Baxi Combi Instant 80 HE Release note

Baxi Combi Instant 80 HE
Baxi Combi Instant 105 HE
Gas Fired Wall Mounted
Condensing Combination Boiler
Installation & Servicing Instructions
Please leave these instructions with the user
S
the

2
Natural Gas
Baxi Combi Instant 80 HE
G.C. o47 075 17
Baxi Combi Instant 105 HE
G.C. o47 075 19
The boiler meets the requirements of Statutory Instrument “ The
Boiler (Efficiency) Regulations 1993 o3083” 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:
otified Body 0051.
Product/Production certified by:
otified Body 0051.
For GB/IE only.
Baxi 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 designed 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.
Everyone who works at Baxi has a commitment to quality
because we know that satisfied customers mean continued
success.
We hope you get a satisfactory service from Baxi. If not,
please let us know.
Baxi is a BS-E ISO 9001
Accredited Company
This product has an energy rating (B) on a scale of A to G.
For more information see www.boilers.org.uk. This is a certification mark.

3
Legislation 4
1.0 Introduction 5
2.0 General La out 6
3.0 Appliance Operation 7
4.0 Technical Data 9
5.0 Dimensions and Fixings 11
6.0 S stem Details 12
7.0 Site Requirements 15
8.0 Installation 21
9.0 Commissioning the Boiler 26
10.0 Completion 28
11.0 Servicing the Boiler 29
12.0 Changing Components 31
13.0 Illustrated Wiring Diagram 41
14.0 Fault Finding 42
15.0 Short Parts List 49
Section Page
Contents

Legislation
4
Codes of Practice, most recent version should be used
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, or valid ACoP equivalents, is
deemed competent.
In IE, this must be carried out by a competent person as stated in I.S. 813 “Domestic
Gas Installations”.
Lifting - This product should be lifted and handled by two people. Stooping should be
avoided and protective equipment worn where necessary. Carrying & lifting equipment
should be used as required, when installing in a loft space.
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.
“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.
The Log Book must be left with the user.
All CORGI registered installers carry a CORGI identification card and have a
registration number. Both should be recorded in your boiler Log Book. You can check
your installer is registered by telephoning [phone] or writing to:-
1 Elmwood,
Chineham Business Park,
Crockford Lane,
Basingstoke. RG24 8WG
Baxi declare that no substances harmful to health are
contained in the appliance or used during appliance
manufacture.
The appliance is suitable onl for installation in GB and IE and
should be installed in accordance with the rules in force, and
onl used in a suitabl 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 ( orthern 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 s stems must be thoroughl flushed and treated with
inhibitor (see section 6.2).
In GB the following Codes of Practice appl :
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 appl :
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.

1.0 Introduction
5
1.1 Description
1. The Baxi Combi Instant 80 HE or 105 HE is a fully
automatic gas fired wall mounted condensing combination
boiler. It is room sealed and fan assisted, and will serve
central heating and mains fed domestic hot water.
2.The unit incorporates a small storage cylinder built into the
boiler providing hot water the moment the tap is turned on.
3. The boiler is set to give a maximum output (condensing)
of 25.2 kW (Instant 80 HE) or 31.0 kW (Instant 105 HE).
4. It is designed for use on atural Gas (G20) and can be
converted to use Propane.
5. The boiler is suitable for use only on fully pumped sealed
heating systems. Priority is given to domestic hot water.
6. The boiler data badge gives details of the model, serial
number and Gas Council number and is situated on the
control box. It is visible when the case front panel is
removed (Fig. 1).
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. 5111073.
9. All s stems must be thoroughl flushed and treated with
inhibitor (see section 6.2).
1.2 Instant Domestic Hot Water
(Expansion Vessel & Pre-Heat Store)
1. The boiler expansion vessel incorporates a small volume
of stored primary hot water.
2. When the boiler has been off and there is then a demand
for domestic hot water the stored primary hot water
ensures that domestic hot water is supplied instantly at
temperature.
3. The stored hot water is part of the primary circuit. This is
not supplied as domestic hot water, which is fresh mains
water heated by a heat exchanger within the boiler.
4. The stored primary hot water temperature is maintained
whilst the boiler is in operation. During a period when there
is no demand for heating or hot water the temperature of
the stored primary hot water will eventually fall. The boiler
will operate occasionally in order to maintain the
temperature. This is indicated by the domestic hot water
mode neon flashing.
1.3 Optional Extras
Various flue extensions, bends, vertical flue kits,control
accessories etc. are available as optional extras. These are
detailed in a separate publication.
Data Badge
Fig. 1
Control Box
Case Front Panel

2.0 General La out
6
2.1 La out
1. Air Pressure Switch
2. Expansion Vessel & Pre-Heat Store
3. Burner Manifold
4. Automatic Air Vent
5. DHW Plate Heat Exchanger
6. Circulation Pump
7. Drain Off Point
8. Pressure Relief Valve
9. Position for Optional Integral Timer
10. Central Heating System Pressure Gauge
11. PCB
12. Control Box
13. 3-Way Valve Assembly
14. Condensate Trap
15. Flame Sensing Electrode
16. Spark Electrode
17. Burner
18. Primary Heat Exchanger
19. Fan Assembly
20. Secondary Heat Exchanger
21. On/Off/Reset Selector Switch
22. Central Heating Temperature Control
23. Domestic Hot Water Pre-Heat Control
24. Flame Failure or Blocked Condensate Drain
25. Safety Thermostat Activated (Boiler or Flue)
26. Fault on Fan or Flue
27. Fault on Pump or Low System Pressure
28. Fault on Hot Water Sensor
29. Fault on Central Heating Sensor
30. Power On
31. Domestic Hot Water Mode
32. Central Heating Mode
33. Burner On
When neons 24 to 29 are constantly illuminated, they
indicate the temperature of the central heating water.
19
18
17
14
15
16
13
12 11
10
9
21 22 23 10 9
7
6
3
4
5
8
2
1
30o40o50o60o70o80o
2
1
0
4
3
bar
Reset
OFF
ON
PREHEAT
30o40o50o60o70o80o
24 25 26 27 28 29
30 31 32 33
20

3.0 Appliance Operation
7
NOTE: All dela timers mentioned in 3.1 and 3.3 are
overridden b domestic hot water demand.
3.1 Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates water
through the primary circuit. At a pre-determined flow
rate the central heating flow switch operates, initiating
the ignition sequence.
2. The main burner ignites at low rate, then the gas valve
controls the gas rate to maintain the heating temperature
measured by the temperature sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the burner
relights automatically (anti-cycling). The pump continues
to run during this period.
4. When the demand is satisfied the burner is
extinguished and the pump continues to run for a period
of 30 minutes (Pump Overrun).
5. If there is no other demand the pre-heat function will
operate if switched on (see Section 3.2).
3.2 Domestic Hot Water - Preheat Mode
(Fig. 3)
1. With the pre-heat function switched on (pre-heat
control fully clockwise), priority is given to the
replenishment of the pre-heat store. The DHW mode
neon ( ) will flash during this function.
2. The diverter valve remains in the DHW priority
position. This allows the pump to circulate hot water to
the store and back to the primary heat exchanger via the
bypass pipe.
3. The automatic ignition sequence commences after
approximately 25 seconds and the burner will light.
4. When the store reaches the desired temperature the
burner is extinguished. The pump continues to run for a
period of 30 seconds.
5. Following a demand for domestic hot water or the
end of a central heating O period, the pre-heat
function restarts.
27 19
16 15 14 13 12
10
9
11
8
17
21
23
20 22
19
28
26
56
7
2
34
1
25
24
18
1 Primary Heat Exchanger
2 Burner
3 Ignition Electrode
4 Flame Sensing Electrode
5 Gas Valve
6 Pump
7 Automatic Air Vent
8 Plate Heat Exchanger
9 Flow Sensor with Filter
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Hydraulic Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel & Pre-Heat Store
27 Domestic Hot Water Temperature Sensor
28 Secondary Heat Exchanger
Ke
Central Heating Mode
Fig. 2
27 19
16 15 14 13 12
10
9
11
8
17
21
23
20 22
19
26
56
7
2
34
1
25
24
18
28
Domestic Hot Water - Preheat Mode
Fig. 3

3.0 Appliance Operation
8
3.3 Domestic Hot Water Mode (Fig. 4)
1. Priority is given to the domestic hot water supply. A
demand at a tap or shower will override any central
heating requirement.
2. The flow of water will operate the DHW flow switch
which requests the 3 way valve to change position. This
will allow the pump to circulate the primary water
through the DHW plate heat exchanger and take the
stored water to give instant hot water.
3. The burner will light automatically and the
temperature of the domestic hot water is controlled by
the temperature sensor.
4. When the domestic hot water demand ceases the
burner will extinguish and the diverter valve will remain
in the domestic hot water mode, unless there is a
demand for central heating.
5. If there is no other demand the pre-heat function will
operate if switched on (see Section 3.2)
IMPORTANT: When the selector switch is in the
‘0’ (Off) position the electrical suppl to the boiler
is isolated. The boiler will not operate and the
integral timer (if fitted) will require resetting once
the selector switch is set to either Position (i) or
Position (ii).
3.4 Frost Protection Mode
1. The frost protection mode is integral to the appliance
and functions only with the selector switch (see Section
2.1) in the domestic hot water and central heating
position. If the system temperature falls below 5° C then
the boiler will fire on its minimum setting until a flow
temperature of 30° C is reached. Further protection can
be incorporated by using a system frost thermostat.
3.5 Pump Protection
1. With the selector switch (see Section 2.1) in either the
central heating or central heating and hot water position
the pump will automatically operate for 1 minute in
every 24 hours to prevent sticking.
27 19
16 15 14 13 12
10
9
11
8
17
21
23
20 22
19
26
56
2
34
1
25
24
18
7
28
1 Primary Heat Exchanger
2 Burner
3 Ignition Electrode
4 Flame Sensing Electrode
5 Gas Valve
6 Pump
7 Automatic Air Vent
8 Plate Heat Exchanger
9 Flow Sensor with Filter
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Hydraulic Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Safety Thermostat
25 Central Heating Temperature Sensor
26 Expansion Vessel & Pre-Heat Store
27 Domestic Hot Water Temperature Sensor
28 Secondary Heat Exchanger
Ke
Fig. 4
Domestic Hot Water Mode

4.0 Technical Data
9
4.1 Combi Instant 80 HE
Temperatures
C.H. Flow Temp (adjustable)
35°C to 85°C max (± 5°C)
D.H.W. Flow Temp
35°C to 65°C max (± 5°C)
dependent upon flow rate
50°C Pre-heat OFF
65°C Pre-heat O ± 5°C
dependent upon flow rate
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 have been certified by 0051.
SEDBUK Declaration For Combi Instant 80 HE
The seasonal efficienc (SEDBUK) is 87.3% (89.3% LPG)
Band B
0
200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Metre (wg)
Flow Rate (l/h)
Pump - Available Head
0
5
4.5
Heat Input CH
Max Min
kW 24.8 10.6
Heat Output CH (Non-Condensing)
Max Min
kW 24 9.8
Electrical Suppl 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption 170W
External Fuse Rating 3A
Internal Fuse Rating
Fuse 2A Fast Blow to BS 4265
Appliance Categor CAT II 2H 3P
Inlet Pressure ( atural Gas - G20)
mbar 20
Burner Injector ( atural Gas - G20)
15 x 1.18mm Diameter
Burner Pressure ( atural Gas - G20)
Max Rate Min Rate
mbar 10.2 ± 0.5 2 ± 0.2
Appliance T pe C12 C32
Heat Output CH (Condensing)
Max Min
kW 25.2 10.1
Heat Input DHW
Max
kW 24.8
Heat Output DHW
Max
kW 24
Flue Terminal Diameter 100mm
Dimensions Projection 125mm
Outercase Dimensions
Casing Height - 780mm
Overall Height Inc Flue
Elbow - 965mm
Casing Width - 450mm
Casing Depth - 345mm
Clearances
Above Casing 200 mm Min
Below Casing 200 mm Min
Front 450 mm Min (For Servicing)
Front 5 mm Min (In Operation)
L.H. Side 5 mm Min
R.H. Side 5 mm Min (In Operation)
20 mm Min (See ote*)
*NOTE: The boiler can be operated with a
clearance of 5mm at the right. This is also sufficient
for routine maintenance. However a clearance of
20mm is required if it is necessary to remove the
secondary heat exchanger. This should be
considered when siting the appliance and in the
event of any subsequent alterations in the area of
installation
Weights kg
Packaged Boiler Carton 56
Installation Lift Weight 44
Connections copper tails
Gas Supply - 22mm
Central Heating Flow - 22mm
Central Heating Return - 22mm
Cold Water Mains Inlet - 15mm
DHW Flow - 15mm
Pressure Relief Discharge - 15mm
NOxClass 3
Electrical Protection IPX5D
Condensate Drain 1” BSP
LPG Propane - G31
Burner Injector 15 x 0.77mm diameter
Burner Pressure
Propane mbar
Inlet Pressures
mbar
Max Rate
21.8 ± 0.5
Min Rate
4.4 ± 0.2
37
Central Heating Primar Circuit
Pressures
bar
Safety Discharge 3
Max Operating 2.5
Min Operating 0.5
Recommend Operating 1-2
DHW Circuit bar
Pressures
Max Operating 8
Min Operating 0.2
Min Operating Pressure
at 13.2 l/min 0.96
Flow Rates l/min
DHW Flow Rate
@ 30°C Rise 11.5
DHW Flow Rate
@ 35°C Rise 9.8
Min Working
DHW Flow Rate 2.5
Pump
Available Head See graph below
Expansion Vessel - (For Central Heating only.
Integral with appliance)
bar
Min Pre-charge Pressure 0.5
litre
Max Capacity of
CH System 80
Primary Water Content 3.0
of Boiler (unpressurised)
Max Gas Rate ( atural Gas - G20)
(After 10 mins)
m3/h 2.62

4.0 Technical Data
10
4.2 Combi Instant 105 HE
Temperatures
C.H. Flow Temp (adjustable)
35°C to 85°C max (± 5°C)
D.H.W. Flow Temp
35°C to 65°C max (± 5°C)
dependent upon flow rate
50°C Pre-heat OFF
65°C Pre-heat O ± 5°C
dependent upon flow rate
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 have been certified by 0051.
SEDBUK Declaration For Combi Instant 105 HE
The seasonal efficienc (SEDBUK) is 87.3% (89.4% LPG)
Band B
0
200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Metre (wg)
Flow Rate (l/h)
Pump - Available Head
0
5
4.5
Heat Input CH
Max Min
kW 30.5 11.9
Heat Output CH (Non-Condensing)
Max Min
kW 29.6 11
Electrical Suppl 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption 180W
External Fuse Rating 3A
Internal Fuse Rating
Fuse 2A Fast Blow to BS 4265
Appliance Categor CAT II 2H 3P
Inlet Pressure ( atural Gas - G20)
mbar 20
Burner Injector ( atural Gas - G20)
15 x 1.25mm Diameter
Burner Pressure ( atural Gas - G20)
Max Rate Min Rate
mbar 12.1 ± 0.5 2.1 ± 0.2
Appliance T pe C12 C32
Heat Output CH (Condensing)
Max Min
kW 31 11.3
Heat Input DHW
Max
kW 30.5
Heat Output DHW
Max
kW 29.6
Flue Terminal Diameter 100mm
Dimensions Projection 125mm
Outercase Dimensions
Casing Height - 780mm
Overall Height Inc Flue
Elbow - 965mm
Casing Width - 450mm
Casing Depth - 345mm
Clearances
Above Casing 200 mm Min
Below Casing 200 mm Min
Front 450 mm Min (For Servicing)
Front 5 mm Min (In Operation)
L.H. Side 5 mm Min
R.H. Side 5 mm Min (In Operation)
20 mm Min (See ote*)
*NOTE: The boiler can be operated with a
clearance of 5mm at the right. This is also sufficient
for routine maintenance. However a clearance of
20mm is required if it is necessary to remove the
secondary heat exchanger. This should be
considered when siting the appliance and in the
event of any subsequent alterations in the area of
installation
Weights kg
Packaged Boiler Carton 57.5
Installation Lift Weight 47
Connections copper tails
Gas Supply - 22mm
Central Heating Flow - 22mm
Central Heating Return - 22mm
Cold Water Mains Inlet - 15mm
DHW Flow - 15mm
Pressure Relief Discharge - 15mm
NOxClass 3
Electrical Protection IPX5D
Condensate Drain 1” BSP
LPG Propane - G31
Burner Injector 15 x 0.77mm diameter
Burner Pressure
Propane mbar
Inlet Pressures
mbar
Max Rate
32.3 ± 0.5
Min Rate
5.2 ± 0.2
37
Central Heating Primar Circuit
Pressures
bar
Safety Discharge 3
Max Operating 2.5
Min Operating 0.5
Recommend Operating 1-2
DHW Circuit bar
Pressures
Max Operating 8
Min Operating 0.2
Min Operating Pressure
at 13.2 l/min 0.96
Flow Rates l/min
DHW Flow Rate
@ 30°C Rise 14.1
DHW Flow Rate
@ 35°C Rise 12.1
Min Working
DHW Flow Rate 2.5
Pump
Available Head See graph below
Expansion Vessel - (For Central Heating only.
Integral with appliance)
bar
Min Pre-charge Pressure 0.5
litre
Max Capacity of
CH System 80
Primary Water Content 3.2
of Boiler (unpressurised)
Max Gas Rate ( atural Gas - G20)
(After 10 mins)
m3/h 3.22

5.0 Dimensions and Fixings
11
Dimensions
A780mm
B345mm
C450mm
D116mm Ø Min.
E185mm
F190mm
G131mm
Domestic Hot
Water Outlet
(15mm)
ColdWater
Inlet
(15mm)
Heating
Return
(22mm)
Heating
Flow
(22mm)
Pressure Relief
Valve
(15mm)
Gas
Inlet
(22mm)
65 mm 65 mm 65 mm 65 mm 65 mm
Tap Rail
360° Orientation
Tube Ø 100mm
DC
B
A
E
G
F
3o
28mm
Condensate
Drain

6.0 S stem Details
12
6.1 Information
1. The Baxi Combi Instant 80 HE and 105 HE Condensing
Combination Boilers are ‘Water Byelaws Scheme - Approved
Products’.
To comply with the Water Byelaws your attention is drawn
to the following installation requirements and notes (IR ).
a) IR 001 - See text of entry for installation
requirements and notes.
b) IR 116 - Byelaw 90 and 91.
c) IR 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 IR s.
6.2 Central Heating Circuit
1. The appliance is suitable for fully pumped SEALED
SYSTEMS O LY.
Treatment of Water Circulating S stems
• 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 upgrading existing systems that exhibit evidence
of sludging, it is advisable to clean the system prior to
treatment in order to remove any sludge and reduce
the likelihood of these deposits damaging new
components.
• 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. The recommended flushing and cleansing agents
are Betz-Dearborn Sentinel X300 or X400 and Fernox
Superfloc Universal Cleanser which 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. The only system
additives recommended are 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 s stem will
invalidate the appliance warrant .
• 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.
6.3 B pass
1. The boiler is fitted with an automatic integral bypass.
6.4 S stem 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 room thermostat,
is recommended.

6.0 S stem Details
13
6.5 S stem Filling and Pressurising
1. 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.
2. There are connection points on the mains cold water
inlet and central heating return isolating taps (Fig. 6) to
which the optional filling loop kit (Part o. 248221) can
be assembled.
3. The filling method adopted must be in accordance
with all relevant water supply regulations and use
approved equipment.
4. Your attention is drawn to: for GB: Guidance G24.2
and recommendation R24.2 of Water Regulations
Guide. for IE: the current edition of I.S. 813 “Domestic
Gas Installations”.
5. The sealed primary circuits may be filled or
replenished by means of a temporary connection
between the 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.
6.6 Expansion Vessel
(Central Heating only)
1. The appliance expansion vessel is pre-charged to 0.5
bar. Therefore, the minimum cold fill pressure is 0.5 bar.
The vessel is suitable for correct operation for system
capacities up to 80 litres. For greater system capacities
an additional expansion vessel must be fitted. For GB
refer to BS 7074 Pt 1. For IE, the current edition of
I.S. 813 “Domestic Gas Installations”.
6.7 Pressure Relief Valve (Fig. 7)
1. The pressure relief valve is set at 3 bar, therefore all
pipework, fittings, etc. should be suitable for pressures in
excess of 3 bar.
2. The pressure relief discharge pipe should be not less
than 15mm dia, run continuously downward, and
discharge outside the building, preferably over a drain. It
should be routed in such a manner that no hazard
occurs to occupants or causes damage to wiring or
electrical components. The end of the pipe should
terminate facing down and towards the wall.
3. The discharge must not be above a window, entrance
or other public access. Consideration must be given to
the possibility that boiling water/steam could discharge
from the pipe.
Fig. 7
Stop
Valve
Double
Check
Valve
DHW
Mains
Inlet
CH
Return
Temporary
Hose
Pressure Relief Valve
Filling Loop
Discharge Pipe
Fig. 5
Fig. 6
Stop
Valve

6.0 S stem Details
14
6.8 Domestic Hot Water Circuit (Fig. 8)
1. All DHW circuits, connections, fittings, etc. should be
fully in accordance with relevant standards, the water
supply regulations.
2. Your attention is drawn to: for GB: Guidance G17 to
G24 and recommendation R17 to R24 of the Water
Regulations Guide. for IE: the current edition of I.S. 813
“Domestic Gas Installations”.
3. A single check valve must be fitted as shown in Fig. 8
to prevent backflow to the supply pipe and to ensure
the efficient operation of the expansion vessel which is
required to accommodate the thermal expansion of the
water.
4. When the domestic water system includes any device
which prevents water expanding back towards the
supply (check valve, loose jumpered stopcock, water
meter, water treatment device), then an expansion
vessel must be fitted (e.g. Zilmet 160ml, R1/215bar).
5. If the hot water expansion is not provided for, then
high pressures can develop which may result in damage
to fittings and devices on the system.
5. The boiler’s maximum working mains pressure is 8
bar, therefore all pipework, connections, fittings, etc.
should be suitable for pressures in excess of 8 bar. A
pressure reducing valve must be fitted for pressures in
excess of 8 bar. The manufacturer of any outlet fittings,
such as a shower valve, may require a lower maximum
pressure. The pressure reduction must take account of
all fittings connected to the DHW system.
6.9 Showers
1. If a shower control is supplied from the appliance it
should be of the thermostatic or pressure balanced type.
Thermostatic type shower valves provide the best
comfort and guard against water at too high a
temperature. Existing controls may not be suitable -
refer to the shower valve manufacturer.
6.10 Hard Water Areas
1. If the area of the installation is recognised as a HARD
WATER AREA then a suitable device should be fitted to
treat the mains water supply to the boiler. Contact your
Water Distribution Company for advice on suitable
devices.
Boiler
Other Tap
Outlets
Expansion
Vessel
To Hot
Taps
Check
Valve
Pressure Reducer
Valve
Stop Tap
Fig. 8

7.0 Site Requirements
15
7.1 Location
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 7.3).
2. If the boiler is sited in an unheated enclosure then it is
recommended to leave the O /OFF Selector Switch in
the domestic hot water and central heating position to
give frost protection.
3. If the boiler is fitted in a room containing a bath or
shower 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. 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 Clearances (Figs. 9 & 10)
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.
* NOTE: The boiler can be operated with a
clearance of 5mm at the right. This is also
sufficient for routine maintenance. However a
clearance of 20mm is required if it is necessar to
remove the secondar heat exchanger. This
should be considered when siting the appliance
and in the event of an subsequent alteration in
the area of installation.
200mm Min
780mm
450mm
200mm Min
20mm/5mm Min
see * OTE:
5mm Min
5mm Min
450mm Min
For Servicing
Purposes
Fig. 9
Fig. 10
In Operation

7.0 Site Requirements
16
7.3 Ventilation of Compartments
1. Where the appliance is installed in a cupboard or
compartment, no air vents are required as the appliance
will run sufficiently cool without ventilation.
7.4 Gas Suppl
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 22mm copper tail
located at the rear of the gas service cock (Fig. 11).
3. Ensure that the pipework from the meter to the
appliance is of adequate size. Do not use pipes of a
smaller diameter than the boiler gas connection
(22mm).
7.5 Electrical Suppl
1. External wiring must be correctly earthed, polarised
and in accordance with the 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 the
ETCI rules.
2. The mains supply is 230V ~ 50Hzfused at 3A.
NOTE: The method of connection to the electricit
suppl must facilitate complete electrical isolation of
the appliance.
Connection ma be via a fused double-pole isolator
with a contact separation of at least 3mm in all
poles and servicing the boiler and s stem controls
onl .
Fig. 11
Gas Service Cock

7.0 Site Requirement
17
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 an
point along its length. There MUST be a fall of AT LEAST
2.5° (50mm per metre) along the entire run.
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 OT 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. An pipe fitted externall must not exceed 3 metres.
7. An condensate discharge pipework external to the
building (or in an unheated part of it e.g. garage) must be
insulated to protect against frost. It is also recommended
that the pipe diameter is increased to 32mm.
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
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
External termination to a drain or gull
Boiler
500mm min
2.5° Minimum fall
External termination to a purpose made soak-awa
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
18
7.7 Flue
NOTE: Due to the nature 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 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. If a terminal is less than 2 metres above a balcony,
above ground or above a flat roof to which people have
access, then a suitable terminal guard must be provided.
Terminal Position with Minimum Distance (Fig. 12) (mm)
A*Directly below an openable window, air vent or any other
ventilation opening. 300
B Below gutter, drain/soil pipe. 25
C Below eaves. 25
D Below a balcony/car port roof. 25
E From vertical drain pipes and soil pipes. 25
F From internal or external corners. 25
G Above adjacent ground or balcony level. 300
H From a surface facing a terminal. 600
I Facing a terminals. 1200
J From opening (door/window) in carport into dwelling. 1200
K Vertically from a terminal on the same wall. 1500
L Horizontally from a terminal on the same wall. 300
M*Above an opening, air brick, opening window etc. 300
*Horizontally to an opening, air brick, opening window etc. 300
* In addition, the terminal should be no nearer than 150mm 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.
L
G
G
E
J
D
K
G
AAD
F
H,I
B,C
F
Likely flue positions requiring
a flue terminal guard
M
Fig. 12
300 min
Terminal
Assembly
TopView Rear Flue
Property Boundary Line
Fig. 13

7.0 Site Requirements
19
7.8 Flue Dimensions
The standard horizontal flue kit allows for flue lengths
between 100mm and 685mm from elbow to terminal
(Fig. 14).
The maximum permissible equivalent flue length is:
Instant 80 HE 4 metres
Instant 105 HE 3 metres
NOTE: Each additional 45° of flue bend will
account for an equivalent flue length of 0.5m.
eg. 45° = 0.5m, 90° = 2 x 45° = 1m etc.
7.9 Flue Trim
1. The rubber flue trim supplied may be fitted to either
the outside wall or on the inner wall of installation.
7.10 Terminal Guard (Fig. 15)
1. When codes of practice dictate the use of terminal
guards, they can be obtained from most Plumbers’ and
Builders’ Merchants.
2. There must be a clearance of at least 50mm between
any part of the terminal and the guard.
3. When ordering a terminal guard, quote the appliance
name and model number.
3. The flue terminal guard should be positioned
centrally over the terminal and fixed as illustrated.
Fig. 14
Fig. 15
100mm 685mm

20
7.0 Site Requirements
7.11 Flue Options
1. The Baxi Combi Instant 80 HE and 105 HE can be
fitted with flue systems as illustrated.
2. The standard flue is suitable only for horizontal
applications.
3. Maximum permissible equivalent flue lengths are:-
Instant Instant
80 HE 105 HE
Concentric 4m 3m
Vertical 4m 3m
Vertical Two-Pipe 12m 12m
4. Any additional “in line” bends in the flue system must
be taken into consideration. Their equivalent lengths
are:-
Concentric Pipes:
45° bend 0.5 metres
93° bend 1.0 metres
Twin Flue Pipe
45° bend 0.25 metres
91.5° bend 0.50 metres
The elbow supplied with the standard horizontal flue is
not included in any equivalent length calculations
5. The illustrations opposite show examples of
maximum equivalent lengths.
6. Full details of part numbers and descriptions of all
optional flue components and kits can be found in the
Baxi Flue Guide.
7. Instructions for guidance and fitting are included in
each kit where appropriate.
Horizontal
Flues
Vertical
Flues
Vertical
Flues
(Twin Pipe)