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