the system intended to be
used for dissipation of residual heat only
is in operation.

Check that the main burner responds correctly to manual on/off operations
of any controls fitted in the gas control circuit. Check, in the following
manner, the operation of the flame failure safety device.

1. Extinguish the main burner by turning off the main gas inlet cock. Refer

to Frames 23 and 24.

2. Check that the display shows "Detection Lockout".

3. Turn on the gas cock and reset by pressing [COPY].

4. Complete the casing assembly. Refer to Frame 13.

5. Important Commissioning / Operating Instructions:

Do not operate this appliance for long periods or take any combustion
readings with the casing or any part of the casing removed.

31 COMBUSTION SYSTEM

SOUNDNESS CHECKS

Remove the upper front casing panel.
Check that there is no leakage of
combustion products around the fan,
secondary heat exchanger and flue
connection, using a smoke match or
smouldering taper.

If any leaks are evident, immediate steps
must be taken to rectify them.

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SERVICING

35 SERVICING

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36 SERVICING - continued

damage the ignition electrode assembly and carefully
detach the ignition leads when removing the left hand
burner. Take care not to damage the detection
electrode when removing the RH burner.

Hinge cleanout cover insulation upwards and to the
left. Remove front access cover (secondary heat
exchanger) insulation by releasing from the retention
tabs.

Unscrew the 5 screws securing the fan assembly and
remove the pressure sensing pipe. Unclip the
capacitor, disconnect the inline connector and remove
the earth lead. Remove the assembly by pivoting it
anticlockwise.

Remove the fan plate, inspect the fan impeller and
clean if necessary.

Concord CXC 48/70
Undo the screws securing the cleanout cover and lift
it off to give access to the flue ways. Lift out the flue
baffles.

Concord CXC 94/116
Undo the screws securing the clean out cover and lift it
off.
Remove the 2 screws securing the distribution plate. Lift
the front edge of the baffle and pull forward to clear the
joggle at the rear.
Lift the RH edge up into the corner until the LH edge
drops below the supporting angle - see diagram.
The baffle can now be removed and access to the flue
ways obtained.

Lift out the flue baffles.

All boilers
Remove all loose deposits from the primary
heat exchanger, especially from between the
fins (using the brush provided) and remove all
debris from the combustion chamber floor.

Examine the burner assembly. Clean the
burner bars by brushing them down with a stiff
bristle (not wire) brush. Check each bar
carefully to ensure that all flame ports are clear,
that there are no cracks and that all surfaces
are free from accumulated deposits.

If available, an industrial vacuum cleaner may
be useful to assist in this work. When cleaning
the burner bars, take care to avoid damage
from rough handling to the ignition or detection
electrodes.

Inspect the ignition and detection electrodes.

Ensure that they are clean and in good
condition.
In particular, check that:

1. The ignition electrode shield and base fixing

screws are tight.

2. The electrodes are correctly positioned -

see Frames 40 or 41.

Remove lower top panel from the boiler casing.

Unscrew the extended nuts at the top of the NOx duct
behind the control box and lift the NOx duct clear of the
burners as illustrated below.

Undo the wing nuts securing the burner front plate.
Pull the front plate forwards, at the top, and lift it out -
taking care not to damage the insulation or the
detection electrode.

On the CXC 48 & 70 remove the screws holding the
HT heat shield from the LH leg of the combustion
chamber. Raise slightly and withdraw the heat shield,
taking care not damage the leads.

The burners may be lifted out after they have been
pushed back to clear the injector. Take care not to

SERVICING

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38 REPLACEMENT OF COMPONENTS - Refer to Frames 5, 40, 41 and 42

GENERAL

WARNING. ALWAYS turn OFF the gas supply at the gas
inlet cock and switch OFF and DISCONNECT the
electricity supply before working on the appliance.

37 SERVICING - continued

Remove the secondary heat exchanger front plate (6
screws) then slide out the secondary heat exchanger
baffles. Clean the fins with the brush provided and remove
all debris.

Reassemble in reverse order.

CXC 94/116 only. Refit the distribution plate.

The secondary heat exchanger baffles (one to each bank
of tubes) must be fitted with their returns uppermost.
Before refitting the secondary heat exchanger front plate
and fan assembly check that the seals are intact. Replace
if necessary.

Do not refit the insulation and casing panels until a leakage
test has been carried out after recommissioning the boiler.

TESTING AFTER SERVICING

After re-assembly restore the electricity and gas supplies.
Light the boiler (refer to the Lighting Instructions) and test for
leaks. Refer to Frame 19 `Testing for Gas Soundness'.

Check burner manifold pressures (Frame 22) and adjust if
necessary (Frames 23 or 24). Finally reset any external
controls to the desired position.

Check that there is no leakage of combustion products
around the fan, secondary heat exchanger and flue
connection, using a smoke match or smouldering taper.

If any leaks are evident, immediate steps must be taken to
rectify them.

To facilitate the replacement of components, remove
and replace the casing top and front panels, fan, NOx
duct and the burner front plate as necessary -
described under `Servicing'.

39 GAS CONTROL VALVE

1. Disconnect the electrical connections to the faulty gas

valve.

2. Check that the gas inlet cock is OFF, unscrew the 4

screws on the gas valve inlet flange, the 4 screws on the
outlet flange and remove the valve.

3. If the valve has a brass restrictor fitted to its outlet,

remove by unscrewing and refit into the new valve. It is
imperative that the gas restrictor is fitted to the low-
rate valve.

4. Replace the gas control valve and re-assemble in

reverse order, ensuring that the arrow indicating the
direction of flow is in the correct position.

5. Ensure that new `O' ring seals are correctly placed in

each flange connection.

6. Test for gas soundness.

7. Recommission the appliance and set the manifold

pressures as described in Frames 22 and 23 or 24.

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40 MAIN BURNER

1. Remove the NOx duct and burner front plate, as

previously described in Frame 35.

2. On the CXC 48 and 70 remove the screws holding the

HT heat shield from the LH leg of the combustion
chamber. Raise slightly and withdraw the heat shield,
taking care not damage the leads.

3. Each burner can be removed by sliding back, to clear the

injector, and then lifting out. Disconnect the ignition leads
from the LH burner and the detection lead from the RH
burner.

4. Remove the 2 screws securing the electrode assembly

and heat shield to the LH burner bracket and the 2
screws securing the detection electrode bracket to the
RH burner.

5. Reassemble in reverse order.

IMPORTANT. Care must be taken to prevent damage to the
combustion chamber insulation when replacing burners.

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42 BURNER AND CONTROLS ASSEMBLY - Exploded View - CXC 94 & 116

SERVICING

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43 OVERHEAT THERMOSTAT

Con 2555

PTP

LEGEND
1. Main gas inlet cock.
2. Gas inlet union.
3. 'O' ring seal.

4. Gas control valve, Low.
5. Gas control valve, High.
6. Spark generator.
7. Burner manifold.

8. Main injector, 3 off.
9. Main (centre/RH) burner, 2 off.
10. Main (LH) burner, 1 off.
11. Ignition electrodes.
12. Overheat thermostat mounting bracket.
13. Overheat thermostat.
14. Detection electrode assembly.
15.

Gas pipe.

16.

Gas restrictor.

PTP

Pressure test point

Overheat

thermostat

Con 1462

Reset

button

1. Remove the split pin from the overheat thermostat pocket

and remove the phial.

2. Loosen the 2 - M3 screws and remove the thermostat

assembly from its fixing bracket.

3. Undo R.H. M4 screw and remove the thermostat cover.

4. Undo the 2 x M4 screws or the centre M10 thin nut,

remove the wires and reconnect them to the new
thermostat body as follows:

`stats

CXC only

numbered

1, 2, 3

C, 1, 2

No. 2.

No.1

Pink

No.3

No. 2.

No.1

Pink

Reconnect the earth terminal.

5. Reassemble in reverse order.

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46 PC BOARD NO. 34

1. Remove the lower front panel.

2. Slacken the 2 screws securing the control box front panel.

Carefully lift it up and hinge forward.

3. Release the ribbon cable from PCB No. 34 by pushing the

retaining tabs sideways.

4. Release all plug connections from the board.

5. Remove the real time clock board (PCB No. RTC/34) from

PCB No. 34 by squeezing the 4 mounting pins and pulling
forwards.

6. Release PCB No. 34 from the 9 plastic mounting pins and

replace the board.

7. Reassemble in reverse order.

44 CONTROL BOX - Exploded View

SERVICING

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4. Printed circuit board No. 34.
5. Back panel.
6. Hinge pin.
7. Controls box.

LEGEND

1. Wiring clamp.
2. Connection box plug.
3. Connection box.

45 CONTROL SENSOR

1. Remove the upper front panel and lower top panel.

2. Remove the sensor from the thermostat pocket in the

rear heat exchanger section by removing the Heyco
bush.

3. Trace the lead back to the connector box behind the

control box. Release the connector box plug (Frame 43).

4. Replace the sensor and reassemble in reverse order.

Ensure that the lead is rerouted along the casing in the
clips provided and check that the sensor is correctly fitted
and secured in the thermostat pocket.

8. Printed circuit board No. 35.
9. Ribbon cable.
10. Printed circuit board No. RTC/34.
11. EMC Filter
12. Controls box fascia (not shown).

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48 PC BOARD NO. RTC/34

47 PC BOARD NO. 35

1. Remove the lower front panel.

2. Slacken the 2 screws securing the control box front

panel. Carefully lift it up and hinge forward.

3. Release the ribbon cable plug from PCB No. 35.

4. Release PCB No.35 from the 6 plastic mounting pins

and replace the board.

5. Reassemble in reverse order.

1. Remove the lower front panel.

2. Slacken the 2 screws securing the control box front

panel. Carefully lift it up and hinge forward.

3. Remove the real time clock board (PCB No. RTC/34)

from PCB No.34 by squeezing the 4 mounting pins and
pulling forwards.

4. Reassemble in reverse order.

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SERVICING

49 COMBUSTION CHAMBER INSULATION REPLACEMENT

The insulation boards used in the combustion chambers
of these products contain man-made fibres, refractory
fillers, organic and inorganic binders and as such are
deemed to be harmless to humans.

Caradon Plumbing Limited, however, recommend that
for your own comfort and to comply with good working
practise the procedure described below is followed.

IMPORTANT. Turn OFF the gas and DISCONNECT the
electricity supply.

To replace the insulation boards the major boiler
components (including the heat exchanger and burners)
have to be removed to gain access to the combustion
chamber.

Prior to removal of the boards the
following protective equipment should be
worn:

· Face mask supplied with the spare part.

· Gloves supplied with the spare part.

1 Damp down the combustion chamber area containing

the insulation boards.

2. Remove the insulation boards. The replacement boards

are supplied in a plastic bag. This bag should be
retained and the discarded boards should now be
placed into it.

3. Sweep any dampened particles and place in the plastic

bag.

4. Fit new insulation boards.

5. Remove the gloves and face mask and place them in

the plastic bag.

6. Wash your hands and any areas of skin which may have

come into contact with any of the particles from the
insulation board.

7. Seal the plastic bag and dispose of it and its contents

into a commercial tip.

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SERVICING

50 AIR PRESSURE SWITCH

Before replacing the pressure switch, the pressure switch reading should be
checked as follows:

Connect the positive side of a manometer to the pressure sensing line from the fan
scroll and the negative side of the manometer to the pressure sensing line
connected to the flue box.

Switch the boiler on. When the fan starts, the combined pressure (cold) should be at
least that shown in the table below:

CXC 48

3.4mbar

CXC 94

2.7mbar

CXC 70

3.2mbar

CXC 116

2.4mbar

If the pressure does not reach this level it is unlikely to be a pressure switch
fault. Check that the fan impeller is clean and free to rotate and that the flue
system and boiler flue ways are free from obstruction.

Do not attempt to adjust the pressure switch setting.

To replace the pressure switch, remove the upper front casing panel.

1. Unscrew the pressure switch from its mounting bracket. Transfer the

electrical connections and sensing pipes to the new pressure switch.

2. Reassemble in reverse order.

51 FAN REPLACEMENT

7. Unscrew the 5 screws securing the fan assembly and

remove the assembly by pivoting it to the right.

8. Unscrew the fan from the fan plate, replace the fan and

reassemble in reverse order.

9. Check that the fan outlet gasket is intact. Replace if

necessary. Reassemble in reverse order.

10. Recommission the boiler and check for leakage around the

fan outlet before refitting the insulation and casing panels.

11. If any leaks are evident immediate steps must be taken to

rectify them.

1. Remove the casing upper front panel and lower top panel.

2. Hinge the cleanout cover insulation upward and to the left.

Remove front access cover (secondary
h/exchanger) insulation by releasing from the retention
tabs.

3. Unclip the capacitor.

4. Disconnect the earth lead.

5. Separate the inline connector, using a small screwdriver.

6. Remove the pressure sensing pipe.

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53 BOILER CONTROL

52 FLOAT SWITCH REPLACEMENT

1. Unscrew the screw located on the top edge of the upper

front panel and remove this panel.

2. Remove the lower top panel.
3. Unplug the Temp/Air/Float plug-in connector from its

connection box located on the RH side and behind the
control box.

4. Disconnect the wires from the terminal block. Refer to

Frame 15.

5. The rear panel (2nd down from the top) is held by 4

screws. Remove the screws and the panel to access the
float switch.

6. Remove the 2 screws and take off the saddle bracket.
7. Turn the hexagon nut anticlockwise to remove the

tension in the seal then withdraw the switch.

8. Fit the new switch, with the line mark at the bottom,

ensuring the float is able to fall from the horizontal - see
diagram.

9. Replace the saddle bracket.
10. Run electrical leads through the clips and wire into the

plug-in connector.

11. Fit the

plug-in
connector
and
replace all
the panels.

WARNING

The ON/STANDBY [1/0] button does NOT electrically
isolate the boiler.

Before attempting any electrical fault finding ALWAYS carry out
the preliminary electrical system checks as detailed in the
Instructions for the British Gas Multimeter or other similar
commercially available meter.

The preliminary electrical system checks are the FIRST
electrical checks to be carried out during a fault finding
procedure.
On completion of any service/fault finding task which has
required the breaking and remaking of electrical connections
the following checks MUST be repeated:

a. Earth continuity
b. Polarity
c. Resistance to earth

Detailed instructions on the replacement of faulty components
are contained in the 'Servicing' section of these Installation &
Servicing Instructions.

GENERAL INFORMATION

If a flow switch is not connected to the boiler a link should be
fitted between the 2 terminals for the flow switch. If the
terminals are left disconnected the display will indicate "No
flow" and the boiler will not operate.

Anticycle will be in operation each time the boiler thermostat is
satisfied and a rapid demand for heat is required. The same
situation will occur if the external controls operate rapidly. This
feature reduces component wear and ensures continuous
troublefree operation. The anticycle duration is one to three
minutes.

If the system pump, with a maximum current of 3A, is
connected to the boiler pump terminals, pump overrun will be
in operation if the flow temperature is greater than 75

C, when

the heat demand is satisfied, and will continue to run until the
boiler flow is less than 75

C. If the flow temperature is less

than 75

C when the demand for heat is satisfied then the

pump will cease to operate.

Frost protection is inbuilt with the boiler. If the flow temperature
falls to approximately 3

C then the boiler will operate until the

flow temperature exceeds 4

C. If an external frost thermostat

is required the internal programmer should be set to 24 hours
under the programme status menu and an external
programmer and frost thermostat wired and connected to the
volt-free external control terminals on the boiler.

There is an option kit available with 2 sets of volt-free contacts.
One set of volt-free contacts is for 'Lockout' and 'Overheat'
combined, and one set of volt-free contacts is for 'Boiler run'.
There is an option kit available to enable temperature
compensation to be used. The outside temperature adjusts the
boiler flow temperature to satisfy the heating load and ensure
efficient boiler operation.
The gas valves operate on a High/Low and Off principle. At
start up, with the flow temperature less than 55

C, the boiler

will start at low rate and after one to three minutes the high
rate gas valve will open. On reaching the set point, determined
by the user, the boiler will go to low rate and when the
temperature reaches the set point plus 3

C the low rate gas

valve will close. When the temperature falls 2

C the boiler will

start at low rate and remain there until the temperature falls to
the set point less 2

C then the high rate gas valve will operate.

On start up the high rate gas valve will operate immediately
after detection if the boiler flow rate is greater than 55

In order to determine the continued correct operation of the
control every 4 hours the boiler will shut down for a maximum
of 30 seconds to do a self -check operation and restart
automatically.
The control will display the number of operational hours of the
boiler to the nearest hour and cannot be reset.

The boiler thermostat has a range of 60-80

C, in 1

C steps,

with an accuracy of ± 2

C and hysteresis of 3

The full sequence control enables 5 attempts at ignition, with 1
minute intervals between attempts, followed by nonvolatile
lockout if detection does not take place.

If the [0/1] switch on the front panel is at 'Standby.....0' then the
pump will continue to run indefinitely. In this state the frost
protection can not operate.
In 'Lockout' the pump will continue to run only if the
temperature is greater than 75

C if it is less then the pump will

be off.

FAULT FINDING

AUL

T FINDING

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PUMP OVERRUN

IF > 75°C OFF < 75°

HIGH RATE

Overrun completed

LOW RATE GAS

Prepurge completed

Flame = ON

IGNITION

DELAY WHILST FAN RUNS

If the HT generator should cease to function it is impossible
to automatically display this condition. Should this fault

occur then:-

would be displayed and the subsequent display screens
would direct attention to the spark generator.

Should a gas valve fail the diagnostics will indicate that it is
valve 1 or 2 that is at fault. If the boiler has a gas line of 2
double solenoids the diagnostics will indicate which
solenoid of the double solenoid is at fault.

The last fault instruction will be retained.

FAULT CODES

Fault codes numbered 1 to 24 are displayed where
applicable. In this event contact Caradon Plumbing
Limited.

SHUTDOWN

Demand = ON

temperature

senses

> than set

point

Demand =

off

Flame = ON

For > 55°C no delay

If < 55°C

1-3 minutes

Reaches

temp > set

point

AUL

T FINDING

FAULT FINDING

54 BOILER CONTROL - continued

The boiler control has a unique fault diagnostic feature which can,
in the unlikely event of a failure, display a message indicating the
nature of the fault to assist a speedy and effective repair.

The faults that are diagnosed are:

- overheat thermostat
- pump
- boiler sensor
- gas valve(s)
- air pressure switch
- fan
- float switch
- outside sensor (if fitted)
with indication of combustion lockout.

In the unlikely event of a fault the display will indicate precisely
the fault and give a step by step indication of the method of
correcting the fault.

55 SIMPLE FLOW CHART OF OPERATION

138423-7.pmd

11/7/2005, 9:48 AM

Concord CXC -

Installation

56 FAULT FINDING DIAGNOSTIC CHART

Change outside

sensor.

Press [COPY]

GAS VALVE

FAULT

BOILER

SENSOR

FAULT

OVERHEAT

FAULT

OUTSIDE

SENSOR

FAULT

Check pump

connections.

Press [COPY]

Press O/H reset

button.

Press [COPY]

Check wiring.
Press [COPY]

Check water

flow.

Press [COPY]

Replace o/h stat.

Press [COPY]

Check system.

Press [COPY]

Refer to
screens

STANDBY

BURNER

LOCK OUT

Check HT leads

and electrode

positions

Change pump.

Press [COPY]

Refer to
screens

Check wiring.

Press [COPY]

PUMP FAULT

R
E
F
E
R

T
O

I
D
E
A
L

B
O
I
L
E
R
S

Is there a

spark ?

AIR FLOW

FAULT

Check fan

rotates.

Replace if

necessary

Refer to
screens

Check gas

pressure.

Press [COPY]

Replace faulty

solenoid.

Press [COPY]

Refer to
screens

Change

gas valve

solenoid.

Press

[COPY]

Observe the display. Take actions as

follows, depending upon the display:

Check system.

Press [COPY]

Replace sensor

Press [COPY]

Press

[COPY]

Check

gas

valve

wiring.

Press

[COPY]

YES

Replace

detection

probe

Boiler will not light

Do any external

controls call for

heat ?

Is 230V ± 10%

available at
appliance ?

Reset timer or

status as

appropriate

Reset external

controls as

appropriate

Carry out electrical

checks.

Check all fuses.

YES

Check boiler

programme timer and

status, as described

in Frame 28.

Does programme

timer require heat ?

Press

[COPY]

Check gas.

Press

[COPY]

Check

pressure

switch.

Replace if

necessary

Check wiring.

Press

[COPY]

Check

detection

probe.

Press

[COPY]

Check wiring to

generator.

Press [COPY]

Replace

generator.

Press [COPY]

Press [1/O] button

FAULT FINDING

AUL

T FINDING

138423-7.pmd

11/7/2005, 9:48 AM

Concord CXC -

Installation

When ordering spare parts please quote:

1. Boiler model
2. Boiler serial no. (refer to data plate on the combustion chamber)
3. Boiler B.G. P.I. No. (refer to the data plate on the combustion chamber)
4. Description
5. Quantity
6. Product no.

The following are parts commonly
required as replacements due to
damage or expendability. Their failure
or absence is likely to affect the safety
and/or performance of this appliance.

Key No.

Description

Qty.

Product No.

Float switch

013 950

Pressure switch Assy ................................................................. CXC 48

139 560

................................................................................................... CXC 70

139 561

................................................................................................... CXC 94

139 562

................................................................................................... CXC116

139 563

Fan Assy (less restrictor plate)

077 124

Restrictor plate ........................................................................... CXC 48

138 689

................................................................................................... CXC 70

138 690

................................................................................................... CXC 94

138 691

................................................................................................... CXC116

138 692

Gas control valves

HONEYWELL VR4605PB 2003 ................................................. CXC 48 & 70

111 867

28A

HONEYWELL VR4605A 1104 ................................................... CXC 94 & 116

138 896

28B

HONEYWELL VR4605AB 1019 ................................................. CXC 94 & 116

111 869

28C

Plug - gas valve .................................................................... CXC 48 & 70

111 872

28D

Plugs and leads - gas valve ................................................. CXC 94 & 116

112 430

28E

Plugs and leads - gas valve ................................................. CXC 94 & 116

112 431

28F

Plugs and leads - gas valve ................................................. CXC 48, 70 94, 116

111 870

28J

Gas valve restrictor .............................................................. CXC 94 to 116

150 371

Spark generator assy. (generator and terminals)

112 721

Main burner injectors ................................. Size 3.4 mm;

CXC 48

111 323

.................................................................. Size 4.12mm;

CXC 70

111 325

.................................................................. Size 4.86mm;

CXC 94

013 177

.................................................................. Size 5.3mm;

CXC116

013 179

Detection electrode BE/3459/SI

112 364

Main burners ............................................. Worgas 70.4.111

CXC 48

150 149

.................................................................. Worgas 70.4.117

CXC 70

150 150

.................................................................. Worgas

CXC 94

139 826

.................................................................. Worgas 70.4.115

CXC116

150 152

Main burner ............................................... Worgas 70.4.112

CXC 48

150 153

.................................................................. Worgas 70.4.118

CXC 70

150 154

.................................................................. Worgas

CXC 94

139 827

.................................................................. Worgas 70.4.116

CXC116

150 156

SHORT LIST OF PARTS

138423-7.pmd

11/7/2005, 9:48 AM

Concord CXC -

Installation

Ignition electrode BE/3417/SI

112 365

Overheat thermostat - RAK 77.4/3835

153 914

Control box assembly complete

112 125

Thermistor

112 289

PCB 34

112 718

PCB 35

112 719

Real time clock

112 749

PCB 34 and real time clock

112 722

Ribbon cable

112 720

Casing upper front control panel (less controls) - white stove enamel

076 947

Casing assembly, complete - white stove enamel ..................... CXC 48

139 488

................................................................................................... CXC 70

139 489

................................................................................................... CXC 94

139 490

................................................................................................... CXC116

139 491

Casing lower front panel - white stove enamel

076 948

Casing LH side panel - white stove enamel
(including nutserts, clips & studs)

CXC 48

077 725

................................................................................................... CXC 70

077 727

................................................................................................... CXC 94

077 729

................................................................................................... CXC116

077 731

Casing RH side panel - white stove enamel
(including nutserts, clips & studs) ............................................... CXC 48

077 726

................................................................................................... CXC 70

077 728

................................................................................................... CXC 94

077 730

................................................................................................... CXC116

077 732

Casing lower top panel - white stove enamel ............................. CXC 48

112 798

................................................................................................... CXC 70

138 387

................................................................................................... CXC 94

138 385

................................................................................................... CXC116

112 752

Casing upper front panel - white stove enamel

112 755

Casing upper top panel - white stove enamel

112 753

Infill panel - upper top panel

112 754

Casing LH upper side panel - white stove enamel

077 222

Casing RH upper side panel - white stove enamel

077 223

Casing upper back panel

112 800

Casing upper middle back panel

138 318

Casing lower middle back panel

139 205

Casing lower back panel

112 801

Key No.

Description

Qty.

Product No.

SHORT LIST OF PARTS

138423-7.pmd

11/7/2005, 9:48 AM