157291-3.pmd

Concord CXS/H -

Installation & Servicing

GENERAL

CAUTION.

To avoid the possibility of injury during the installation, servicing or cleaning of

this appliance, care should be taken when handling edges of sheet steel components.

Boiler

CXS 40/H

CXS 50/H

CXS 60/H

CXS 70/H

CXS 80/H

CXS 90/H

CXS 100/H

CXS 110/H

CXS 120/H

Number of sections

Flow tappings

Rc (in. BSP)

2 x 2 at rear

Return tappings

Rc (in. BSP)

2 x 2 at rear

Maximum static head

metres (feet)

61.0 (200)

Maximum pressure

bar (p.s.i.)

6.0 (87)

Gas inlet connection

Rc (in. BSP)

3/4 (3/4)

1 (1 )

Min. dynamic gas

mbar gauge

15.5

16.5

15.0

16.0

17.5

16.0

17.5

pressure required at boiler inlet in.w.g.

6.2

6.6

6.0

6.4

7.0

6.4

7.0

Electricity supply

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

Nominal flue size (to BS. 835)

m m

150

175

200

250

in.

Diverter outlet socket

m m

184

213

238

288

internal diameter

in.

7.3

8.4

9.4

11.2

Length of burner bars (overall)

m m

377

497

617

737

837

14.8

19.5

24.3

29.0

33.7

Main burner injectors (3 off)

size, mm

3.4

3.82

4.12

4.57

4.86

5.2

5.3

5.5

5.6

Approximate dry weight

210

265

330

395

490

lb.

463

584

727

871

1078

Water content

litre

gal.

4.8

6.6

8.2

9.9

11.5

Table 1- Performance Data

Table 2 - General Data

Boiler

CXS 40/H

CXS 50/H

CXS 60/H

CXS 70/H

CXS 80/H

CXS 90/H

CXS 100/H

CXS 110/H

CXS 120/H

Boiler Input

Gross

33.8

42.2

50.7

59.1

67.6

76.0

84.5

92.9

101.3

Low Rate

Btu/hr x 1000 115.3

144.1

172.9

201.7

230.5

259.3

288.2

317.0

345.8

Nett

30.4

38.0

45.7

53.3

60.9

68.5

76.1

83.7

91.3

Btu/hr x 1000 103.8

129.8

155.8

181.7

207.7

233.6

259.6

285.6

311.5

Boiler Input

Gross

48.3

60.3

72.4

84.5

96.5

108.6

120.7

132.7

144.8

High Rate

Btu/hr x 1000 164.7

205.8

247.0

288.2

329.3

370.5

411.7

452.8

494.0

Nett

43.5

54.3

65.2

76.1

87.0

97.8

108.7

119.6

130.4

Btu/hr x 1000 148.3

185.4

222.5

259.6

296.7

333.8

370.9

408.0

445.0

Boiler output

100

110

120

High Rate

Btu/hr x 1000 136.5

170.6

204.7

238.8

273.0

307.1

341.2

375.3

409.4

Gas rate

High

4.60

5.75

6.90

8.05

9.20

10.35

11.50

12.64

13.79

/h 162.4

203.0

243.6

284.2

324.8

365.4

406.0

446.6

487.1

Approx. flue

4.5% CO

&100°C.m

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

0.12

gas volume

4.5% CO

& 212°F. ft.

106

127

148

170

191

212

233

254

Manifold setting pressure

mbar

9.7

9.8

10.2

10.0

9.3

9.6

10.7

11.1

12.1

High

in.w.g.

3.9

4.1

4.0

3.7

3.8

4.3

4.4

4.8

Manifold setting pressure

mbar

4.8

5.0

4.9

4.6

4.7

5.2

5.4

5.9

Low

in.w.g.

1.9

2.0

1.8

1.9

2.1

2.2

2.4

Part load efficiency (Gross)

81.9

81.6

82.7

82.0

82.5

83.2

83.4

82.4

Seasonal efficiency (SEDBUK)*

[80.4]% [80.3]% [80.4]% [80.4]% [80.4]% [80.4]% [80.4]% [80.4]% [80.4]%

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

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

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Concord CXS/H -

Installation & Servicing

GENERAL

CONTENTS

Air Supply. ......................................................................... 8

Boiler Assembly - exploded view. .................................... 9

Boiler Clearances. ............................................................ 5

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

CXS 40/H-90/H. .......................................................... 22
CXS100/H-120/H ........................................................ 23

Casing Assembly. ........................................................... 12

Chimney System. .............................................................. 8

Commissioning. .............................................................. 17

Controls. ............................................................................ 4

Electrical Connections. .................................................. 14

Electrical Supply. .............................................................. 8

Fault Finding. ................................................................... 28

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

Gas Supply. ........................................................................ 8

Hydraulic Resistance. ...................................................... 5

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

Installation. ........................................................................ 9

Mandatory Requirements. ............................................... 7

Option Kits. ........................................................................ 4

Pump. ................................................................................ 6

Servicing. ........................................................................ 20

Short List of Parts. ......................................................... 30

Site Assembled Boilers. ................................................. 26

Static Head Requirements. .............................................. 6

System Connections. ..................................................... 11

Ventilation. ........................................................................ 8

Water Circulation. ............................................................ 4

Water Connections. ......................................................... 4

Water Treatment. ............................................................. 6

Wiring Diagrams. ............................................................ 15

Concord CXS 40/H - 120/H (Natural gas)

B.G. Certified - P.I. No. 87/AQ/103

Destination Countries: GB & IE

INTRODUCTION
CONSTRUCTION

BOILER BODY

The sectional boiler body is of cast iron and is supplied
assembled on a sheet steel combustion chamber with an integral
draught diverter. The boiler can be supplied in sectioned form to
special order for site assembly - refer to the section headed
`Instructions for Site Assembled Boilers'.

CASING

The casing is manufactured in stove enamelled sheet steel
and is easily assembled on site.

BURNERS

The 3 burners are of stainless steel construction.

Gas Safety (Installation and Use) Regulations
or rules in force.

It is the law that all gas appliances are installed and serviced by
a CORGI registered installer 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 CXS 40/H-120/H range of boilers has been tested
and certified by British Gas to prEN656 for use with Natural gas
only.

Multiple boiler installations

The Concord CXS/H range is certificated for use in
multiple boiler installations, providing that the following
conditions are satisfied.

1. A downdraught thermostat kit MUST be fitted to ALL boilers

in the installation.

2. A maximum of 6 boilers may be used with a single flue

header.

3. For clearances see Frame 2.

A comprehensive guide to multiple installations of Concord
CXS/H boilers is available.

WARNING. Failure to use a downdraught kit on every boiler in
a multiple boiler installation will negate the certification of the
installation and therefore contravene the essential requirements
of the Gas Appliance Directive.

Note. The CXS 40/H, CXS 50/H and CXS 60/H 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 Ideal Limited in writing. If in doubt please enquire.
Any direct connection of a control device not approved by Caradon
Ideal 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.

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Concord CXS/H -

Installation & Servicing

GENERAL

Boiler Size

Cold Feed

Open Vent

CXS 40/H - 50/H

3/4

CXS 60/H-120/H

1/4

Sealed system filling point - refer to Frame 8

Flow and return connections are 2" BSP.

A 1" BSP tapping is provided in the redundant return flange for the
cold feed or expansion vessel connection.

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 6.0 bar (87 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:
Table 3

WATER CONNECTIONS

GAS CONTROLS

The boiler lights at Low rate (approximately 70% of Full rate) by
direct burner ignition. After about 1 minute the boiler goes to
High rate and will continue at High rate until the thermostat
sensor set point is reached. The boiler will then drop to the Low
rate; if the temperature continues to rise the boiler will go Off, if
the temperature falls the boiler will revert to High rate.

ELECTRICAL CONTROLS

The boiler is supplied with 2 printed circuit boards; Board
S4561B1047 is the ignition board containing the flame-proving
logic; Board W4115A1020 contains the electronic thermostat and
pump overrun timer. A preset overheat thermostat is also provided.
The mains voltage supply is via a terminal plug in connection at
the control box. The control box displays neons indicating boiler
status as follows:

- Boiler on
- Lockout
- Overheat

A 4 minute anti-cycle delay is built in to the controls to prevent
rapid cycling.

FROST PROTECTION

Frost protection is incorporated in the boiler as long as there is a
permanent Live supply wired to Terminal L1 on the terminal plug-
in connection at the control box and the boiler thermostat knob is
not switched to Off.

If the temperature sensed by the boiler thermostat falls to about
5

C the boiler will fire until the temperature reaches 18

Note that this is designed to protect the boiler and may not
necessarily protect remote parts of the system.

The mains voltage supply is via a terminal plug-in connection at
the control box.

OPTION KITS

Remote Indication Kit
This kit gives the facility of remote indication of boiler status.

Pressure Gauge Kit
A pressure gauge kit is available.

Downdraught Thermostat Kit
This kit is optional when used on a single CXS/H installation,
but mandatory when used on a multiple boiler installation.

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.

The range of boilers is NOT suitable for:
1. Gravity DHW systems.
2. Gravity heating systems.
3. Direct domestic hot water supply.

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 for approximately 6 minutes after the burner shuts down
and, in order to make use of this, the pump must be wired to the
appropriate terminal L2 (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 1.
Examples shown on Graph 1
a. For the CXS 90/H and CXS 100/H 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 CXS 70/H and CXS 80/H 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 &18 illustrate the control
methods for achieving the above.

3. Pump selection should take account of the hydraulic resistance

given in Graph 2.

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Concord CXS/H -

Installation & Servicing

GENERAL

CLEARANCES & DIMENSIONS

Boiler Size

CXS 40/H CXS 50/H CXS 60/H CXS 70/H CXS 80/H CXS 90/H CXS 100/H CXS 110/H CXS 120/H

Front clearance

mm (in)

750 (29

1/2

)

Rear clearance

mm (in)

150 (6)

300 (12) 300 (12) 300 (12) 300 (12)

Side clearance

mm (in)

50 (2)

100 (4)

Dimension A

m m

750

882

1042

1212

1385

1/2

3/4

1/2

Dimension B

m m

108

122

135

190

160

1/4

7/8

3/8

1/2

1/4

Dimension C

m m

931

893

5/8

3/16

Dimension D

m m

177

187

224

271

321

3/8

7/8

5/8

Dimension E

m m

116

163

213

3/4

1/8

5/8

1/2

3/8

Table 4

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
50mm.

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:

CXS 40/H, 50/H, 60/H, 70/H & 80/H

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

CXS 90/H,100/H, 110/H & 120/H

Clearance between boilers = 100mm

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

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.

100

CON5217

Example A

Example B

CXS 1

10/H & CXS 120/H

CXS 100/H & CXS 90/H

CXS 80/H & CXS 70/H

CXS 40/H

CXS 60/H & CXS 50/H

Heat Load During Pump Overrun (kW)

Water Volume in Circuit during Pump Overrun (litres)

Relationship between load and water volume for the

minimum capacity of water circuit during the 6 minute

pump overrun period for different boiler outputs.

Graph 1 - Heat Load / Water Volume

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

190 200

160 170 180

120

110

100

Graph 2 - Hydraulic Resistance

Hydraulic Resistance (mbar)

Flow (litres/min)

C(20

F) - CXS 40/H

C(20

F) - CXS 50/H

C(20

F) - CXS 60/H

C(20

F) - CXS 70/H

C(20

F) - CXS 80/H

C(20

F) - CXS 90/H

C(20

F) - CXS 100/H

C(20

F) - CXS 1

0/H

C(20

F) - CXS 120/H

CON5218

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Concord CXS/H -

Installation & Servicing

GENERAL

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 & 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.

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

to the redundant boiler return tapping. 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. The final position will
depend upon the particular characteristics of the system.
Pumping over of water into the expansion cistern must be
avoided.

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.

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.

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.

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 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.

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.

CXS 40/H

0.28

3.7

CXS 50/H

0.34

4.5

CXS 60/H

0.41

5.4

CXS 70/H

0.48

6.3

CXS 80/H

0.55

7.3

CXS 90/H

0.62

8.2

CXS 100/H

0.68

CXS 110/H

0.75

9.9

CXS 120/H

0.82

10.9

3 OPEN VENTED SYSTEMS - Minimum static head requirements

CON5349

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Concord CXS/H -

Installation & Servicing

GENERAL

SEALED (PRESSURISED) SYSTEMS

Working pressure 6.0 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

automatic reset. In the event of shutdown 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 are 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

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: Water Supply.
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

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
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.

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.
For the reason stated, Caradon Ideal Limited strongly
recommend that when necessary the system is thoroughly
cleaned, prior to the use of stable inhibitor, which does not require
continual topping up to combat the effects of hardness salts and
corrosion on the heat exchangers of the boiler and associated
systems.

Caradon Ideal Limited advise contact directly with specialists
on water treatment such as:

Fernox Manufacturing Co. Ltd., or Sentinel Division,
Tandem House,

Betz Dearborn Ltd.,

Marlowe Way,

Widnes,

Croydon,

Cheshire, WA8 8UD

Surrey, CRO 4XS

Tel. 0151 424 5351

Tel. 0870 601 5000

INSTALLATION REQUIREMENTS

The appliance must be installed by a CORGI registered installer.

The installation of the boiler must be in accordance with the
relevant requirements of the Gas Safety Regulations, current
I.E.E. (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.

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.

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Concord CXS/H -

Installation & Servicing

GENERAL

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 and
BS.5440:2;2000

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.

Tests for spillage of products from the draught diverter when
the extractor fan is running and all doors and windows are shut
should be carried out after installation, If spillage is detected,

the area of permanent ventilation must be increased.

CHIMNEY SYSTEM

To ensure the safe and satisfactory operation of the boiler then

the chimney system (which may be common or individual, in

the case of twin or multiple boiler installations) must be
capable of the complete evacuation of combustion products at

all times. The effective height of the chimney terminal(s) above

the boiler outlet(s) must ensure sufficient buoyancy to
overcome the resistance of the bends, tees and runs of the

flue pipe involved and shall terminate in a down draught free

zone. The number of bends and lengths of horizontal flue pipe
used should be kept to a minimum in order to reduce gas flow

resistance.

Compliance with the recommendations made in BS.6644;
IGE UP/10 Installation of Gas Appliances in Industrial and

Commercial Premises and the 'Third Edition of the 1956 Clean

Air Act Memorandum' should be strictly observed where
applicable.

The chimney design should avoid the formation of excessive

quantities of condensate. For this reason it is recommended

that all chimneys are insulated and lined. In the case of brick
or similar structures a stainless steel rigid or flexible flue liner

(grade 304/316) may be used in conjunction with a 50 mm