Worcester Combi RSF 240 User guide

....---~~~ORCESTER------.
Bosch Thermotechnik
240 Combi RSF
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
GC NUMBER 47 311 12
BOILER OUTPUT
Automatic Modulating Control
To Domestic Hot Water
Minimum 9.2 kW (31 ,400 Btu/h)
Maximum 24.0 kW (82,000 Btu/h)
To Central Heating
Minimum 9.2 kW (31,400 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
I
I

Contents ,
1. Instailation Requirements............................................. Page 2
2. General Information...................................................... Page 2
3. Technical Data................................................................ Page 4
4. Siting the Appliance...................................................... Page 5
5. Siting the Flue Terminal................................................ Page 6
Sa. Vertical Flue System .................................................. .... Page 6
6. Air Supply .............................................. ......................... Page 7
7. Sealed System .. ..... ... ...... .. .......... .. ... .. .... ... .... .... .......... .... Page 7
8. Open Vent Primary Water System ............................... Page 8
, 1. Installation Regulations
1.1 Gas Safety (Installation and Use) Regulations 1984
Ail gas appliances must be instailed by a competent person in
accordance with the above regulations. Failure to instaii appli·
ances 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, con·
fer immunity from legal obligations. In particular the instaiiation
of this appliance must be in accordance with the relevant require·
ments of the Gas Safety (Installation and Use) Regulations 1984 as
amended, current lEE Wiring Regulations, local Building Regula·
tions, Building Standards (Scotland)(Consolidation) and byelaws of
the local Water Company. Health and Safety Document No. 635
(Electricity at Work Regulations). 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 domes·
tic purposes.
BS 5440:1 :1990 Flues and Ventilation for gas appliances of rated
input not
exceeding 60 kW: Flues.
BS 5440:2:1989 Flues and Ventilation for gas appliances of rated
input
not exceeding 60kW: Air Supply.
BS 6891 :1 988 Installation of low pressure gas pipework instaila·
tions up to 28 mm (R 1 ).
1.4 To ensure that the instaiiation 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.
0
2. General Information
2.1 This appliance is not suitable for external instaiiation.
2.2 The appliance controls are set to provide a maximum out·
put of 24 kW for the domestic hot water and a central heating
load of up to 16.1 kW.
2.3 The control circuit provides automatic ignition. Apermanent
pilot is not used.
2.4 PRINCIPLE APPLIANCE COMPONENTS See Fig 1.
A low thermal capacity Gas to Water heat exchanger.
A Wnter to Water heat exchanger to provide domestic hot water.
Fully modulating controls in the central heating and domestic
hot water modes of operation.
An expansion vessel, pressure gauge and pressure relief valve.
Aby·pass for the central heating system.
Temperature safety cut·out controls.
2
9. Domestic Hot Water ................ ...................................... Page 9
1
o. Electrical ............................................... .......................... Page 10
11 . Instaiiation ...................... ............................................... Page 13
12. Commissioning .......... .................................................... Page 18
13. Instructions to the User ....................... ......................... Page 19
14. Inspection and Servicing ...................... ........................ Page 20
15. Replacement of Parts.................................................... Page 22
16. Short Parts List ........................ ...................................... Page 29
17. Operational Flow Diagram ............... :............................ Page 30
18. Fault Finding ................................................................... Page 32
Awater flow regulator.
Astandard horizontal
flue assembly giving flue lengths from
1 00 mm to 1 000 mm.
An optional extra extension flue kit to provide for flue lengths
up to 2000 mm long.
An optional vertical flue system.
An optional facia mounted programmer instead of the standard
Operating Switch.
2.5 ELECTRICAL SUPPLY
Mains supply: 240V ~, 50 Hz, 270 watts. External fuse 3A.
Internal fuses: T2A (F1) and T315mA (F2).
2.6 GAS SUPPLY
The boiler requires 2.81 m3 /h (99.3 ft3/hr) of gas. 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 table below gives an indication of limiting gas pipe
lengths and the allowance to be made for fittings. Refer to
BS6891 for further information.
The meter governor should deliver a dynamic pressure of 20
mbar (Sin wg.) at the appliance, equivalent to a pressure of
about 18.5·19 mbar at the gas valve.
The complete installation, including the gas meter, must be test·
ed for soundness and purged. Refer to BS 6891 .
TOTAL LENGTH OF
GAS SUPPLY PIPE (metres)
Pipe
Diameter
3 6 9
(mm)
Gas Discharge Rate (m3/h)
2.9
--
15
8.7 5.8
4.6
22
18.0 12.0
9.4 28
Note:
Each fitting used in the gas line from the meter is equivalent to a
length of straight pipe which must be added to the straight pipe
length to give the total length.
ie: Elbow = 0.5 metres, Tee = 0.5 metres, 90° Bend = 0.3 metres.
2.7 PACKING
The appliance and flue components are packed in separate car·
tons.
2.8 GENERAL INSTALLATION
The appliance is supplied for connection to a sealed system but
is suitable for use with an open vent system. The connections
are supplied as an optional kit.
The specified ventilation openings made into a wall or compart·
ment door must not be obstructed.
If the appliance is to be fitted into a compartment then the com·
partment must conform to the requirements of BS 6798: 1987:
Section 6.
Do not place anything on top of the appliance.
The clearances specified for servicing must be maintained.

Fig. 1. Appliance water flow diagram.
Waterflow
manifold
L___
Automatic air vent
Gas to Water
heat exchanger
Boiler
4---,
'
'
'
I
PressJre relief valve
- Domestic hot water out
-- Mains cold water in
- Central heating return
-- Central heating flow
2.9 FLUE
The appliance has a multi-directional horizontal fanned flue
system - right, left or rear.
The standard flue assembly length is from 100 mm to 1000 mm.
An extension flue length from 1001 mm to 2000 mm is avail-
able.
A vertical flue is available with a primary flue length from 500
mm to 2000 mm.
Aterminal guard, '!Vpe 1<2, GC 393 553, is available from 1bwer
Flue ComporterttS, Vale Rise, 'lbnbridge, TN9 1TH.
Do not allow the flue terminal fitted to the outside wall to
become obstructed or damaged.
An optional extra internal flue fixing kit is available. When
ordering the kit the following part number must be quoted -
ZEGAS206. For fitting instructions refer to Section 11.4.
2.1 0 CONTROLS
The electronic control system and gas valve modulate the heat
input
in response to the central heating and domestic hot water
temperature settings between
minimum and maximum.
The operating Switch provides for the selection of domestic hot
water
only (WATER) or central heating and domestic hot water
(HEATING & WATER) or OFF.
Afada mounted programmer Is available as an opliortal extra. A
remote mounted programmer may be connected to the
appli<mr.P.
The integral facia displays indicate the status of the appliance.
There is provision for the connection of a mains voltage room
thermostat and/or a frost thermostat.
The electronic co~trols prevent rapid cycling of the appliance in
the central heating mode.
3
2.11 SYSTEM NOTES
WARNING
Check that no dirt is left in either the gas and water pipework
as this could cause damage to the appliance. Thoroughly flush
the heating system and the cold water mains supply. Purge
the gas supply before finally connecting the appliance ..
The water pipe connections throughout a sealed system must
be capable of sustaining a pressure of upto 3 bar.
Radiator valves must conform to the requirements of BS2767
(10): 1972.
The relief valve discharge must be directed away from any elec-
trical components or where it would cause a hazard to the user.
Adrain 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 a mains pressure of up to 10 bar.
Thermostatically controlled or pressure equalising shower
valves will guard against the flow of water at too high a temper·
ature.
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 simultane-
ously 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 switched 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
Domestic Hot Water: With a demand for hot water the burner
will light at its maximum setting and then automatically adjust
its output
to maintain thP. tP.mperature of the delivered water.
When hot water is no longer required, the burner will extin-
guish. The pump will continue to run for a short period to dissi-
pate the residual heat from the appliance.
Central Heating: With a demand for heating the burner will light
at its minimum setting and gradually increase to give the maxi·
mum output. The output of the appliance is then automatically
adjusted
to maintain the temperature of the system. The output
can reduce down
to a minimum of 9.2 kW. If the system no
longer requires even the minimum output to maintain the
desired
room temperature the burner will extinguish. The pump
will continue to run to dissipate the residual heat from the appli·
ance. The appliance will remain off for a fixed period of two min-
utes before re-lighting to automatically meet the system require-
ments.
Domestic Hot Water and Central Heating: The appliance will
supply heat to the central heating system as required. A
demand
for domestic hot water ctl a lap or shower wtll overrldP.
the central heating requirement for the period of the domestic
hot water demand.
When hot water is no longer required the
burner
will extinguish and the appliance will return to the cen-
tral heating state and its normal mode of operation. The pump
will continue to run to dissipate the residual heat from the appli-
ance as necessary.

, 3. Technical Data
The Data Plate is fixed to the control box casing.
TABLE 1
TABLE 2 - Flue Details
NOMINAL
BOILER RATINGS
Horizontal Flue (Side or Rear)
mm
inches
Output Input
Burner Setting
Gas Rate
Pressure
Wall Hole Diameter
110 4.25
kW Btu/h
kW Btu/h m bar. in.wg. m3/h ft
3/h Wall Hole Diameter
(using optional extra
Internal fitting kit)
150 6
9.2 31,400 13.0
44,300
2.0 0.8
1.22 43.0
Standard Flue -Minimum Length 100 4
16.1
54,900 21.0 71,600 6.3 2.5 1.97
69.5
Standard Flue -Maximum Length 1000 39
24.0 82,000 30.0
102,300 14.0
5.6
2.81 99.3
Extended Flue -Maximum Length 2000 78
TABLE 3
AVAILABLE PUMP
HEAD
Boiler Output
Head
Min. Flow Rate
Temp. rise across
heating flow
kW
Btu/h metres
feet litres/min
gal/min
and return
9.2
31,400 4.9 15.9 12.0
2.64
11 °( (20°f)
16.1
54,900 2.54 8.25
21.0 4.63
24.0
82,000 2.0
6.5 21.0
4.63
16'C (29'F)
Vertical Flue mm inches
Ceiling Hole Diameter 120 4.75
Minimum PrimaryDuct Length 500 20
Maximum Primary Duct Length 2000 78
TABLE4
SPECIFICATIONS
CENTRAL HEATING FLOW FITTING
22 mm Compression
CENTRAL HEATING RETURN FITTING
22 mm Compression
COLD WATER MAINS INLET FITTING
15 mm Compression
DOMESTIC HOT WATER OUTLET FITTING
15 mm Compression
GAS INLET FITTING
Rc1;2
PRESSURE RELIEF VALVE DISCHARGE FITTING
15 mm Compression
OVERALL HEIGHT (including flue elbow) 1100
mm (43.3 in.)
CASING HEIGHT
900 mm (35.4 in.)
CASING WIDTH
450 mm (17.7 in.)
CASING DEPTH
320 mm (12.6 in.)
WEIGHT (including water) 47.6
kg (105lb.)
INSTALLATION WEIGHT
45.6 kg (1 00 lb.)
PACKAGED WEIGHT
48.5 kg (1 07 lb.)
TABLE 5
SPECIFICATIONS
PRIMARY WATER CAPACITY
2.7litres (0.6 galls.)
MAXIMUM COLD SUPPLY PRESSURE
10 Bar (150 psi)
MINIMUM COLD SUPPLY PRESSURE (WORKING) FOR MAXIMUM HOT WATER FLOW
1.6 Bar (23.5 psi)
MINIMUM COLD SUPPLY PRESSURE (WORKING) TO OPERATE THE APPLIANCE
0.6 Bar (9 psi)
MAXIMUM CENTRAL HEATING FLOW TEMPERATURE Nominally 82°C (180°F)
MAXIMUM
STATIC HEAD (PRIMARY)
25 metres (81 ft)
MIMIMUM STATIC HEAD (PRIMARY)
0.3 metres (1 ft)
OUTPUT TO DOMESTIC HOT WATER
Modulating 9.2-24 kW
(31 ,400-82,000 Btu/h)
OUTPUT TO CENTRAL HEATING
Modulating 9.2-24 kW
(31 ,400-82,000 Btu/h)
MAXIMUM DOMESTIC HOT WATER FLOW RATE FROM THE APPLIANCE Nominally 8.5 litres/min (±15%) •
(1.87 gallons/min)
EQUIVALENT DOMESTIC HOT WATER FLOW RATE TO GIVE A TEMPERATURE RISE
Nominally 9.8litres/min
OF 35°C (2.16 gallons/min)
4

4. Siting The Appliance
4.1 The appliance may be installed in any room although par·
ticular attention is drawn to the requirements of the current
I.E.E. Wiring Regulations and, in Scotland, the electrical provi·
sions 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 contain·
ing 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 does not require any special wall protection.
4.4 The wall must be capable of supporting the weight of the
appliance. See 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.
Installation
Servicing
Above the flue elbow 30mm 30mm
Above - Vertex Flue 150mm 150mm
In front 600mm 600mm
Below 230mm 230mm
Right hand side 20mm 20mm
Left hand side
Smm Smm
4.7 The appliance can be installed in a cupboard 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 13 mm. See BS 6798:1987.
4.9 No combustible surface must be within 75 mm of the cas-
ing. See BS476:4.
4.10 The distance between the inner face of a cupboard door
and the cabinet front should not be less than 75 mm.
4.11 Always consider the possible need to disconnect the pipes
from the appliance after installation.
4.12 The appliance has a vertical flue option. See Section Sa.
Fig. 2. Appliance casing dimensions and required clearances.
100mm
r:~: :.~.~.~~.~~~:~:•1ys~~
for installation and servicing.
..,.._._....___....__.., ________________ ..,
I
I
I
I
I
I
I
I
I
I
I
///////////
I ( I I f
I I
150m
I I
I I
I
m
I I
I
----- -i -------
I
I I
I I
I I
I I
I
l225mm ..... I
I I
I I
I I
I I
I I
I I
900m
Ill
Mounting wall
SIDE VIEW
600 mm
Space required in front
I
I
I I
FRONT VIEW
I
I I
for installation and servicing.
320mm
I
I
I
I
I
I
I
I
I
I
I
I
I
I
450 mm
I
I
I
/ Fixing holes
I r-- 41.3 mm CRS. ____,
I ~-~0~: __ f _________ ..J
1
1 I
~ 1 Space required below 5 mm 1 : 1
! li
I
114-J "llfI
/). 1 for installation and servicing. Space required at left hand side ---+-1 I+- -+1
/). _________ j + for installation and servicing. !L ______________ _j
20mm
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
~
Space required at right hand side
fu1 insl~ll~tion and servicing.
5

Fig. 3. Appliance pipework connections.
~, ~ORCESTER 240
POvmiOH.
WATER•oo
OfFoo
HEATING&WAURee u
=m= :e··,_
- = :..:::;.r -
OE!d.o.ND.
Central heating flow ---lr-----t
Central heating return
Mains cold water in --1----
Pressure relief valve discharge --+--------- 306 mm --..-j
..I \ ..
. .
min TEMPERATURE ma•
Gas cock -1-------------405 mm -------~
5. Siting the Flue Terminal
See Fig. 4
5.1 The flue must be installed as specified in BS 5440:Part 1.
5.3 The terminal must not cause an obstruction nor the dis-
charge cause a nuisance.
5.4
If the terminal is fitted within 850 mm of a plastic or painted
gutter
or within 450 mm of painted eaves then an aluminium
shield at least 750 mm 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. See Sec-
tion 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 sit·
ing where this could cause a nuisance should be avoided.
5.8 Take care to ensure that combustion products do not enter
ventilated
roof voids.
Fig. 4. Siting of the flue terminal.
MINIMUM SITING DIMENSIONS FOR POSITIONING THE BALANCED
FLUE TERMINAL.
A
6
Sa. Vertical Flue System
5a.1 A vertical flue with a primary length of between 500 mm
and 2000 mm can be fitted to the appliance.
5a.2
It is recommended that any secondary flue be of the twin·
walled type such as that manufactured by Rite-Vent or Selkirk.
Refer to BS 5440: Pt.1 for details of secondary flue lengths.
5a.3
The secondary flue must fit into a Gas Council approved
ridge tile or GC1 terminaL
5a.4 Fitting instructions for a vertical flue are enclosed with the
flue kit.
TERMINAL POSITION MIN. DISTANCE
--·~-
A-Directly below an openable window or
300 mm (12in.)
other opening
e.g. air brick.
B-Below gutters, soil pipes or drain pipes.
75mm
(3in.)
C-Below eaves.
25mm
(1in.)
0-Below balconies or car port roof. 25mm
(1in.)
E-From vertical drain pipes and soil pipes.
25mm
(1in.)
F
-From internal or external corners. 25mm
(1in.)
G-Above ground, roof or balcony level. 300
mm (12in.)
H-From a surface facing aterminal. 600 mm (24in.)
I
-From a terminal facing a terminal. 1200
mm (47in.)
J -From an opening in a car port (e.g. door,
window) into dwelling. 1200 mm (47in.)
K-Verlicdlly frum d lermindl un lhe ~dme
wall. ·tSOmm
(6tn.)
L-Horlzontally from a terminal on the same
wall. 300
mm (12ln.)
M-From door, window or air vent (achieve
where possible).
150mm
(6in.)

6. Air Supply \
6.1 The appliance does not require a separate vent for combus-
tion air.
6.2 Installations in cupboards or compartments require perma-
nent 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. The clearances required
7. Sealed Syst~m ·
See Figs. 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 pressure relief valve operates at 3 bar (45lb/inl The dis-
charge must be directed away from electrical components 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 10 litre expansion vessel is charged to 0.5 bar and is
suitable for a static head of 5 metres (17 .5ft). The pressure can
be increased if the static head is greater than 5 metres (17 .5ft).
7.6 With an initial system pressure of 0.5 bar, a system capacity
of about 104litres can be accommodated. Refer to BS 707 4 Pt. 1
for more information. The charge pressure can be increased but
with a decrease in system volume.
Fig. 5. Sealed primary water system.
Lockshield valve. Radiator valve.
lllllllll J
Note. A drain cock should be installed at
the lowest point of the heating circuit and
beneath the appliance.
7
for Installation and Servicing will normally be adequate for venti·
lation. See Section 4.6.
6.4 The minimum free areas required are given below.
Position of
Air from
Air direct
air vents the
room
from outside
High Level
277 cm
2• 138cm2•
(43 in
2
.)
(21.5 in
2)
Low Level
277 cm
2• 138cm2•
(43 in
2
.)
(21.5 in
2
.)
6.5 Refer to BS 6798 and BS 5440:2 for additional information.
7.7 The filling point must be at low level. See Figs. 5 and 6.
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. See Figs. 5 and 6
7.9 The make-up vessel must be fitted with a non-return valve.
7.1 0 Repeated venting loses water from the system. It is essen·
tial that this water is replaced and the system pressure main·
tained.
7.11 Connections to the mains water supply must not be made
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.
7.16 To make use of the extra heating available from the appli·
ance at the end of any demand, it is recommended that a single
small radiator be left permanently open.
A~~li•nr.e r.••ino.
H~=t2:1•t- ·Gas to Water
heat exchanger
Sealed system
.... -·--expansionvessel
-·Water to Water
heat exchanger
Central heating
by-pass adjuster -~+-----l-++-----1
Fill point -----'
Heating return
Heating flow.
Domestic hot water out
~
I
I
Note. The mains cold inlet
connection to the appliance
must come before any other
connection from the cold supply.
Domestic
cold water.
__ British Standard
stop valve.
Fixed spindle type.
+- Water main.

Fig. 6. System filling and make-up.
Heating Return
Non return
valve
+-
Worcester Combi·Fill System
8. Open Vent Primary Water System
See Fig. 7
8.1 The size of the flow and return pipework is given in Section
3 - Table 4. The components required to connect the appliance
to an open vent system are available as an optional extra kit.
8.2 The feed and expansion cistern should be arranged so that
there
is a minimum static head of 0.3 metres (12in.) above the
top of the appliance or above the highest point in the heating
circuit, whichever is the higher. See Fig. 7.
8.3 The feed and vent pipe should be 22 mm diameter and rise
Fig. 7. Open vent water system.
S.H.-Minimumstatic head 300mm 112 in.)
measured from the top surface of the
appliance or highest point in the heating
system to the water level in the feed and
expansion tank.
Feed and expansion tank
-------,
Lockshield valve. Radiator valve.
lllllllll J
11111111
Note. A drain cock sho~ld be installed at
the lowest point of the heating circuit and
beneath the appliance.
I
I
I
I
I
I
I
I
I
I
8
Heating Return
Auto
air vent
~""'i'illt-- Fill Point
' Heating Return
300mm 112in) min.
above the highest
point of the system.
continuously from the appliance to the feed and expansion cis·
tern.
8.4 Apressure
relief valve is not required on an open vented sys·
tern. If the pressure relief valve is left in position then a discharge
pipe must be fitted which terminates in a position such that any
water or steam discharge does not cause a hazard to the occu·
pants or damage electrical components.
8.5
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 point.
8.6 The pump is set to maximum and must not be reset.
8. 7 To make use of the extra heating available from the appli·
ance at the end of any demand, it is recommended that a single
small radiator be left permanently open.
Central heating
Appliance casing.
t-!~~~·t-- Gas to Water
heat exchanger
-·Water to Water
heat exchanger
by-pass adjuster -~+-+-!-+--'
Fill point ---- .../
Heating return
Heating flow.
Domestic hot water out
I
Note. The mains cold inlet
connection to the applianoe
must come before any other
connection from the cold supply.
Domestic
cold water.
-- British Standard
stop valve.
Fixed spindle type.
.., Water main.

9. Domestic Hot Water
I
9.1 The following are general requirements and, if necessary,
reference should be made to the local Water Company before
fitting the appliance.
9.2 MAINS COLD WATER INLET. Devices capable of preventing
the flow of expansion water must not be fitted unless separate
arrangements have been made.
An expansion vessel connection
point (Rc'/2)
is provided adjacent to the flow switch within the
appliance.
A Zilmet 2160 expansion vessel
is the preferred type. A thread
sealant compatible with potable water must be used.
9.3 The final 600 mm of the mains cold water connection to the
appliance should be made
in copper tube only.
9.4 The appliance is suitable for a mains pressure of up to 10
bar (150 lb/in').
9.5 The appliance is fitted with a mains supply isolating valve.
9.6 The maximum domestic hot water flow rate is 8.5
litres/min. (± 15%) (1 .87 gallons/min.).
9.7 In winter (when the mains inlet water temperature is lower)
a reduced flow rate at the taps will be required to achieve the
maximum hot water delivery temperature available
in warmer
weather.
9.8 It is a requirement that long pipe runs to the taps or shower
should
be insulated to prevent the rapid cooling of domestic hot
water after a tap or shower has been turned off. Refer to
BS5546:1990.
9
9.9 Hot and cold taps and mixing valves used with this appli-
ance must be suitable for operating at a pressure ofup to 10 bar
(150 lb/in').
9.10 No anti-syphonage arrangements are necessary except for
some loose head showers. See also Section 9.11 following.
9.11 Thermostatically controlled or pressure equalising shower
valves
will guard against the flow of water at too high a temper-
ature.
9.12 The head of a loose head shower must not fall closer than
25
mm (1 in.) above the top edge of the bath to prevent its
immersion
in bath water. Alternatively the shower must be fit-
ted with an anti-syphonage device at the point of the flexible
hose connections.
9.13 The supply of hot and cold mains water direct to a bidet is
permitted, (subject to local Water Company requirements), pro-
vided 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 nec-
essary.
9.14 As the maximum temperature of the Water to 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.
Installation of a scale inhibitor assembly should be
in accor-
dance with the requirements of the local Water Company. An
isolating valve should be fitted to allow servicing. The water
hardness can be determined using a standard test paper or by
reference to the local Water Company.

· 10. ElecJrical
See Figs. 8, 9, 10,11 and 12.
1 0.1 MAINS SUPPLY. 240 V - , 50 Hz, 270 watts.
External Fuse 3A. Internal Fuses: T2A (F1) and T315mA (F2).
10.2 It must be possible to completely isolate the appliance.
10.3 Connection to the mains supply should be via a double
pole isolator with a contact separation of 3mm in all poles and
supplying the appliance and controls only.
10.4 The appliance must be earthed.
10.5 Mains Cable. 0.75 mm
2
(24 x 0.20 mm) to BS 6500 Thble
16.
Ifa new cable is needed it must be connected into the terminals
marked L (Brown or Red lead), N (Blue or Black lead) and the
Fig. 8. Wiring Diagram-Control panel and facia.
(All components shown viewed from front of appliance)
earth stud and
be held securely in the cable clamp. For access
refer to Section 14.
10.6 The wiring between the appliance and the electrical supply
shall comply with current lEE Wiring Regulations and any local
regulations which apply.
10.7 If a room and/or frost thermostat is to be fitted refer to
Figs. 11 and 12. 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.
1 0. 9 A time switch or programmer can be fitted externally to the
appliance.
1 0.1 0 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.
r-----------T---------------r-------------------,
! Indicator Lights I Operating Switch I = :
I I ~I I
I POWER ON I WATER w I I
I I OFF br;: 1 I
I : HEATING & WATER w I I
I DEMAND I br I I
I 9 I I
I : I max I
~-------------~ ---------- __ JL_____ --------------~
I Temperature Control I
:______________ ----------- __ P~e~i~eter__ _ ______________ j
Control Facia
Control Panel
.---------------
,.D.,
-cbr:!!! I
r-----·---- br-1 I -----.,
1
1
TO TO TO TO
SPARK FAN GAS VALVE GAS VALVE
ELECTRODE MAIN PILOT
-----.,
SEQUENCE
BOARD
~m· ~ ~ ~~ [;JrEsr OverheatThermostat I
br • 3X o X11 bk bk :
• • 410 3 8F2 FUSE I
br~1 4 tJ I
r----bl
0 2
XB MAIN DRIVER BOARD I
I 0 3 ~ F1 I
I ~~XJ FUSE X
11
~1 y
o 3E 2 pk
4E X5 X4 X3 X2 3 v
l12 31 2312345123 4561234 5 si
'€ gyblbrbr orr 11111 wyg vr wwrr y y
gy '-!-~ _ffl!OJJJ!!t r1 Jr~ !ttt tr_ r~
~y PV~MP '(tPU:MP 11 ~ ... ~ ~W~AOTER ~~ ~
F CENTRAL DOMESTIC GAS VALVE
'--------' OVERRUN :;; !Q DIVERTER HEATING HOT WATER MODUREG
THERMOSTAT 51 ~ VALVE SENSOR SENSOR REGULATOR
12 ~ MICRO.SWITCH
COLOUR CODE
br-brown bl-blue gy-green and yellow bk-black or-orange
r-red w-white y-yellow g-grey v-violet pk-pink
/'
10
..,
__ _,

Fig. 9. Wiring diagram-Components outside control panel.
(All components shown viewed from front of appliance)
,------------
,---------
r
I
I
I
I
I
I
I
I
I
I
I
I
/
/
I COLOUR CODE
~ br-brown bl-blue gy-green and yellow bk -black or-orange
I ~ r-red w-white y-yellow g-grey v-violet pk-pink
I I -·- -·--.-=;!
_ _1..---. ---· ----------·-- . L.-·-
L-.---
.T·-·-·
I I
I I
I I
I I
I ~
I
I
Spark Electrode @
w
br bl
-------l
---...... I
", I
1 I
1 I
I I
Pump
Overrun
Thermostat
or
----~
_____ _j I
__ _l_L.
-::·. :==:.::=..:.-. r-r·
: I
I I
I I
I I
I I
/) I
____ __,// I
I
I
I _
__, ------- --l
E H
11
Gas Valve
~~ Domestic Hot
~'W) Water Sensor
r r
J
Main Valve
Modureg
Regulator
Pilot Valve
I
I
I
I
I
I
I
I
I
I
I
• ..L

LIVE
IN
black
POWER ON
INDICATOR
black
DEMAND
INDICATOR
,---
1
X111PIN 11
FLSE F1
T2A
FROST THERMOSTAT IIF FITTED!
~------------X4-IP.IN~~~-~~41~PIN_5_1------------------~--~
X41PI~ Jl
t:ro"Nn
X101'1~ 3•
white X10 (PIN 21
O~ER.aTING SWITCH
(OR PROGRAMMER)
WATER DIVERTER VALVE
MICRO SWITCH
grey
DHW
X31PIN 31
'
I
I
L ________ _
X51PIN 11
brown
PUMP OVERRUN THERMOSTAT
orange
L- -----------------------
X51PIN 21
X61PIN 31
brown
TRANSFORMER
OVERHEAT THERMOSTAT
-;,w.,.;;;,-,.., l ~ i""'B.i
I 15 15 BOARD
RELAY RY1
ELECTRONICS
FUSE F2
T315 mA
X31PIN 41
red
ELECTRONICS
X31PIN 51
CENTRAL HEATING SENSOR
DOMESTIC HOT WATER SENSOR
TEMPERATURE CONTROL POTENTIOMETER
I
I
I
.0..01
I
I
I
I
"'
""
~
a:
CN2
I PIN L21
white
~
;;;:
:3
w
a:
brown
CN51PIN FLI
CN21PIN L31
brown
I
I
I I
SAFETY
I CIRCUITS H.,_:;;;:..;;;:_-1
I
I
I
_____ _J
L ----
N
N
N
Fig. 10. Functional flow diagram.
PUMP
~------------------------------------------------~N
~--------------------------------------------------~N
Fig. 11 . Room thermostat
connections.
Remove link.
Terminal X4 on
main driver board.
Hcneywell room thermostat
T60608 (or similar.)
Fig. 12. Frost thermostat
connections.
Terminal X4 on
main driver board.
Honeywell frost thermostat
T 4160A (or similar.)

11 . Installation
The appliance is supplied suitable for fitting to a sealed system.
If it is to be fitted to an open vent system refer to Section 11 .2
following and Section 8.
11 .1 The standard flue length is from 1 00 mm to 1000 mm
measured from the appliance casing to the outer wall.
The extended flue length is from 1 001 mm to 2000 mm. Only
one extension may be used.
The flue must be installed as specified in BS 5440 Part 1.
Avertical
flue system is available. Instructions for fitting a verti·
cal flue system are enclosed with the flue kit.
Note. READ THIS SECTION FULLY BEFORE COMMENCING
INSTALLATION ·
11 .2 GENERAL FIITING.
Check that the appliance carton contains:- Appliance
Installers Instruction Pack Appliance Mounting Plate
Users Information Pack Installer Hardware Pack
Fig. 13. Appliance mounting plate and flue position.
0
.L.._----L..-f--71-~:~:~::::: __ :;.l--~~"~~E-
Rear flue opening centre line indicators
REAR FLUE POSITION
Fig. 14. Marking out the side flue position.
Mounting wall
Mounting plate
13
Check that the position chosen for the appliance is in accor-
dance with the instructions given in Sections 4 and 5.
The distance from the bottom of the mounting plate to the top
of the appliance casing is 1 06mm.
Hold the appliance mounting plate to the wall. Check that the
plate
is horizontal. See Fig 13.
Mark the position of the fixing holes and the position of the flue
hole centre line onto the wall. Draw a horizontal line along the
bottom
of the mounting plate.
Rear Flue - Mark a vertical line through the flue hole centre point.
Measure upwards 208 mm from the bottom of the mounting
plate
and mark the point. This is the centre point of the flue duct
hole. See Fig 13.
Side Flue -Extend a horizontal line from the bottom of the
mounting plate along the appropriate wall. Check
that it
remains horizontal and measure
208 mm upwards and mark a
horizontal
line. Measure 130 mm from the junction of the walls
and mark a vertical line which will then give the position of the
flue hole. See Fig 14.
SIDE FLUE POSITION
Side flue hole
110mm dia.
(150 mm dia. for
internal fixing).
208 mm
~------ ""-......_ Sidewall 1
I '-...
I "'-.
........
..........
·........r-~

Drill the two fixing holes 60 mm deep for No. 12 size plugs. Cut
the flue duct hole at 110 mm diameter (150 mm dia. for internal
fitting). Ensure that the hole is horizontal through the wall.
Fix the appliance mounting plate, and check that it is horizontal
before tightening the two screws.
The gas and water pipes can be led towards the appliance at
this stage.
See Fig 3. It is recommended that temporary connec·
tions be made to thoroughly flush the central heating system.
Also flush the primary cold water supply pipe before the appli·
ance is fitted to the wall.
Hang the appliance onto the wall. Drill (at a slight rising angle)
through the two appliance fixing holes at the bottom of the cas·
ing. Plug and fix the casing bottom. Connect the gas, water and
pressure relief valve connections to the appliance. A 15 mm
shut·off valve (supplied with the Installer Pack) must be fitted to
the cold water supply connection. See Fig 3.
Remove the cabinet front panel and the inner casing cover. Refer
to Section 14.3 (a and b).
Sealed System:
Unscrew and discard the automatic air vent cap. See Fig 15.
Open Vent System:
Undo the three screws securing the casing sealing plate. Discard
the plate and retain the gasket. See Fig 16. Remove and discard
the automatic
air vent. Fit the preformed pipe (optional extra)
using the three screws, washers and gasket. See Fig 1 7. Connect
the feed and expansion tank.
If the air and flue duct assembly is to be fitted from inside the
room then the ducts must
be cut to length, assembled and
inserted through the
wall at this stage before fitting the flue
elbow to the appliance. Refer to Section 11 .3 following for the
assembly
of the air and flue ducts.
Remove the fan. See Section 14.3(e).
Fig. 15. Automatic air vent.
Unscrew and discard the cap
Automatic air vent
!Sealed systems only)
lllllll111 mmm
Feed and vent connection --
!Open vent water system only)
Gas to Water heat exchanger
14
Fig. 1 6. Cover plate (Sealed Systems).
Appliance casing top panel
Cover plate fixing screws (3)
Fig. 1 7. Pipe connection for open vent
systems.
Appliance casing top panel
To Gas to Water heat exchanger
Fig. 18. Flue elbow fixing.
Flue elbow
Apply a smear of
silicone sealant to
~----11-------1 --plain end of elbow
Appliance top panel

11.3 AIR AND FLUE DUCT PREPARATION AND
ASSEMBLY
Check the contents of the standard flue duct kit against the
packing list. Similarly check the extension duct kit if applicable.
Remove all the packing from the ducts and terminal assem·
bly.
The standard flue kit accommodates a flue assembly up to 1000
mm in long measured from the appliance casing to the outer
wall face. See dimension L
Figs. 19 and 20. When dimension L is
greater than 1000 mm the extension flue assembly will be re·
quired.
Measure and cut the air and
flue ducts to length ensuring that
the cuts are square and free from burrs. Always check the
dimensions before cutting the ducts.
EXTERNAL FITTING OF THE DUCT ASSEMBLY
Rear Flue Assembly
Measure distance L. See Fig 19
Air duct length = L + 73 mm.
Flue duct length = L + 128 mm.
Fig. 19. Flue duct length (rear flue).
Do not cut the drilled end of either duct.
Assemble the air and
flue ducts to the terminal. Drill through the
holes
in the terminal into the air duct and fix using the screws
provided. See
Fig. 21. )oin the extension ducts to the standard
ducts as indicated
in Fig. 22 applying a smear of silicone sealant
to the end of the
flue duct. Drill and screw together the air ducts.
Push the assembly through the wall from outside the premises.
Fix the assembly to the flue elbow.
Drill through the holes in the elbow into the flue duct and fix
with the screws provided. Access is gained by slightly withdraw·
ing the flue duct. Spread a smear of silicone sealant around the
elbow and push the air duct into position.
Drill and fix the air
duct to the elbow. See
Figs. 21 and 23.
Align
the flue elbow with the spigot on the appliance using
silicone sealant.
See Fig. 18.
Align the clamp with the top of the spigot. Seal any small gaps
in the spigot beneath the clamp with a small quantity of sealant.
Make good the internal and external brickwork or rendering.
Refit the fan. Do not use any sealant on the joint. Replace the
inner casing cover.
~ 11l
--,....-~-- ------- r ~-:akegood
I
I
/ I I --..,
/ I Flue assembly : I
10mm--.:
I ~~--- ----
I
1 /
,----------~
'
External wall face
Rear face of appliance and face of mounting wall.--
Note. Diagram shows the appliance mounted
on an internal wall but in many cases will be
mounted directly on to the external wall, in
which case L will be the overall thickness of the
external wall.
Fig. 20. Flue duct length (side flue).
L Distance between rear face of appliance and
!-----___;;.;.__ ___ __,+-- external wall face including any rendering.
~>-------- __ R:-_:···""
/ I I --..,
/ I Flue assembly
1 I
I I :
1 tomm-J r :
I I
~•
~~---- ----- ---1._ ~~~~
I /
,----------~
'
Appliance side panel -
L
15
Distance between side panel and external wall
face including any rendering.

Fig. 21 . Flue elbow, ducts and terminal assembly.
~d:...._ __ .j... Airducttoterminal
rLL- ~ d fixing screws
Flue duct
I
Flue elbow
t:e elbow to air duct fixing screws
-~::C:====::::;\::i._..:._....., ~ Airducllength • L+ 73 mm (rear flue) ----~
Appliance casing _ L+ t70 mm (side flue)
Flue terminal
L ---------1
Fig. 22. Flue assembly using the extension ducts.
r------- Flue duct length • L+ 128mm (rear flue) -------------------1
I
Appliance casing -
Fig. 23. Flue elbow.
Access to the flue duct fixing holes
Flue elbow to flue duct fixing holes
L+ 225 mm (side flue)
Air duct fixing screws
+
Standard flue duct
Smear of silicone sealant
Flue duct extension
+
Air duct extension
Appliance cosing
I
Standard air duct ~
Air duct length •L+ 73mm (rear flue) ------------~
L+ 170 mm (side flue)
16
L
Assemble the air and flue ducts to the terminal. Drill through the
holes in the terminal into the air duct and fix using the screws
provided. See Fig. 21. join the extension ducts to the standard
ducts
as indicated in Fig. 22 applying a smear of silicone sealant
to the
end of the flue duct. Drill and screw together the air ducts.
From outside, push the assembly through the wall and enter the
ducts
into the flue outlet elbow.
Pull back the air duct slightly to allow access to the flue duct.
Drill through the holes in the elbow into the flue duct and fix
with the screws provided. Spread a smear of silicone sealant
around the
elbow and push the air duct into position. Drill and
fix the air duct to the elbow. See Figs. 21 and 23.
Align the flue elbow with the spigot on the appliance using
silicone sealant. See Fig. 18.
Align the clamp with the top of the spigot. Seal any small gaps
in the spigot beneath the clamp with a small quantity of sealant.
Make good the internal and external brickwork or rendering.
Refit the fan. Do not use any sealant on the joint. Replace the
inner casing cover.
Side Flue Assembly
Measure distance L. See Fig. 20.
Alr duct length =L + 170 mm.
Flue duct length = L + 225 mm.
Do not cut the drilled end of either duct.
11 .4 INTERNAL FITTING OF THE DUCT ASSEMBLY
(rear and side flues)
Measure and cut the ducts as previously described for external
fitting (Section 11.3). Fix the ducts to the terminal and fit the

rubber sealing gasket and clamp to the terminal. Centralise the
gasket and tighten the
clamping ring. See Fig. 24. Slide the flue
centring ring, available from Worcester Heat Systems, onto the
air duct and tighten the screw. See Fig. 25. Fix the ducts and
terminal assembly to the
flue outlet elbow as described in
Section 11.3 preceding.
Push the assembly through the wall so that the gasket flange is
against the outside face of the wall. See Fig. 25.
Align the flue elbow with the spigot on the appliance. Align the
clamp with the top of the spigot.
Seal any small gaps in the
spigot beneath the clamp with a small quantity of sealant.
See Fig. 18.
Refit the fan. Do not use any sealant on the joint. Replace the
inner casing
cover.
Seal the gap around the duct with the flexible seal provided and
make good. See Fig. 25.
Fig. 24. Terminal assembly for internal
fitting of the flue.
11.5 FINAL INSTALLATION
Check that all the water connections and the gas connection
have been tightened.
If a facia mounted programmer is to be fitted, unscrew the
upper
two screws holding the facia panel in place and carefully
lower the facia. See Fig 26.
Unplug the Operating Switch from terminal X1 0 on the main
driver board. See Fig. 8. Unscrew the four screws holding the
switch plate and remove the complete Operating Switch assem-
bly. Fit the programmer and tighten the four screws. Plug the
programmer
into terminal X1 0 on the main driver board.
Lower the control box as described in Section 14.3(d).
Connect the mains electrical supply to the appliance and con-
nect any room and/ or frost thermostats. The electrical leads to
the room and frost thermostats must pass through the appropri·
ate holes in the control panel and be fixed with the cable clamps
provided. See Fig. 27.Refit the facia panel.
Test the gas supply pipework up to the appliance for soundness
as indicated in BS 6891.
Refer to Section 12 for a full description of the filling, venting
and, with a sealed system, the pressurising of the system.
Ifthe appliance is not to be commiSSioned immediately, replace
the cabinet front panel. Check that the gas supply, the electrical
supply and the water connections are all turned off.
If the premises are to hP. !P.ft unn~~upiP.ri during frosty condi·
tions, then commission the appliance as described in Section 12
and leave it under the control of the frost thermostat or leave
operating continuously with the room thermostat set at 6°C.
17
Fig. 25. Duct and terminal assembly for
internal fitting of the flue.
Duct assembly
Air duct
Fig. 26. Appliance casing and control
equipment fixings .
• ,.
Inner casing cover fixing screws (4)
• •
p c
Control box fixing screws (2)
Upper facia panel fixing screws (2)
l
I
•
--·
., .... C
m:e
0''0(1
~ .,_;;.. .
-·
lll.I.Ma•w•n•-
~I \ '
- ,.-..,""""-
-
Lower facia panel fixing sc1ews (2)

-
~
[;]
.------ 0 ..
• •
[ill
rn
It
rn
~
SEQUENCE
..
m
BOARD
'-
TO TO
GAS VALVE GAS VALVE
MAIN ~LOT
Fig. 27. Electrical cable exits from control box.
" 12. Commissioning 0-
12.1 The appliance is dispatched with the controls set to pro·
vide a maximum output for domestic hot water of 24 kW
(82,000 Btu/h) and satisfy a central heating load of 16.1 kW
(54,900 Btu/h).
The controls can be reset to incr~ase the heat load capability to
24 kW (82,000 Btu/h). Refer to Section 12.4- Central Heating. It
is not necessary to set the output below 16.1 kW (54, 900
Btu/h) as it is automatically modulated to satisfy lower heat
loads.
Domestic
Hot Water System. Check that the mains water sup·
ply 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, must
be inspected and tested for soundness and purged as indicated
in BS 6891.
12.2 APPLIANCE AND CENTRAL HEATING SYSTEM
PREPARATION
Remove the cabinet front panel.
Check that the electrical supply and the gas service to the appli-
ance are off. See Fig 3.
Check that all the water connections throughout the system are
tight.
Open the system valves at the appliance. See Fig 3. Open all the
radiator
valves, fill the system and vent each radiator in turn.
On sealed systems the automatic air vent, (fixed to the flow
manifold) will vent the appliance. Remove the boiler inner casing
cover
to check that the air vent cap has been removed. See Figs
15 and 26. Replace the cover immediately.
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. 28. Lower the control box to
gain access. Refer to Section 14.3(d).
SEALED SYSTEMS ONLY
Set the Expansion Vessel Pressure
The charge pressure of the expansion vessel as despatched is
0.5 ba1; which is £:J~]Liival£:Jnt to a static head of 5 metres (17ft).
The charge pressure must not be less than the static head at the
point
of connection. See Fig. 5. ASchraider type tyre valve is fit-
ted 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/ins') and check for water soundness. Release water from the
TO
FAN
18
m
~
MAIN DRIVER BOARD
GJ
Earth MAINS
TO TO
TO TO TO TO
PUMP
PUMP
WATER CENTRAL DOMEsnC GAS VALVE
OVER-RUN
DIVERTER HEATING HOT WATER MODUREG
THERMOSTAT
VALVE SENSOR. SENSOR REGULATOR
MICRO-SWITCH
TO ROOM THERMOSTAT -
'-TO FROST THERMOSTAT
IOPTIONALI
!OPTIONAL)
system using the 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 to 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 sys-
tem pressure.
If the pressure indicated on the pressure gauge is greater than
2.6 bar when operating at the maximum central heating
tem-
perature, an extra expansion vessel must be fitted to the system
as close as possible to the appliance central heating return con-
nection.
The appliance (as despatched) can accommodate a system vol-
ume 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 speci-
fied replacement must be fitted .
12.3 PROGRAMMER
Any programmer fitted on the appliance should be set up at this
stage
following the instructions sent with the programmer. The
programmer will retain the settmg for up to four weeks following
an interruption in the electricty supply.
Fig. 28. Pressure relief valve.
Test knob
Pressure relief valve discharge pipe

12.4 APPLIANCE OPERATION
Check that the electrical supply to the appliance is off.
Set the Operating Switch (or Programmer) to OFF.
Remove the inner casing cover. Refer to Section 14.3(b).
Disconnect the electrical connections from the main solenoid.
Do not leave them unprotected. See Fig. 29. Turn on the gas
supply and reconnect the electricity supply.
Set the Operating Switch (or Programmer) to HEATING &
WATER. A continuous ignition spark will occur until the pilot is
alight and sensed by the control circuit. The fan will run but the
main burner will not light. Test for gas soundness at the joint
between the pilot pipe and the burner with leak detection fluid.
Observe the pilot flame. It should be about 18-20 mm long and
envelope the spark electrode tip. If not, refer to Section 14.4.
See Fig. 35. If the pilot still does not light, contact Worcester
Heat Systems Service Department.
Set the Operating Switch (or Programmer) to OFF and discon·
nect the electrical supply at the mains.
Replace the inner casing cover.
Reconnect the electrical connections to the gas valve.Loosen the
burner pressure test point
screw and connect a pressure gauge.
See Fig 29.
Domestic Hot Water
Set the Operating Switch (or Programmer) to WATER and fully
open a hot tap.
The boiler should light at a burner pressure of between 14 and
15mbar
(5.6 and 6.0 in. wg.). If the burner pressure is low, check
that the supply pressure at the
gas valve is at least 19 mbar (7.6
in.wg).
Note: The burner pressure is factory set and if (after checking
that the supply pressure
is sufficient) the correct pressure is not
obtained then Worcester Heat Systems
Service Department
should be contacted.
If the appliance does not light, check that the it is not in the
overheat 'lockout' state
by pressing the thermostat reset button.
See Fig. 30.
Gradually close the hot tap and check that the burner pressure
drops. Fully open the tap and check that the burner pressure ris·
es. Fully close the tap and check that the burner goes off. The
pump will continue running until the appliance has cooled to a
preset temperature.
Set the Operating Switch (or Programmer) to OFF.
Central Heating
Check that all the radiator valves are open. Set the room thermo·
stat and the Central Heating Temperature Control to maximum.
On sealed systems check that the system is prP.ssurisP.rl anr:l set
to the required pressure as indicated on the gauge.
Set the Operating Switch (or Programmer) to HEATING &
WATER.
The burner will light.
The appliance will modulate its output from 9.2 kW (31 ,400
Btu/h) to the set output of 16.1 kW (54, 900 Btu/h) over a peri·
od of about two minutes.
Check the system to ensure that all the radiators are heating up
evenly.
Shut down all but one of the radiators and observe the burner
pressure
fall. Open all of the radiator valves and check that the
burner pressure
rises.
Balance the system so that the required temperature difference
across the central heating flow and return pipes is obtained. See
Table 3.
Adjust the central heating by-pass valve until the same tempera·
ture difference is obtained. See Fig 31. This should be carried out
with only a single radiator operating. If thermostatic radiator
valves are fitted then one rudiator should be left uncontrolled.
The bypass valve should never be fully closed.
19
Ifthe heat load is in excess of 16.1 kW (54, 900 Btu/h) then reset
the controls
to the maximum of 24 kW (82,000 Btu/h) by care·
fully rotating the adjustment potentiometer to its maximum
postion.
Access is gained to the adjustment point by lowering
the electrical control box. Indicate the new setting pressure on
the data plate.
Set the room thermostat to minimum and check that the burner
goes out. Reset the room thermostat to maximum and the burn·
er will relight and follow the normal operating procedure.
Check for proper ignition of the burner after a break in the gas
supply. '!Urn off the gas service cock and wait for 60 seconds.
The main burner and pilot will go out but sparking from the
electrode
will continue. Carefully open the gas service cock and
observe the burner relight and
follow the normal sequence of
operation.
Set the Operating Switch (or Programmer) to OFF.
'!Urn off the gas service cock and the electrical supply to the
appliance.
Drain the system while the appliance is still hot.
Refill, vent and, with a sealed system, re·pressurise as described
in Section 12.2.
Domestic Hot Water and Central Heating
'!Urn on the electricity supply to the appliance and open the gas
supply
cock at the appliance.
Set the Operating Switch (or Programmer) to HEATING &
WATER. If a programmer is fitted, set the domestic hot water to
Continuous or 24Hrs and the central heating to ON. The burner
will light and heat will pass into the system. '!Urn on a hot water
tap
and check that fully heated hot water is discharged from the
tap.
Close the tap and the burner will go off. The appliance will then
return
to the central heating mode and automatically balance
with the system requirements.
Set the Operating Switch (or Programmer) to OFF and the burner
will go out.
12. 5 COMPLETION OF COMMISSIONING
Disconnect the pressure gauge and tighten the test point screw.
Restart the appliance and check for gas soundness around the
test point
screw.
Refit the cabinet front panel.
If the appliance is being passed over to the user immediately,
refer to Section 13 -Instructions to the User and set the controls
to the user's requirements.
If the appliance is to be left inoperative, check that the Operating
Switch is set to OFF. '!Urn off the gas service cock and switch off
the electricity supply.
Ifthere is any possibility of the appliance ctm.l system being left
inoperative during frosty conditions, drain the appliance and
system.
For short inoperative periods leave the boiler under the
control
of a frost thermostat or operating continuously under
the
control of a room thermostat set at 6°C.
. '
13. Instructions To The User
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 the heating system is not to
be used in frosty weather.
13.3 Tell the user the sealed system set pressure if applicable.
13.4 Tell the user of the importance of regular servicing. Worces·
tcr He<:~t Systems Ltd offer a comprehcm;ivc muintcnunce con·
lrcl(.:l.
13.5 Set the system controls to the user's requirements.
13.6 If an external programmer has been fitted which has a pro··
grammable domestic hot water facility then it is suggested that
Lhis be sel to Continuous or the equivalent.

Fig. 29. Gas valve.
Electrical connections- Main valve
(brown • blue • green/yellow)
Maximum pressure adjuster -------.
Minimum pressure adjuster __j
Note. Turn the nuts clockwise
to increase and anti-clockwise
to doc<M• <ho '"""" ~
Modureg cap
Modureg regulator head
Fig. 30. Overheat thermostat reset button.
Overheat thermostat reset button
=ro.:e-''',
- = ~ -
, '
I \
. . .
min TEMPERATURE max
Fig. 31 . Central heating by-pass adjuster.
Central heating flow
-:J'NI--7-f.--7-----;---- Pressure compensating tube
20
connection
f.--- Inlet pressure test point
01
"4. Inspection and Servicing "
14.1 To ensure continued efficient operation of the appliance it
must be checked and serviced
as necessary at regular inter·
vals. The frequency of servicing will depend upon the particu·
Jar installation conditions and usage, but once per year should
generally be adequate.
The extent of the service required by
the appiiance is determined by the operating condition of the
appliance when tested
by fully qualified engineers.
Any service work must be carried out by competent engineers
such as
British Gas or Corgi registered personnel.
14. 2 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. See Sec-
tion 6 - Air Supply.
Check the system and remake any joints or fittings which show
signs of leakage.
Refill, vent and, with a sealed system, re-pressurise as described
in Secti011 12. 2.
Operate the appliance and the system taking note of any faults.
Warning
Disconnect the electrical supply at the mains and turn off the
gas supply at the gas service cock on the appliance before ser-
vicing. See Fig. 3.
After completing the service always test for gas soundness as
indicated in BS 6891.
14. 3 DISMANTLE THE APPLIANCE
To carry out a full and comprehensive service of the appliance
remove the following parts to gain access to the components
which need to be checked or serviced.
(a) Cabinet Front Panel. Hemove by lifting off the supports.
(b) Inner Casing Cover. Remove the cabinet front panel.
Unscrew the four screws securing the cover to the casing and lift
off. Sec Fig 26.
(c) Facia Panel. Check that the electricity supply to the appli-
ance is turned off. Remove the cabinet front panel as described
in Section 14.3(a). Unscrew the two upper screws as shown in
Fig 26 and lower the facia taking care not to damage the pres-
sure gauge capillary tube or electrical connections.