203567-1.pmd

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.

Table 1 Performance Data

Boiler

F90

F140

F180

F220

F270

F310

Boiler output

Max

89.52

132.17

173.36

220.99

271.32

310.93

(non-condensing)

Btu/h

305,450

450,950

591,500

754,000

925,750

1,060,900

Mean 70ºC

Min

11.232

Btu/h

38,300

Boiler output

Max

92.644

136.755

179.344

228.575

280.704

321.47

(condensing)

Btu/h

316,100

466,600

611,900

779,900

957,750

1,096,850

Mean 40ºC

Min

12.516

Btu/h

42,700

Boiler Input

Nett

135

176

223

272

310

Max Rate

Btu/h

313,900

460,600

600,500

760,900

928,050

1,057,700

Gross

102.1

149.9

195.4

247.5

301.9

344.1

Btu/h

348,350

511,450

666,700

844,450

1,030,100

1,174,050

Boiler Input

Nett

Min Rate

Btu/h

40,950

Gross

13.3

Btu/h

45,400

Maximum Gas Rate

9.73

14.27

18.61

23.58

28.76

32.78

G20 (20mbar)

344

504

657

833

1016

1158

Approx. flue gas

@ max. rate m

153

225

293

372

453

517

volume (@80ºC) i.e. non-condensing ft

5400

7950

10350

13140

16000

18260

Max. Flue Resistance

100

Flue Gas CO

@ Max Rate

9.2

@ Min. Rate

9.0

NOx with O

= 0% mg/kWh

<73

ppm

<41

Seasonal Boiler Efficiency (Building Regs L2)

94.0

94.1

94.2

94.3

94.4

94.5

Note.
Natural gas consumption is calculated using a calorific value of
37.8MJ/m

(1038Btu/ft

) gross or 34 MJ/m

(910 Btu/ft

) nett at

15ºC and 1013.25 mbar.
a. For l/s divide the gross heat input (kW) by the gross C.V. of

the gas (MJ/m

)

b. For ft/h

divide the gross heat input (Btu/h) by the gross C.V.

of the gas (Btu/ft

HEALTH & SAFETY DOCUMENT NO. 635

The electricity at work regulations, 1989. The manufacturer's
notes must NOT be taken, in any way, as overriding statutory
obligations.

IMPORTANT. These appliances are CE certified for safety and
performance. It is, therefore, important that no external control
devices, e.g. flue dampers, economisers etc., are directly
connected to these appliances unless covered by these
Installation and Servicing Instructions or as otherwise
recommended by Ideal Stelrad Group in writing. If in doubt
please enquire.
Any direct connection of a control device not approved by Ideal
Stelrad Group could invalidate the certification and the normal
appliance warranty. It could also infringe the Gas Safety
Regulations and the above regulations.

* Electricity supply and Fuse rating for pumps etc. refer to manufacturer's instructions.

Table 2 General Data

Boiler

F90

F120

F180

F220

F270

F310

Gas supply

2H - G20 - 20 mbar

Gas supply connection

R (in. BSP)

Flow connection

R (in. BSP)

Return connection

R (in. BSP)

Hydraulic Resistance @ 11Cº

mbar

350

425

520

660

900

1075

Hydraulic Resistance @ 20Cº

mbar

100

130

160

225

275

325

Max Press (sealed system)

bar (psi)

6 (87)

Maximum Static Head

m (ft)

61 (200)

Boiler Electricity Supply

230V - 50Hz

Boiler Fuse Rating

A (F)

Power Consumption (boiler only)

145

210

290

362

435

507

Air Inlet

m m

150

Flue Size dia

m m

150

200

Condensate drain

m m

Water Content

l (gal)

10.1 (2.2)

14.2 (3.1)

18.3 (4.0)

22.4 (4.9)

26.5 (5.8)

30.6 (6.7)

Boiler dry weight (unpacked)

kg (lb)

153 (337)

182 (401)

223 (492)

261 (575)

301 (664)

345 (761)

Installation & Servicing

GENERAL

CONTENTS

Boiler Clearances. ............................................................ 7

Commissioning and Testing. ......................................... 32

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

Electrical Supply. .............................................................. 5

Fault Finding. ................................................................... 36

Flue System Design. ......................................................... 4

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

Gas Supply. ........................................................................ 5

Introduction. ...................................................................... 3

Initial Lighting. ................................................................. 32

Installation. ...................................................................... 11

Performance Data. ........................................................... 2

Servicing. ........................................................................ 34

Short List of Parts. ......................................................... 39

Ventilation. ...................................................................... 10

Water Circulation. ............................................................ 5

Water Connections. ......................................................... 7

Water System Requirements. ......................................... 9

Water Treatment. ............................................................. 5

Wiring Diagrams. ............................................................ 17

Natural Gas only
PI No. 1312 BR 4912
Destination Countries: GB, IE

Key to symbols
IE = Ireland, GB = United Kingdom (Countries of destination)
PMS = Maximum operating pressure of water.
B23 = An appliance intended to be connected to a flue which

evacuates the products of combustion to the outside of
the room containing the boiler. The combustion air is
drawn directly from the room. The fan is up stream of
the combustion chamber.

C63 = A room sealed appliance intended to be connected to a

separately approved and marketed system for the
supply of combustion air and discharge of combustion
products. The fan is up stream of the combustion chamber.

INTRODUCTION

The imax plus II boilers are fully automatically controlled, floor
standing, fanned, super efficient, low NOx condensing appliances.
The comprehensive boiler controls built into the appliance
include:
·

0-10V BMS

Volt free alarm contacts

Burner hours run meters

Weather compensating heating curve using outside
temperature sensor (supplied with boiler)

The boilers can draw their combustion air from the room or via
ducting from the outside.
Through a sophisticated control system combined with premix
burner technology and an aluminium heat exchanger, the boilers
are capable of high operating efficiencies of >94% (gross) and
low emissions.
These boilers are certified to meet the requirements of the EC
Gas Appliance Directive, Boiler Efficiency Directive, EMC and
Low Voltage Directive.

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.
4. Single feed indirect cylinders.

CONSTRUCTION

The construction is of a sectional design with individual burners,

fans, gas valves and ignition/supervision controls. A non-return

valve ensures no reverse circulation of flue products through

modules not operating. The sectional heat exchanger is of cast

aluminium. A stainless steel sump collects the flue products and

diverts them to the flue, whilst allowing drainage of condensate

products.

LOGIC OF OPERATION

When the boiler receives a call for heat, the Modular Boiler Drive

(MBD) calculates the necessary output according to the

difference between the set flow temperature (or compensated

flow temperature for a CH call when using an outside sensor)

and the boiler modules combined flow temperature. The

circulation pump is started whilst operating a DHW control valve,

if required, and the first module fan is run up to starting speed. A

spark is started and the gas valve opens. Ignition must occur in 5

seconds and once detected the module starts operating.

Subsequently, additional modules are likely to start in the same way.
The boiler principle method of operation is to run as many

modules simultaneously, at the lowest possible load, for

maximum efficiency. For example:
If an imax plus II F180 with 180kW max. input is only requested to

provide 72kW.
72

÷ 4 = 18kW per module

Therefore, the boiler operates all modules at 18kW.
If the required load is less than the min. 12kW per module, then

one module after the other is automatically shutdown and the

load shared by the remaining modules. The modules with the

lowest number of hours run are automatically chosen to satisfy

the demand.

OPTIONAL EXTRA KIT

Tank Sensor Kit

Air Inlet Socket and Blanking Plate Kit

SAFETY

Current Gas Safety (Installation and Use) Regulations or rules
in force.
It is the law the that all gas appliances are installed and serviced
by a CORGI registered installer, or in IE a competent person, in
accordance with the regulations below. Failure to install
appliances correctly could lead to prosecution. It is in your own
interest, and that of safety, to ensure the law is complied with.

Installation & Servicing

GENERAL

The installation of the boiler MUST also be in accordance with
the latest I.E.E. (BS7671) Wiring Regulations, local buildings
regulations, bye-laws of the local water authority, the building
regulations and the Building Standards (Scotland) and any
relevant requirements of the local authority.
Detailed recommendations are contained in the following codes
of practice:
BS 5854

Flues and Flue Structures in Buildings.

BS.6644

Installation of gas fired hot water boilers of rated
inputs between 70kW and 1.8MW (net) (2nd and
3rd family gases).

BS.6880

Low temperature hot water heating systems of
output greater than 45kW.
Part 1 Fundamental and design considerations.
Part 2 Selection of equipment.
Part 3 Installation, commissioning and
maintenance.

73/23 EEC

Low Voltage Directive (Relevant Standard is
EN60335.1).

89/336 EEC Electro Magnetic Compatibility Directive.
IGE/UP/1

Soundness testing and purging of industrial and
commercial gas installations.

IGE/UP/2

Gas installation pipework, boosters and
compressors on industrial and commercial
premises.

IGE/UP/10

Installation of gas appliances in industrial and
commercial premises.

SAFE HANDLING OF SUBSTANCES

No asbestos, mercury or CFCs are included in any part of the

boiler or its manufacture.

GAS SUPPLY

The local gas supplier should be consulted, at the installation

planning stage, in order to establish the availability of an

adequate supply of gas. An existing service pipe must NOT be

used without prior consultation with the local gas supplier.
A gas meter can only be connected by the local gas supplier or

by a registered CORGI engineer, or in IE a competent person.
An existing meter should be checked, preferably by the gas

supplier, to ensure that the meter is adequate to deal with the

rate of gas supply required. A minimum working gas pressure of

15 mbar MUST be available at the boiler inlet.
Do not use pipes of smaller size than the boiler inlet gas

connection.
The completed installation MUST be tested for gas soundness

and purged in accordance with the appropriate standards listed

above.
Gas Boosters
A gas booster is required if the gas pressure available at the

boiler is lower than that required to attain the flow rate for

maximum input rating.
Location of the booster requires careful consideration but should

preferably be closer to the boiler rather than the gas meter.

Ventilation should also be considered to ensure ambient

temperatures do not exceed designed recommendations.

Further guidance is provided in IGE/UP/2 as listed above.

FLUE INSTALLATION

IMPORTANT: It is the responsibility of the installer to ensure, in
practice, that products of combustion discharging from the

terminal cannot re-enter the building or any other adjacent

building through ventilators, windows, doors, other sources of

natural air infiltration, or forced ventilation / air conditioning.

If this should occur the appliance MUST be isolated from the gas

supply, labelled as 'unsafe' until corrective action can be taken.
Terminal Position
Due to the high efficiency of the boilers pluming will occur.

Vertical termination is recommended and terminal positions

which could cause problems should be avoided. Particular care

should be taken in the case of large output boiler installations,

and complying with the requirements of the Clean Air Act.
The flue must be installed in accordance with the appropriate

Building Regulations and standards listed above.

FLUE SYSTEM DESIGN

Due to the high efficiency of these boilers, the flue gas

temperatures are low and the buoyancy in the stack will be

relatively small. The imax plus II condensing boiler is supplied

with integral fans which are fully matched to the boiler in each

case to provide correct combustion air flow and overcome the

flue resistance.
The power of these fans 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

maximum pressure available at the base of the flue to overcome

flue resistance is 100Pa (0.4" w.g.). This includes the

resistance of any air ducts used to connect the air inlet direct to

outside air. Care should be taken with tall flue systems to

ensure excess buoyancy is not created. A negative pressure

must not be created at the boiler flue outlet.
See table below for approximate maximum straight flue lengths.

The addition of elbows and their positions in the flue will have a

significant effect on the maximum flue length. Consult with your

flue supplier for detailed design work.

Boiler

F90

F140

F180

F220

F270

F310

Flue Size (mm) Ø150

Ø150

Ø200

Approx. max.
Straight Flue

240

109

171

120

Length (m)

Material
With no requirement for buoyancy to discharge flue products and

with low flue gas temperatures, single wall flues are suitable for

most installations. Care should still be taken to maintain

compliance with building regulations and relevant standards.
The type of flue pipe used should be 316 grade Stainless Steel

or be of equivalent corrosion resistance. Advice regarding the

availability of proprietary types of flue system can be obtained by

contacting Ideal Stelrad Group. All joints or connections in the

flue system must be impervious to condensate leakage. Low

points in the flue system should be drained using pipe of

material resistant to condensate corrosion. All drains in the flue

should incorporate a water trap.
Care should also be taken in the selection of flue terminals as

these tend to accentuate the formation of a plume and could

freeze in cold weather conditions.
Care should be taken to ensure the specification of the chimney

is suitable for the application by reference to the manufacturers

literature. The Technical Support Department of Ideal Stelrad

Group, can offer advice on the design of suitable chimney

systems.

NOTE TO THE INSTALLER: LEAVE THESE INSTRUCTIONS ADJACENT TO THE BOILER.

Installation & Servicing

GENERAL

Note.

With the boiler firing at maximum rate, the temperature
differential should not be less than 10degC.
- Higher flow rates required for lower temperature

differentials could lead to erosion of the heat exchanger
water ways.

With the boiler operating at minimum waterflow rate, the
temperature differential should not be greater than 20degC.
Lower flow rates generating higher temperature differentials
will lead to lockout of the boiler.

The lower the return temperature to the boiler, the higher the
efficiency. At return temperatures of 55ºC and below, the
difference becomes more marked because the water in the
flue gases starts to condense, releasing its latent heat.

The air vent inside the boiler is not for ventilation of the whole
system. An additional air vent should be fitted to the highest point
of the system.
Drain taps MUST be located in accessible positions, which
permit the draining of the whole system including the boiler and
hot water storage vessel. The boiler is equipped with its own
drain tap, but this must not be used for draining of the whole
system as this could lead to system dirt gathering in the heat
exchanger, causing damage.
In installations were all radiators have been provided with a
thermostatic valve (TRV), or all heating zones have individual
zone isolation valves, then a bypass will be required to ensure
water circulation through the boiler during pump overrun. A mixing
header (see separate section) will perform this task. Alternatively
this can be best achieved by means of a pressure differential
valve, which is installed in a bypass between the flow and return
pipes. If a bypass is used it should be fitted at least 6m from the
boiler, and be capable of allowing a minimum flow rate to achieve
a temperature differential of no greater than 20degC at minimum
gas input.

WATER TREATMENT

The imax plus

boiler has an ALUMINIUM alloy heat exchanger.

Corrosion will always occur within a heating/hot water system to
a greater or lesser degree irrespective of water characteristics,
unless the initial fill water from the mains is treated. For these
reasons Ideal Stelrad Group strongly recommends that the
system be thoroughly cleaned prior to the use of a stable inhibitor
which does not require continual topping up to combat the effects
of hardness, salts, and corrosion on the heat exchanger and its
associated systems.
Therefore it is important that if water treatment is used it is
suitable for the material of the heat exchanger. The ONLY water
treatments approved are Fernox Copal or MB1 or GE Betz
Sentinel X100 inhibitors and associated water treatments, which
must be used in accordance with manufactures instructions.
Current suitability should be confirmed directly with the
manufacturer.

Sentinel Performance Solutions
The Heath Business & Technical Park
Runcorn, Cheshire. WA7 4QX
Tel 0800 389 4670
www.sentinel-solutions.net

Fernox Manufacturing Co. Ltd.,
Cookson Electronics, Forsyth Road,
Sheerwater, Woking, Surrey, GU21 5RZ
Tel: 01799 521133

Artifically softened water must NOT be used to fill the system.

CONDENSATE DRAIN

A condensate drain is provided on the boiler. This drain must be

connected to a drainage point on site incorporating a water trap

as detailed in Frame 11. All pipework and fittings in the

condensate drainage system MUST be made of plastic - no

other materials may be used. See Frame 11 for connection

details.
IMPORTANT. Any external runs must be kept to a minimum and

insulated. This is to avoid freezing in cold weather causing

blocking.

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.

Ideally the boiler should be placed on a plinth exceeding the
plan area of the boiler by 75mm on each side and at least
100mm high, in order to assemble the condensate trap (refer to
Frame 11). An alternative to this base would be a 100mm deep
well next to the boiler (refer to Frame 6).

The boiler must not be fitted outside.

ELECTRICAL SUPPLY

WARNING This appliance must be earthed.

A 230V - 50Hz mains supply is required, fused at 3 amps.

Wiring external to the appliance MUST be in accordance with the
current I.E.E. (BS7671) Wiring Regulations and any local
regulations which apply.

The point of connection to the mains should be readily
accessible and adjacent to 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 to avoid overheating. In order to
control pump operation after burner shutdown the boiler control
box incorporates a 5 minute pump overrun facility. A system
pump must therefore be connected to the terminals provided in
the boiler. This connection must be done via a relay.

When sizing pumps, reference should be made to the
appropriate graphs 1 or 2 which show the boiler resistance
against flow rates to achieve the required temperature
differential.

Flow rates for common systems using either 11 degC or 20
degC temperature differentials are given in the table below and
highlighted on graphs 1 and 2. These figures are based on an
appliance running in condensing mode. Slightly lower flow rates
would be required for an appliance run in non-condensing
mode.

Table 3

11 deg C

20 deg C

imax plus II F90

2.01 l/s

1.11 l/s

imax plus II F140

2.97 l/s

1.63 l/s

imax plus II F180

3.89 l/s

2.14 l/s

imax plus II F220

4.96 l/s

2.73 l/s

imax plus II F270

6.09 l/s

3.35 l/s

imax plus II F310

6.98 l/s

3.84 l/s

Installation & Servicing

GENERAL

BOILER DIMENSIONS, CONNECTIONS AND CLEARANCES

223

348

223

= =

T
O

D
E

R
E

S
E

T
E

425

i B

268

250

350

125

Gas
Flow
Return
Conde nsate drain

:
:
:
:

2"
2"

G
M
R

2
3
4
5
6
7

695
695
832
968

1102
1236

140
180
220
270

310

150
150
150
200
200
200

153 kg
182 kg
223 kg
261 kg
301 kg
345 kg

695

455

137

103

053

483

212

452

137

106

483

212

RIGHT HAND SIDE VIEW
(Delivery condition for
R.H. side connections)

LEFT HAND SIDE VIEW
(Prenotches for left
side connections)

UPPER VIEW

FRONT VIEW

Warning:
Flow/Return connections change their position whether they are
on the R.H. or on the L.H. side of the boiler (see views on the left).

Flue connection shown on RH side, options shown dotted at rear or left.

Model

Modules No. off

Weight

Connections

im8885

The boiler must be positioned to ensure adequate space
available for access during operation and service. It must also
comply with relevant local byelaws and safety regulations.
Recommended minimum clearances are as follows:

Rear - 450 mm; or 300mm for F90 and F140 with no rear flue.

Sides - Minimum clearance of 50 mm one side only, with 450
mm on opposite side for flue baffle access and pipework
connections. For side flue outlet increase to 600 mm
clearance. For pipework only allow 300 mm clearance.

Top - 600 mm

Front - 600 mm; except compartment access doors may be
closer, but not less than 200 mm, and 600 mm must still be
available for service across the full width of the boiler.

Installation & Servicing

GENERAL

Detail reference should be made to the appropriate
standards listed on page 4.

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

The vertical distance between the pump and feed/
expansion cistern MUST comply with the pump
manufacturer's minimum requirements, to avoid
cavitation. Should these conditions not apply either
lower the pump position or raise the cistern above the
minimum requirement specified by Ideal Stelrad
Group. The isolation valves should be fitted as close
to the pump as possible.

The boiler is fitted with an automatic air vent. This air
vent must never be shut off, as this could result in dry
firing of the boiler and subsequent damage to the heat
exchanger.

The information provided is based on the following
assumptions:

1. An independent open vent/safety pipe connection is

made immediately after the system flow pipe
connection.

2. An independent cold feed/expansion pipe

connection is made immediately after the open
vent/safety pipe connection.

3. The maximum flow rate through the boiler is based

on a temperature difference of 11ºC at full boiler
output.

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.

6. Both open vent/safety pipe and cold feed/expansion

pipes must be of adequate diameter to suit the
output of the boiler. Refer to Tables 4 and 5.

OPEN VENTED SYSTEM REQUIREMENTS

Rated output

Minimum bore

Nominal Size (DN)'

61 to 150

151 to 300

301 - 600

'Steel pipe sizes complying with medium or heavy quality or
BS 1387.

Table 4 Open Vent Pipe Sizes

Rated output

Minimum bore

Nominal Size (DN)

in'

61 to 150

151 to 300

301 - 600

'Steel pipe sizes complying with medium or heavy quality or
BS 1387.

Table 5 Cold Feed Pipe Sizes

Note.
Refer to Frames 23 and 24 for typical system arrangements.

Feed/expansion

cistern

Open vent
safety pipe

3 m
minimum
see notes

System
flow

Inverted cold
feed entry

Cold

Feed

Water

level

(cold)

Open vent

System
return

Connections

to boiler

ima 5791

Note.
·

With a cold feed head of <8m, the pump must
be fitted on the return to the boiler.

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

Installation & Servicing

GENERAL

Working pressure 6.0 bar maximum, 0.8 bar minimum.

There is no minimum water pressure switch on the boiler, with
safety thermostats providing protection against dry firing.
However, should a minimum water pressure switch be
required in the system a ¼" connection is available on the
return manifold. The electrical connections should be made in
series with the minimum gas pressure switch.

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.

SEALED SYSTEM REQUIREMENTS

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.

Expansion 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 0.8
bar (11.6 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.

VENTILATION

Detail reference should be made to BS.6644:2005. The
following notes are for general guidance only:

If ventilation is to be provided by means of permanent high and
low vents communicating directly with outside air, then
reference can be made to the sizes below. For other
ventilation options refer to BS. 6644.2005.

Dust contamination in the combustion air may cause blockage
of the burner slots. Unless the boiler room provides a dust
free environment then direct connection of the air intake via
ducting to clean outside air should be used.

Open Flue Installations
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).

Room Sealed Installations
A minimum of 2cm

free area per kW of net heat input at

both high and low level is required for boiler rooms. For
enclosures refer to BS6644.

The temperature within a boiler room shall not exceed
25ºC within 100mm of the floor, 32ºC at mid height and
40ºC within 100 mm of the ceiling.

Installation & Servicing

INSTALLATION

UNPACKING

The imax plus II is delivered assembled and protected by a plastic bag
inside a strong cardboard box and fixed on a pallet. This allows the
boiler to be handled by a forklift. The boiler with the packaging can go
through a door 800mm wide, whereas, without packaging, it can go
through a door 700mm wide.
To unpack the boiler:
-

Carefully remove the straps, then lift off the cardboard box.

Remove the protective plastic bag.

Safely dispose all packing materials. The plastic bag must be kept
away from children.

Remove the strap securing the front and left hand panels, and place
in a safe place.

Remove the screw securing the top panel to the back panel. Remove
remaining panels and place in a safe place.

Remove the flue manifold.

Lift out all the loose contents as listed and leave in a safe place.

Remove the bolts securing the boiler legs to the pallet before lifting
the boiler off the pallet taking due care with respect to its weight.
When lifting the boiler the weight must be supported by the boiler
frame and not the sump.

CONTENTS
-

Assembled boiler

Front case attached to the back panel

Right hand panel attached to the left hand panel

1m condensate pipe placed behind back panel

Flue manifold

Installation & Servicing / User Instructions

Log Book

Warranty Certificate

Outside Sensor c/w emc filter

Gasket & screws for flue manifold

Screws for fixing top panel

Condensate drain T-piece

Condensate elbows 2 off

Condensate blanking plug

Flue socket

Flue socket gasket

Flue socket lip seal

SYSTEM CONNECTIONS ORIENTATION

Note.
It may be necessary to fit the casing panels through which the
service connections will pass before making these
connections. However, in general it is advisable to leave the
panels off as long as possible to prevent the chance of
damage occurring. See Frame 12.
As delivered the boiler comes with water, gas and flue
connections all on the right side. It is possible to change their
orientations before fitting the boiler as follows.
Flue Connections
It is possible to combine flue connections at any of the
positions of left, right and rear. To change connections, simply
remove the blanking plates from the connection required and
attach the flue connections. Seal off the unused connections
with the removed blanking plates.
Air Connections
Boiler sizes 90-310 are delivered with an air inlet filter fitted on
the right side with the left side and rear connections blanked
off. If required the filter can be moved to the left side, using
the removed end panel and blanking plate on the right side.
Boiler sizes 180-220 have an air inlet filter fitted to both sides.
Boiler sizes 270-310 have filters fitted to both sides and the
rear. Ducting air directly to the boiler from outside is possible
to the left or right side or rear by the removal of all filter(s) and
the use of air inlet spigot kit(s). These kits are obtainable
from the boiler manufacturer.
Note.
To enable cleaning of the heat exchanger, access is required
to lower a baffle secured to the bottom of the heat exchanger.
As factory fitted, access to the securing screw is through the
R/H flue manifold connection. This can be reversed to give
access through the L/H flue manifold connection. See
Servicing section for details.
Water Connections
To maintain hydraulic balancing it is important that if changing
to left hand connections, that both are changed. The
procedure is as follows:
-

Remove all casing panels.

Remove the global flow and return NTC temperature
sensors from the manifolds.

Remove the auto air vent and pressure gauge connection
from the flow manifold.

Remove the drain tap and blanking plug from the return
manifold.

Unbolt and remove the manifolds taking care not to disturb
any seals.

Rotate the return manifold through 180º and re-attach in
place of the original flow manifold. Fit the auto air vent and
pressure gauge connections to it. Fit the global flow NTC
temperature sensor to the top edge fixing nearest the outlet
connection.

Rotate the flow manifold through 180º and re-attach in place
of original return manifold. Fit the drain tap and blanking
plug to it. Fit the global return NTC temperature sensor to
the top edge fixing nearest the inlet connection.

When commissioning the appliance special care should be
taken to ensure water soundness around all the
connections that have been remade.

Gas Connection
The gas connection can be made on either the right or left
hand. To reverse the connection use the following procedure:
-

Remove the side panels.

Disconnect all gas valve inlet elbows from the manifold,
retaining the sealing washers.

Disconnect the leads from the gas pressure switch.

Remove the fasteners securing the gas manifold and rotate
through 180º before re-securing.

Re-connect the leads to the gas pressure switch.

Re-connect the gas valve inlet elbows to the manifold using
new sealing washers if any show signs of damage.

Gas soundness test all the connections.

Note.
When reversing the gas manifold on the imax plus

90 it is

necessary to move the blanking plug from the first hole to the
third hole.

INST

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Installation & Servicing

INSTALLATION

WATER CONNECTION

The boiler flow and return pipes are terminated with 2" BSP
male taper threads on either the right or left hand side of the
appliance (see Frame 8 for reverse connection details). Water
returning from the system should be connected to the lower
pipe, with the flow water connection coming from the top pipe.

If installing the boiler onto an existing system it is strongly
recommended that the system be thoroughly flushed before
connecting the boiler. When connecting to a new system it is
still important to flush the whole system in accordance with the
relevant standards.

10 GAS CONNECTION

The boiler gas supply pipe is terminated in a 1 ½" BSP
male taper connection on the right or left-hand side of the
appliance (see Frame 8 for reverse connection details).

A minimum working gas pressure of 15mbar (6" w.g.) must
be available at the boiler inlet. Due to the presence of a

minimum gas pressure switch it is therefore important to
carefully calculate the gas supply pipe size to avoid nuisance
shutdown.

A suitable gas cock (not supplied) must be fitted directly onto the
appliance gas inlet pipe to allow isolation of the boiler. The gas
connection should be suitable for being disconnected to enable
servicing (see servicing section).

11 CONDENSATE DRAIN

A condensate drain for the boiler should be assembled as
shown below. This can be built using the parts provided plus
other pieces not supplied. The parts provided are 40mm
plastic pipe. All additional pipework and fittings in the
condensate drain system must also be made of plastic. No
other material may be used.

When routing the condensate drain from the boiler, care
should be taken to ensure alignment with one of the knock out
panels on the casing.

The routing of the drain must be made to allow a minimum fall
of 30mm per m. Suitable supports should be used to
maintain this.

If the boiler is not installed on a plinth then a well will be
required to accommodate the condensate trap.
(Refer to Frame 6).

The condensate system from the boiler must be connected to a
drainage point, preferably within the building. Any external runs
must be kept to a minimum and insulated. This is to avoid
freezing in cold weather causing blocking.

Once connected the condensate trap should be filled initially
through the elbow provided, before fitting of the condensate
blanking plug.

175

minimum

ima 5775

TO THE CONDENSATE
DRAIN

INITIAL SIPHON
FILLING-UP POINT

CONDENSATE

BLANKING PLUG

(SUPPLIED)

CONDENSATE
T-PIECE
(SUPPLIED)

CONDENSATE ELBOW
(SUPPLIED)

PARTS TO FORM TRAP
(NOT SUPPLIED)

THESE PIECES CUT FROM

1M PIPE (SUPPLIED)

CONDENSATE

ELBOW

(SUPPLIED)

BOILER HOUSE

FLOOR

The upper part of the drain
pipe shall not be higher
than the tray bottom

BASE (Min. H 100mm)

INST

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TION

Installation & Servicing

INSTALLATION

12 CASING PANEL FIXING

The panels should be fitted before firing the boiler. The
method of assembling the panels is as follows:

1. Remove any knockouts from the panels required for

service connections.

2. Fit the side panels by pressing them on to the latch studs.

3. Fit the front and back panels by engaging the bottom edges

over the tabs on the frame feet and then pressing the
panels against the latch studs.

4. Place the top panel in place and press down to engage the

latch studs. Then secure the top panel to the top edges of
the front and back panels using the 2 screws provided in
the hardware pack. These screws must be fitted to ensure
and comply with electrical safety requirements.

Note.
Connect the earth leads provided to the earth points on the
panels as they are fitted to the boiler.

13 FLUE CONNECTION

See Frame 8 for alternative connection orientation details.

To fit the flue manifold, first hang the rectangular gasket over
the 3 studs along the top edge of the flue outlet from the
sump. Engage the flue manifold over these 3 studs and
secure with the 3 nuts and 3 screws provided. Take care in
aligning the gasket to ensure a good seal.

To fit the flue socket to the flue manifold, attach the adhesive
backed gasket to the matching face and then secure in place
with the 4 screws provided. Fit the round silicon lip seal into
the recess within the flue socket outlet. When fitting the flue
to the flue socket, take care not to disturb the lip seal. The
flue should be supported in such a way as to not place a
load on the flue manifold.

14 ELECTRICAL CONNECTIONS

Warning. This appliance MUST be earthed.

A mains supply of 230V 50Hz is required. The mains supply

should be fitted with a fuse rated at 3 amps.

Wiring external to the boiler MUST be in accordance with the
current I.E.E. (BS. 7671) Wiring Regulations and any local
regulations.

Connection should 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 unswitched socket serving only the boiler and
system controls. The means of isolation must be accessible
to the user after installation.

When making mains electrical connections to the boiler it is
important that the wires are prepared in such a way that the
earth conductor is longer than the current carrying conductors,
such that if the cord anchorage should slip the current carrying
conductors become taut before the earth carrying conductor.

WARNING. Sensor cables must be separated from cables in
the 230V circuit. For this purpose two conduits are provided.
Refer to Frame 17 for terminal strip connections.

Note.

A. As condensate will be produced under nearly all conditions,

it is essential that all joints are impervious to leakage.

B. Air ducts may be fastened to the air inlet collar if

combustion air is to be drawn direct from outside.

C. A max. 100Pa is available from the boiler internal fans to

overcome the combined resistance of all flue and air ducts
fitted to the appliance. The flue design should be such that
a negative pressure is not created at the boiler flue outlet.

INST

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Installation & Servicing

INSTALLATION

15 MAINS ELECTRICAL CONNECTIONS

1. The appliance MUST be wired with a permanent live supply. Use the plug 'A'

provided for this purpose. The mains supply must meet with the regulations in
Frame 14. The boiler is phase sensitive so correct connection of the live and
neutral wires is essential. The supply must not be interrupted by any system
controls. Controlling the mains input in this way will prevent the pump over-run
sequence and may cause damage to the heat exchanger.

2. A system pump must be connected to the boiler via a relay to ensure pump over-

run. A 230V AC output is provided for this purpose on terminals 11, 12 & 13.

16 CH CONTROLS CONNECTIONS

Note.
For some of the optional control methods it will be necessary
to access the parameter mode. This is done by entering the
Service Code described in Frame 26 and must only be
performed by trained installers and Service Engineers.

1. Timer/Thermostat with Optional Weather Compensation

The boiler can be operated with a timer and/or room
thermostat. Terminals (5 & 6) with a 24V supply and return
are available to be switched, open/closed circuit, by a timer
and/or room thermostat. The boiler senses open circuit as
no call for heat and closed circuit as call for heat. Mains
voltage MUST NOT be applied to these terminals. Optional
fitting of the outside sensor (provided with the boiler) to
terminals 3 & 4 is automatically detected. The flow
temperature is then compensated against outside
temperature in CH mode. See frame 34

for details on the

specific behaviour of the boiler with this control and how to
modify the heating curve.

2. Outside Sensor with Night Time Set Back

The boiler can be operated with a permanent call for heat,
with the flow temperature compensated against outside
temperature in CH mode. It is necessary to change
parameter A 1st digit to '1x' see Frame 29. The outside
sensor (provided with the boiler) should be connected to
terminals 3 & 4. To control the night time setback period
(period of lower room temperature) a timer should be
connected across terminals 5 & 6. These terminals
provide a 24V supply and return to be switched open/
closed circuit. Open circuit enables the night time set back
period. If no night time set back period is required then a
link wire should be placed across terminals 5 & 6. Mains
voltage MUST NOT be applied to these terminals. See
Frame 35

for details on the specific behaviour of the boiler

with this control and how to modify the heating curve.

3. BMS Control

The boiler can be operated using a BMS control. It is
necessary to change parameter A 1st digit to '2x' and
parameter 7 to '00' see Frame 29. A BMS can be used to
operate the boiler using a 0-10V signal to control the set
flow temperature. The positive signal from the BMS should
be connected to terminal 9 and the ground signal to
terminal 10. An alarm signal in the event of a lockout is
available to the BMS from terminals 14 & 15. In the event of
a lockout the boiler closes the circuit between these
terminals. A link wire should be connected between
terminals 5 & 6. Open circuit would enable the parallel
shift controlled by parameter 7. See Frame 35

for details

on the specific behaviour of the boiler with this control, and
how to modify the relationship between signal voltage and
set flow temperature.

Note.
Fitting the Outside Sensor

A. The sensor should be located on an external wall of the

building to be heated. Fix the sensor to a north/north-east
facing wall to avoid direct radiation from the sun. The
sensor should be located to avoid any heating effect from
the boiler flue.

B. To fix the sensor to the wall, unscrew the sensor box plastic

cover and screw/plug the sensor body to the wall. Wire a
twin core 0.5mm

cable to the sensor via cable gland

provided. Avoid running this cable alongside mains
voltage cables.

C. Connect the emc filter provided with the sensor to terminals

3 and 4 in the boiler. Connect the cable from the sensor to
the emc filter. The connections can be made irrespective
of polarity.

ELECTRICAL CONNECTION OF SYSTEM PUMP

n a

n c

11 1 2 13

L ine

N e u tra l

3-contact relay

n a

n c

11 1 2 13

L ine

N e u tra l

System pump

3-contact relay

System pump

NO CALL
FOR HEAT

CALL
FOR HEAT

i
ma721

Note.
All 230V wiring and 24V wiring MUST be kept

separate. For this reason separate conduits are

provided for bringing wiring into the boiler.

INST

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Installation & Servicing

INSTALLATION

17 DHW CONTROL CONNECTIONS

If the boiler is providing both CH and DHW and
the CH circuit is to operate at a reduced
(condensing) temperature, then it is necessary to
differentiate between CH and DHW heat
demands. The boiler will react accordingly by
adjusting the flow temperature and operating
pumps or valves to divert the flow.

A demand for DHW always has priority over CH.
The flow temperature is controlled by PARAs 1 &
B. To limit the boiler output during DHW demand
to match the storage cylinder capacity. See
Frame 21.

1. Tank Thermostat

DHW demand can be controlled with a timer
and/or tank thermostat. Connection to
terminals 7 & 8, with a 24V supply and return,
are available to be switched, open/closed
circuit, by a timer and/or tank thermostat. The
boiler senses open circuit as no call for DHW
and closed circuit as call for DHW. Mains
voltage MUST NOT be applied to these
terminals.

2. Tank Sensor Kit

DHW demand can be controlled using a Tank
Sensor Kit available from Ideal Stelrad Group.
Connection should be made to terminals 7 &
8, with the boiler automatically detecting its
presence. Full installation instructions come
with the kit. This sensor has the advantage of
providing the boiler with the actual stored
DHW temperature, allowing closer output
matching and reduced cycling. Use of a tank
sensor kit cannot be timer controlled.

A diverting valve or a separate pump can perform
DHW supply by a storage tank connected to the
boiler. The factory setting is for a pump, but this
can be changed using PARA A. Connection of
the pump or valve should be made via a relay to
terminals 16, 17 & 18.

BMS

CONNECTION

STORAGE TANK

SENSOR OR

THERMOSTAT

ON-OFF

ROOM THERMOSTAT

AND/OR ON/OFF

TIMER

OUTSIDE

SENSOR

PRIMARY SYSTEM

PUMP

ALARM SIGNAL

(VOLT FREE CONTACT)

DHW PUMP OR

3-WAY VALVE

MAIN SUPPLY

FROM THE

FILTER

230 V

24 V

ADDITIONAL

SECURITY

(LOW

WATER

PRESSURE)

T he intervention of the

additional security

provokes the block of the

boiler and error code

is displayed.

E 26

im8132

ELECTRICAL CONNECTION OF THE THREE WAY VALVE

ELECTRICAL CONNECTION OF A DHW PUMP

n a

n c

1 6 17 18

D H W ta nk

B oiler A B

A H e a tin g syste m

L in e

3-contact relay

N e u tra l

3-WAY VALVE CONNECTION
DHW tank

satisfied

Lin e

N eu tral

D H W ta nk

B oiler A B

A H ea tin g sys te m

3-contact relay

3-WAY VALVE CONNECTION
DHW tank

not satisfied

1 6 17 18

n a

n c

D H W pu m p
D H W

Tank satisfied

L in e

N e utra l

3-contact relay

1 6 17 18

n a

n c

L in e

N e utra l

D H W

pump

D H W

Tank not satisfied

3-contact relay

1 6 17 18

i
ma

5778

INST

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TION

Installation & Servicing

INSTALLATION

18 INTERNAL WIRING

00331506

230 V

24 V

CONDUIT FOR 230

V CA

CONDUIT FOR 24

V CA

C V I

SECURITY

THERMOST

A
T

TRANSFORMER

TST

RED

BLUE

BROWN

BLUE

BROWN

BLUE

YEL/GREEN

BOARD SUPPL

AM-5

FAN SUPPL

230v - 50 Hz

RED

BROWN

GIA/VER

(2 - 3 - 4 ELEMENTS)

(5 - 6 - 7 ELEMENTS)

T
A
NGENTIAL

FAN

KIT

BLUE

1 2 3

BLUE

YEL/GREEN BROWN

RED

BROWN

BLUE

BROWN

INTERRUT

R
E

BLUE

NTC

LOCAL

Ntc 8

Ntc 7

Ntc 6

Ntc 5

Ntc 4

Ntc 3

Ntc 2

Ntc 1

BLUE

X9-1

X9-2

X9-3

X9-4

X9-5

X9-6

X9-7

X9-8

X9-10

Ntc 9

RED

GREEN

O
WN

VIOLET

ORANGE

WHITE

GREY

BLACK

-PUMP

YEL/GREEN

BROWN

X1-3

X1-5 X1-6

X1-2

X1-1 X1-4 X1-7

F
A

N SUPPL

230 V - 50 Hz

FIL

T
ER

RED

FIL

TER

RED

FIL

TER

RED

F
A
N 1

2 3

F
A
N 2

X12

2 3

N
3

X13

2 3

N
4

X14

2 3

F
A
N 5

X15

2 3

F
A
N 6

X16

2 3

F
A
N 7

X17

2 3

RED

X3-7

X3-1

X3-2

X3-5

BLACK

BLUE

BROWN

CVI 1

X2-7

X2-1

X2-2

X2-5

CVI 2

BROWN

BLUE

X1-1

X1-2

X1-5

X1-7

X2-1

X2-2

X2-5

X2-7

X3-1

X3-3

AM-5

SUPPLEMENT

Y
BOARD 1

CVI 3

C
VI 2

X1-1

X1-2

X1-5

X1-7

X2-1

X2-2

X2-5

X2-7

X3-1

X3-3

AM-5

SUPPLEMENT

AR
Y
BOARD 2

CVI 5

C
VI 6

BROWN

BLUE

X1-1

X1-2

X1-5

X1-7

X3-1

X3-3

AM-5

SUPPLEMENT

AR
Y
BOARD 3

CVI 7

BROWN

BLUE

FLAT CABLE

PC INTERF

ACE

(OPTIONAL)

DISPLA

LINE OUT

LINE IN

BLACK

BROWN

WHITE

VIOLET

ORANGE

CONT

A
T
T
O

RELE'I

AM-4

X2-5

X2-6

X1-2

X2-3

X2-4

X2-2 X2-1

X1-1

D.H.W

+ 0 - 10 V

P
A
RT

. Z

FAN. 1

VM 1

(A)

BLUE

BROWN

YEL/GREEN

X12 12

BLUE

RED

BLACK

WHITE

FAN. 2

VM 2

(A)

VM3-4-

5-6-7

YEL/GREEN

BROWN BLUE

BLACK

BLUE

BLACK

BLUE

BROWN

BLUE

YEL/GREEN

BROWN

RED
RED

BLUE

YEL/GREEN

BROWN

VIOLET
WHITE

ORANGE
ORANGE
RED
BLACK
GREEN

GREEN
BLACK
WHITE

BLACK

BLUE

YEL/GREEN

(M5)

BLUE

BROWN

FIL

TER

MAIN SWITCH

230 V - 50 Hz

GREEN

RED

GREEN

WHITE

X10-3

RED
BLACK
WHITE

WHITE

X10-1

X10-2

X4-2
X4-1

X4-6

X5-2

X5-1

MINIMUM GAS

PRESSURE

SWITCH

GLOBAL

NTC 2

RETURN

GLOBAL

NTC1

FLOW

X1-1

X1-2

X1-5

X1-7

AM5

WHITE

BLACK

RED

WHITE

BLACK

BLUE

BROWN

ORANGE

BLUE

RED

BLACK

BLUE

BROWN

BLUE

RED

BLACK

WHITE

YEL/GREEN

FAN SUPPL

230 V - 50 Hz

im8133

INST

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Installation & Servicing

INSTALLATION

19 INTERNAL WIRING CONT'D

Detail of electrical connections on the 'CVI' control boards mounted directly onto the gas valves.

10K

E. ACC.

E. RIV.

E. ACC.Ignition electrode
E. RIV Ionisation electrode
PR

Rest button (on fascia panel)

Lockout warning light (within reset button)

High limit thermostat (local)

Fan air pressure switch

L - N

Supply terminals on CVI

1-2

Ionisation signal to MBD

WARNING!

To disconnect the

ignition lead from the

CVI hold directly on

the terminal (fast-on)

and not on the lead.

ima 5789

20 CONTROL BOARD LOCATIONS

The MBD is the main control board, which determines how
many modules should fire, the rate required and the flow
temperature required. It can communicate directly with the
CVI controls of 2 modules.

The AM-5 board is a supplementary board used with boilers
containing more than 2 modules. It provides the interface
between the MBD and an additional 2 modules per AM-5
board. See Frame 22 for guidance on how the AM-5 dip
switches should be configured.

MBD

AM-5

AM-4

7 m

odules

and

6 m

odules

3 a

nd 4

odules

im8886

310

The AM-4 board provides several interface functions. It
provides the functionality required for controlling the boiler with
the BMS 0-10V system. This board controls operation of a
DHW pump or valve. The output in DHW mode can also be
limited by this board, see Frame 21.

The CVI boards are attached directly to the gas valves of the
modules they control. When instructed by the MBD they provide
the safe ignition and flame supervision of their modules.

INST

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Installation & Servicing

INSTALLATION

DHW Output Limiting
It is possible to limit the output of the boiler when working in DHW mode. This is in
order to avoid overheating when the DHW storage tank absorbed input is less than the
boiler produced output. To limit the DHW output of the boiler change the DIP switch
settings on the AM-4 board (see Frame 20 for location of AM-4 board). By changing the
DIP switch settings you can exclude 1, 2 or 3 modules from firing in DHW mode, see
table below for settings:

AM-4

0-10 V

DHW
Tank
NTC

DIPSWITCH 1

DIPSWITCH 2

21 INTERFACE BOARD - AM4 supplementary Board

Output Reduction

-135 kW

-90 kW

-45 kW

None

Dip

Switch

Configuration

Examples of a

1 module

2 modules

3 modules

All modules

imax plus II

available

F180

(45 kW)

(90 kW)

(135 kW)

(180 kW)

Examples of a

4 modules

5 modules

6 modules

All modules

imax plus II

available

F310

(175 kW)

(220 kW)

(265 kW)

(310 kW)

The Modular Boiler Drive (MBD), see Frame 20 for location,
manages to check a two-burner group (2 x 45 = 90 kW). For
boilers with outputs greater than 45 kW, 1, 2 or 3
supplementary AM-5 boards are included, each of them
managing to check up to 2 burners. For example, a boiler with
5 burners (230 kW) is equipped with two supplementary AM-5
boards.
The supplementary boards have two small dip-switches,
which must be positioned according to the diagram shown
below. The setting operation is carried out during manufacture
and must also be done on site in case of service replacement.

22 INTERFACE BOARD - AM5 Supplementary Board

Thermal Element

AM-5

N.1

AM-4

Thermal Element

AM-5

N.2

AM-4

Thermal Element

AM-5

N.1

Thermal Element

AM-5

N.3

AM-4

Thermal Element

AM-5

N.2

Thermal Element

AM-5

N.1

AM-5 SUPPLEMENTARY BOARD
AM-5 and AM-4 boards positioning for an imax plus II 140 or 180

POSITION OF DIPSWITCHES

AM-5 and AM-4 boards positioning for an imax plus II 220 or 270.

AM-5 and AM-4 boards positioning for an imax plus II 310.

AM-5

DIPSWITCH 1

DIPSWITCH 2

POSITION OF DIPSWITCHES

INST

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TION

Installation & Servicing

INSTALLATION

23 EXAMPLES OF HEATING SYSTEMS

T
O

D
E

R
E

S
E

T
E

11 12 13

16 17 18

Flow

Return

Primary

System

Pump

Filter

Mixing

Header

Heating circuit

Heating

System

Pump

ima 5781

Storage

tank output

boiler output

3 way diverting valve

Heating system with DHW production (storage tank Output = Boiler Output) and mixing
header.

Note.

If PARA 'A' 2nd digit is set to 0, it means you wish to have a 3
way valve normally open towards the CH circuit (radiator
circuits from AB to A). Upon DHW request, terminal 11 is
energised which, through a relay, powers the 3-way valve,
thus closing port A and opening port B. Simultaneously
terminal 16 is energised which, through another relay, powers
the primary system pump.

If PARA 'A' 2nd digit is set to 2, it means you wish to have a 3 way
valve normally open towards the storage tank (DHW circuit from
AB to B). Upon CH request, terminal 11 is energised which,
through a relay, powers the 3-way valve, thus closing port B and
opening port A. Simultaneously terminal 16 is energised which,
through another relay, powers the primary system pump.

T
O

D
E

R
E

S
E

T
E

11 12 13

Flow

Return

Primary

System

Pump

Filter

Mixing

Header

Heating circuit

Heating

System

Pump

ima 5780

Heating System with one Group of Radiators (controlled by thermostatic valves)

INST

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Installation & Servicing

INSTALLATION

24 EXAMPLES OF HEATING SYSTEMS CONT'D

Installation of Two Boilers in Cascade, with Mixing Header and One or more Radiator Groups

D
E

T
E

7
6

O
D

S
T

E
P

11 12 13

Flow

Return

Flow

Return

Boiler pump

or storage

tank pump

non return
valve

Boiler pump or
storage tank

Filter

Mixing

Header

Heating circuit

Heating system
pump

ima 5782

DHW Storage Tank with DHW Pump Installed on the Secondary Circuit, in Parallel with the Heating Circuit.

7
6

T
O

S
E

16 17 18

11 12 13

ima 5783

Flow

Return

Filter

Primary

System

Pump

Mixing header

non return
valve

Heating circuit

Heating
system pump

DHW
pump

DHW

tank

Note.
The primary system pump would be off while the DHW pump is running with PARA A second digit set to 'x1'. This would
only give adequate circulation if the DHW pump was connected into the primary circuit, shown to the left of the mixing
header above. However, in the case shown it will be necessary to run the primary system pump with the DHW pump
for correct circulation. To achieve this set PARA A second digit to 'x0'.

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INSTALLATION

25 CONTROLS OPERATION AND DISPLAY

During normal operation of the imax plus II, the status of the appliance can be determined from the display.

The first digit shows the status of the boiler, the last 2 digits display the current flow temperature, except with
status 1, 2 or 5 when the number indicates the burner module about to start.

All other displays refer to error messages, see Frames 46 and 47 for details.

Reset

Display

Mode

Step

Store

+ -

On/Off switch

Reset buttons for the
different modules

Operation and indications on the display (example with 7 modules)

Pressure

gauge

ima 5784

On/Off Switch
The on/off switch turns the mains power on/off within the
boiler. It does not isolate the boiler from the mains. Therefore
it is important that the boiler is isolated at the external mains
connection point before removing any casing panels.
Module and Reset Buttons
If a module locks out then its Reset Button becomes
illuminated. To reset the module you must hold down this
button whilst pressing the reset key.
Mode Key
The default mode of the boiler is standby. By pressing the
mode key it is possible to change the mode.
By pressing the mode key once, PARA mode (abbreviation for
parameter) is displayed. In this mode it is possible to change
the settings of the boiler control module. The first 3
parameters are accessible to all, and the remaining
parameters are accessible to an installer once he has
entered the service code.
By pressing the mode key again, DATA mode is displayed. In
this mode it is possible to read information on the operation of
the boiler.

The following modes are only for use by trained installers and
servicing engineers. Access is only available after entering the

service code.
By pressing the mode key again, TEST mode is displayed. In

this mode it is possible to run either the entire boiler or

individual burners at max. or min. rate.
By pressing the mode key again, HOUR mode is displayed. In

this mode it is possible to read the hours of each individual

burner.
If no key is pressed for 15 minutes the boiler automatically

returns to standby mode, unless operating in TEST mode.
Step Key
Having selected the mode required the step key is used to

move through the options available to be changed or checked.
+/- Key
By pressing the top or bottom of this key it is possible to

increase or decrease a value.
Store Key
After a setting has been changed, pressing the store button

holds this new value in the memory. This key is also used to

move through some options available as sub menus within
DATA mode.

Display Status

Boiler Status

0_xx

Standby: no heat request

1_xx

The fan of the burner to be ignited is running in prepurge

2_xx

The safety time of the burner to be ignited is operative

3_xx

Burner 'on' in CH mode

4_xx

Burner 'on' in DHW mode

5_xx

The fan of the burner to be ignited is being set to start speed.

6_xx

Burner 'off' in CH mode because a set value has been reached.

7_xx

Pump overrun in CH mode.

8_xx

Pump overrun in DHW mode.

9_xx

Burner 'off' in DHW mode because a set value has been reached.

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Installation & Servicing

INSTALLATION

26 SERVICE CODE

To access the full list of parameters and the TEST and HOUR
modes , it is first necessary to enter the service code. This is
only to be used by trained installers and service engineers.
To enter the code:
Press and hold down the mode and step keys throughout the
following operation.

The letter C will be displayed along with a randomly generated
2-digit number.
Use the +/- key to change the value to 79.
Press the store key and the value will flash.
The mode and step keys can now be released and full access
is now available.

Shows the value of the displayed parameter

Shows the number of the parameter displayed (from 1 to 9 and from A to N)

The User has
access to these
three parameters
only (see Frame 28)

The User has no access
to these parameters.
Only the installer or
service technician can
get access by previously
enterin
(see Frame 26)

g the service code

By pressing store

store

r
es

i
ng

mode

By pressing

step

By pressing Step,
without any service code.

By pressing

step

As above

it selects :
- parameters
- data (all/single)
- test (all/single)

ch ooses

the mo de

It d isp lays when

in DATA mode.

It st or es when

in PARA mode.

+/- :

it in cr eases

or decr eases

the displ ayed

valu e

Reset

the boile r

e parameter number is not displayed.

By pressing

(see Frame 30)

step

(see the following page)

As above

i
ng

mode

r
es

i
ng

mode

By pressing

step

By pressing

step

By pressing

step with service code, see Frame 28 and 29

By pressing

step

By pressing

step

By pressing

step

By pressing

step

By pressing

step

By pressing

step

By pressing

store

By pressing

store

By pressing

store

By pressing

store

By pressing

store

By pressing

store

By pressing

store

By pressing

store

By pressing

step

1. 60

X XXX

2. 01

1. 50

3. 80

4. XX

9. XX

A. XX

N. XX

. XX

. XXX

XXXX

Single burner (1 to 7) DATA
are not accessible to the
user. Only the Installer can
enter DATA by a service
code (see Frame 26)

figure is stored
after flashing once

By pressing store the

change to

Status Number see Frame 25

Flow Temperature or Burner under Ignition

= Stand-by mode Dispaly

ima 5785

DATA
relevant
to
total
appliance

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Installation & Servicing

INSTALLATION

27 SERVICE CODE CONT'D

i
ng

ode

By pressing step

(see Frame 32)

By pressing

bur.1

OFF

and

are flashing

alternately.

ALL

OFF

and

are flashing

alternately.

bur.7

OFF

and

are flashing

alternately.

By pressing

(see Frame 33)

step

bur.1

XXXX

and

are flashing alternately

By pressing step

bur.2

XXXX

and

are flashing alternately

By pressing

step

bur.7

XXXX

and

are flashing alternately

By pressing

step

By pressing

step

By pressing

step

By pressing

step

Display in

mode

Stand-by

i
ng

ode

it selects:
- parameters
- data (all/single)
- test (all/single)

ch oo ses

the mod e

It d ispla ys when

in DATA mode.

It st or es when

in PARA mode.

+/- :

it in cr eases

or decr eases

the displayed

valu e

Reset

the boile r

The User has no access
to these modes.
Only the installer or
service technician can
get access by previously
entering the service code

For combustion test at
max. - output of the whole boiler.

For combustion test at
min. output of the whole boiler.

For combustion test at
max. output of the burner 1.

For combustion test at
min. output of the burner 1.

For combustion test at
max. output of the burner 7.

For combustion test at
min. output of the burner 7.

XXXX

X XXX

imax 5786

see Frame 33

(see Frame 26)

see Frame 33

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Installation & Servicing

INSTALLATION

28 PARAMETER MODE

By pressing the mode key once, PARA mode (abbreviation for
parameter) is displayed. In this mode it is possible to change
the settings of the boiler control module.

DHW Storage Temperature Setpoint (degC)

Press

Display

Description

P A R A

Press

Display

Parameters accessible to user

MODE

STEP

Lower

Limit

Upper

Limit

Factory

Setting

2. 0 1

STEP

CH and DHW Options

00 = CH & DHW are both off
01 = CH is on, DHW is off
02 = CH is on, DHW is off, System pump runs continuously
11 = CH & DHW are both on
12 = CH & DHW are both on, System pump runs continuously

1. 6 0

Maximum CH Flow Temperature Setpoint (degC)

STEP

3. 8 0

Flow Temperature Minimum Design Setpoint (degC)

Press

Display

Description

Parameters accessible to trained installers and service engineers only, after entering service code.

STEP

Lower

Limit

Upper

Limit

Factory

Setting

4. 2 0

see Frame 34 for guidance

Outside Temperature Minimum Design Value (degC)

STEP

-20

-10

5. 2 0

see Frame 34 for guidance

Minimum Flow Temperature Blocking Setpoint (degC)

STEP

6. 2 0

see Frame 34 for guidance

Night time Setback Parallel Shift (degC)

STEP

7. 2 0

see Frame 35 for guidance

1st digit - Outside Temperature Correction (degC)
see Frame 34 or 35

STEP

8. 0 0

2nd Digit - CH hysteresis (degC)

-5x

CH Pump Overrun Time (minutes)

STEP

9. 2 0

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Installation & Servicing

INSTALLATION

29 PARAMETER MODE CONT'D

1st Digit - CH type

Press

Display

Description

STEP

Lower

Limit

Upper

Limit

Factory

Setting

A. 0 1

0x = Timer/Thermostat with optional weather compensation
1x = Outside Sensor with Night Time Set back
2x = BMS 0-10V Control

DHW set value increase (degC)

STEP

B. 2 0

Temperature added to parameter 1 (see Frame 28) for boiler flow
temperature required to satisfy DHW demand

Maximum fan speed CH (hundreds rpm)

STEP

NOT

ADJUST

C. 2 0

Maximum fan speed DHW (hundreds rpm)

STEP

D. 2 0

Minimum fan speed (hundreds rpm)

STEP

E. 2 0

Ignition fan speed (% of parameter C)

STEP

F. 2 0

2nd Digit - DHW type
x0 = 3-way valve normally open to CH system
x1 = DHW pump
x2 = 3-way valve normally open to DHW tank

NOT

ADJUST

NOT

ADJUST

NOT

ADJUST

NOT

ADJUST

NOT

ADJUST

NOT

ADJUST

NOT

ADJUST

Flow temperature set point at 0V (degC)

STEP

G. 2 0

Flow temperature set point at 10V (degC)

STEP

H. 2 0

127

1st digit - Number of module lockouts required to close alarm contacts

STEP

J. 2 0

DHW hysteresis (degC)

STEP

L. 2 0

1st digit - Burner System

STEP

N. 2 0

NOT

ADJUST

NOT

ADJUST

x2 to x7

When using 0-10V BMS

2nd digit - DHW pump overrun time (30 second increments)

2nd digit - Number of Modules

0x = Ideal normal setup

2x to 7x

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Installation & Servicing

INSTALLATION

By pressing the mode key twice, DATA mode is displayed. In this mode it is possible to read information on the operation of the boiler.

30 DATA MODE

Press

Display

Press

Display

Description

Unit

Local flow temperature, NTC1

ºC

Local return temperature, NTC2

ºC

Module 1 fan speed setpoint

rpm

Module 1 actual fan speed

rpm

Data Accessible only to the Installer by previously entering the service code. Data relevant to individual burners.

Local flow temperature, NTC1

ºC

Local return temperature, NTC2

ºC

Module 2 fan speed set point

rpm

Module 2 actual fan speed

rpm

Local flow temperature, NTC1

ºC

Local return temperature, NTC2

ºC

Module 3 fan speed set point

rpm

Module 3 actual fan speed

rpm

Local flow temperature, NTC1

ºC

Local return temperature, NTC2

ºC

Module 4 fan speed set point

rpm

Module 4 actual fan speed

rpm

Local flow temperature, NTC1

ºC

Local return temperature, NTC2

ºC

Module 5 fan speed set point

rpm

Module 5 actual fan speed

rpm

STEP

B U R 1

STORE

1 . X X

2 . X X

X X X X
X X X X

STEP

B U R 2

STORE

1 . X X

2 . X X

X X X X
X X X X

STEP

B U R 3

STORE

1 . X X

2 . X X

X X X X
X X X X

STEP

B U R 4

STORE

1 . X X

2 . X X

X X X X
X X X X

STEP

B U R 5

STORE

1 . X X

2 . X X

X X X X
X X X X

Press

Display

Description

Unit

Global flow temperature

ºC

Global return temperature

ºC

DHW temperature

ºC

Outside temperature

ºC

N/A

ºC

Flow temperature set point

ºC

Fan speed set point

rpm

Output calculated in % (100% per module)

Data Accessible to Installer and User. Data relevant to the whole boiler.

STORE

T O T

1 . X X
2 . X X

3 . X X

4 . X X
5 . X X
6 . X X

X X X X

STEP

8 . X X

D A T A

Press

Display

MODE

Twice

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Installation & Servicing

INSTALLATION

32 TEST MODE

By pressing the mode key three times, TEST mode is displayed. In this mode it is possible to run either the entire boiler or
individual burners at max. or min. rate. This mode is useful for measuring the combustion and gas rates.

Press

Display

Press

Display

Press

Description

Test mode off for all burner modules

Test mode high for all burner modules

Test mode low for all burner modules

Test mode off for burner module 1

Test mode high for burner module 1

Test mode low for burner module 1

Test mode off for burner module 2

Test mode high for burner module 2

Test mode low for burner module 2

Test mode off for burner module 3

Test mode high for burner module 3

Test mode low for burner module 3

Test mode off for burner module 4

Test mode high for burner module 4

Test mode low for burner module 4

STEP

A L L

STEP

B U R. 1

STEP

B U R. 2

STEP

B U R. 3

STEP

B U R. 4

STORE

O F F

H H H

L L L

O F F

H I

L O

O F F

H I

L O

O F F

H I

L O

O F F

H I

L O

Test mode off for burner module 5

Test mode high for burner module 5

Test mode low for burner module 5

STEP

B U R. 5

STORE

O F F

H I

L O

Test mode off for burner module 6

Test mode high for burner module 6

Test mode low for burner module 6

STEP

B U R. 6

STORE

O F F

H I

L O

Test mode off for burner module 7

Test mode high for burner module 7

Test mode low for burner module 7

STEP

B U R. 7

STORE

O F F

H I

L O

T E S T

Press

Display

MODE

Three times

A L L

Press

Display

STEP

O F F

+ =

FLASHING
ALTERNATELY

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Installation & Servicing

INSTALLATION

100

-25 -20 -15 -10 -5

Outside Temperature (ºC)

t
Fl

w T

empera

(
º
C)

10 15 20 25

Parameter

Parameter 4

Parameter 6

Parameter 3

i
ma5770

Graph 3

By pressing the mode key four times, HOUR mode is
displayed. In this mode it is possible to read the hours run of
each individual burner. Press the step key to select the burner
whose hours run you want to read. The burner number as well
as the number of hours run will flash alternatively. See the
table below to interpret the readings.

33 HOUR MODE

Display Operation time range

Multiplication coefficient

x.xxx

From 0.000 to 9.999 hours Multiply the figures before decimal point by

1000 and the figures after comma by 1

xx.xx

From 10.00 to 99.99 hours Multiply the figures before decimal point by

1000 and the figures after comma by 10

xxx.x

From 100.0 to 999.9 hours Multiply the figures before decimal point by

1000 and the figures after comma by 100

To reset all burner hours to zero, first of all the text HOUR
should be displayed. Now press and hold the STORE key for
2 seconds. The text CLR will appear to indicate that all hours
have been reset to zero.

34 HEATING MODE OPERATION

1. Timer / Thermostat with Optional Weather

Compensation

The timer/thermostat generates and ends the call for heat
by opening and closing the circuit connected across
terminals 5 & 6. Without the outside sensor connected,
PARA 3 fixes the boiler set flow temperature. If the
outside sensor is connected (automatic detection) then
the set flow temperature varies with changes in outside
temperature (heating curve) in accordance with graph 3.

Note.
Use of the outside sensor reduces cycling and increases
the efficiency of the boiler by reducing the return
temperature, which allows the boiler to operate in
condensing mode.

The heating curve can be adjusted using the following
parameters (see also Frame 26 and 28):

Parameter 3: Highest set flow temperature required on the

coldest day.

Parameter 4: Lowest set flow temperature required on a

warm day (20ºC).

Parameter 5: The coldest day the heating system is

designed to work against.

Parameter 6: If according to the heating curve the required

set flow temperature is lower than this value
(parameter 6), then the call for heat is blocked
and the boiler will not fire.

Parameter 8: If the outside sensor is not reading the outside

temperature accurately, it is possible to adjust
the reading using this parameter by +/- 5ºC.

The burner will switch on when the Global Flow Temperature
(NTC1) is less or equal to the set flow temperature +5ºC - CH
hysteresis (parameter 8 2nd digit). The burner 'on' will
however be blocked if the set flow temperature is less or equal
to the Blocking CH Flow Temperature (parameter 6).

The burner will switch off when the Global Flow Temperature
(NTC1) is greater than the set flow temperature +5ºC.

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INSTALLATION

3. BMS Control

When controlling the boiler with a BMS the set flow
temperature is controlled by a 0-10V D.C. signal. The
relationship between the signal voltage and the set flow
temperature (heating curve) is given in graph 5.

The heating curve can be adjusted using the following
parameters (see also Frames 26, 28 and 29):

Parameter G: Required set flow temperature at 0V.

Parameter H: Required set flow temperature at 10V.

Parameter 6: If according to the heating curve the

required set flow temperature is lower than
this value (parameter 6), then the call for
heat is blocked and the boiler will not fire.

The burner will switch on when the Global Flow
Temperature (NTC1) is less or equal to the set flow
temperature +5ºC - CH hysteresis (parameter 8 2nd digit).
The heat demand will however be blocked if the set flow
temperature is less or equal to the Blocking CH Flow
Temperature (parameter 6).

The burner will switch off when the Global Flow
Temperature (NTC1) is greater than the set flow
temperature + 5ºC.

35 HEATING MODE OPERATION CONT'D

2. Outside Sensor with night Time Set Back

With the boiler configured to run with an outside sensor,
there is a permanent call for heat. The set flow temperature
varies with changes in outside temperature (heating curve)
in accordance with graph 4. With a timer connected across
terminals 5 & 6, the set flow temperature is set back by a
fixed amount in response to the circuit being open. This
allows the building temperature to be dropped during
periods e.g. night-time.

The heating curve can be adjusted using the following
parameters (see also Frames 26 and 28):
Parameter 3: Highest set flow temperature required on the

coldest day.

Parameter 4: Lowest set flow temperature required on a

warm day (20ºC).

Parameter 5: The coldest day the heating system is

designed to work against.

Parameter 6: If according to the heating curve the required

set flow temperature is lower than this value
(parameter 6), then the call for heat is
blocked and the boiler will not fire.

Parameter 7: When a timer opens the circuit connected

across terminals 5 & 6, the set flow
temperature is reduced by this value.

Parameter 8: If the outside sensor is not reading the

outside temperature accurately, it is possible
to adjust the reading using this parameter by
+/-5ºC.

The burner will switch on when the Global Flow Temperature
(NTC1) is less or equal to the set flow temperature +5ºC - CH
hysteresis (parameter 8 2nd digit). The burner on will however
be blocked if the set flow temperature is less or equal to the
Blocking CH Flow Temperature (parameter 6).

The burner will switch off when the Global Flow Temperature
(NTC1) is greater than the set flow temperature +5ºC.

100

-25 -20 -15 -10 -5

Outside Temperature (ºC)

t
Fl

w T

empera

(
º
C)

10 15 20 25

Parameter

Parameter 4

Parameter 6

Parameter 7

Parameter 3

i
ma5793

Graph 4

100

0.0

2.5

5.0

DC-Voltage [V]

t
Fl

w T

mpera

(
º
C)

7.5

10.0

i
ma5771

settable maximum

settable minimum

Blocking CH

Flow Temperature

(Parameter 6)

set

10V

(Parameter

)

set

(Parameter

Graph 5

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INSTALLATION

36 FROST PROTECTION

The imax plus II boiler has built into its control system the
facility to protect only the boiler against freezing.

If the boiler global flow temperature falls below 7ºC, the
primary system pump circulates water around the water
circuit. The pump will only switch off when the global flow
temperature exceeds 10ºC.

If the boiler global flow temperature falls below 3ºC, the boiler
will fire at minimum rate in CH mode. When the global flow
temperature exceeds 10ºC the burner switches off and the
pump enters the overrun period before switching off.

37 COMMISSIONING AND TESTING

A. ELECTRICAL INSTALLATION

1. Checks to ensure electrical safety should be carried

out by a competent person.

2. ALWAYS carry out the preliminary electrical system

checks, i.e. earth continuity, polarity, resistance to earth
and short circuit, using a suitable meter.

B. GAS INSTALLATION

1. The whole of the gas installation, including the meter,

should be inspected and tested for soundness and then
purged in accordance with the recommendations of the
relevant standards listed on page 4.

38 INITIAL LIGHTING

1. Check that the system has been filled and the boiler is not

air locked - air in the boiler could damage the heat
exchanger. The air vent located in the boiler flow manifold
must never be shut off.

2. Check that all drain cocks are closed and any valves in the

flow and return are open.

3. Check that the GAS SERVICE COCK IS ON.

4. Fill the condensate trap with water before putting the unit

into operation (see frame 11 for guidance).

5. Check the indication on the pressure gauge (sealed

system installations). If the pressure is less than 0.8 bar
the system should be filled up first.

6. Switch the electricity supply ON and check all external

controls are calling for heat. Check the control panel
switch is on.

7. The boiler will commence with the ignition cycle as follows:

- After 5 seconds the system pump and if required DHW

pump/valve are energised.

- The CVI of the first module chosen to fire is energised.

- After 5 seconds the fan of this module is started and run

at the starting speed for 10 seconds to allow for pre-
purge. Note. The fans of the other modules also run to
balance the flueways.

- Whilst operating in pre-purge the air pressure switch,

actuated by the fan, switches from C-NO (open position)
to C-NC (closed position).

- After pre-purge the ignition spark starts and the gas valve

is opened.

- If after the safety time no ignition is detected the gas valve

is closed and the ignition spark stopped. After 5 seconds
the ignition sequence is started again.

- If after 3 attempts no ignition is detected then the module

is put in lock out mode and the relevant red push button is
illuminated on the controls panel.

- To reset the burner hold down the illuminated button and

press the reset button.

- The remaining modules will follow this ignition sequence

one at a time.

8. Operate the boiler for 20 minutes and check the gas rate.

See Frames 27 and 32 for details on how to set the boiler to
run at maximum rate. Then check the CO

levels at

minimum rate, see Frame 39.

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INSTALLATION

Smoke sampling point

ima 7237

40 GENERAL CHECKS

Make the following checks for correct operation.
1. The correct operation of ANY secondary system controls

should be proved. Operate each control separately and
check that the main burner or circulating pump, as the
case may be, responds.

2. Water circulation system;

a. With the system HOT examine all water connections for

soundness.

b. With the system still HOT, turn off the gas, water and

electricity supplies to the boiler and drain down to
complete the flushing process.

c. Refill and vent the system, clear all air locks and again

check for water soundness.

d. Balance the system.

3. Check the condensate drain for leaks and check it is

discharging correctly.

4. Finally set the controls to the User's requirements.

41 HANDING OVER

Routine Operation
Full instructions covering routine lighting and operation of the
boiler are given in the User's Instructions. Draw the attention
of the boiler owner or their representative to these
instructions. 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 these Installation and Servicing/User Instructions and
Log book 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.
After servicing, complete the service section of the Log book
and return to the owner or their representative.
Recommend that the contract for this work should be made
with the regional gas authority or a CORGI registered heating
installer, or in IE a comptent person.

39 BURNER PRESSURE ADJUSTMENT

The following burner pressure adjustment must be followed when service
replacement of a gas valve is required. This procedure should also be
followed to check if adjustment is required during commissioning and
servicing.

1. Unscrew the sampling point cap and insert the analyser sensor.

2. In Test mode (see Frames 27 & 32) set burner 1 to low with all other burners

OFF.

3. Read the percentage of CO

, which must be between 8.8 and 9.0%. If the

reading is not between these values, then adjustment of the gas valve is required.

Note.
If the CO

reading is very low, check for blockages on the burner, flue and heat exchanger.

4. To adjust the gas valve using screw 'A', first remove the protective cap using a 'high' torque tool. By

turning the adjustment screw 'A' clockwise the CO

% increases, while it decreases anti clockwise.

5. Switch burner 1 OFF and repeat procedure for remaining burners.

ima 7238

INST

ALLA

TION

Installation & Servicing

SERVICING

42 SAFETY

It is the law that any service work must be carried out by a
registered CORGI installer, or in IE a competent person.

WARNING. Always turn off the gas supply at the gas
service cock, and switch off and disconnect the electricity
supply to the appliance and any external controls before
servicing or replacing components.

IMPORTANT.

After completing the servicing or replacement of components
always:

Test for gas soundness after reconnecting the gas at the
inlet connection and at all the individual gas valve inlets.

Check the water system is correctly filled and free from air.

Check all casing panels are correctly fitted and secured and
earth leads connected.

As each burner is ignited, immediately check the gas valve
connections to the burner hood for gas soundness, and
check the burner seal for soundness.

With the system hot, examine all water connections for
soundness.

Check the gas rate and measure the combustion CO/CO

content. Refer to Frames 27 and 32

for reference on how to

run the boiler at maximum rate. The CO/CO

ratio of the flue

gas should not be greater than 0.004 ratio.

Check burner pressure adjustment, see Frame 39.

Complete the boiler log book.

Carry out functional checks as appropriate.

43 SERVICING SCHEDULE

To ensure the continued safe and efficient
operation of the appliance it is recommended
that it is checked at regular intervals and
serviced as necessary. The frequency of
servicing will depend upon the installation
condition and usage but should be carried out
at least annually.

Ideal Stelrad Group does 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.

Before Servicing
1. Light the boiler and carry out function

checks, noting any operational faults.

2. Run the boiler for 10 minutes and then

check the gas consumption rate and
measure the combustion CO/CO

content.

For reference on how to force the boiler to
maximum rate see Frames 27 and 32.

Step One - Disassembly
1. Turn off the gas supply at the gas service

cock and disconnect the gas supply from the
boiler gas manifold. Switch off and
disconnect the electricity supply to the
appliance and any external controls.

2. Remove the 2 screws securing the top panel

to front/back panels. Now pull all the casing
panels off their latch studs and remove,
taking care to disconnect their earth leads.

3. Remove the cover of the fan box 'A' by removing screws 'B'.
4. Remove the grommets 'C' on the bottom of the fan box to gain

access to the securing bolts.

5. Remove the bolts 'D1 - D2 - D3 - D4' securing the burners

and fan box to the combustion chamber, using a 13mm
socket wrench and ring spanner.

6. Remove the 'E' fixing screws on the 2 sides of the gas

manifold. Remove the sheet metal protections 'F' on the 2
sides of the gas manifold.

SER

VICING

Installation & Servicing

SERVICING

10 m

Standard
position

Position
during
cleaning

44 SERVICING SCHEDULE CONT'D

7. Lift the gas manifold and resecure, at the 2

sides, in a position 10mm higher than the
standard one. It is possible to get this position
by securing the gas manifold flanges in
correspondence with holes 'G', using the
screws removed from holes 'E'.

8. Lift the fan box/burner hoods 'L' up at the rear

and locate the supporting poles 'I' in the holes
'M'.

9. Gain access to the condensate sump 'N' by

removing the cleaning plate 'O' or flue manifold
(dependant on position of fixing screw for heat
exchanger baffle 'P'). Remove screw securing
heat exchanger baffle 'P' and lower into bottom
of condensate sump.

Step Two - Cleaning
10. Carefully remove the burner gaskets which

need replacing with each cleaning of the burner.

11. Lift out the individual burners and blow

compressed air through the metal fibre side of
the burner. Do not brush the metal fibre side of
the burner. If they show any signs of damage
they must be replaced.

12. Inspect the heat exchanger (some aluminium oxide build up in the heat

exchanger is quite normal). To clean the heat exchanger, if necessary,
spray water down the flueways taking care not to wet the electrodes or any
other electrical equipment.

13. Inspect the electrodes for any signs of distortion and check for cracks in

the ceramic. Replace if necessary.

14. Remove one or two inspection covers from the condensate sump. Scrape

out any deposits.

15. Blow compressed air down the flueways.

16. Check the flue terminal is unobstructed and that the flue system is sealed

correctly.

17. Disassemble the condensate trap and flush through with water to remove

any debris.

18. Inspect any air inlet filters fitted to

the fan box and clean using
compressed air from inside the
air box outwards. Replace filters if
necessary.

Step Three - Rebuilding
19. Reassemble in reverse order,

using new burner gaskets.

20. Check the condensate trap is full

of water before firing the boiler.

21. Refer to Frame 42 for reference to

final safety checks.

22. Complete the Log Book.

SER

VICING

Installation & Servicing

FAULT FINDING

FAUL

T FINDING FAUL

T FINDING

SAFETY

Refer to Frame 42 for essential guidance on safety when

carrying out fault finding.
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

Polarity

Resistance to earth

BLANK DISPLAY
In the case of a blank display, check the following:
-

Check the ribbon cable is correctly fitted to the display

board.

Check that mains voltage is provided across terminals 19

and 20.
-

If no power available, check external fuse.

Check the ON/OFF switch is set to ON.

Check the fuse '2AF' mounted on the MBD.

Before replacing any blown fuses check for short circuits

on the 230V circuit, with particular attention given to the

wiring of external pumps or valves. Loads in excess of 1A

per external pump/valve will blow the fuse '2AF'.

If power supply and fuses are OK, the MBD needs

changing.

WARNING. The external fuse and fuse '2AF' are part of the

230V circuit. Make sure the power is off before checking.

BOILER DOES NOT SATISFY CH REQUEST
-

Check the connections of all external controls are correct.

Check the condition of all wiring to external controls.

Check the CH pump and its wiring.

Check that the parameters are set correctly for the chosen

control method.

BOILER DOES NOT SATISFY DHW REQUEST
-

Check the tank sensor/thermostat and its wiring.

Check the 3-way valve/DHW pump and its wiring.

Check that the parameters are set correctly.

BURNER MODULE LOCKOUTS
Note. To carry out checks on individual burner modules, it is

advised that all external controls are switched to 'OFF' so no

heat demand is placed on the boiler. Individual burners can

then be fired in TEST mode, see Frames 26 & 32.
When a burner module locks out, the corresponding red reset

button illuminates on the fascia.
Note. The blinking red LED on a CVI board indicates that it is

functioning correctly.
To reset the boiler, press and hold the illuminated red reset

buttons of each failed module and press the reset button on

the fascia.

45 FAULT FINDING

The air pressure switch does not close:
In this situation the fan runs for 60 seconds, then goes into

lockout, illuminating the relevant push button on the fascia.
-

Check the condition and connections of the silicon tubes to

the air pressure switch.

Measure the signal across the air pressure switch. If

greater than 53 Pa replace the air pressure switch. If less

than 53 Pa check the following:
- Check for any blockages in the passage of air through

the boiler and then out through the flue.

- Check that the flue has been sized correctly and does

not create excessive resistance (>100 Pa).

- Check for dirt build up on the back of the burner skin

(see servicing section).

- Check operation of fan.

High limit thermostat is open:
In this situation the module goes into lockout, and after

approximately 30 seconds the relevant push button on the

fascia becomes illuminated.
If the module has overheated:
-

Check for presence of water in the heat exchanger.

Check for adequate water circulation through the section.

If the module has not overheated:
-

Replace faulty overheat thermostat.

No flame is detected despite visible ignition through

sightglass:
-

Check the connection to the ionisation electrode.

Check for any distortion of the ionisation electrode, or

cracking of the ceramic.

Check that the resistance between the probe and earth is

not zero.

If all above OK, replace CVI board.

No ignition:
-

Check for a visible spark on the ignition electrode through

the sightglass. If not visible, check condition of electrode

and wiring. If all OK replace CVI board.

Check the gas valve opens correctly. Due to the nature of

the gas valve a burner pressure is difficult to measure.

Therefore it is advised that a manometer is connected to

the gas valve inlet pressure test point. When the gas valve

is energised a drop in pressure will be visible, if the valve

has opened correctly. If this is not the case, remove the CVI

board from the gas valve and measure the gas valve

solenoid resistance values. V1 should measure

approximately 2.9k

, V2 should measure approximately

1.4k

. If measured values differ significantly from these,

replace the valve. If values are OK replace CVI board.

If ignition electrode and gas valve are functioning correctly,

check the condition of burner. Refer to service section on

how to clean burner, and replace if any signs of damage

are evident.

Detail of electrical connections on the 'CVI' control boards mounted directly onto the gas valves.

10K

E. ACC.

E. RIV.

E. ACC.Ignition electrode
E. RIV Ionisation electrode
PR

Rest button (on fascia panel)

Lockout warning light (within reset button)

High limit thermostat (local)

Fan air pressure switch

L - N

Supply terminals on CVI

1-2

Ionisation signal to MBD

WARNING!

To disconnect the

ignition lead from the

CVI hold directly on

the terminal (fast-on)

and not on the lead.

ima 5789

Installation & Servicing

FAULT FINDING

FAUL

T FINDING FAUL

T FINDING

46 FAULT FINDING CONTD

Error Code Description

Alarm

L1 4

Local Temperature NTC 1 short circuit

L2 4

Local Temperature NTC 2 short circuit

L3 4

Local Temperature NTC 3 short circuit

L4 4

Local Temperature NTC 4 short circuit

L5 4

Local Temperature NTC 5 short circuit

L6 4

Local Temperature NTC 6 short circuit

L7 4

Local Temperature NTC 7 short circuit

L8 4

Local Temperature NTC 8 short circuit

L1 3

Local Temperature NTC 1 open circuit

L2 3

Local Temperature NTC 2 open circuit

L3 3

Local Temperature NTC 3 open circuit

L4 3

Local Temperature NTC 4 open circuit

L5 3

Local Temperature NTC 5 open circuit

L6 3

Local Temperature NTC 6 open circuit

L7 3

Local Temperature NTC 7 open circuit

L8 3

Local Temperature NTC 8 open circuit

E31

Global Flow NTC short circuit

E36

Global Flow NTC open circuit

E32

Global Return NTC short circuit

E37

Global Return NTC open circuit

Possible Causes and Solutions
-

The Local Flow Temperature NTC of the aluminium section is defective.

The Global Return Temperature NTC is defective.

The water circulation through the aluminium section involved is insufficient

ERROR CODES RELATED TO LOCAL OPERATING TEMPERATURE SENSORS

Note. In the case of more than one NTC failure at the same time, the most important one prevails.
E.g. "E" failures prevail on "L" failures; if "L" codes are equivalent, the code with the lowest first digit prevails; in the case that
the first digits are equivalent, the code with the highest second digit prevails.

Error Code Description

Alarm

L1 2

Local Flow Temperature of Aluminium section 1 > 98ºC

L2 2

Local Flow Temperature of Aluminium section 2 > 98ºC

L3 2

Local Flow Temperature of Aluminium section 3 > 98ºC

L4 2

Local Flow Temperature of Aluminium section 4 > 98ºC

L5 2

Local Flow Temperature of Aluminium section 5 > 98ºC

L6 2

Local Flow Temperature of Aluminium section 6 > 98ºC

L7 2

Local Flow Temperature of Aluminium section 7 > 98ºC

L8 2

Local Flow Temperature of Aluminium section 8 > 98ºC

L1 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 1 is too high

L2 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 2 is too high

L3 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 3 is too high

L4 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 4 is too high

L5 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 5 is too high

L6 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 6 is too high

L7 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 7 is too high

L8 1

The difference between the Global Return Temp. and the Local Flow Temp. of Aluminium section 8 is too high

Possible Causes and Solutions
As for the above mentioned conditions, they can be due to wiring break, short circuit or failure of the NTC involved, or over
heating of the aluminium section.

ERROR CODES RELATED TO LOCAL OVERHEAT TEMPERATURES