Baxi Maxflow Combi WM User guide

Baxi Maxflow Combi WM Please leave these instructions with
the user
Gas fired Wall Mounted Combination Boiler
with Unvented Hot Water storage
Comp No247308 - Iss 3 – 6/00
Installation and
Servicing Instructions

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Page 2
Baxi Maxflow Combi WM
G.C. No47 075 03
Baxi Limited is one of the leading
manufacturers of domestic heating products in
the UK.
Our first priority is to give a high quality service
to our customers. Quality is built into every
Baxi product -products which fulfil the
demands and needs of customers, offering
choice, efficiency and reliability.
To keep ahead of changing trends, we have
made a commitment to develop new ideas
using the latest technology - with the aim of
continuing to make the products that
customers want to buy.
Baxi is also the largest manufacturing
partnership in the country. Everyone who
works at the company has a commitment to
quality because, as shareholders, we know
that satisfied customers mean continued
success.
We hope you get a satisfactory service from
Baxi. If not, please let us know.
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 0051.
Product/Production certified by:
Notified Body 0051.
For GB/IE only.
Baxi is a BS-EN ISO 9001
Accredited Company

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Contents - Page 3
Section
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
Introduction
General Layout
Appliance Operation
Technical Data
Dimensions and Fixings
System Details
Site Requirements
Installation
Commissioning the Boiler
Servicing the Boiler
Changing Components
Illustrated Wiring Diagram
Fault Finding
Short Parts List
Page
4
5
6
7
8
9
13
18
23
25
27
36
38
42

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1.0 Introduction – Page 4
NOTE: 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.
Baxi UK Limited declare that no substances harmful to
health are contained in the appliance or used during
appliance manufacture.
1.1 Description
1. The Baxi Maxflow Combi WM is a fully automatic gas
fired wall mounted combination boiler incorporating a 54
litre unvented hot water storage cylinder. It is room sealed
and fan assisted.
2. The boiler is designed for use with a fully pumped,
sealed and pressurised system and provides central
heating and hot water at mains pressure. It incorporates a
pump, diverter valve, pressure relief valve, expansion
vessel and pressure gauge.
3. As supplied the boiler will automatically modulate to
provide a central heating output between 10.4kW and 28.0
kW. The maximum output to central heating can be
adjusted between 10.4 kW and 28.0 kW (see Section 9.2).
The maximum output available for domestic hot water is
28.0 kW.
4. The boiler has been approved to the Building
Regulations for unvented hot water storage systems and
the Local Authority must be informed of the intention to
install.
IMPORTANT: The installation of unvented hot water
storage systems and their components must only be
carried out by suitably qualified personnel.
Consideration should be given to Building Regulations
document G3.
5. The components supplied in the box marked ‘Unvented
Kit” MUST be fitted to the mains water supply in
accordance with the instructions included.
6. It is designed for use on Natural Gas (G20) and can be
converted to use Propane or Butane.
7. A label giving details of the model, serial number and
Gas Council number is situated on the rear of the facia
panel (Fig. 1).
8. The boiler data badge is positioned inside the left hand
outercase panel (Fig. 2).
9. The boiler is intended to be installed in residential /
commercial / light industrial E.M.C. environments on a
governed meter supply only.
10. The boiler must be installed with one of the purpose
designed flues such as the standard horizontal flue kit.
11. All systems must be thoroughly flushed and
treated with Inhibitor (see section 6.2).
“Benchmark” Log Book
As part of the industry-wide “Benchmark” initiative all Baxi
boilers now include an Installation, Commissioning and
Service Record Log Book. Please read the Log Book
carefully and complete all sections relevant to the appliance
and installation. These include sections on the type of
controls employed, flushing the system, burner operating
pressure etc. The details of the Log Book will be required in
the event of any warranty work. Also, there is a section to
be completed at each subsequent regular service visit.
1.2 Installation
1. The appliance is suitable for installation only in G.B.
and I.E. and should be installed in accordance with the
rules in force. For Ireland install in accordance with l.S.813
“Installation of Gas Appliances”. The installation must be
carried out by a CORGI Registered Installer or other
competent person and be in accordance with the relevant
requirements of current Gas Safety (Installation and Use)
Regulations, the Building Regulations (Scotland)
(Consolidation), the Local Building Regulations, the
Current I.E.E. Wiring Regulations and the bye laws of the
Local Water Undertaking. Where no specific instructions
are given, reference should be made to the relevant
BRITISH STANDARD CODES OF PRACTICE.

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2.0 General Layout – Page 5
2.1 Layout
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Fan Assembly
Sensing Electrode
Pressure Relief Valve
Automatic Air Vent
Circulation Pump
Gas Valve Assembly
Facia and Control Panel
Optional Integral Timer
Pressure Gauge
Electrical Box
Motorised Valve
Burner
Spark Electrodes
Heat Exchanger
Expansion Vessel
Air Pressure Switch
Cylinder Safety Valve
Hot Water Storage Cylinder
Central Heating Temperature Control
Domestic Hot Water Temperature Control
ON/OFF Selector Switch
Indicator Neons
Reset Button
Flame Failure Reset Button
Pressure Gauge
2.2 Optional Extras
KIT PART No
HORIZONTAL FLUE KITS
1M Flue Extension (use two kits for 2M etc.) 247723
0.5 M Flue Extension 247724
Flue Bend - 45º (Reduce overall length of flue 247725
by 0 5m when fitting this bend)
Flue Bend . 90º(Reduce overall length of flue 247726
by 1 m when fitting this bend)
Wall Liner/Internal Fixing 236441
VERTICAL FLUE KITS
See the Boiler Installers Guide
CONTROL ACCESSORIES
Programmable Room Thermostat (24 hour) 236254
Programmable Room Thermostat (7 day) 238326
Integral Electronic Timer Kit (7 day) 247207
Integral Electro-Mechanical Timer Kit 247206
(12 hour am/pm)
FUEL KIT
LPG Conversion. Propane / Butane 247372

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3.0 Appliance Operation – Page 6
Main Heat Exchanger 14 Heating Flow
Automatic Air Vent 15 Heating Return
Burner 16 Cold Water Inlet
Ignition Electrodes 17 Domestic Hot Water Outlet
Flame Sensing Electrode 18 Flow Restrictor
Differential Pressure Switch 19 Hot Water Storage Temperature
Sensor
Gas Valve 20 Temperature/Pressure Relief Valve
Primary Flow Temperature Sensor 21 Storage Cylinder
3-Way Diverter Valve 22 Secondary Heat Exchanger
0 Pump 23 Central Heating Expansion Vessel
1 By-Pass 24 Safety Unit Thermostat
2 Pressure Gauge 25 Central Heating Pressure Relief Valve
3 Gas Inlet
1.3 Boiler Operation
1. The boiler operating mode is controlled by the selector
switch on the control panel. When set to it will operate
in the Domestic Hot Water and Central Heating modes.
For Domestic Hot Water only the selector switch should be
set to .
2. Domestic hot water supply always takes priority over
central heating. If a demand for hot water is required
during a central heating period, the boiler will automatically
switch to hot water mode until the demand is satisfied i.e.
storage water has reached the set temperature.
Interruption to the central heating only occurs when there
is a demand for hot water and should not be apparent to
the User.
3. Central Heating Mode (Fig. 4)
If there is a call for central heating the diverter valve
operates and the pump circulates the primary heating
water, operating the differential pressure switch. The fan
will run at full speed; once the air pressure switch has
been proved the burner will light. The burner output then
automatically adjusts to suit the system demand; as the
temperature of the heating water in the boiler approaches
that set by the adjustable central heating control knob the
burner output is reduced. When this set temperature is
reached, the burner extinguishes and the fan stops. The
pump continues to run for 3 minutes to prevent residual
heat build up in the boiler. The burner will not re-light for 3
minutes unless there is a demand for domestic hot water
during this period.
4. Domestic Hot Water Mode (Fig. 5)
When there is a demand for hot water (temperature of
stored hot water is below that set by the thermostat), the
pump will start to circulate the primary heating water,
operating the differential pressure switch. The fan will run
at full speed; once the air pressure switch has been proved
the burner will light. The burner output then automatically
adjusts to suit the demand required to raise the
temperature of the domestic hot water within the store to
the temperature set by the adjustable domestic hot water
control knob. When this temperature is reached the burner
extinguishes and the fan stops. The pump continues to run
for 3 minutes to prevent residual heat build up in the boiler.
When the hot water demand has been satisfied, the 3-way
diverter valve operates to divert the primary heating water
to the central heating, if the selector is set to and
there is a C.H. demand.
3.2 Frost Protection Mode
1. The frost protection feature will operate when the
selector switch is in the central heating and domestic hot
water mode.
The gas and electrical supplies to the boiler must be on
and the system pressure between 0.5 and 2.5 bar.
2. If the system temperature falls below 5º C, then the
boiler will fire until the water temperature has been raised.
3. Further frost protection can be incorporated by using a
frost thermostat to protect the whole system.
3.3 Pump Protection
1. With the selector switch in either operating position the
pump will automatically operate for 1 minute in every 24
hours to prevent sticking.

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4.0 Technical Data – Page 7

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5.0 Dimensions and Fixings – Page 8

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6.0 System Details – Page 9
6.1 Information
1. The Baxi Maxflow Combi WM Combination Boiler is a
‘Water Byelaws Scheme - Approved Product’.
To comply with the Water Byelaws your attention is drawn
to the following installation requirements and notes (IRN).
a) IRN 001--See text of entry for installation
requirements and notes.
b) IRN 116 - Byelaw 90 and 91.
c) IRN 302 - Byelaw 14.
2. Reference to the WRc publications, Water fittings and
materials directory’ and ‘Water supply byelaws guide’ give
full details of byelaws and the IRNs.
6.2 Central Heating Circuit
1. The appliance is suitable for fully pumped SEALED
SYSTEMS ONLY.
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.
•For optimum performance after installation this boiler
and its associated central heating system must be
flushed in accordance with the guidelines given in BS
7593 “Treatment of water in domestic hot water central
heating systems”.
•This must involve the use of a proprietary cleanser,
such as BetzDearborn Sentinel X300 or X400, or
Fernox Superfloc. Full instructions are supplied with
the products, but for immediate information please
contact BetzDearborn (0151 420 9563) or Fernox
(01799 550 811) directly.
•For long term protection against corrosion and scale,
after flushing it is recommended that an inhibitor such
as BetzDearborn Sentinel X100, or Fernox MB-1 or
Copal is dosed in accordance with the guidelines
given in BS 7593.
Failure to flush and add inhibitor to the system
may 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 the Baxi Helpline.

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6.0 System Details – Page 10
6.3 Bypass
1. The boiler has an integral bypass and in most cases
this should suffice. However in certain circumstances, e.g.
on systems where there is a high resistance and TRV’s are
fitted to all the radiators it may be necessary to fit an
external by-pass. For example, a 15mm pipe between the
flow and return controlled by a valve, or an uncontrolled
radiator.
6.4 System Control
1. The boiler is designed for use in a heating system that
incorporates external controls, i.e. a minimum of a timer
device.
2. Suitable timer kits are available as optional extras.
3. For optimum operating conditions and maximum
economy the fitting of a programmable thermostat, such as
one of the Baxi Maxflow Combi WM Controllers, is
recommended.