Worcester Highflow 400 BF User guide

Highflow 400
BF
FLOOR STANDING COMBINATION APPLIANCE FOR CENTRAL
HEATING AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
BOILER OUTPUT
To Hot Water On/Off Control
Maximum 24.0 kW (82,000 Btu/h)
To Central Heating On/Off Control. Range Rated
Minimum 8.8 kW (30,000 Btu/h)
Maximum 24.0 kW (82,000 Btu/h)
IMPORTANT: THIS APPLIANCE IS FOR USE WITH NATURAL GAS ONLY
THESE INSTRUCTIONS APPLY IN THE UK ONLY
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER
This appliance must be installed by a competent person in accordance
with the Gas Safety (Installation and Use) Regulations 1998
Bosch Group
GC NUMBER 47 311 19

1.1 Gas Safety (Installation and Use) Regulations 1994 as
Amended in 1996: All gas appliances must be installed by a
competent person in accordance with the above regulations.
Failure to install appliances correctly could lead to prosecution.
1.2 The manufacturers notes must not be taken, in any way, as
overriding statutory obligations.
1.3 The compliance with a British Standard does not, of itself,
confer immunity from legal obligations. In particular the
installation of this appliance must be in accordance with the
relevant requirements of the following: Gas Safety (Installation
and Use) Regulations 1994 (as Amended in 1996), current IEE
Wiring Regulations, local Building Regulations, Building
Standards (Scotland) (Consolidation), byelaws of the local Water
Company and Health and Safety Document No. 635 (Electricity
at Work Regulations 1989). The British Gas Material and
Installation Specification for central heating and hot water. It
should be in accordance with the relevant recommendations of
the following British Standards:
BS 6798:1987 Specification for Installation of gas fired hot water
boilers of rated input not exceeding 60 kW
BS 5449:1990 Central Heating for Domestic Premises
BS 5546:1990 Installation of gas hot water supplies for domestic
purposes.
BS 5440:1:1990 Flues and Ventilation for gas appliances of rated
input not exceeding 60kW: Flues.
BS 5440:2:1989 Flues and ventilation for gas appliances of rated
input not exceeding 60kW: Air Supply.
BS 6891:1988 Installation of low pressure gas pipework
installations up to 28mm (R1)
1.4 To ensure that the installation will perform to the highest
standards, the system and components should conform to any
other relevant British Standards in addition to those mentioned
in the instructions.
1.5 The appliance complies with the Essential Requirements of
the Gas Appliance Directive and other Directives currently
applicable.
1.6 This appliance contains no asbestos products. There is no
potential hazard due to the appliance being electrically unsafe.
There are no substances used that are a potential hazard in
relation to the COSHH Regulations 1988.
2.1 This appliance is not suitable for external installation.
2.2 The appliance controls are set to provide a maximum
output of 24 kW for the hot water and a central heating load of
up to 24 kW.
2.3 A permanent pilot is used to provide ignition.
2.4 PRINCIPLE APPLIANCE COMPONENTS
A low thermal capacity Gas to Water heat exchanger
A water to water heat exchanger to provide hot water.
A heatbank having a nominal capacity of 60 litres of circulating
primary hot water positioned in the lower half of the appliance.
A water diverter valve to direct the boiler output either to hot
water or central heating as required.
Multifunctional gas valve and electrical control system to
individually control the hot water and central heating.
An integral circulating pump.
Boiler and hot water temperature control thermostats providing
control for central heating and hot water.
A User’s Operating Switch for selection of water only or heating
and water.
A by-pass for central heating system.
An electronic control board which enables the pump to run on
for a period of a about five minutes to allow the boiler section to
cool after each operating cycle.
An expansion vessel, pressure gauge and pressure relief valve.
Temperature safety cut-out controls.
A water flow regulator and flow switch in the domestic supply.
A standard horizontal rear flue kit to accommodate a flue length
of 229mm to 407mm.
An optional flue kit to provide for flue lengths up to a maximum
of 610mm.
2.5 ELECTRICAL SUPPLY
Mains supply: 230V ~ 50Hz, 150 watts. External fuse 3A.
Internal fuse 3.15A (20mm) fast blow.
2.6 GAS SUPPLY
The boiler requires 2.84 m3/h (100.3 ft3/hr ) of gas with a
calorific value of 37.78 MJ/m3. (1014 Btu/ft3.) The gas meter and
supply pipes must be capable of supplying this quantity of gas
in addition to the demand from any other appliances being
served. The following table gives an indication of limiting gas
pipe lengths and the allowance to be made for fittings. Refer to
BS 6891 for further information.
The meter governor should deliver a dynamic pressure of 20
mbar (8in wg.) at the appliance.
The complete installation including the gas meter must be tested
for soundness and purged. See BS 6891.
2. General Information
1. Installation Requirements
2
10. Electrical ...................................................................... Page 11
11. Installing the Appliance ............................................ Page 13
12. Commissioning the Appliance ................................ Page 18
13. Instructions to the User ............................................ Page 20
14. Inspection and Service .............................................. Page 20
15. Replacement of Parts ................................................ Page 21
16. Operational Flow Diagrams ...................................... Page 36
17. Fault Finding .............................................................. Page 38
18. Component Parts List ................................................ Page 44
1. Installation Requirements ........................................ Page 2
2. General Information .................................................. Page 2
3. Technical Data ............................................................ Page 5
4. Siting the Appliance .................................................. Page 6
5. Flue Terminal Position ................................................ Page 8
6. Air Supply .................................................................... Page 8
7. Sealed System ............................................................ Page 9
8. Open Vent System ...................................................... Page 10
9. Hot Water Supply ........................................................ Page 10
Contents
Total Length of Gas Supply Pipe (metres)
369
8.7 5.8 4.6 22
18.0 12.0 9.4 28
Gas
Discharge
Rate (m3
/hr)
Pipe
Diameter
(mm)

2.7 PACKING
The appliance and flue components are packed in separate
cartons.
2.8 GENERAL INSTALLATION
The appliance is supplied for connection to a sealed system but
is suitable for use with an open system.
The specified ventilation openings made into a wall or
compartment door must not be obstructed.
If the appliance is to be fitted into a compartment then the
compartment must conform to the requirements of BS 6798:
1987:Section 6.
The clearances specified for installation and servicing must be
maintained.
2.9 FLUE
The appliance has a balanced flue system.
A terminal guard, Type E, GC No 393 547, is available from Tower
Flue Components, Vale Rise, Tonbridge, TN9 1TB.
The standard horizontal flue assembly length is from 229mm to
407mm.
Extended flue lengths up to 610mm are available using the
optional extended flue kit.
Do not allow the flue terminal fitted to the outside wall to
become obstructed or damaged.
2.10 CONTROLS
The electronic control system via the gas valve operates the heat
input in response to the central heating and hot water
temperature settings.
The Operating switch provides for the selection of hot water
(WATER) only or central heating and hot water (HEATING and
WATER) or OFF.
A facia mounted programmer is available as an optional extra. A
remote mounted programmer may be connected to the
appliance.
The control thermostats for central heating and hot water are
mounted on the integral facia.
There is provision for the connection of a mains voltage room
thermostat. Refer to Section 10.
Frost Protection. When the appliance and heating system are
exposed to low temperatures it is advised to fit a frost
thermostat Refer to Section 10.
Thermostatic radiator valves can be used in the system. The
appliance incorporates an adjustable by-pass between the
central heating flow and return.
3
Return Valve
Flow Valve
Water Manifold
(Top Section)
Manual Air Vent
Pressure Relief
Valve
By-Pass
Adjuster
Water to Water
Heat Exchanger
Water Manifold
(Bottom Section)
Water Diverter
Valve
Open Vent
Position
Drain
(Secondary Water)
Circulating
Pump
Drain
(Primary Water)
Heat-Bank
Capacity 60 Litres
Sealed System
Expansion
Vessel
Boiler
2
Gas to Water
Heat Exchanger
Appliance
Cabinet
Central
Heating
Flow
Central
Heating
Return
Domestic
Hot Water
Out
Mains Cold
Water In
Water Filter Flow Switch
Automatic Air
Vent Water Flow
Regulator
3
4
5
1
Fig. 1. Appliance water flow diagram.
C.H. Thermostat ZAGAS041 Heatbank Overheat Thermostat ZAGAS044
Safety Temperature Limiter SSAHAR013 H.W. High Limit Thermostat SSAHAR253
H.W. Thermostat ZAGAS042
1
2
3
4
5

2.11 SYSTEM NOTES
WARNING
CHECK THAT NO DIRT IS LEFT IN EITHER THE GAS OR WATER
PIPEWORK AS THIS COULD CAUSE DAMAGE TO THE APPLIANCE.
THE BOILER AND SYSTEM SHOULD BE FLUSHED OUT AND
CLEANSED AS PER BS 7593. THE DOMESTIC WATER SUPPLY
SHOULD BE THOROUGHLY FLUSHED AND THE GAS SUPPLY
PURGED BEFORE FINALLY CONNECTING THE APPLIANCE.
The water pipe connections throughout a sealed system must be
capable of sustaining a pressure of up to 3 bar.
Radiator valves must conform to the requirements of
BS.2767(10):1972.
The relief valve drain outlet must be directed away from any
electrical components or where it would cause a hazard to the
user.
A drain cock to BS 2879 must be fitted to the lowest point of the
system.
For circuit design purposes it is important that due note is taken
of the information given in Table 3 relating to the available pump
head.
2.12 SHOWERS, BIDETS, TAPS AND MIXING VALVES
Hot and cold taps and mixing valves used in the system must be
suitable for operating at mains pressure.
Thermostatically controlled or pressure equalising shower
valves will guard against the flow of water at too high a
temperature.
Hot and cold mains fed water can be supplied direct to an over-
rim flushing bidet subject to local water company
requirements.
With all mains fed systems the flow of water from the individual
taps will vary with the number of outlets operated
simultaneously and the cold water mains supply pressure to the
property. Flow balancing using ‘Ball-o-Fix’ type valves is
recommended to avoid an excessive reduction in flow to
individual outlets. For further information contact Worcester
Heat Systems Ltd.
2.13 SAFETY CONSIDERATIONS
The appliance must not be operated in a waterless condition.
The appliance must not be operated with the boiler inner casing
cover removed.
Work must not be carried out on the appliance without the gas
and electricity supplies being turned off.
Checks must be made to ensure that the ventilation openings
made into walls and partitions are of the correct size and are not
obstructed.
2.14 OPERATION
See Fig. 1.
Hot Water Mode:
With the appliance in a stand-by condition, i.e. heatbank at the
temperature set by the hot water control thermostat, burner off,
pump off and a demand is made for hot water;
The flow switch will energise the pump and circulate primary hot
water around the boiler and water to water heat exchanger. The
burner will light at its maximum setting to maintain the
temperature of the heatbank.
When hot water is no longer required the appliance will continue
to operate, the burner will cycle a number of times, until the
heatbank has returned to temperature. The pump will continue
to run for about five minutes to disipate the residual heat from
the appliance.
Note: The appliance may be used for Hot Water only before the
Central Heating circuit is connected.
Central Heating Mode:
With the appliance in a stand-by condition and a demand is
made for heating:
The water diverter valve will open, the pump will energise
circulating primary water around the heating system and the
burner will light to the nominal setting pressure.
With the system at the temperature set by the Temperature
Control Knob, on the facia, the burner will cycle to maintain
output to the system.
If the system no longer requires output to maintain the desired
room temperature, the burner will extinguish. The pump will
continue to run for about five minutes to dissipate the residual
heat from the appliance and then switch off.
When the primary water has cooled sufficiently below the
temperature set by the Temperature Control Knob, the burner
will light, pump will energise and the process will be repeated.
Hot Water and Central Heating mode:
The appliance will supply heat to the central heating system as
required. A demand for hot water at a tap or shower will override
the central heating function for the period of the hot water
demand.
When hot water is no longer required the burner and pump will
continue to operate until the heatbank is back to the required
temperature.
The appliance will return to the central heating state and its
normal mode of operation.
4

5
AVAILABLE PUMP HEAD
BOILER OUTPUT HEAD MIN. FLOW RATE TEMPERATURE RISE
ACROSS HEATING
kW Btu/h Metres Feet L/min. Gal/Min. FLOW AND RETURN
8.8 (30,000) 6.1 20.0 11.5 2.5
11.0 (37,000) 5.4 17.5 14.0 3.1
13.0 (44,350) 4.9 16.0 17.0 3.7 11°C (20°F)
HEATING 15.0 (51,200) 4.2 13.5 19.5 4.3
RANGE 17.0 (58,000) 5.3 17.0 15.0 3.3
19.0 (64,800) 4.85 16.0 17.0 3.7 16°C (24°F)
21.0 (71,500) 4.4 14.5 19.0 4.2
23.0 (78,500) 5.2 17.0 16.0 3.5 21°C (38°F)
24.0 (82,000) 5.0 16.5 16.5 3.6
Table 3
DRY WEIGHT OF APPLIANCE 96kg (212lb)
PACKAGED WEIGHT OF APPLIANCE 98kg (216lb)
MAXIMUM INSTALLATION WEIGHT 156kg (344lb)
Table 4: Nominal Weight of Appliance
NOMINAL BOILER RATINGS (10 minutes after lighting the appliance)
MODE OUTPUT INPUT BURNER SETTING GAS RATE
PRESSURE
kW Btu/h kW Btu/h m bar. in. wg. m3/h ft3/h
8.8 (30,000) 11.6 (39,500) 2.2 0.9 1.11 39.2
11.0 (37,000) 14.3 (48,600) 3.2 1.3 1.36 48.0
13.0 (44,350) 16.6 (56,700) 4.4 1.8 1.58 55.5
HEATING 15.0 (51,200) 19.0 (64,850) 5.7 2.3 1.81 63.9
RANGE 17.0 (58,000) 21.4 (72,950) 7.2 2.9 2.04 72.0
19.0 (64,800) 23.8 (81,150) 8.9 3.6 2.27 80.2
21.0 (71,500) 26.2 (89,350) 10.7 4.3 2.50 88.3
23.0 (78,500) 28.6 (97,600) 12.8 5.1 2.73 96.4
24.0 (82,000) 29.8 (101,700) 14.1 5.6 2.84 100.3
HOT WATER 24.0 (82,000) 29.8 (101,700) 14.1 5.6 2.84 100.3
Table 1
FLUE DETAILS
mm inches
WALL HOLE WIDTH 380 15.0
WALL HOLE DEPTH 280 11.0
STANDARD FLUE MINIMUM LENGTH 229 9.0
STANDARD FLUE MAXIMUM LENGTH 407 16.0
EXTENDED FLUE MAXIMUM LENGTH 610 24.0
Table 2: Flue System.
Note: The appliance is factory pre-set to satisfy a central heating requirement of 15 kW (51,200 Btu/h). The output must be adjusted to
suit the heating system when commissioning the appliance.
See Fig. 2 and 3.
The Data Plate is fixed to the top of the control box casing.
3. Technical Data

4.1 THE APPLIANCE MAY BE INSTALLED IN ANY ROOM
ALTHOUGH PARTICULAR ATTENTION IS DRAWN TO THE
REQUIREMENTS OF THE CURRENT I.E.E. WIRING
REGULATIONS AND, IN SCOTLAND, THE ELECTRICAL
PROVISIONS OF THE BUILDING REGULATIONS APPLICABLE IN
SCOTLAND, WITH RESPECT TO THE INSTALLATION OF
APPLIANCES IN ROOMS CONTAINING BATHS OR SHOWERS.
WHERE A ROOM SEALED APPLIANCE IS INSTALLED IN A
ROOM CONTAINING A BATH OR SHOWER, ANY ELECTRICAL
SWITCH OR APPLIANCE CONTROL USING MAINS ELECTRICITY
MUST NOT BE ABLE TO BE TOUCHED BY A PERSON USING THE
BATH OR SHOWER.
4.2 The appliance is not suitable for external installation.
4.3 The appliance is floor standing, the floor must be firm and
level. Special floor protection is not required.
4.4 The floor must be capable of supporting the weight of the
appliance. Refer to Section 3 Table 4.
4.5 If the appliance is to be fitted in a timber framed building
refer to the British Gas publication “Guide for Gas Installations in
Timber Framed Housing”.
4.6 The following clearances must be available for installation
and for servicing. See Fig. 2.
4.7 The appliance can be installed in a cupboard to be used for
airing clothes provided that the requirements of BS 6798 and
BS 5440:2 are strictly followed.
4.8 The airing space must be separated from the boiler space by
a perforated non-combustible partition. Expanded metal or rigid
wire mesh are acceptable provided that the major dimension is
less than 13mm. See BS 6798:1987.
4.9 No combustible surface must be within 75mm of the casing.
See BS476:4.
4.10 The distance between the inner face of a cupboard door
and the cabinet front should not be less than 75mm.
4.11 Always consider the possible need to disconnect the pipes
from the appliance after installation.
4.12 L.P.G. INSTALLATION
The appliance shall not be installed in a room or internal space
below ground level when it is intended for use with L.P.G. This
does not preclude the installation into rooms which are
basements with respect to one side of the building but open to
ground level on the opposite side.
4. Siting The Appliance
6
Installation Service
Above the appliance 450mm 10mm
In front 600mm 600mm
Right side 5mm 5mm
Left side 300mm 5mm
SPECIFICATIONS
CENTRAL HEATING FLOW 22mm Copper Tube
CENTRAL HEATING RETURN 22mm Copper Tube
COLD WATER MAINS INLET 15mm Copper Tube
DOMESTIC HOT WATER OUTLET 22mm Copper Tube
GAS INLET 22mm Copper Tube
PRESSURE RELIEF VALVE DRAIN CONNECTION 22mm Copper Tube
OVERALL CASING HEIGHT 860mm (33.8 in.)
OVERALL CASING WIDTH 600mm (23.6 in.)
OVERALL CASING DEPTH 600mm (23.6 in.)
Table 5:
SPECIFICATIONS
PRIMARY CAPACITY INCLUDING HEATBANK 60 Litres (13.2 galls.)
MAXIMUM INLET DOMESTIC WATER PRESSURE 10 Bar (150 psi)
MINIMUM INLET DOMESTIC WATER PRESSURE (WORKING) 1.0 Bar (15.0 psi)
FOR MAXIMUM HOT WATER FLOW
MINIMUM INLET DOMESTIC WATER PRESSURE (WORKING) 0.1 Bar (1.5 psi)
TO OPERATE THE APPLIANCE
MAXIMUM CENTRAL HEATING FLOW TEMPERATURE Nominally 82°C (180°F)
MAXIMUM STATIC HEAD – PRIMARY 30m (97ft.)
MINIMUM STATIC HEAD – PRIMARY 1.0m (3.3ft.)
OUTPUT TO DOMESTIC HOT WATER 24.0kW (82,000 Btu/h)
OUTPUT TO CENTRAL HEATING 8.8 to 24.0kW (Adjustable)
(30,000 to 82,000 Btu/h)
MAXIMUM DOMESTIC HOT WATER FLOW RATE FROM THE APPLIANCE Nominally 18.0 l/min. ± 15% (3.96 gall/m)
EQUIVALENT HOT WATER FLOW RATE FROM THIS APPLIANCE TO GIVE 20 l/min. (4 gall/m)
30°C RISE (SPECIFIC RATE)
Table 6:

7
600
Duct Width
Flue Position
Rear View Side View
Flue position on
rear of inner
casing
All pipes set in
25mm from rear
of appliance
Appliance
Front
Duct Height
247
572
275
335
550
785
830
120
95
75
25
25
30 ➄
➂
➃
➁
➀
➅
➆
50
115
347
64
Fig. 3. Appliance pipework connections and flue position.
Pipe Connections
1 Central Heating Flow 22mm
2 Central Heating Return 22mm
3 Mains Cold Water In 15mm
4 Hot Water Out 22mm
5 Gas Inlet 22mm
6 Pressure Relief Drain 22mm
7 Open Vent (optional extra) 22mm
1200
Side View Front View
600
910
610
600
Cabinet Depth
600
Cabinet Width
300 5
Space required in front
for installation and
servicing
Space required for
installation
Space required for
servicing
Surface may be
fixed after
installation. A gap
of 10mm is
required above the
appliance
Space required
under fixed
surface
Space required
for installation
Space required
left-hand side
for installation
Space required
each side for
servicing
Floor
Level
450860
1310
Cabinet Height
10
Wall
Fig. 2. Appliance cabinet dimensions and minimum clearances required.

A
G
D
H I
FJ
E
A
B C
G
M
FF
L
L
K
K
5.1 The flue must be installed as specified by BS 5440:Part 1and
the building regulations.
NOTE: Installations coming under the jurisdiction of Building
Control should adhere to the increased clearances.
5.2 TERMINAL POSITION. See Fig. 4.
5.3 The terminal must not cause an obstruction nor the
discharge a nuisance.
5.4 If the terminal is fitted within 850mm of a plastic or painted
gutter or within 450mm of painted eaves then an aluminium
shield at least 750mm long should be fitted to the underside of
the gutter or painted surface.
5.5 If a terminal is fitted less than 2 metres above a surface to
which people have access then a guard must be fitted. Refer to
Section 2, Item 2.9.
5.6 The terminal guard must be evenly spaced about the flue
terminal and fixed to the wall using plated screws
5.7 In certain weather conditions a terminal may steam and
siting where this could cause a nuisance should be avoided.
5.8 Take care to ensure that combustion products do not enter
ventilated roof voids.
6.1 The appliance does not require a separate vent for
combustion air.
6.2 Installations in cupboards or compartments require
permanent vents for cooling purposes, one at high level and one
at low level, either direct to outside air or to a room. Both vents
must pass to the same room or be on the same wall to the
outside air.
6.3 There must be sufficient clearance around the appliance to
allow proper circulation of ventilation air. Refer to Section 4,
Item 4.6.
6.4 The minimum free areas required are given below.
6.5 Refer to BS 6798 and BS 5440:2 for additional information.
6. Air Supply5. Flue Terminal Position
8
POSITION OF AIR FROM AIR DIRECT
VENTS THE ROOM FROM OUTSIDE
HIGH LEVEL 270 cm2135 cm2
(42 in2) (21 in2)
LOW LEVEL 270 cm2135 cm2
(42 in2) (21 in2)
Fig. 4. Siting of the flue terminal.
MINIMUM SITING DIMENSIONS FOR POSITIONING THE BALANCED
FLUE TERMINAL
TERMINAL POSITION MIN. DISTANCE
A– Directly below an opening, air brick,
window etc. 1500mm (60 in.)
A1– Above an opening, air brick,
window etc. 300mm (12 in.)
A2– Horizontaly to an opening, air brick,
window etc. 600mm (60 in.)
B– Below gutters, soil pipes or drain pipes. 300mm (12 in.)
C– Below eaves. 300mm (12 in.)
D– Below balconies or car port roof. 600mm (24 in.)
E– From vertical drain pipes and soil pipes. 75mm (3 in.)
F– From internal or external corners. 600mm (24 in.)
G– Above ground, roof or balcony level. 300mm (12 in.)
H– From a surface facing a terminal. 600mm (24 in.)
I– From a terminal facing a terminal 600mm (24 in.)
J– From an opening in a car port (e.g. door
window) into dwelling. 1200mm (47 in.)
K– Vertically from a terminal on the same
wall. 1500mm (59 in.)
L– Horizontally from a terminal on the same
wall. 300mm (12 in.)
M– From door, window or air vent (achieve
where possible). 300mm (12 in.)
A1
A2

See Fig. 5. and .6.
7.1 The system must comply with the requirements of BS 6798
and BS 5449:1.
7.2 The appliance must not be operated without the system
being full of water, properly vented and pressurised.
7.3 The safety valve operates at 3bar (45lb/in2). The discharge
must be directed away from electrical items or where it might be
a hazard to the user.
7.4 The pressure gauge indicates the system pressure which
must be maintained.
7.5 The 12 litre expansion vessel is charged to 0.5 bar and is
suitable for a static head of 5m (17.5ft). The pressure can be
increased if the static head is greater than 5m (17.5ft).
7.6 With an initial system pressure of 0.5 bar, a system capacity
of about 104 litres can be accommodated. Refer to BS 7074 Pt 1
for more information.
7.7 The filling point must be at low level. See Fig. 5.
7.8 Water loss must be replaced. See Fig. 6. The connection
should be made in the central heating return as close to the
appliance as possible.
7.9 The make-up vessel must be fitted with a non-return valve.
7.10 Repeated venting loses water from the system. It is
essential that this water is replaced and the system pressure
maintained.
7.11 There must be no connection to the mains water without
the authority of the local Water Company.
7.12 The pump is set at maximum and must not be adjusted.
7.13 Connections in the system must resist a pressure of up to
3 bar.
7.14 Radiator valves must conform to BS 2767(10):1972.
7.15 Other valves used should conform to the requirements of
BS 1010.
7. Sealed System
9
Heating return
Non return
valve Non return valve Hose union
Test cock Temporary hose
Stop cock
Auto
air vent
Heating return
Stop
cock
Fill point
Non return
valve
Make up
vessel
300 mm (12 in) min.
above the highest
point of the system.
Fig. 6. System filling and make-up.
Top-up Bottle
Non-Return
Valve
Hot Water
Out
Mains
Cold
Water
Lockshield Valve Radiator Valve
Heating Flow Heating Return
Spherical Plug Ball Valve for
appliance servicing
British Standard Stop
Valve.
Fixed spindle type
Water Main
NOTE: A drain cock should
be installed at the lowest
point of the heating circuit and
beneath the appliance.
Appliance
(Refer to
Fig. 1
for appliance
Water Flow
diagram)
Fig. 5. Sealed primary water system.

See Fig. 7 and 19.
8.1 The appliance is supplied suitable for connection to a sealed
system. If it is to be used with an open vent system then the
instructions given below must be followed.
8.2 A 22mm preformed combined feed and vent pipe available
as an optional extra must be connected to the appliance. See
Section 11.3 and Fig. 19.
Note: Refer to Section 3, Table 5, for the sizes of the flow and
return pipework.
8.3 The feed and expansion cistern should be arranged so that a
minimum static head of 1.0m (3.3 ft) above the top of the
appliance or above the highest point in the heating circuit,
whichever is the highest, is achieved. See Fig. 7.
8.4 The feed and vent pipe must rise continuously from the
appliance to the feed and expansion cistern.
8.5 A safety valve is not required on an open vented system.
With the safety valve left in position then a pipe must be fitted
which terminates such that any discharge does not cause a
hazard to the occupants or damage to electrical components.
8.6 Air within the appliance will be expelled via the feed and
vent connection or dissipated into the rest of the system which
must be fitted with manual air vents at any high points.
8.7 The pump is set to maximum and must not be reset.
8. Open Vent Primary System
10
Hot Water
Out
Mains Cold
Water
Lockshield Valve Radiator Valve
Heating Flow
Heating
Return
22mm dia. Vent Pipe
Circulating Pump
Spherical Plug Ball Valve for
appliance servicing
Combined feed and vent
pipe (22mm).
Must rise continuously.
Disconnect the flexible hose from behind the
circulating pump. The expansion vessel and
flexible hose are not required in the open vent
system and may be discarded. Fit the 22mm
vent pipe supplied as on optional extra.
British Standard Stop Valve.
Fixed spindle type
Water Main
NOTE: A Drain Cock should be
installed at the lowest point of the
heating circuit and beneath the
appliance.
STATIC HEAD (S.H.)
Minimum Static Head 1.0m (3ft). Measured
from the top surface of the appliance or the
highest point in the heating system to the
water level in the feed and expansion tank.
Appliance
(Refer to
Fig. 1 for
appliance
Water Flow
diagram)
Part view showing
Vent Pipe connection
Fig. 7. Open vent water system.
S.H.
9.1 The final 600mm of the mains cold water connection to the
appliance should be made in copper tube only.
9.2 The appliance is suitable for a mains pressure of up to 10 bar
(150 lb/in2).
9.3 The appliance is fitted with a mains supply isolating valve.
9.4 The maximum hot water flow rate is 18 l/min ±15%
(3.9 gall/min).
9.5 In winter, when the mains inlet water temperature is lower a
reduced flow rate, achieved at the tap, will increase the required
delivery temperature.
9.6 It is suggested that long pipe runs to the taps or shower
should be insulated to prevent the rapid cooling of hot water
after the tap or shower has been turned off.
9.7 Hot and cold taps and mixing valves used with this
appliance must be suitable for operating at a pressure of up to
10 bar (150 lb/in2).
9.8 Anti-syphonage arrangements are normally not necessary.
See paragraph 9.10 following.
9.9 Thermostatically controlled or pressure equalising shower valves
will guard against the flow of water at too high a temperature.
9.10 The head of a loose head shower must not fall closer than
25mm (1in) above the top edge of the bath to prevent its immersion
in bath water. Alternatively the shower must be fitted with an anti-
syphonage device at the point of the flexible hose connections.
9.11 The supply of hot and cold mains water direct to a bidet is
permitted, subject to local Water Company requirements,
provided that the bidet is of the over-rim flushing type. The
outlet(s) should be shrouded and unable to have any temporary
hand held spray attached. No anti-syphonage arrangements are
necessary.
9.12 As the maximum temperature of the hot water heat
exchanger is limited by the control circuit, there is normally no need
for water treatment to prevent scale accumulation. In exceptional
circumstances a device to prevent scale formation can be fitted.
9.13 Installation of a scale inhibitor assembly should be in
accordance with the requirements of the local Water Company.
An isolating valve to allow servicing should be fitted.
9.14 The water hardness can be determined using a standard
test paper or by reference to the local water company.
9.15 A miniature expansion vessel (Zilmet R1/2, 160 ml, 15 bar),
available as an optional extra, may be fitted into the domestic
water supply circuit if there is evidence of water hammer.
To fit the expansion vessel:
(i) Remove the front cover. Refer to Section 14 paragraph
14.2 a, and Fig. 16.
(ii) Unscrew the hexagon headed screw located below the
flow switch. See Fig.16.
(iii) Screw the expansion vessel into the connection using
thread sealant compatible with potable water.
9. Domestic Water Supply

Refer to Figs. 8, 9, 10 and 11.
10.1 Mains Supply 230V ~ 50Hz 150 watts. External Fuse 3A.
Internal Fuse 3.15A (20mm) fast blow.
10.2 The electrical supply must be connected by a qualified
electrician..
10.3 A fused double pole isolator with a contact separation of
3mm in all poles MUST be used to supply the appliance and
controls.
10.4 The appliance must be earthed.
10.5 Mains Cable: PVC insulated 0.75mm2(24x0.20mm) to BS
6500 Table 16. If a new cable is needed it must be connected
into the terminals marked L (Brown or Red lead), N (Blue or Black
lead) and (Green/Yellow or Green) and be held securely in the
cable clamp. Ensure the Earth conductor is longer than the
current carrying conductor, so that if the cable slips in its
anchorage, the current carrying conductors become taut before
the Earth conductor. For access refer to Section 14.
10.6 The wiring between the appliance and the electrical supply
shall comply with current IEE Wiring Regulations, and any local
regulations which apply.
10.7 If a room and/or frost thermostat is to be fitted refer to
Fig.10.
The thermostats must be suitable for use on mains voltage.
10.8 A facia mounted programmer is available as an extra.
Instructions are supplied with the programmer kit. See Fig. 11.
10.9 A timeswitch or programmer can be fitted externally to the
appliance.
10.10 SAFETY CHECK
After installation or in the event of an electrical fault the
electrical system shall be checked for short circuits, fuse failure,
incorrect polarity of connections, earth continuity and resistance
to earth.
10. Electrical
11
MAINS
IN
HOT WATER
CONTROL STAT
br
X12
HEATING
CONTROL STAT
OPERATING
SWITCH
STANDBY
INDICATOR
DEMAND
INDICATOR
CONTROL
FACIA
br
w
g
gy
bl
br
X11
br
bl
gy
INTERNAL
FAN
HOT WATER
HIGH LIMIT
STAT
FLOW
SWITCH
PUMP
DIVERTER
VALVE HILO MAIN
GAS VALVE
HEATBANK
OVERHEAT
STAT
1
gy 1
CONTROL
BOARD
ROOM
THERMOSTAT
(OPTIONAL)
FROST
THERMOSTAT
(OPTIONAL)
EARTH PLATE
w
g
br
w
X2
X13
X7 X15
X4
X14 X1
X8 X5
X10
X3
1
X6
1
1
11
1
ww1
bk bk bk bk
pk pk
bl br br bl
bk bk
br bl or or
bl br
gy
X16 1
rr1
1
1
SPILLAGE DISCHARGE
SAFETY DEVICE (OPEN FLUE)
OR
ORANGE LINK ACROSS
TERMINAL X8 (BALANCED FLUE)
gg
Fig. 8. Wiring diagram.

12
X14
(PIN 4)
LIVE
SUPPLY
red
HEATBANK
OVERHEAT
STAT
HIGH/LOW
GAS VALVE
N
STANDBY INDICATOR
FROST THERMOSTAT (IF FITTED)
N
black
X3 (PIN 4)
L
X14
(PIN 1)
FUSE 3.15A
QUICK
BLOW
red
brown
X12
(PIN 2)
X13 (PIN 5) X13 (PIN 4)
X13 (PIN1)
X13
(PIN 3)
X12 (PIN 4)
X12 (PIN3)
X13
(PIN 2)
N
white
OPERATOR
SWITCH OR
PROGRAMMER
HEATING
HOT
WATER
brown blue
X1
(PIN 3) X1
(PIN 1)
HOT WATER
FLOW
SWITCH
HOT WATER
CONTROL
THERMOSTAT
pink
pink
X2
(PIN 1) X2
(PIN 3)
OPTIONAL
LINK
1
10
9
5
6
13 14
X16
(PIN 2)
black
HOT WATER
HIGH LIMIT
STAT
X16 (PIN 1)
N
black
PUMP DIVERTER
VALVE
brown
X10 (PIN 1) X7 (PIN 3)
SPILLAGE
DISCHARGE
SAFETY DEVICE
(OPEN FLUE)
orange orange
X8
(PIN 1) X8
(PIN 2) X6
(PIN 1)
VDR
(SUPPRESSOR)
N
brown
X4
(PIN 1)
INTERNAL
FAN
MAIN
GAS
VALVE
grey
CONTROL
BOARD
grey
ROOM THERMOSTAT (IF FITTED)
NN
N
brown
N
X11
(PIN 4)
ELECTRONICS
ELECTRONICS
WITH
5 MINS' OFF
DELAY
DEMAND INDICATOR
N
RLA
RLB
HEATING
CONTROL
STAT
X15 (PIN 2)
WHITE
X15 (PIN 3)
WHITE
RLC
X3 (PIN 5)
black
X5
(PIN 2)
brown
ORANGE LINK
(BALANCED FLUE)
Fig. 9. Functional flow diagram.
To External Programmer
Note: If programmer fails, link
connector terminals, as shown by
dotted line, to create temporary
heat availability.
Switched central
heating from
programmer
Switched hot
water from
programmer
Live supply
to programmer
Neutral
Connector
X12 on
control
board
Plug-in
connector
4
3
2
1
Fig. 11. External programmer connections.
54321
54321
Connector X13
on control board
Connector X13
on control board
Room thermostat
Frost thermostat
Remove link
Live Neutral
Switched live
Fig. 10. Room/frost thermostats and programmer.

The appliance is supplied suitable for fitting to a sealed system. If
it is to be fitted to an open vent system refer to paragraph 11.3
and Section 8.
11.1 GENERAL FITTING
The following description covers one method of installation.
Extra space may be required for installation if connections are
made in a different way.
Compression fittings may be used on all water connections to
allow for the fitting of the appliance and servicing.
Pipework must be routed so as not to obstruct access to the
circulating pump, diverting valve, gas valve, water to water heat
exchanger or heat bank.
Removable sections are provided in the cabinet top panel to
facilitate vertical pipe connections if required.
Check that the appliance carton contains :
Installer’s Instruction Pack
User’s Information Pack
Hardware Pack.
Appliance
Carefully remove the appliance from the cardboard package and
plinth.
Check the position chosen for the appliance is in accordance
with the instructions given in Sections 4 and 5.
Also refer to Fig. 2.
Do not place the appliance in its final position at this stage.
The weight of the appliance empty is 96 Kg., more than one
person may be required when moving the appliance.
Depending on site conditions it may be helpful to pre-plumb the
appliance before moving it into position. Fitting unions or stub
pipes to the appliance pipework should be done at this stage.
Refer to Section 3 and Fig. 3.
Before the appliance is fitted to the central heating system,
thoroughly flush the heating system and the mains cold water
supply pipe.
To gain access to the appliance remove the cabinet front and top
panel and place the facia and control box in the Service Position:
(i) Lift the cabinet front panel off the top location and clear
the lower return over the kick strip. See Fig. 12.
(ii) Unscrew the two screws securing the facia to the outer
edges of the cabinet accessible under the facia. Ease the
facia and control box forwards on the slide rails until fully
extended. See Fig. 12.
(iii) Lift the assembly upwards through 90° into the Service
Position. Lodge in the Service Position on the outer
locations. See Fig. 12.
(iv) Unscrew the two screws behind the control panel securing
the cabinet top panel. See Fig. 12.
(v) Lower the facia and control box to the fully extended
position. Ease the cabinet top panel forwards
approximately 20mm and lift clear of the appliance. See
Fig. 12. Return the facia and control box to the Service
Position.
11.2 FLUE PREPARATION
Having decided upon the most suitable position for the
appliance the hole for the balanced flue assembly must now be
marked on the wall.
From the dimensions given in Fig. 13 carefully mark the wall to
position the hole for the balanced flue assembly.
Cut a hole in the wall 380mm (15.0 in.) wide x 280mm (11.0 in.)
high for the balanced flue air duct. Make good any plaster or
brickwork.
Measure the wall thickness W from the inner face of the wall to
the outside face. See Fig. 13.
From the carton containing the flue kit (either standard or
extended) remove the flue terminal, flue duct, air duct and the
package containing the following items :-
4 off - M5 Hex Head screws
2 off - M5 Shakeproof Washers
4 off - No 8 wall plugs
4 off - No 8 wood screws
1 off - roll of ducting tape
1 off - tube of silicon sealant
Fit the air ducts together and adjust their total length until it
corresponds with the dimension W + 40mm.
Using the ducting tape provided firmly tape the joint. See Fig. 14.
Check the total length before continuing.
Apply the silicone sealant in a bead approximately 10mm (0.3 in)
diameter around the air duct spigot located on the rear of the
inner casing. See Fig. 15.
Fit the air duct to the appliance, secure with the two M5 bolts
and shakeproof washers provided, through the holes in the rear
of the inner casing. See Fig. 15.
Carefully slide the appliance into the final position, passing the air
duct through the hole in the wall, with the rear of the appliance
base plate parallel with the wall or skirting board. See Fig. 15.
Remove one screw holding the expansion vessel in position and
gently lower until resting on the floor. See Fig. 16.
Unscrew the four screws securing the inner casing cover. Remove
the cover. See Fig. 16.
Remove the two screws fixing the front of the flue hood to the
top of the combustion chamber. Ease the flue hood clear of the
combustion chamber. See Fig. 15.
From outside, make good the gap between the air duct and the
brickwork. Ensure the air duct is not distorted when filling the
gap.
Fit the flue terminal to the air duct and mark the position of
the four fixing holes. Drill four holes 5mm (0.19 in.) diameter x
30mm (1.25 in.) deep in the wall and fit the wall plugs
provided.
Fix the flue terminal to the wall using the four No. 8 wood
screws.
Note: The flue terminal is not symmetrical and the narrow air
inlet gap is at the top. The top flange is marked TOP.
From inside the appliance enter the flue duct, plain end first.
Engage the flue duct over the front half of the flue duct attached
to the flue terminal. Slide in the flue duct and secure the flange to
the inner casing with the screws provided but do not tighten. See Fig. 15.
Engage the spigot on the flue hood into the flue duct and slide
into position on the heat exchanger. Fix into position with the
two screws at the front.
Tighten the screws securing the flange of the flue duct to the
inner casing.
11.3 FIXING THE APPLIANCE
Always support the appliance pipework when tightening.
Sealed System.
Connect a 22mm copper drain pipe to the discharge connection
at the rear of the appliance.
Ensure:
(i) any discharge does not fall onto electrical components or
where it might be a hazard to the user. See Fig. 18.
(ii) the pipe must fall throughout its length.
Open Vent System.
If the appliance is to be used on an open vent system the
expansion vessel and flexible hose are not required. Remove
from the bottom manifold connection and discard. Fit the 22mm
copper vent pipe, supplied as an optional extra, to this
connection. See Fig. 19.
11. Installing The Appliance
13

To access the open vent connection remove the pump head.
Withdraw the two securing clips from the pump body. Ease the
pump forwards about 10mm off the “O” ring seals. It is not
necessary to disconnect the electrical cable. The cable is
sufficient to allow the pump head to rest on top of the appliance.
Do not allow the pump head to be suspended by the cable.
Secure the pump head. See Figs. 16 and 19.
Connect the gas pipe to the gas inlet on the appliance at the left
hand side.
Connect the water system pipes at the rear of the appliance.
Thoroughly flush the whole of the water system with cold water.
Fill the system venting the appliance and check for water
soundness. Refer to Section 12.
Reassemble the cabinet top panel. Do not replace the inner
casing front or cabinet front until the commissioning has taken
place. Refer to 11.4 and Section 12.
11.4 FINAL INSTALLATION
Check that all the water connections and the gas connection
have been tightened.
Facia Mounted Programmer (where applicable).
Remove the facia panel as described in Section 11.1. Refer to
Fig. 12.
Unplug the Operating Switch connection at the control board.
Unscrew and retain the four nuts and washers securing the
switch mounting plate to the facia. Remove the plate. Fit the
programmer to the facia and fix using the four nuts and
washers. Plug the lead into the connection on the control board.
See Fig. 11. The programmer can be set when the electricity
supply has been turned on at the commissioning stage.
Connect the mains electricity supply to the appliance and
connect any room and/or frost thermostats. Refer to Section 10,
Figs. 8 and 10. The leads from the thermostats must pass through
holes provided in the control box at the right hand side and be
clamped using the strain relief bushes provided in the pack.
Check that the control box and facia can be withdrawn into the
Service Position before fixing any leads outside the appliance.
Refit the control box and facia in the reverse order.
Test the gas supply for soundness as indicated in BS 6891.
If the appliance is not to be commissioned immediately, replace
the inner casing front cover, expansion vessel and cabinet front
panel. See Fig. 12
Check that the gas supply, the electricity supply and the water
connections are all turned off.
14
Lift facia and control box
into the service position
E
G
A
F
L
M
J
K
H
B
D
E
C
A Facia and control box fixing screws
B Cabinet top panel fixing screws
C Cabinet to panel fixing lugs
D Flue assembly clamping screw
E Facia fixing screws
F Hot water control thermostat knob
G Heating control thermostat knob
H Kick strip fixing screws
J Cabinet side panel front location
K Cabinet side panel fixing lugs
L Cabinet front panel (no fastenings)
M Primary system drain. Remove kick
strip for access
To gain access to the appliance:
1. Lift cabinet front panel Loff top
location and clear the return edge over
the kick strip.
2. Remove screws Aand ease facia and
control box forwards on the slide rails.
3. Remove screws B, accessible under
cabinet top panel. Ease panel
forwards clear of location Cand
remove.
4. Lift facia and control box through 90¡
into the service position. Lodge in
position on the outer locations.
To gain access to the control box
from the service position:
1. Pull the thermostat knobs F and G
clear of the facia.
2. Remove screws E.
3. Ease facia out of control box. Take
care not to over stretch the capilary
tubes or wiring.
4. Support the facia out of the control box
when carrying out installation or
service operations.
Fig. 12. Cabinet, facia, control box and flue assembly fixing screws.

15
Outside rendering
(if applied)
Floor level
Floor level
347 x 247
Duct size
Space required at
left-hand side for
installation
Space required at
right-hand side for
installation
Aperture cut through wall to accept
balanced flue assembly. This
dimension may vary depending on
whether any floor covering is
removed and/or an insulating sheet is
placed between the appliance and
the floor
Inside plaster
Wall thickness (W)
to include any
surface finish,
inside or outside
W
280
300 600
380
347
5
40
56
247
570
280
555
555
860
Fig. 13. Balanced flue appliance wall preparation.
245mm
(9.6in.)
345mm
(13.5in.)
W
Fig. 14. Air duct adjustment.

16
Raise control box Telescopic flue
duct Tape joint
Wall thickness
230mm (9in.) minimum
610mm (24in.) maximum
10mm (0.4in.) diameter
continuous seam of
silicone sealant all
around (see below)
Flue hood
Flue hood fixing
screws
Inner casing
Lowered expansion
vessel
Floor level
Drill and plug wall.
Secure terminal to
wall with four
screws
Telescopic
air duct
Flue hood fixing
screws
10mm (0.4in.)
diameter continuous
seam of silicone
sealant all around
Air duct spigot located
on the rear of the
inner casing
Part front view of inner casing
with front cover removed
Flue duct fixing
screws
Fig. 15. Arrangement of balanced flue and terminal.

17
Fig. 18. Discharge pipe connection for sealed
system.
Base plate
Rear view of
appliance
Cabinet side
panel
Pressure relief
drain connection
Discharge pipe must be 22mm
copper fall continuously throughout
its length and discharge to a safe
visible position
Circulating pump
Domestic water expansion
vessel connection
To lower the expansion vessel
follow instructions 1 to 4:
1. Remove cabinet front panel.
Refer to Fig. 12.
2. Raise facia and control box
into the service position.
Refer to Fig. 12.
3. Unscrew one fixing screw.
4. Lower expansion vessel to
rest on the floow.
By-pass adjusting screw
Pressure relief valve
Primary manual air vent Inner casing fixing screws (4)
Central heating flow valve
Central heating return
valve
Control Box
Mains cold water inlet
valve
Heatbank overheat
thermostat reset button Refer to figure 17 for
details of this area
Water diverter valve
Gas valve
Gas service cock Flexible hose
Domestic drain
Gas valve electrical supply plug
Heatbank
Hot water and heatbank
overheat thermostat pocket
Expansion vessel lowered into
service position
System pressure
gauge
Hinge
Facia
Fig. 16. Layout of components with expansion vessel in service position.
Remove securing clip
Ease pump head forwards
off the ÒOÓ ring seals
Remove securing clip
ÒOÓ ring seals
Disconnect the flexible hose from the bottom
manifold and fit the open vent pipe supplied as
an optional extra
Fig. 19. Open vent position and pipework.
Central Heating
Flow Valve
Central Heating
Return Valve
Pressure Relief
Valve
By-pass Adjusting
Screw.
Turn clockwise
to close
Manual Air
Vent
Fig. 17. Central heating flow and return valves,
by-pass adjustment, pressure relief and
manual air vent.

12.1 The appliance is despatched with the controls set to
provide a maximum output for domestic hot water of 24 kW
(82,000 Btu/h) and satisfy a central heating load of 15 kW
(51,200 Btu/h).
The controls can be reset to increase or decrease the heat load
capability from 8.8 kW (30,000 Btu/h) to 24 kW (82,000 Btu/h).
Refer to Section 12.4, Appliance Operation (Central Heating Mode).
Domestic Hot Water System
Check that the mains water supply has been fully flushed out at
installation.
Central Heating System
Check that the central heating system has been fully flushed out
at installation.
Gas Service
The complete system, including the meter, shall be inspected
and tested for soundness and purged as indicated in BS 6891.
12.2 APPLIANCE AND CENTRAL HEATING SYSTEM
PREPARATION
If the cabinet front panel was replaced on final installation (Refer
to Section 11.1) remove the panel before starting the
commissioning procedure. See Fig. 12.
Check that the gas service and the electrical supply to the
appliance are turned off. See Fig. 16.
Raise the facia and control box into the Service Position. Refer to
Section 11.1 and Fig. 12.
Lower the expansion vessel into the Service Position and remove
the inner casing front cover. See Fig. 16.
Check that all the water connections throughout the system are
tight.
Open the system valves at the appliance. See Fig. 17.
Open all the radiator valves, fill the system and vent each
radiator in turn.
Vent the heatbank from the manual air vent. See Fig. 17. The
automatic air vent (fixed to the flow manifold) will vent the boiler
section for sealed systems.
Do not replace the inner casing front cover until instructed in
Section 12.4 Appliance Operation.
Check that the pressure relief valve operates by turning the knob
anti-clockwise until it releases. Water should be expelled from
the discharge pipe. See Fig. 17.
Sealed Systems Only
Set the Expansion Vessel Pressure.
12. Commissioning The Appliance
18
Flame length 18-20mm Pilot assembly fixing screws
Pilot head
Pilot injector
Pilot assembly
Spark electrode
Pilot shield
Spark electrode guide
Spark electrode lead
Spark electrode location clip groove
Fig. 20. Pilot burner assembly.
Operating
button
230V electrical
supply to On/Off
solenoid
Inlet pressure
test point
High/Low burner
pressure adjusting
screws under plastic
cap. See below.
Burner setting
pressure test point
High/Low
solenoid
B
A
C
Retaining
screw
230v electrical
supply plug to
High/Low solenoid
A Ð Adjustment for domestic hot water (High) gas
pressure setting
B Ð Adjustment for heating (Low) gas pressure
setting
C Ð Plastic cap
Fig. 21. Gas control valve adjustment.

The charge pressure of the expansion vessel (as supplied) is 0.5
bar, which is equivalent to a static head of 5 metres (17 ft). The
charge pressure must not be less than the static head at the
point of connection. See Fig. 16. A Schraider type tyre valve is
fitted to the expansion vessel to allow the charge pressure to be
increased if necessary.
Set the System Pressure.
Fill the system until the pressure gauge shows 2.5 bar (37
lb/ins2) and check for water soundness. Release water from the
system using the pressure relief valve test knob until the System
Design Pressure is obtained up to a maximum of
1.5 bar.
System Design Pressure in bar = Static Head of the System in
bar + 0.3
Note: 1 bar is equivalent 10.2 metres (33.5 ft) of water
Set the movable pointer on the pressure gauge to coincide with
the indicating pointer giving a permanent record of the set
system pressure. See Fig. 16.
If the pressure indicated on the pressure gauge is greater than
2.5 bar when operating at the maximum central heating
temperature, an extra expansion vessel must be fitted to the
system as close to the appliance central heating return
connection as possible.
The appliance (as despatched) can accommodate a system
volume of about 104 litres. Refer to BS 7074 Part 1. If the system
volume is in excess of that accommodated by the expansion
vessel fitted to the appliance then an extra vessel must be fitted
as close as possible to the central heating return connection of
the appliance.
Any extra vessel fitted must be pressurised to the same figure as
the integral vessel. If the expansion vessel fails then the specified
replacement must be fitted.
12.3 PROGRAMMER
Any programmer fitted to the appliance should be set up at this
stage following the instructions sent with the programmer.
12.4 APPLIANCE OPERATION
Check that the electrical supply to the appliance is off.
Turn the room thermostat (if fitted) to maximum.
Set the Operating Switch (or Programmer) to OFF.
In order to thoroughly vent the appliance and system the
appliance may be operated without gas turned on as follows:
Switch on the electricity supply.
Note: Immediately the mains electricity is applied to the
appliance the electronic control board is energised causing the
pump to run on for about five minutes. This occurs whether or
not the controls are calling for heat. The pump will subsequently
only run in the course of the normal operation of the boiler.
Set the Operating switch (or Programmer) to Heating and Water
and the Hot Water thermostat to maximum. The pump will run
but the main burner will not light. Primary water will circulate
around the appliance.
Allow the appliance to operate in this condition for a few
minutes before setting the Hot Water thermostat to the Off
position.
Set the Heating thermostat to maximum and room thermostat (if
fitted) to maximum. The water diverter will open to central
heating and the appliance will operate as previously.
Primary water will now circulate around the central heating
system. Allow the appliance to operate in this condition for a few
minutes. Vent all radiators during this period until air is cleared
from the system.
When the system has been vented sufficiently set the Heating
thermostat to the Off position.
Note: The water diverter valve, in the de-energised condition, is
always open to Hot Water. The controls give priority to reheating
the heatbank following a demand for hot water. If the valve fails
to open when energised to the central heating system, hot water
will still be available.
The valve does not have a manually open position.
Set the Operating Switch (or Programmer) to OFF.
Switch off the electrical supply.
The appliance and central heating system should now be vented.
Continue the appliance operation:
Turn on the gas supply. Check for gas soundness around the gas
valve.
Light the pilot by pressing in the grey button on the gas valve
and operating the red igniter button. When the pilot has lit
continue to hold the grey button for a further 20 seconds and
then release it slowly.
If the pilot does not stay alight, twist the gas valve button anti-
clockwise. Wait for 3 minutes and repeat the operation until the
pilot remains lit.
Test for gas soundness at the joint between the pilot pipe and the
burner with leak detection fluid. See Fig. 20.
Observe the pilot flame. It should be about 20mm (3/4in) long
and envelope the thermocouple tip. See Fig. 20.
Put the Operating Switch (or Programmer) to OFF and disconnect
the electrical supply at the mains.
IMPORTANT: Replace the inner casing cover and reposition the
pressure vessel. See Fig. 16.
Loosen the burner pressure test point screw and connect a
pressure gauge. See Fig. 21.
Hot Water Mode
Set the Operating Switch (or Programmer) to Water. Turn the Hot
Water thermostat to maximum. Turn the Heating thermostat to
Off.
The boiler should light at a burner pressure of between 13.9 and
14.4 mbar (5.6-5.8 in wg). Allow the boiler to fire for at least 10
minutes before checking the gas pressure.
Note: It may be necessary to open a hot tap to maintain the
boiler firing.
If the burner pressure is low check that the supply pressure at
the gas valve is at least 19 mbar (7.6in wg). See Fig. 21.
Hot Water (High) Gas Pressure
The burner (High) pressure is factory set and is NOT adjustable in
the Hot Water mode. If the gas supply pressure is correct but the
correct burner pressure is not achieved, contact Worcester Heat
Systems Service Department.
Check several times the main burner lights smoothly and goes
out, by operating the Hot Water thermostat, before proceeding
to check the Heating (Low) gas pressure.
Note: If the electrical supply to the appliance is interrupted at
the isolation switch or a power failure occurs whilst the burner is
firing, the boiler will normally relight automatically when the
power supply is restored. However, depending upon
circumstances it may be necessary to reset the overheat
thermostat before the appliance will operate.
Close the hot water tap (if necessary). The burner will be
extinguished and the pump will continue running until the
appliance has cooled to a preset temperature.
Set the Operating Switch (or Programmer) to Off.
Central Heating Mode
Check that all the radiator valves are open. Set the room
thermostat, if fitted, to maximum and the Heating thermostat to
maximum. Turn the Hot Water thermostat to Off.
Sealed Systems: Check the system is pressurised and set to the
required pressure as indicated on the gauge. See Fig. 16.
Set the Operating Switch (or Programmer) to Heating and Water.
The boiler should light at a burner pressure of 5.7 mbar. (2.3 in
wg).
Heating (Low) Gas Pressure
The burner (Low) pressure is factory preset to satisfy a central
heating demand of up to 15 kW (51,200 Btu/hr). For different
heating requirements the gas (Low) pressure must be
adjusted to suit the installation.
The output to central heating is adjustable from a minimum
of 8.8 kW (30,000 Btu/hr) to a maximum of 24 kW (82,000
19

Btu/hr). Refer to Section 3, Table 1, for Nominal Boiler
Rating.
Allow the boiler to fire for at least 10 minutes before checking the
(Low) gas pressure.
Ensure all the radiators are heating up evenly.
To adjust the Heating (Low) Gas Pressure:
(a) Remove the grey plastic cover over the pressure
adjustment screws on the gas valve. Place a small
screwdriver in one of the slots and carefully lift the cap.
See Fig. 21.
(b) Using a small blade width screwdriver, turn the screw ‘B’
clockwise to increase and counter-clockwise to decrease
pressure until the desired setting is achieved.
(c) Operate the Heating thermostat several times to ensure
the main burner ignites smoothly before checking that the
gas valve switches from High to Low pressure correctly.
(d) Using the Hot Water and Heating control thermostats,
switch the appliance, from High to Low and back several
times to ensure correct gas pressures. Replace the plastic
cap ‘C’
(e) If the Heating (Low) Gas Pressure has been changed set the
indicator arrow on the data plate to the new setting.
Balance the system so that the required temperature difference
across the heating flow and return pipes is obtained. See Section
3, Table 3.
Adjust the by-pass valve until the same temperature difference is
obtained. See Figs. 16 and 17. This should be carried out with
only a single radiator operating.
If thermostatic radiator valves are fitted then one radiator should
be left uncontrolled. The bypass valve should never be fully
closed.
Set the room thermostat to minimum and check that the burner
goes out.
Reset the room thermostat to maximum and the burner will re-
light following the normal operating procedure.
Check for the proper ignition of the burner after a break in the
gas supply.
Turn off the gas service cock and wait for 60 seconds. The main
burner and pilot will go out. Carefully open the gas service cock
and manually relight the pilot then following the normal
sequence of operation check that the burner re-lights normally.
Put the Operating switch (or Programmer) to OFF. Switch off the
gas service cock and the electrical supply to the appliance.
Drain the heating system whilst the appliance is still hot. Refer to
Fig. 12. for the position of the appliance drain point.
Refill, vent and re-pressurise (sealed systems) as described
previously.
Hot Water and Central Heating Mode
Turn on the electricity supply and open the gas supply cock to
the appliance.
Relight the pilot using the same procedure described earlier in
this section.
Set the Operating Switch (or Programmer) to Heating and Water.
If a programmer is fitted set the Hot Water to Continuous or
24Hrs and the Heating to On.
Set the Hot Water thermostat to MAXIMUM. The main burner
will relight and the boiler will heat the water stored in the
heatbank. Once the heatbank has been satisfied the appliance
will switch off.
Turn on any hot water tap to maximum. After a short period the
burner will re-ignite. If hot water has not yet reached the tap,
wait until it does, then turn the tap off. The boiler will fire until
the heatbank has reheated and switch off.
Set the Operating Switch to Hot Water. If a programmer is fitted
set the Hot Water to Continuous and the Heating Off. Repeat the
previous hot water draw off
Set the Operating Switch to Heating and Hot Water. If a
programmer is fitted set to Continuous or 24 Hrs and the
Heating to ON. Set both appliance thermostats to maximum. The
boiler will fire and commence to heat up the radiators. Allow to
operate for 45 minutes, venting as necessary. Check for water
soundness.
Note: From cold it will take about 12 minutes for the heatbank to
be satisfied before the central heating system will receive heat.
IMPORTANT: The complete appliance must be checked for water
leaks. Should any leaks be found they must be rectified before
proceeding further.
Set the Operating Switch to OFF, or if a programmer is fitted,
switch to OFF. Switch electrical supply off at the mains. Set both
appliance thermostats to OFF.
Drain water from the appliance and the system from the drain
points while the water is still hot.
Refill the appliance and system. Repeat commissioning
operation under “Hot Water and Central Heating mode.”
Check for correct operation of User’s Controls including the room
thermostat (if fitted) and leave set to customer’s requirements.
12.5 COMPLETION OF COMMISSIONING
Disconnect the pressure gauge and tighten the test point screw.
Re-start the appliance and check for gas soundness around the
test point screw.
Refit the expansion vessel and cabinet front panel. See Fig. 12
and 16.
If the appliance is being passed over to the User immediately
refer to Section 13, Users Instructions and set the controls to the
user’s requirements.
If the appliance is to be left inoperative check that the Operating
Switch or programmer is set to OFF. Turn the gas service cock to
off and switch off the electricity supply.
If there is any possibility of the appliance and system being left
inoperative during frosty conditions then drain the appliance
and system.
For short inoperative periods leave the appliance under the
control of a frost thermostat, if fitted, or operating continuously
under the control of a room thermostat set at 6°C.
13.1 Tell the user how to operate the appliance and hand over
the Users Instructions leaflet.
13.2 Tell the user what to do if the heating system is not to be
used in frosty weather. Also tell the user that if the appliance is
not to be used for long periods during frosty weather, the system
must be drained and the gas and electricity supplies turned off.
13.3 Tell the user the Sealed System set pressure if applicable.
13.4 Tell the user of the importance of regular servicing. Worcester
Heat Systems Ltd offer a comprehensive maintenance contract.
13.5 Set the system controls to the users requirements.
13.6 If an external programmer has been fitted which has a
programmable hot water facility then instruct the user how to
set up the programme.
To ensure continued efficient operation of the appliance it must
be checked and serviced as necessary at regular intervals. The
frequency of servicing will depend upon the particular
installation conditions and usage, but once per year should
generally be adequate. The extent of the service required by the
appliance is determined by the operating condition of the
appliance when tested by fully qualified engineers.
It is the law that any service work must be carried out by competent
engineers such as British Gas or Corgi registered personnel.
14.1 PRE-SERVICE INSPECTION
Check that the flue terminal and the terminal guard, if fitted, are
clear.
If the appliance is in a compartment check that the ventilation
openings in the compartment door or walls are clear. Refer to
Section 6, Air Supply.
14. Inspection And Servicing
13. Instructions To The User
20