Potterton Promax 12 SL Quick guide

© Baxi Heating UK Ltd 2007
Installation & Service Instructions Promax SL
Range
These instructions include the Benchmark Commissioning Checklist
and should be left with the user for safe keeping.

2© Baxi Heating UK Ltd 2007
Natural Gas
Potterton Promax 12 SL
G.C.No41 591 79
Potterton Promax 15 SL
G.C.No41 591 87
Potterton Promax 18 SL
G.C.No41 591 80
Potterton Promax 24 SL
G.C.No41 591 88
Potterton Promax 30 SL
G.C.No41 591 89
This product has an energy rating (A) on a scale of A to G.
For more information see www.boilers.org.uk. This is a certification mark.
Building Regulations and the Benchmark
Commissioning Checklist
Building Regulations (England & Wales) require notification of
the installation of a heating appliance to the relevant Local
Authority Building Control Department. From 1 April 2005 this
can be achieved via a Competent Persons Self Certification
Scheme as an option to notifying the Local Authority directly.
Similar arrangements will follow for Scotland and will apply in
Northern Ireland from 1 January 2006.
CORGI operate a Self Certification Scheme for gas heating
appliances.
These arrangements represent a change from the situation
whereby compliance with Building Regulations was accepted as
being demonstrated by completion of the Benchmark Logbook
(which was then left on site with the customer).
With the introduction of Self Certification Schemes, the
Benchmark Logbook is being withdrawn. However, a similar
document in the form of a commissioning checklist and service
interval record is incorporated at the back of these instructions.
This company is a member of the Benchmark initiative and fully
supports the aims of the programme. Its aim is to improve the
standards of installation and commissioning of central heating
systems in the UK and to encourage the regular servicing of all
central heating systems to ensure safety and efficiency.
Building Regulations require that installations should comply
with manufacturer's instructions. It is therefore important that
the commissioning checklist is completed by the installer. The
relevant section of Building Regulations only relates to
dwellings. Therefore the checklist only applies if the appliance is
being installed in a dwelling or some related structure.
The flowchart opposite gives guidance for installers on the
process necessary to ensure compliance with Building
Regulations.
© Baxi Heating UK Ltd 2007 All rights reserved. No part of this publication may
be reproduced or transmitted in any form or by any means, or stored in any
retrieval system of any nature (including in any database), in each case whether
electronic, mechanical, recording or otherwise, without the prior written
permission of the copyright owner, except for permitted fair dealing under
Copyrights, Designs and Patents Act 1988.
Applications for the copyright owner’s permission to reproduce or make other
use of any part of this publication should be made, giving details of the proposed
use, to the following address:
The Company Secretary, Baxi Heating UK Ltd, The Wyvern Business Park,
Stanier Way, Derby, DE21 6BF.
Full acknowledgement of author and source must be given.
WARNING: Any person who does any unauthorised act in relation to a
copyright work may be liable to criminal prosecution and civil claims for damages.
Baxi Heating UK Ltd is a
BS-EN ISO 9001 Accredited Company
The code of practice for the installation,
commissioning & servicing of central
heating systems.
“Potterton” supports

Installer Notification Guidelines
3
© Baxi Heating UK Ltd 2007
Choose Building
Regulations Notification
Route
Contact your relevant Local
Authority Building Control
(LABC) who will arrange
an inspection or contact
a government approved
inspector
LABC will record the data
and will issue a
certificate of compliance
CORGI will record the data and
will send a certificate of
compliance to the property
You must ensure that the
notification number issued by
CORGIis written onto the
Benchmark Checklist
Scheme Members only
Call CORGI on: 0870 88 88 777
or log onto:
www.corgi-notify.com
within 10 days
If you notify via CORGI Scheme,
CORGI will then notify the
relevant Local Authority
Building Control Scheme
on member's behalf
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions
Competent Person's
Self Certification Scheme
Building Control
Complete the
Benchmark Checklist
Install and Commission this
appliance to manufacturer's
instructions

Legislation
4© Baxi Heating UK Ltd 2007
This company declares that no substances harmful
to health are contained in the appliance or used
during appliance manufacture.
The appliance is suitable only for installation in GB and IE
and should be installed in accordance with the rules in
force, and only used in a suitably ventilated location.
In GB, the installation must be carried out by a CORGI
Registered Installer. It must be carried out in accordance
with the relevant requirements of the:
• Gas Safety (Installation & Use) Regulations.
• The appropriate Building Regulations either The Building
Regulations, The Building Regulations (Scotland), Building
Regulations (Northern Ireland).
• The Water Fittings Regulations or Water Byelaws in
Scotland.
• The Current I.E.E. Wiring Regulations.
Where no specific instructions are given, reference should
be made to the relevant British Standard Code of Practice.
In IE, the installation must be carried out by a competent
Person and installed in accordance with the current edition
of I.S. 813 ‘Domestic Gas Installations’, the current Building
Regulations and reference should be made to the current
ETCI rules for electrical installation.
All systems must be thoroughly flushed and treated
with inhibitor (see section 6.2).
IMPORTANT - Installation, Commissioning, Service & Repair
This appliance must be installed in accordance with the manufacturer’s instructions and
the regulations in force. Read the instructions fully before installing or using the
appliance.
In GB, this must be carried out by a competent person as stated in the Gas Safety
(Installation & Use) Regulations.
Definition of competence: A person who works for a CORGI registered company and
holding current certificates in the relevant ACS modules, is deemed competent.
In IE, this must be carried out by a competent person as stated in I.S. 813 “Domestic
Gas Installations”.
NOTE: The addition of anything that may interfere with the normal operation of the
appliance without express written permission from the manufacturer or his agent could
invalidate the appliance warranty. In GB this could also infringe the Gas Safety
(Installation and Use) Regulations.
Warning - Check the information on the data plate is compatible with local supply
conditions.
All CORGI registered installers carry a CORGI identification card and have a
registration number. You can check your installer is registered by telephoning
0870 4012300 or writing to:-
1 Elmwood,
Chineham Business Park,
Crockford Lane,
Basingstoke. RG24 8WG
or check online at www.corgi-gas-safety.com
Codes of Practice, most recent version should be used
In GB the following Codes of Practice apply:
Standard Scope
BS 6891 Gas Installation.
BS 5546 Installation of hot water supplies for domestic
purposes.
BS 5449 Forced circulation hot water systems.
BS 6798 Installation of gas fired hot water boilers.
BS 5440 Part 1 Flues.
BS 5440 Part 2 Ventilation.
BS 7074 Expansion vessels and ancillary equipment for
sealed water systems.
BS 7593 Treatment of water in domestic hot water
central heating systems.
In IE the following Codes of Practice apply:
Standard Scope
I.S. 813 Domestic Gas Installations.
The following BS standards give valuable additional information;
BS 5546 Installation of hot water supplies for domestic
purposes.
BS 5449 Forced circulation hot water systems.
BS 7074 Expansion vessels and ancillary equipment for
sealed water systems.
BS 7593 Treatment of water in domestic hot water
central heating systems.
The boiler meets the requirements of Statutory Instrument “ The Boiler (Efficiency)
Regulations 1993 No3083” and is deemed to meet the requirements of Directive
92/42/EEC on the energy efficiency requirements for new hot water boilers fired with
liquid or gaseous fuels:-
Type test for purpose of Regulation 5 certified by:
Notified Body 0087.
Product/Production certified by:
Notified Body 0086.
For GB/IE only.

Safe Manual Handling
5
© Baxi Heating UK Ltd 2007
General
The following advice should be adhered to, from when first handling the boiler to the final stages of installation, and also during maintenance.
Most injuries as a result of inappropriate handling and lifting are to the back, but all other parts of the body are vulnerable, particularly shoulders, arms and
hands. Health & Safety is the responsibility of EVERYONE.
There is no ‘safe’ limit for one man - each person has different capabilities. The boiler should be handled and lifted by TWO PEOPLE.
Do not handle or lift unless you feel physically able.
Wear appropriate Personal Protection Equipment e.g. protective gloves, safety footwear etc.
Preparation
Co-ordinate movements - know where, and when, you are both going.
Minimise the number of times needed to move the boiler - plan ahead.
Always ensure when handling or lifting the route is clear and unobstructed. If possible avoid steps, wet or slippery surfaces, unlit areas etc. and take special
care on ladders/into lofts.
Technique
When handling or lifting always use safe techniques - keep your back straight, bend your knees. Don’t twist - move your feet, avoid bending forwards and
sideways and keep the load as close to your body as possible.
Where possible transport the boiler using a sack truck or other suitable trolley.
Always grip the boiler firmly, and before lifting feel where the weight is concentrated to establish the centre of gravity, repositioning yourself as necessary.
See section 8.3 of these instructions for recommended lift points.
Remember
The circumstances of each installation are different. Always asses the risks associated with handling and lifting according to the individual conditions.
If at any time when installing the boiler you feel that you may have injured yourself STOP !!
DO NOT ‘work through’ the pain - you may cause further injury.
IF IN ANY DOUBT DO NOT HANDLE OR LIFT THE BOILER - OBTAIN ADVICE OR ASSISTANCE BEFORE PROCEEDING !!

© Baxi Heating UK Ltd 2007
1.0 Introduction 7
2.0 General Layout 8
3.0 Appliance Operation 9
4.0 Technical Data 10
5.0 Dimensions and Fixings 11
6.0 System Details 12
7.0 Site Requirements 16
8.0 Flue Options 20
9.0 Plume Displacement 25
10.0 Installation 29
11.0 Electrical 35
12.0 Commissioning the Boiler 37
13.0 Fitting the Outer Case 38
14.0 Servicing the Boiler 39
15.0 Changing Components 41
16.0 Short Parts List 48
17.0 Fault Finding 49
Benchmark Checklist 58
Section Page
Contents
6
Contents of Pack
The pack contains:-
• Boiler
• Wall Plate
• Template & ‘Quick Fit’ Guide
• Literature Pack
• Fittings Pack

1.1 Description
1. The Potterton Promax SL range are gas fired room
sealed fan assisted condensing central heating boilers.
2. The maximum output of the Potterton Promax 12 SL is
40,330 Btu/hr,15 SL model is 52,000 Btu/hr, 18 SL model
is 60,770 Btu/hr and 24 SL model is 75,000 Btu/hr. The
maximum output of the 30 SL model is preset at 75,000
Btu/hr but can be set to 100,000 Btu/hr (see section 10.8).
All boilers automatically adjust their outputs according to
the system load.
3. It is designed for use on Natural Gas (G20).
4. The boiler is suitable for fully pumped open vented
central heating and domestic hot water systems and sealed
systems.
5. A label giving details of the model, serial number and
Gas Council number is situated on the rear of the lower
door panel (Fig. 1).
6. The boiler data badge is positioned on the air box door
(Fig. 2).
7. The boiler is intended to be installed in residential /
commercial / light industrial E.M.C. environments on a
governed meter supply only.
8. The boiler must be installed with one of the purpose
designed flues such as the standard horizontal flue kit, part
no 236921.
1.2 Important Information
Man-made mineral fibre
• Some component parts of this appliance (insulation pads,
gaskets and rope seals) are manufactured from man-made
mineral fibre.
• Prolonged or excessive exposure to this material may
result in some irritation to the eyes, skin or respiratory
tract.
• It is advisable to wear gloves when handling these items.
• Irritant dust will only be released from the items if they
are broken up or subjected to severe abrasion. In these
instances a suitable dust mask and goggles should be worn.
• Always thoroughly wash hands after installation, servicing
or changing components.
• When disposing of any items manufactured from man-
made mineral fibre care must be exercised.
• If any irritation of the eyes or severe irritation of the skin
is experienced seek medical attention.
1.0 Introduction
7
© Baxi Heating UK Ltd 2007
Fig. 1
Data Badge
Air Box Door
Lower Door Panel Position of Label
Fig. 2

2.0 General Layout
8© Baxi Heating UK Ltd 2007
2.1 Layout (Figs. 3,4,5 & 6)
1. Wall Plate
2. Flue Elbow
3. Heat Exchanger
4. Burner
5. Air Box
6. Fan Protection Thermostat
7. Fan Assembly
8. Condensate Trap
9. PCB Housing Assembly
10. Gas Tap
11. Gas / Air Ratio Valve
12. Flow Pipe Connection
13. Return Pipe Connection
14. Flow Temperature Safety Thermostat - Black
15. Flow Temperature Thermistor - Red
16. Flow Switch (dry fire protection)
1
2
3
4
5
6
7
9
8
10
11
15 14
12
13
16
Fig. 4
Fig. 3
Fig. 5
Fig. 6

3.0 Appliance Operation
9
© Baxi Heating UK Ltd 2007
3.1
1. Switched Live On: When the switched live switches
on if the flow temperature is less than the set point
then pump overrun occurs. When the switched live
switches on if the flow temperature is greater than the
set point then pump overrun occurs.
2. Pump On: The pump is on while the fan, spark
generator and gas valve are off. After 10 seconds if the
flow switch has made then fan pre-purge occurs. After
10 seconds if the flow switch has not made then anti-
cycle occurs.
3. Fan Pre-Purge: The pump and fan are on while the
spark generator and gas valve are off. After 5 seconds
ignition occurs.
4. Ignition: The pump, fan, spark generator and gas
valve are on. If a flame is detected then burner on
occurs. If a flame is not detected within 5 seconds and
less than 5 ignition attempts have been made then fan
purge occurs. If a flame is not detected within 5
seconds and 5 ignition attempts have been made then
ignition lockout occurs.
5. Burner On: The pump, fan and gas valve are on
while the spark generator is off. Flow temperature is
controlled by varying the fan speed (and thereby the
gas rate) to achieve optimum operation. If the flow
temperature is greater than the set point or the TRVs
all shut down then fan post purge occurs.
6. Fan Post Purge: The pump and fan are on while the
spark generator and gas valve are off. After 5 seconds if
the TRVs are not shut down then pump overrun
occurs. After 5 seconds if the TRVs are shut down then
anti-cycle occurs.
7. Pump Overrun: The pump is on while the fan, spark
generator and gas valve are off. After 1 minute anti-
cycle occurs.
8. Anti-cycle: The pump, fan, spark generator and gas
valve are off. After 3 minutes if the flow temperature is
less than the set point then pump on occurs. After 3
minutes if the flow temperature is greater than the set
point then pump overrun occurs.
9. Ignition Lockout: The pump, fan, spark generator
and gas valve are off. The boiler can only be reset by
manually using the reset button.
Mains On.
Flow
temperature less
than set point ?
YES
5 second
Fan Pre-Purge.
Flame Detected ?
Burner On.
Ignition
Lockout.
5 second
Ignition Period.
All TRVs
shut down ?
Ignition done and
5 attempts made ?
Ignition done
and less than 5
attempts made ?
Flow switch made ?
NO
YES
YES
YES
10 second
Pump On.
All TRVs
shut or Flow temperature
greater than set point ?
5 second
Fan Post Purge.
1 minute
Pump Overrun.
3 minute
Anti-cycle.
NO
YES
YES
YES
NO

Appliance Category CAT I 2H
4.0 Technical Data
10 © Baxi Heating UK Ltd 2007
Horizontal
Flue Terminal Diameter 110mm
Dimensions Projection 150mm
Outercase Dimensions
Overall Height Inc Flue Elbow - 750mm
Casing Height - 600mm
Casing Width - 390mm
Casing Depth - 280mm
Weights kg
Packaged Boiler Carton 36.2
Packaged Flue Kit 3.6
Installation Lift Weight 26.0
Connections
Gas Supply - 1/2in BSPT
Central Heating Flow - 22mm
Central Heating Return - 22mm
Condensate Drain - 1 in BSP
Recommended System
Temperature Drop
Condensing 20°C 36°F
Heat Input (Q)(Gross) Max Min
12 model kW 13.34 10.2
Btu/hr 45,518 34,840
15 model kW 16.88 10.2
Btu/hr 57,600 34,840
18 model kW 20.18 10.2
Btu/hr 68,850 34,840
24 model kW 24.50 10.2
Btu/hr 83,600 34,840
30 model kW 33.76 10.2
(see note) Btu/hr 115,200 34,840
Heat Output (P)
(Non Condensing 70° C Mean Water Temp)
Max Min
12 model kW 11.82 9.14
Btu/hr 40,330 31,180
15 model kW 15.24 9.14
Btu/hr 52,000 31,180
18 model kW 17.81 9.14
Btu/hr 60,770 31,180
24 model kW 22.00 9.14
Btu/hr 75,000 31,180
30 model kW 30.18 9.14
Btu/hr 102,980 31,180
Electrical Supply 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption 80W
External Fuse Rating 3A
Internal Fuse Rating (BS 4265)
Fuse 3.15 AT (PCB)
Inlet Pressure at Gas Valve (Natural Gas)
Min 18.1 mbar
Max 22.5 mbar
(see Section 12.1)
Injector (Natural Gas)
6.5mm Diameter
Clearances
(For unventilated compartments see Section 7.2)
Both Sides 5mm Min
Above Casing 200mm Min
Below Casing 50mm Min
Front (For Servicing) 500mm Min
Front (In Operation) 5mm Min
010203040
20
40
60
80
100
120
140
160
180
200
220
Water Flow Rate (litres/min)
Pressure Drop (mbar)
8
17
25
33
42
50
58
66
75
83
91
Pressure Drop (in wg)
Hydraulic Resistance Chart
Appliance Type C13 C33 C53
Nox Class 5
Heat Output (P)
(Condensing 40° C Mean Water Temp)
Max Min
12 model kW 12.81
Btu/hr 43,400
15 model kW 16.49 10.1
Btu/hr 56,260 34,520
18 model kW 19.27
Btu/hr 64,898
24 model kW 23.8 10.1
Btu/hr 81,200 34,520
30 model kW 32.61 10.1
Btu/hr 113,280 34,520
Water Content
litres 2.6
pints 4.6
Static Head
max 30 metres (100 ft)
min 1 metre (3.25 ft)
Low Head 0.2m (8 in) min
System Detail
fully pumped open vented & sealed systems
Gas Connection
G1/2” B.S.P. Thread
Controls
boiler thermostat, safety thermostat,
flow switch, electronic flame sensing,
temperature protection thermostat &
condensate blockage sensor
NOTE: The maximum output of the 30
model is factory set at 22.0kW (75,000
Btu/hr). This can be altered to 30.18kW
(102,980 Btu/hr) - see section 10.8.
For 12 model - The efficiency is 90.5%
For 15 model - The efficiency is 91.3%
For 18 model - The efficiency is 90.4%
For 24 model - The efficiency is 90.9%
For 30 model - The efficiency is 90.9%
This value is used in the UK Government’s Standard
Assessment Procedure (SAP) for energy rating of
dwellings. The test data from which it has been
calculated has been certified by 0087.
SEDBUK Declaration
Electrical Protection IPX2
CO/CO2 Ratio Up to a maximum
of 0.004 Flow Temperature (adjustable)
55° C to 78° C (± 5° C)
CO2 Level 9% ± 1%
Max Gas Rate (2H - G20 - 20mbar)
(After 10 Mins)
(12) (15) (18) (24) (30)
Btu/hr 40,950 52,000 61,400 75,000 102,980
m3/hr 1.34 1.64 1.94 2.31 2.95
ft3/hr 47.3 52.1 68.5 83.3 104.2

5.0 Dimensions and Fixings
11
© Baxi Heating UK Ltd 2007
DIMENSIONS
A600mm
B280mm
C390mm
D150mm Ø Min.
E162.5mm
F96mm
SIDE FLUE (left and right)
For every 1m of horizontal flue
length, the clearance above the top
of the flue elbow should be 27.5mm
to incorporate the 1.5° fall in the flue
from the terminal to the elbow.
The 1.5° fall provided by the elbow
is to allow condensate to run back to
the boiler, for disposal through the
condensate discharge pipe.
Flue length (Y)
up to 1m
1m - 2m
2m - 3m
Clearance (X)
27.5mm
55mm
82.5mm
360° Orientation
Tube Ø 110mm
DC
B
A
E
F
Y
1.5°
X
1.5°
Fig. 7
Fig. 8

6.0 System Details
12 © Baxi Heating UK Ltd 2007
6.1 Water Circulating Systems
1. The appliance is suitable for use with open vent fully
pumped systems and sealed systems .
The following conditions should be observed on all
systems:
• The static head must not exceed 30m (100ft) of water.
• The boiler must not be used with a direct cylinder.
• Drain cocks should be fitted to all system low points.
• All gas and water pipes and electrical wiring must be
installed in a way which would not restrict the servicing
of the boiler.
• Position isolating valves as close to circulating pump as
possible.
• It is recommended that the return pipe is fitted with an
automatic air vent as close to the boiler as is practical.
6.2 Treatment of Water Circulating
Systems
• All recirculatory water systems will be subject to
corrosion unless an appropriate water treatment is
applied. This means that the efficiency of the system
will deteriorate as corrosion sludge accumulates within
the system, risking damage to pump and valves, boiler
noise and circulation problems.
• When fitting new systems flux will be evident within
the system, which can lead to damage of system
components.
• All systems must be thoroughly drained and flushed
out. Using, for example Betz-Dearborn Sentinel X300
or X400 or Fernox Superfloc Universal Cleanser. They
should be used following the flushing agent
manufacturer’s instructions.
• System additives - corrosion inhibitors and flushing
agents/descalers should be suitable for aluminium and
comply to BS7593 requirements, e.g Betz-Dearborn
Sentinel X100 and Fernox-Copal which should be used
following the inhibitor manufacturer’s instructions.
Failure to flush and add inhibitor to the system will
invalidate the appliance warranty.
• It is important to check the inhibitor concentration
after installation, system modification and at every
service in accordance with the manufacturer’s
instructions. (Test kits are available from inhibitor
stockists.)
• For information or advice regarding any of the above
contact Technical Enquiries.

6.0 System Details
13
© Baxi Heating UK Ltd 2007
6.3 Pipework
1. The sizes of flow and return pipes from the boiler should
be determined by normal methods, according to the
requirements of the system. The connections on the boiler
are 22mm.
2. A 20 °C (36°F) drop in temperature across the system is
recommended for condensing boilers. Existing radiators may
be oversized and so allow this, but where radiator sizing is
marginal it may be advisable to retain a system temperature
drop of 11°C (20°F).
NOTE: On 30 models 28mm pipe should be used to
connect to the boiler flow and return.
3. In systems using non-metallic pipework it is necessary to
use copper pipe for the boiler Flow and Return. The copper
must extend at least 1 metre from the boiler and include any
branches (Fig. 9).
6.4 Low Head Installation
1. Using a close couple arrangement the minimum head is as
shown in the diagrams (Figs. 10 & 11) subject to the
following conditions:
a) The pump being adjusted to give a 20°C drop across
the boiler.
b) The pump must be fitted on the flow.
c) The pump must be fitted in accordance with the
pump manufacturer's instructions.
d) The open vent pipe must be taken up from a tee in a
horizontal section of the flow pipe.
An alternative Low Head Installation (Fig. 12)
2. For heads below 400mm then a combined vent and feed
pipe may be connected. This must be a minimum of 22mm
diameter. It is recommended that an air separator is fitted
when using a combined feed and vent pipe.
6.5 Pump
1. Providing that the cold feed and open vent pipe are
positioned correctly (e.g. the system is not prone to
pumping over, air entrainment etc.) the pump may be fitted
on the primary return pipe.
Typical Low Head Installation
If Conditions Require,
This System Possible
Alternative Low Head Installation
Boiler
500mm
45°
22mm
Open Vent
1000mm
Min
150mm
Max
15mm
Cold
Feed
400mm
Min Head
Return
Pump
Flow
Boiler
500mm
45°
22mm
Open Vent
400mm
Min Head
1000mm
Min
Automatic Air
Vent 15mm
Cold
Feed
150mm
Max
Return
Pump
Flow
Return
Pump
Flow
Boiler
200mm
Min
Air
Separator
22mm
Feed & Vent
Pipe
Fig. 10
Fig. 11
Fig. 12
Boiler
Flow
Return
Copper
0.5m
Copper
1m
Copper
0.5m
Fig. 9

6.0 System Details
14 © Baxi Heating UK Ltd 2007
6.6 System Controls
This boiler does not require a bypass.
This boiler does not require a permanent live.
The pump only needs wiring directly to the boiler for
fully TRV’d systems.
1. To comply with Part L1 of the Building Regulations the
heating system into which the boiler is installed should
include the following:
a) zone controls
b) timing controls
c) boiler control interlocks
2. Such a system needs to be fully pumped and must
provide independent temperature and time control to
both the heating and hot water circuits and have a boiler
interlock.
3. The boiler should be controlled so that it operates on
demand only. Where it is proposed to effect control by
thermostatic radiator valves, a room thermostat (or
other device such as a flow switch - a flow switch is
integral to this boiler) should also be provided to switch
off the boiler when there is no demand for heating or
hot water.
4. The interlock for the CH circuit can be provided by
either a Room Thermostat or a fully TRV’d system with
the pump wired back to the boiler without a bypass.
Connection diagrams for both options for Y and S plan
systems are shown.
Y Plan
Diverter
Valve
Cylinder
Stat
Room
Stat
Boiler
Pump
Timer
230V
50Hz
LNE
L
N
CH on
HW on
HW off
LNE
L N P/FE
b
g/y w
o
gr
1
C2
g/y
S Plan
Valve
Cylinder
Stat
Room
Stat
Boiler
Pump
Timer
230V
50Hz
LNE
L
N
CH on
HW on
LNE
L N P/FE
Motor
S Plan
Valve
Motor
o
o
gr
b
g/y
b
gr
br
br
Y Plan
Diverter
Valve
Cylinder
Stat
Boiler
Pump
Timer
230V
50Hz
LNE
L
N
CH on
HW on
HW off
LNE
L N P/FE
b
g/y
o
gr
1
C2
w
g/y
S Plan
Valve
Cylinder
Stat
Boiler
Pump
Timer
230V
50Hz
LNE
L
N
CH on
HW on
LNE
L N P/FE
Motor
S Plan
Valve
Motor
o
o
gr
b
g/y
b
gr
br
br
Y Plan, Room Thermostat System, CH Interlocked By Room Thermostat
At least the Radiator(s) near the Room Thermostat not TRV’d
Pump run from Switched Live
By-pass permitted but not required for Part L1 compliance
S Plan, Room Thermostat System, CH Interlocked By Room Thermostat
At least the Radiator(s) near the Room Thermostat not TRV’d
Pump run from Switched Live
By-pass permitted but not required for Part L1 compliance
Y Plan, Fully TRV’d System, CH Interlocked By Boiler Flow Switch
Room Thermostat should not be fitted
Pump must be run from Boiler P/F connection for Part L1 compliance
By-pass not permitted (must be valved off) for Part L1 compliance
S Plan, Fully TRV’d System, CH Interlocked By Boiler Flow Switch
Room Thermostat should not be fitted
Pump must be run from Boiler P/F connection for Part L1 compliance
By-pass not permitted (must be valved off) for Part L1 compliance
Key to colours
b - Blue
br - Brown
w - White
o - Orange
gr - Grey
g/y - Green/Yellow

6.0 System Details
15
© Baxi Heating UK Ltd 2007
6.7 Sealed Systems (Fig. 13)
1. SAFETY VALVE - A safety valve complying with the
requirements of BS 6750 Part 1 must be fitted close to
the boiler on the flow pipe by means of a horizontal or
vertically upward connection with no intervening valve
or restrictions and should be positioned to facilitate
testing. The valve should be pre-set and non-adjustable
to operate at a pressure of 3 bar (45 Ibf/in2). It must be
arranged to discharge any water or steam through a pipe
to a safe outlet position.
2. PRESSURE GAUGE - A pressure gauge of minimum
range 0-4 bar (0-60 Ibf/in2) with a fill pressure indicator
must be fitted to the system, preferably at the same
point as the expansion vessel in an easily visible position.
3. EXPANSION VESSEL - An expansion vessel
complying with the requirements of BS 4814 must be
fitted to the system by means of a connection close to
the inlet side of the circulating pump in accordance with
the manufacturers instructions, the connecting pipe being
unrestricted and not less than 15mm (1/2in) nominal size.
The volume of the vessel should be suitable for the
system water content and the nitrogen or air charge
pressure should not be less than the system static head
(See Table. 1).
Further details of sealed system design can be obtained
from BS 5449 and the British Gas publication entitled
'Specifications for Domestic Wet Central Heating
Systems'.
4. FILLING POINT - A filling point connection on the
central heating return pipework must be provided to
facilitate initial filling and pressurising and also any
subsequent water loss replacement / refilling. The sealed
primary circuits may be filled or replenished by means of
a temporary connection between the primary circuit and
a supply pipe provided a ‘Listed’ double check valve or
some other no less effective backflow prevention device
is permanently connected at the inlet to the circuit and
the temporary connection is removed after use. The
filling method adopted must be in accordance with all
relevant water supply regulations and use approved
equipment.
Your attention is drawn to, for GB: Guidance G24.2 and
recommendation R24.2 of the Water Regulations Guide.
for IE: the current edition of I.S. 813 “Domestic Gas
Installations”.
5. MAKE UP SYSTEM - A method of replacing water
lost from the system should be provided either by
means of a make up vessel of not more than 3 litres (5
pints) capacity, mounted above the highest point of the
system, or by re-pressurisation of the system.
6. VENTING - A method of venting the system during
filling and commissioning must be provided by fitting
automatic air vents or by venting manually.
7. HOT WATER STORAGE - The hot water storage
vessel must be of the indirect coil type. All components
used in the system must be suitable for operation at
110°C (230°F) and at the pressure allowed by the safety
valve.
Safety
Valve
Pressure
Gauge
Pump
Filling
Point
Air
Vent
3 Litre
Top Up Bottle
(if required)
Radiator
Circuit
Expansion
Vessel
System Drains at
Low Point
Max Boiler Flow
Temp = 82° C
Boiler
Fig. 13
Table. 1
Vessel Charge
Pressure (Bar)
0.5
1.0
1.5
Initial System
Pressure (Bar)
0.5
1.0
1.5
2.0
1.0
1.5
2.0
1.5
2.0
Multiply Total
Water Content Of
System By (Litres)
0.067
0.112
0.207
0.441
0.087
0.152
0.330
0.125
0.265
Method of determining minimum valve of
expansion vessel volume for sealed systems
using Potterton Boilers
System Volume = 75 litres
Vessel Charge Pressure = 1.0 bar
Initial System Pressure = 1.5 bar
75 x 0.152 = 11.4 litres
Expansion Vessel Volume
Example :-
Then :-
NOTE
Where a vessel of the calculated size is not obtainable then
the next available larger size should be used.
Stop
Valve
Double
Check
Valve
DHW
Mains
Inlet
CH
Return
Temporary
Hose
Stop
Valve
Fig. 14

7.0 Site Requirements
16 © Baxi Heating UK Ltd 2007
7.1 Location
NOTE: Due to the high efficiency of the boiler a
plume of water vapour will be discharged from the
flue. This should be taken into account when siting
the flue terminal.
1. The boiler may be fitted to any suitable wall with the
flue passing through an outside wall or roof and
discharging to atmosphere in a position permitting
satisfactory removal of combustion products and
providing an adequate air supply. The boiler should be
fitted within the building unless otherwise protected by a
suitable enclosure i.e. garage or outhouse. (The boiler
may be fitted inside a cupboard - see Section 7.2).
2. If the boiler is sited in an unheated enclosure then it is
recommended to incorporate an appropriate device for
frost protection in the system controls.
3. If the boiler is fitted in a room containing a bath or
shower, it can only be fitted in zone 3, (Figs. A & B shows
zone dimensions for a bathtub. For other examples refer
to Section 601 of the Current I.E.E. Wiring Regulations)
reference must be made to the relevant requirements.
In GB this is the current I.E.E. Wiring Regulations and
Building Regulations.
In IE reference should be made to the current edition of
I.S. 813 “Domestic Gas Installations” and the current
ETCI rules.
4. The boiler installation does not require any specific
safety precautions in respect of flammable building
materials. However, if the boiler is to be fitted into a
building of timber frame construction then reference
must be made to the current edition of Institute of Gas
Engineers Publication IGE/UP/7 (Gas Installations in
Timber Framed Housing).
7.2 Ventilation of Compartments
1. Where the boiler is installed in a cupboard or
compartment, no air vents are required for cooling
purposes providing that the minimum dimensions below
are maintained.
Sides 15mm
Top 200mm
Bottom 50mm
Front 30mm
2. If the boiler is installed in a smaller cupboard or
compartment it must be ventilated according to
BS 5440 Part 2 and the minimum clearances given in
section 4.0 “Technical Data” maintained.
3. Any compartment should be large enough to house
the boiler only.
NOTE: The ventilation label on the front of the outer
case MUST NOT BE REMOVED when the appliance is
installed in a compartment or cupboard.
Zone 2
Zone 1
Zone 0
Zone 2
Zone 3
Zone 3
Zone 2
Window
Recess
Window
Recess
0.6 m 2.4 m
Ceiling
Outside
Zones
Outside Zones
Zone 3
Zone 3
Zone 2
Zone 2
Zone 1
Zone 0
2.25 m
Zone 2
Window
Recess
3.0 m
2.4 m
0.6 m
Fig. A
Fig. B
In GB Only
In GB Only

7.0 Site Requirements
17
© Baxi Heating UK Ltd 2007
7.3 Clearances (Figs. 15 &16)
1. A flat vertical area is required for the installation of the
boiler.
2. These dimensions include the necessary clearances
around the boiler for case removal, spanner access and air
movement. Additional clearances may be required for the
passage of pipes around local obstructions such as joists
running parallel to the front face of the boiler.
3. For unventilated compartments see Section 7.2.
7.4 Gas Supply
1. The gas installation should be in accordance with the
relevant standards. In GB this is BS 6891. In IE this is the
current edition of I.S. 813 “Domestic Gas Installations”.
2. The connection to the appliance is a 1/2in BSPF.
3. Ensure that the pipework from the meter to the
appliance is of adequate size to ensure correct operation.
Do not use pipes of a smaller diameter than the boiler
gas connection.
7.5 Electrical Supply
1. External wiring must be correctly earthed, polarised and
in accordance with relevant regulations/rules. In GB this is
the current I.E.E. Wiring Regulations. In IE reference
should be made to the current edition of ETCI rules.
2. The mains supply is 230V ~ 50Hz fused at 3A.
NOTE: “The method of connection to the electricity
supply must facilitate complete electrical isolation of the
appliance”.
Note! There is no method of isolating the boiler, at the
user interface.
Connection may be via a fused double-pole isolator with a
contact separation of at least 3mm in all poles and servicing
the boiler and system controls only.
WARNING: The PCB Control and Fan
Assembly are 325 Vdc. Isolate at supply
before access.
50mm
600mm
390mm
200mm
5mm Min
5mm Min
5mm
500mm
For Servicing
Purposes
Fig. 15
Fig. 16 In Operation
1.5°
280mm

7.0 Site Requirements
18 © Baxi Heating UK Ltd 2007
7.6 Condensate Drain
FAILURE TO INSTALL THE CONDENSATE
DISCHARGE PIPEWORK CORRECTLY WILL AFFECT
THE RELIABLE OPERATION OF THE BOILER
The condensate discharge pipe MUST NOT RISE at any
point along its length. There MUST be a fall of AT LEAST
2.5° (50mm per metre) along the entire run.
NOTE: It is unnecessary to fit an air break in the discharge
pipe.
1. The condensate outlet terminates in a 1” BSP nut and seal for
the connection of 21.5mm (3/4in) plastic overflow pipe which
should generally discharge internally into the household drainage
system. If this is not possible, discharge into an outside drain is
acceptable.
2. Ensure the discharge of condensate complies with any
national or local regulations in force.
BS 6798:2000 & Part H1 of the Building Regulations give
further guidance.
3. The discharge pipe should be run in a proprietary drain pipe
material e.g. PVC, PVC-U, ABS, PVC-C or PP.
4. Metal pipework is NOT suitable for use in condensate
discharge systems.
5. The pipe should be a minimum of 21.5mm diameter and
must be supported using suitably spaced clips to prevent
sagging.
6. It is advisable to keep the condensate pipe internal.
7. External runs greater than 3 metres or runs in cold areas
should use 32mm waste pipe.
8. If the boiler is fitted in an unheated location the entire
condensate discharge pipe should be treated as an external run.
9. In all cases discharge pipe must be installed to aid disposal of
the condensate. To reduce the risk of condensate being
trapped, as few bends and fittings as possible should be used.
10. When discharging condensate into a soil stack or waste pipe
the effects of existing plumbing must be considered. If soil pipes
or waste pipes are subjected to internal pressure fluctuations
when WC's are flushed or sinks emptied then back-pressure
may force water out of the boiler trap and cause appliance
lockout.
Examples are shown of the following methods of termination:-
i) to an internal soil & vent pipe
ii) via an internal discharge branch (e.g. sink waste)
iii) to a drain or gully
iv) to a purpose made soakaway
It is also permissible to discharge into a downpipe carrying
rainwater, providing this pipe connects to a foul water drain.
Boiler
2.5° Minimum fall
Termination to an internal soil and
vent pipe
450mm min
Boiler
2.5° Minimum fall
External termination via internal discharge
branch
e.g sink waste - downstream
Sink
Pipe must terminate
above water level but
below surrounding
surface
Boiler Pipe must terminate above
water level but below
surrounding surface
2.5° Minimum fall
Termination to a drain or gully
Boiler
500mm min
2.5° Minimum fall
Termination to a purpose made soak-
away
Holes in the soak-away must
face away from the building
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run

7.0 Site Requirements
19
© Baxi Heating UK Ltd 2007
N
I
I
G
F
M
I
AAF
H
J,K
D
E
H
Likely flue positions requiring
a flue terminal guard
C
RA
I
J,K
I
L
S
B
T
U
7.7 Flue
NOTE: Due to the high efficiency of the boiler a plume of
water vapour will be discharged from the flue. This should
be taken into account when siting the flue terminal.
1. The following guidelines indicate the general requirements
for siting balanced flue terminals. For GB recommendations are
given in BS 5440 Pt.1. For IE recommendations are given in the
current edition of I.S. 813 “Domestic Gas Installations”.
2. If the terminal discharges onto a pathway or passageway,
check that combustion products will not cause a nuisance and
that the terminal will not obstruct the passageway.
3. Take into consideration the effect the plume of vapour may
have on neighbours when siting the flue.
4. Adjacent surfaces close to the flue terminal may need
protection from the effects of condensation. Alternatively a flue
deflector kit (part no. 248167) is available.
5. For installation of the flue into an internal corner at the
25mm dimension the flue deflector kit (part no. 248167) must
be fitted.
6. * Reduction to the boundary is possible down to 25mm but
the flue deflector kit (part no. 248167) must be fitted.
7. If required a suitable terminal guard is available from Baxi for
use with the flue deflector.
8. For fitting under low soffits and eaves it is acceptable for the
flue to project upto 500mm from the face of the wall to the
inside of the air intake. This can be painted if required using a
suitable external paint.
9. If a terminal is less than 2 metres (783/4in) above a balcony,
above ground or above a flat roof to which people have access,
then a suitable terminal guard must be provided.
IMPORTANT:
• Only ONE 25mm clearance is allowed per installation.
• Under car ports we recommend the use of the plume
displacement kit.
• The terminal position must ensure the safe and
nuisance - free dispersal of combustion products.
Fig. 17
Fig. 16a
300 min
Terminal
Assembly
Top View Rear Flue
Property Boundary Line
NOTE: The distance from a fanned draught appliance terminal
installed parallel to a boundary may not be less than 300mm in
accordance with the diagram below
Table. 2
Terminal Position with Minimum Distance (Fig. 17) (mm)
AaDirectly below an opening, air brick, opening
windows, etc. 300
BaAbove an opening, air brick, opening window etc. 300
CaHorizontally to an opening, air brick, opening window etc. 300
D Below gutters, soil pipes or drain pipes. 25
E Below eaves. 25
F Below balconies or car port roof. 25
G From a vertical drain pipe or soil pipe. 25
H From an internal (i) or external (ii) corner. (i) 25 (ii) 115
I Above ground, roof or balcony level. 300
J From a surface or boundary line facing a terminal. 600
K From a terminal facing a terminal (Horizontal flue). 1200
From a terminal facing a terminal (Vertical flue). 600
L From an opening in carport (e.g. door, window)
into the dwelling. 1200
M Vertically from a terminal on the same wall. 1500
N Horizontally from a terminal on the same wall. 300
R From adjacent wall to flue (vertical only). 300
S From an adjacent opening window (vertical only). 1000
T Adjacent to windows or openings on pitched and flat roofs. 600
U Below windows or openings on pitched roofs. 2000
aIn addition, the terminal should be no nearer than 150 mm to an
opening in the building fabric formed for the purpose of accommodating
a built-in element such as a window frame. See BS 5440 Pt. 1.
*
Opening Window
or Door
100mm
MIN.
Fig. 17c
Plume
Displacement Kit
Air Inlet
IMPORTANT: If fitting a Plume
Displacement Flue Kit, the air inlet
must be a minimum of 100mm from
any opening windows or doors (see
Section 9.0).

8.0 Flue Options
20 © Baxi Heating UK Ltd 2007
8.1 Horizontal Flue Systems
Concentric
The maximum equivalent lengths are 4m (horizontal) or
(vertical). Their lengths exclude the standard elbow and
flue/terminal assembly (horizontal) and terminal assembly
(vertical).
Any additional “in line” bends in the flue system must be
taken into consideration. Their equivalent lengths are:
Concentric Pipes: 45° bend 0.5 m
93° bend 1.0 m
NOTE: Flue length is measured from point X to Y as
shown.
X
Y
X
Y
Plume Displacement 70/110 dia Kit
1M Extensions, 45° & 93° bends
are also available - see Section 9.0
NOTE: Horizontal flue pipes should always be installed with a 1.5° fall from the
terminal to allow condensate to run back to the boiler.
Y
X
This bend is equivalent to
0.5 metre
Total equivalent length (upto 4m) =
A+B+2x45°Bends
B
A
This bend is equivalent to
0.5 metre
Horizontal
Flue System Examples