Potterton Prima 30B User guide

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30B, 40B, 50B & 60B
balanced flue gas fired boiler
THIS APPLIANCE IS FOR USE WITH NATURAL GAS (G20) ONLY
Installation and Servicing Instructions
LEAVE THESE INSTRUCTIONS ADJACENT TO THE GAS METER

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POTTERTON PRIMA 30B G.C. No. 41 .605.94
POTTERTON PRIMA 40B G.C. No. 41 .605.95
POTTERTON PRIMA 50B G.C. No. 41 .605.96
POTTERTON PRIMA 60B G.C. No. 41 .605.97
IMPORTANT This appliance must be installed by a competent person as stated in the Gas Safety (Installation and Use)
Regulations 1994.
Prima boilers are certified for safety, it is therefore important that no external control devices (eg. flue dampers,
economisers etc.) be directly connected to these appliances unless covered by these installation instructions or otherwise
recommended in writing. Any direct connection of a control device not approved by Potterton could invalidate the
certification and the normal warranty.
LIST OF CONTENTS
General Page No.2 Installation Instructions Page No. 12
Optional Extras Page No.2 Commissioning Page No. 20
Accessories Page No.3 Servicing Instructions Page No. 22
Installation Data Page No.3 Health and Safety Information Back Page
Boiler Dimensions Page No.3 Control Systems )
Site Requirements Page No.5 Pipework and Wiring Guide, ) Supplied in Literature pack
User Instructions )
GENERAL - Page 2
Once the pilot has been lit Potterton Prima B boilers are
automatic in operation. They are wall mounted natural
draught balanced flue appliances, using a cast iron heat
exchanger and are available in four outputs ranging from
5.86-17.58kW (20,000-60,000 Btu/h).
The boilers which are designed to provide domestic hot water
and/or central heating must be used on INDIRECT hot water
systems only. The cast iron heat exchangers suitable for use
on. open vented gravity hot water/pumped central systems or
fully
pumped systems which may be sealed or open vented.
The standard balanced flue system (Part No.230043)
can be adjusted telescopically for wall thicknesses of
230mm-380mm (9-15’). Further adjustment can be made
down to a minimum wall thickness of 76mm (3) by
cutting the ducts.
For convenience, a lOOmm-175mm (4”-7’) telescopic
flue kit (Part No.230400) is available as an alternative to
the standard.
OPTIONAL EXTRAS - Page 2
The following are available as optional extras:-
FLUE EXTENSION KIT, suitable for a maximum wall
thickness of 610mm (24in)
Part No. 230230.
Part No. 230400
TERMINAL GUARD Part No.903766 to be used when the
terminal is fitted less than 2m above a balcony, above ground
or above a flat roof to which people have access.
PUMP COVER KITS, to conceal a pump at the top of a
boiler, in the following sizes:
Fixed (6in high) Part No. 225418
Adjustable (7in-1 2in) Part No. 225419
Adjustable (l3in-l8in) Part No. 225420
Adjustable (l9in-24in) Part No. 225421

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ACCESSORIES - Page 3
The following range of Potterton Myson system controls are
also available and further information will be provided on
request.
Electronic Programmer EP2001, EP3001, EP4001, EP5001
and EP6000.
Programmable Electronic Thermostat PET 1.
Thermostatic Radiator Valve.
Electronic Cylinder Thermostat PTT2 or PTT1 00
Electronic Room Thermostat PRT2 or PRT1 00
Motorised Zone Valve M5V222 or MSV228
Motorised Diverter Valve M5V322
INSTALLATION DATA - Page 3
The installation of the boiler must be in accordance with the
latest relevant requirements of the Gas Safety (Installation
and Use) Regulations 1994, local building regulations, lEE
Wiring Regulations and the byelaws of the local Water
Undertaking.
Detailed recommendations are contained in the following
British Standard Codes of Practice:-
BS6798. BS5440 Part 1.
BS5440 Part 2. BS5449 Part 1.
BS5546, BS4814,
BS6891 BUILDING REGULATIONS.
MODEL WATER BYELAWS.
BRITISH GAS PUBLICATION DM2.
GAS SAFETY (INSTALLATION AND USE)
REGULATIONS 1994.
BUILDING STANDARDS (SCOTLAND)
REGULATIONS.
BOILER DIMENSIONS - Page 3
Figure 1 BOILER DIMENSIONS

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BOILER DIMENSIONS - Page 4
Figure 2 GENERAL ARRANGEMENT

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SITE REQUIREMENTS - Page 5
These boilers are not suitable for external installation. The
appliance may be installed in any room, although particular
attention is drawn to the requirements of the current lEE
wiring regulations and, in Scotland, the electrical provisions
of the Building Standards applicable in Scotland with
respect to the installation of the appliance in a room
containing a bath or shower.
Where a room-sealed appliance is installed in a room
containing a bath or shower, any electrical switch or
appliance control, utilising mains electricity, should be so
situated that it cannot be touched by a person using the
bath or shower.
If installed in a bathroom, the point of connection to the
external electricity supply MUST be outside the room.
Where the installation of the boiler will be in an unusual
location special procedures may be necessary and BS6798
gives detailed guidance on this aspect.
Ensure that the gas supply pipe and meter are large
enough for this appliance and any others that may be run
off the same meter. Reference should be made to BS6891.
Boiler Mounting Surface.
The boiler must be mounted on a flat wall, which may be of
combustible material and must be sufficiently robust to take
the weight of the boiler. The requirements of the local
authorities and the Building Regulations must be adhered
to.
IMPORTANT NOTICE:
TIMBER FRAMED HOUSES
If the appliance is to be fitted in a timber framed building, it
should be fitted in accordance with British Gas Publication
‘Operational Procedures for Customer Service’ Part 19. If in
any doubt, advice should be sought from the local region of
British Gas.
Clearances Around the Boiler
The following minimum clearances must be maintained
after installation for correct operation and servicing of the
boiler:-610mm (2ft) at the front of the boiler.
5mm (0.2in) each side of the boiler.
50mm (2in) at the top, except where the optional pump
cover is to be fitted, when 178mm (7in) should be allowed.
102mm (4in) at the bottom.
Additional clearances to these may be required for
installation and are left to the discretion of the installer.
Ventilation
If the boiler is to be installed in a confined space such as a
cupboard, the space will need ventilating. Openings must
be provided at the top and bottom of the cupboard each of
which should have a free area as shown in TABLE 1.
Further details for installation of a boiler within a
compartment are given in BS6798.
TABLE 1
PRIMA B Area for air Area for air
from room from outside
sq. in sq. cm sq. in sq. cm
30 16 103 8 52
40 22 140 11 70
50 27 174 14 87
60 33 208 17 104
Siting of Balanced Flue Terminal
If a terminal is less than 2m above a balcony, above
ground or above a flat roof to which people have access
then a suitable guard should be fitted (Part No. 903766).
Refer to BS5440 Part 1 for further guidance. The minimum
spacings from the terminal to obstructions and ventilation
openings are shown in Figure 3.
Note:
Where a flue is fitted less than 1000mm from a plastic or
painted gutter or 500mm from painted eaves, an aluminium
shield of 1000mm length should be fitted to the underside
of gutter or eave.
Any car port or other add-on extension should consist of a
roof or a roof and one other wall. If it consists of a roof and
two other walls the installation shall be treated as suspect
and further advice sought.

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SITE REQUIREMENTS - Page 6
Figure 3 THE SITING OF BALANCED FLUE TERMINAL BOILER
POSITION MINIMUM DISTANCE
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
DIRECTLY BELOW AN OPENABLE
WINDOW, AIR VENT, OR ANY OTHER
VENTILATION OPENING
BELOW GUTTER, DRAIN/SOIL PIPE
BELOW EAVES
BELOW A BALCONY OR CAR PORT
ROOF
FROM VERTICAL DRAIN PIPES AND
SOIL PIPES
FROM INTERNAL OR EXTERNAL
CORNERS
ABOVE ADJACENT GROUND OR
BALCONY LEVEL
FROM A SURFACE FACING THE
TERMINAL
FACING TERMINALS
FROM OPENING (DOOR/WINDOW) IN
CARPORT INTO DWELLING
VERTICALLY FROM A TERMINAL ON
THE SAME WALL
HORIZONTALLY FROM A TERMINAL
ON THE SAME WALL
ADJACENT TO OPENING
mm
300
300
300
600
75
600
300
600
600
1200
1500
300
300
ELECTRICITY SUPPLY
A 240 volts — 50Hz., single phase electricity supply fused at
3A must be provided in accordance with the latest edition of
the lEE wiring regulations and any other local regulations
that may apply. The current rating of the wiring to the boiler
must exceed 3 amperes and have a cross sectional area of
at least 0.75mm2 in accordance with BS6500 1990 Table
16. The method of connection to the electricity supply
MUST
facilitate complete isolation of the appliance, preferably by
the use of a fused three-pin plug and unswitched,
shuttered socket outlet, both complying with the
requirements of BS1363. Alternatively, connection may be
made via a fused double pole isolator having a contact
separation of 3mm in all poles and serving the appliance
and system controls only.
TECHNICAL DATA - Page 6
Maximum Working Head 30.5m (l00ft)
Minimum Working Head (Fully pumped systems) 150mm (6in)
Minimum Circulating Head (Gravity systems) 1.2m (4ft)
Gas Supply Pressure 20 mbar
Maximum Flow Temperature 82 º C
Electricity Supply 240v -50Hz fused at 3A
Flow/Return Connection 28mm copper
Gas Supply Connection Rc, ½ (½ in BSP Female)
Power Consumption 20 watts
30 & 40 model 50 & 60 model
Water Content 1.8 litre 2.5 litre
0.4 gal 0.55 gal
Appliance Weight - installed 39.2 kg 46.8 kg
86.0 lbs 103.3 lbs
Appliance Weight - lift 31.0 kg 38.5 kg
68.0 lbs 85.0 lbs

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TECHNICAL DATA - Page 7
BOILER
SIZE INJECTOR SIZE GAS RATE m3/h (ft3/h) INPUT kW(Btu/h) OUTPUT kW(Btu/h) BURNER mbar PRESSURE in wg
Min 0.72 (25.68) 7.79 (26579) 5.86 (20000) 6.8 2.7
30 2.6mm 0.89 (31.75) 9.63 (32858) 7.33 (25000) 11.2 4.5
Max 1.06 (37.88) 11.49 (39204) 8.79 (30000) 15.2 6.1
Min 1.08 (38.55) 11.69 (39900) 8.79 (30000) 8.5 3.4
40 3.1 mm 1.25 (44.80) 13.59 (46370) 10.26 (35000) 11.2 4.5
Max 1.41 (50.51) 15.32 (52280) 11.72 (40000) 15.0 6.0
Min 1.43 (51.11) 15.5 (52900) 11.72 (40000) 10.3 4.1
50 3.5 mm 1.59 (56.71) 17.20 (58700) 13.19 (45000) 12.8 5.1
Max 1.74 (62.32) 18.90 (64500) 14.65 (50000) 15.8 6.3
Min 1.81 (63.79) 19.35 (66022) 14.65 (50000) 10.0 4.0
60 3.9 mm 1.94 (69.22) 21.00 (71650) 16.12 (55000) 11.5 4.6
Max 2.09 (74.78) 22.68 (77400) 17.58 (60000) 13.5 5.4
Circulation Pump Selection
The resistance through the heat exchangers when
operating with a water flow rate producing an 110 C
temperature rise at maximum boiler output is shown in
TABLE 2. If other controls, such as three-position valves
are used in the system, the resistance through them,
quoted in their manufacturers literature must be taken into
account. The pump may be fitted on either the flow or
return and on FULLY PUMPED systems MUST be wired
directly to the boiler terminal block, see Fig 21. It must be
fitted with two isolating valves which are positioned as
close to the pump as possible. Isolation of the valves must
always leave the open vent unobstructed.
Figure 4 PRESSURE LOSS ACROSS BOILER

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TECHNICAL DATA - Page 8
THE SYSTEM
The boiler must be used on INDIRECT hot water systems
only. It is suitable for use on open vented gravity hot
water/pumped central heating systems or fully pumped
systems which may be sealed or open vented.
The system should be designed so that the maximum static
head does not exceed 30.5m (l00ft) and a minimum on fully
pumped systems of 150mm (6in). See Fig 5. Gravity
domestic hot water circuits should have a minimum
circulating head of 1.2m (4ft). See Fig 6. Excessive
horizontal runs should be avoided, but if this not possible
the circulating head should be increased.
If the boiler is to be used on a system with gravity hot water
the bulb of the overheat thermostat should be repositioned
as shown on Figs 2 & 18.
To prevent reverse circulation in the gravity circuit when the
pump is running an injector disc is provided to form an
injector tee at the return connection on the boiler.
See Fig 17.
To prevent nuisance operation of the overheat thermostat,
it is important that where electrically operated zone valves
are used the boiler is wired so that it does not cycle when
the zone valves are closed. Also systems fitted with
controls that close both hot water and central heating
circuits while the boiler is still hot must be fitted with a by-
pass circuit to dissipate the residual heat within the boiler.
Further information on by-pass arrangements is provided in
later notes and illustrations.
Drain-off taps should be fitted in the pipework close to the
boiler and in low points in the system.
NOTE
Although the system can be emptied using the drain-off
taps in the pipework around the system, to empty the boiler
it is necessary to remove the drain-off plug situated in the
return header at the lower right-hand side of the casting.
See Fig 2.
COMBINED GRAVITY HOT WATER AND
PUMPED CENTRAL HEATING SYSTEMS
Where a cylinder thermostat and zone valve are fitted to
control the temperature of the domestic hot water it is
recommended that a by-pass be installed in the gravity
circuit. A suggested method of doing this is shown in Fig 6
where the bathroom radiator is connected into the gravity
circuit and is fitted with two Iockshield valves. Mechanically
operated thermostatic domestic hot water temperature
control valves which allow the boiler to operate when the
valve is closed
MUST NOT BE FITTED.
FULLY PUMPED SYSTEMS
The pump must always be wired directly to the
boilerterminal block as shown in Fig 21. If a three port
diverter valve is used as shown in Fig 5 a by-pass is not
necessary since one circuit is always open.
Where a pair of two port valves are used, a by-pass is
necessary. The total length of the by-pass circuit taken
from the boiler connections should be greater than 4
metres of 22mm pipe. It should be fitted with a lockshield
valve and adjusted to maintain a minimum flow through the
boiler of 4.5 litres/mm (1 gal/mm), see Figs 5 &7.
Systems fitted with controls which allow the boiler to
operate when both the hot water and central heating
circuits are closed (i.e. mechanically operated thermostatic
control valves) must be fitted with a by-pass circuit capable
of:-
1. Dissipating a minimum of 1 kW (3400 Btu/h).
2. Maintaining a minimum water flow through the boiler of
9 litres/mm (2 gal/mm).
A suggested method of meeting these requirements by
using a bathroom radiator fitted with two lockshield valves
is shown in Figs 5 & 7.
Additional system information can be found in the Control
Systems, Pipework and wiring guide.
SEALED SYSTEMS (FULLY PUMPED)
The installation must comply with the
requirements of BS6798 and BS5449 Part 1.
The British Gas publication ‘British Gas

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TECHNICAL DATA - Page 9
Specification for Domestic Wet Central Heating Systems’
should also be consulted.
Safety Valve
A non-adjustable spring-loaded valve, pre-set to operate at
3bar (451bf/in2) shall be used. It must comply with BS6759
Part 1 and include a manual testing device. It shall be
positioned in the flow pipe either horizontally or vertically
upwards and close to the boiler. No shut-off valves are to
be placed between the boiler and safety valve. The valve
shall be installed into a discharge pipe which permits the
safe discharge of steam and hot water such that no hazard
to persons or damage to electrical components is caused.
Pressure Gauge
A pressure gauge incorporating a fill pressure indicator,
covering the range 1 -4 bar (60lbf/in2) shall be fitted to the
system. It should be connected to the system, preferably at
the same point as the expansion vessel. Its location should
be visible from the filling point.
Expansion Vessel
A diaphragm-type expansion vessel to BS4814 Part 1 shall
be fitted close to the inlet side of the pump. The connecting
pipework should not be less than 15mm (½ in nominal).
Pipework connecting the expansion vessel should not
incorporate valves of any sort. Methods of supporting the
vessel are supplied by the manufacturer. The nitrogen or
air charge pressure of the expansion vessel shall not be
less than the hydrostatic head, (height of the top of the
system above the expansion vessel). To size the expansion
vessel it is first necessary to calculate the volume of water
in the system in litres. The following volumes may be used
as a conservative guide to calculating the system volume.
Boiler Heat Exchanger 6.5 litres
Small Bore Pipework 1 litre per kW of
system output
Micro Bore Pipework 7 litres
Steel Panel Radiators 8 litres per kW
of system output
Low Water Capacity
Radiators 2 litres per kW
of system output
Hot Water Cylinder 2 litres
If the system is extended, the expansion vessel may have
to be increased unless previous provision has been made
for the extension. Where a vessel of the calculated size is
not available, the next available larger size should be used.
The boiler flow temperature is controlled at approximately
82 ºC.
The vessel size can now be determined from the following
table where V = System volume in litres
Vessel Charge
Pressure (bar) 0.5 1.0
Initial System
Pressure (bar) 0.5 1.0
Expansion Vessel
Volume (litres) Vx0.833 Vx0.11
This is a general guide; if it is required to be more accurate
refer to BS7074.
Cylinder
The hot water cylinder must be an indirect coil type or a
direct cylinder fitted with an immersion calorifier suitable for
operating at a pressure of 0.3bar (5 lbf/in2) in excess of
safety valve setting. Single feed indirect cylinders are not
suitable for sealed systems.
Method of Make-Up
Provision shall be made for replacing water loss from the
system either:-
i) from a make-up vessel or tank mounted in a position
higher than the top point of the system, and connected
through a non-return valve to the system on the return
side of all heat emitters.
or
ii) Where access to a make-up vessel would be difficult
by using the mains top up method or a remote
automatic pressurisation and make-up unit as
illustrated in Fig 7 METHODS 1 & 2.
Mains Connection
There shall be no connection to the mains
water supply or to the water storage tank which supplies
domestic water even through a non-return valve, without
the approval of the local Water Authority.

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TECHNICAL DATA - Page 10
Filling Point
The system shall be fitted with a filling point at low level
which incorporates a stop valve to BS1010 and a double
check valve
(approved by the National Water Council) to be fitted in this
order from the system mains. refer to Fig 7 METHOD 1.
Figure 5 OPEN VENTED FULLY PUMPED SYSTEM WITH A COMBINED FEED AND VENT
Figure 6 OPEN VENTED GRAVITY DOMESTIC HOT WATER PUMPED CENTRAL HEATING

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TECHNICAL DATA - Page 11
Figure 7 FULLY PUMPED SEALED SYSTEM

12
INSTALLATION INSTRUCTIONS - Page 12
It is the law that all gas appliances are installed and
serviced by competent persons as stated in the Gas Safety
(Installation and Use) Regulations 1994.
Electrical installation and servicing should be carried out by
a competent person in accordance with the I.E.E. Wiring
Regulations.
For Health and Safety information see back page.
The boiler and its associated equipment will arrive on site in
two cardboard cartons. The contents of each carton is as
follows:-
CARTON 1
Boiler
Template
Side Infill Panels (2 off)
Literature Pack containing:
Installation & Servicing Instructions
Users Instructions
Control System Pipework and Wiring Guide Auxilliary Pack
containing
Gas Service Cock
Accessory Packs
Adjustment screws
CARTON 2
Inner Flue Product Tube
Outer Flue Product Tube
Air Box
Air Tube
Terminal
Boiler Mounting Plate
Figure 9 SECURING BOILER MOUNTING PLATE
Using wall plugs, screws and washers (accessory pack A)
attach boiler mounting plate to wall. Ensure that it is level
and the correct way round, i.e. flange on plate entering
hole in wall.
Figure 8 TEMPLATE
Place template in proposed boiler position, (the minimum
side clearances are automatically allowed
for).Refer to page 5 for top and bottom clearances which
can be measured from template. Ensure that the template
is level, mark hole positions ‘A’ and large flue outlet hole.
Remove template and carefully cut flue outlet hole through
wall.
DriII holes ‘A’ to a depth of 50mm using a 7mm drill.

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INSTALLATION INSTRUCTIONS - Page 13
Figure 10 PREPARING BOILER
The controls cover should have been removed when
unpacking the boiler, if not pull controls cover forward
25mm, lower to release from the four side fixings and pull
forward clear of the thermostat knob.
Remove door by undoing the two lower fixing screws and
lift door off the two upper hinge brackets.
Remove two screws securing the fluehood and remove
fluehood by sliding forward to disengage it from rear
location

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INSTALLATION INSTRUCTIONS - Page 14
Figure 11 ATTACHING AIR BOX
The flue system provided with the boiler is telescopic and
can be adjusted to suit wall thicknesses of 230mm-380mm
(9in-l5in). Wall thicknesses down to 76mm (3 in)are catered
for by shortening the Air Box, Inner Flue Product Tube (see
Figs 11 & 14), the Air Tube and Outer Flue Product Tube
(see Figs 13 & 15). Each tube is to be shortened at its plain
end by the amount shown in the following table.
For wall thicknesses between 100mm-
175mm (4in-7in), the alternative telescopic
Flue Kit can be used for additional convenience.
Using the packaging material to protect the boiler from
damage, lay the boiler on its side and secure the Air Box to
the boiler using the nine M4 screws from accessory pack
B. Engage adjustment screws into the boiler legs but do
not screw in fully at this stage.
WALL
THICKNESS AIR BOX AIR TUBE
INNER FLUE
PRODUCT TUBE
OUTER FLUE
PRODUOTTUBE
76mm (3m)
102mm (4in)
127mm (5in)
152mm(6in)
178mm (7in)
203mm (8in)
150mm (5.9in)
137mm (5.4in)
124mm (4.9in)
111mm(4.4in)
98mm (3.9in)
85mm (3.4in)
70mm (2.8in)
45mm (1.8in)
20mm (0.8in)
0 0
0 0
0 0

15
INSTALLATION INSTRUCTIONS - Page 15
Figure 12 LIFTING AND ALIGNING BOILER
Lift boiler onto the mounting bracket and adjust the boiler
position to obtain a minimum of 5mm clearance from any
side wall or cupboard.
Secure boiler to the mounting bracket using 5mm screw
from accessory pack C.
Undo the screws securing the transportation feet. Discard
feet and screws.
Correct vertical alignment with rear wall as necessary using
the adjustment screws.
Remove the temporary cardboard packing pieces from
either side of the casing.

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INSTALLATION INSTRUCTIONS - Page 16
Figure 13 SEALING AIR TUBE TO AIR BOX
Figure 14 ASSEMBLING INNER FLUE
PRODUCT TUBE AND FLUEHOOD
Pass Inner Flue Product Tube through hole in rear of boiler
and secure using two 5mm screws from accessory pack C.
Refit fluehood.
Working from outside the building, slide the plain end of the
Air Tube into Air Box leaving the tabs on the Air Tube flush
with outside wall face. Using the adhesive tape from
accessory pack D seal joint between Air Tube and Air Box.
Make good outside wall surface.
Figure 15 ASSEMBLING TERMINAL Figure 16 SECURING TERMINAL
Engage the four self-tapping screws from accessory pack E
into the pre-drilled holes in the end of the Outer Flue
Product Tube as illustrated but do not fully tighten.
NOTE: these screw positions are not symmetrical to ensure
correct assembly with the Terminal.
Slide Terminal on to the Outer Flue Product Tube,
engaging fully, the slots in the Terminal under the heads of
the four screws in the Outer Flue Product Tube. Secure
terminal by tightening the four screws.
Slide the Terminal Assembly into the Air Duct engaging the
Outer Flue Product Tube over the Inner Flue Product Tube.
Push Terminal back until the Terminal flange touches the
wall. Mark the position of the two Terminal fixing holes
(which also pass through the holes in the Air Tube Tabs)
on the wall.
Temporarily remove Terminal assembly. Drill Terminal
fixing holes using a 5mm drill and insert wall plugs from
accessory pack F into holes.
Refit Terminal assembly and secure using two screws from
accessory pack F. Centrally fit Terminal Guard over
Terminal if applicable using suitable screws and wall plugs.

17
INSTALLATION INSTRUCTIONS - Page 17
Figure 17 PIPE CONNECTIONS
Connect the system pipework to the boiler, compression
fittings are recommended. If however, capillary fittings are
used, it is essential to temporarily remove the thermostat
bulb from the flow pipe before soldering.
A drain off tap should be installed close to the boiler if it is
in a low point of the system.
On combined gravity hot water/pumped central heating
installations the flow and return pipes for both the gravity
hot water circuit and pumped central heating circuits must
be connected to tees fitted directly to the flow and return
pipes on the boiler.
The gravity circuit should be installed in 28mm copper pipe.
28mm tees should be used.
The injector disc (accessory pack G) must be positioned in
the pumped return branch of the tee as illustrated in Figs
17 & 17B.
Remove gas service cock from the auxilliary pack and
attach it to the union nut on the inlet to the gas assembly.
With the inlet connection of the gas service cock facing to
the rear, connect the gas supply pipe.
Figure 17B WARNING: UNDER NO CIRCUMSTANCES
SHOULD A ‘REDUCING SET’ BE FITTED
Figure 18
NOTE
The boiler is despatched with the overheat thermostat bulb
positioned for FULLY
PUMPED OPEN VENTED OR SEALED SYSTEMS.
ONLY if the boiler is to be used on a GRAVITY DHW
system should the bulb of the overheat thermostat be
repositioned as described below, to prevent nuisance
operation of the overheat thermostat.
Remove clip securing overheat thermostat bulb to the flow
pipe.
Uncoil the thermostat capillary and route it through the two
retaining clips attached to the front flange on the top panel.
Position the thermostat bulb in the indent in the return pipe
and secure in this position using the clip previously
removed.

18
INSTALLATION INSTRUCTIONS - Page 18
Figure 19 PRINCIPAL OF WIRING
WIRING
WARNING: This appliance must be earthed.
The boiler and all external control circuit wiring must be
supplied from the same single isolating switch and should
be fused at 3A.
Care must be taken to ensure that all wiring to the boiler is
kept clear of sharp edges and hot surfaces.
Ensure that the earth conductor is longer than the L, N, and
SWL from the point of anchorage, so that the current
carrying conductors become taut before the earth
conductor, if the cable is pulled out of the cable clamp.
The boiler terminal block which is situated in the control box
is not designed to accept wiring from all the on site controls
and therefore the installer will usually need to incorporate a
suitable junction box or Potterton electronic Programmer.
The principle of wiring is shown in Fig 19. It should be
noted that the pump must be wired directly to the boiler
terminal block on FULLY PUMPED systems and to the
junction box or programmer on combined GRAVITY HOT
WATER/PUMPED CENTRAL HEATING
systems.
Figure 20 ACCESS TO THE BOILER
ELECTRICAL TERMINAL BLOCK
Remove control box securing screw and lower the control
box to gain access to the boiler terminal block.
Figure 21 WIRING THE BOILER FOR A FULLY PUMPED
SYSTEM
Route a four core cable through the plastic bush at the rear
of the control box and the cable clamp as illustrated Fig 21,
and connect it to the boiler input terminals as follows:-
Permanent live to terminal marked MAINS ‘L’
Neutral to terminal marked MAINS ‘N’ Earth to terminal
marked MAINS
Switched live from external controls to terminal marked
MAINS SwL.
If there are no secondary controls fitted connect the SwL
terminal to permanent live in the external junction box.
Secure the cable within the cable clamp by tightening the
securing screws.
Following the pump manufacturers instructions connect the
pump supply wires to terminals marked PUMP, L, N and
on the boiler terminal block.
Route the cable through the plastic bush in the rear of the
control box and cable clamp as illustrated Fig 21. Secure
cable in cable clamp by tightening the two securing screws.
Close control box and replace securing screw.

19
INSTALLATION INSTRUCTIONS - Page 19
Figure 22 WIRING THE BOILER FOR
COMBINED GRAVITY HOTWATER/PUMPED
CENTRAL HEATING SYSTEM
Route a three core cable through the plastic bush in the
rear of the control box and the cable clamp as illustrated in
Fig 22. Connect the cable to the boiler input terminals as
follows:-
Switched live on the GRAVITY DHW control
circuit to terminal marked MAINS ‘SwL’ Neutral to terminal
marked MAINS ‘N’ Earth to terminal marked MAINS
Secure the cable within the clamp by tightening the two
securing screws.
The pump should be connected to PUMPED CENTRAL
HEATING control circuit at the junction box. See Fig 19.
Figure 23 FUNCTIONAL FLOW DIAGRAM
Figure 24 BOILER WIRING DIAGRAM
Figure 24A FITTING SIDE
INFILL PANELS
If required, the gap between
the casing sides and rear
wall can be closed off using
the infill panels supplied.
Ensure the casing surface is
FULLY CLEAN AND DRY.
Remove the protective
backing paper
from the adhesive strip on
the infill panel, carefully
align and press into place,
applying FIRM EVEN
pressure down the FULL
LENGTH of contact area
between panel and case. If
conditions are near
freezing, the boiler case
should be warmed prior to
application of the infill panel.

20
COMMISSIONING - Page 20
Open Vented Systems
Remove the pump and flush out the system thoroughly with
cold water. Refit the pump, fill and vent the system and
examine for leaks.
Sealed Systems
The system can be filled using a sealed system filler pump
with a break tank or by any other method approved by the
local Water Authority. Refer to FIG 7 and BS6798 1987.
Remove pump and flush out the system thoroughly with
cold water. Re-fit the pump. Fill and vent the system until
the pressure gauge registers 1 .5 bar (22.Slbf/in2), examine
for leaks. Raise the pressure until the safety valve lifts. This
should occur within + 0.3 bar of the pre-set lift pressure of 3
bar. Release water to attain the correct cold fill pressure.
All Systems
The whole of the gas installation including the meter should
be inspected and tested for soundness and purged in
accordance with the recommendations of BS6891.
Fit the case door into position by lifting it onto the top hinge
brackets and secure it with the lower two fixi’ng screws.
First Lighting
WARNING: Before lighting the boiler, ensure that the
CASE DOOR HAS BEEN CORRECTLY FITTED and that
the sealing strip fitted to the case door is forming a tight
seal with the main boiler casing.
A. Ensure that the pump and radiator isolating valves are
open.
B. Turn the boiler thermostat to the ‘O’ position.
C. Turn on the main gas supply and the gas service cock
on boiler.
D. Ensure that the time control, if fitted is in an ‘ON’
condition, and that the room and/or cylinder
thermostats, where fitted are set to high temperatures.
E. Switch on the external electricity supply to the boiler. In
the event of an electrical fault after installation of the
appliance, preliminary electrical system checks must
be carried out as described in the BG multimeter
instruction book. The checks to be carried out are:
A - Earth Continuity, B - Short Circuit, C - Polarity, D -
Resistance to Earth.
F. Partly depress and turn the gas control knob clockwise
ensuring the symbol lines up with the datum mark
on the gas valve body. See Fig 25. This ensures that
the valve is in the ‘OFF’ condition.
G. Partly depress and turn the control knob anti-clockwise
until the symbol * lines up with the datum mark on the
gas valve body. Press and hold in the control knob and
press the spark generator button until a click is heard.
Release the spark generator button and repeat
operation until the pilot ignites. See Figs 2 & 25.
Hold in the control knob for a further 15 seconds. On
release the pilot should remain alight.
Partly depress and turn the control knob anti-clockwise
until the symbol lines up with the datum mark on the
gas valve body.
NOTE:
On first lighting, establishment of the pilot flame may be
slightly delayed due to the presence of air in the pipework.
If the pilot fails to light or goes out at any time, immediately
turn the control knob clockwise as far as possible, then
release it and wait three minutes before repeating the
lighting procedure. The control knob should not be touched
during this period.
H. Turn the boiler thermostat on and to a high setting and
the main burner will light.
I. Set the boiler thermostat and the room and/or cylinder
thermostat(s) and time control, where fitted, to their
required operating conditions.
J. Check soundness of all appliance gas carrying
components and joints using leak detection fluid and a
mirror where necessary.
K. Switch off the boiler, using the thermostat knob.
FINAL ADJUSTMENT
A. Remove the screw from the burner pressure
test nipple on the gas control valve and fit a
pressure gauge to the test nipple.
See Fig 25.
B. Turn on the boiler thermostat, then check that the
pressure is in accordance with the values stated under
TECHNICAL DATA. The burner pressure is factory set
to the maximum stated.
C. If burner pressure adjustment is necessary, remove
the screwed cap from the gas control valve, see Fig 25
, and turn the screw beneath clockwise to increase
pressure and anti-clockwise to reduce pressure.
D. With the burner set to its correct pressure, the firing
rate given in TECHNICAL DATA should also be
obtained and this should be checked by meter reading
10 minutes after the main burner has been lit.
E. Shut down the boiler, remove the pressure