Diplomat HE installation guide
APRIL 1990 |
This boiler is tested and certificated to BS 5978 by British Gas PLC.
Fig. 1
Table 1
Table 2
Fig. 10
Fig. 11
Fig. 12
The Boiler
Performance Details
General Data
Installation/Ciearance/Electrical Supply
Gas. Supply
Water Circulation Systems
Casing 9-14 Sections
Casing 16-20 Sections
Boiler Feet 9-14 Sections
~ Boiler Feet 16-20 Sections
- Installation Instructions
Multi-functional Control Valve
Component Replacement
— Sparge Pipe 9-14 Sections
Pilot Burner Assembly
Wiring Diagram
Block Diagram of GAs Control Assembly
Pump Overrun
Fault Finding
Short Parts List
Ui Ul
Fig. 1 Diplomat HE 9-14 Sections.
< 7255———»
o] > 110-
Fig.2 Diplomat HE 16-20 Sections.
— 110 —
hat - - — 935 ———»
—# 225 +255 +
et — 2 LO ——
Ц, Gas Connection Entry
(gas supply pipe to be no closer than 10Cmm to casing panel}
1. Flow Connection 3. Drain Off Cock
2. Return Connection
Sections 9 10 12 14 16 18 20
A 590 590 600 600 580 580 580
B 634 696 | 820 944 | 1054 | 1176 | 1298
C 729 791 935 1059 1310 1430 1555
Clearances |
Front - 500mm (to withdraw burner bars)
Rear - 50mm
Top - 600mm {to clean flueways)
Left Hand Side ~ 130mm
Right Hand Side - 200mm (to make flow and return connections)
No. of Sections 9 10 12 14 16 18 20
Boiler KW 53.4 59.6 73.3 84.5 96.9 105.6 115.5
Input Btu/hr x 1000 | 182.0 | 203.5 | 250.0 | 288.5 | 330.5 | 360.1 | 393.8
Boiler KW 43.0 | 48.0 | 59.0 | 68.0 | 78.0 | 85.0 | 93.0
Output Btu/hr x 1000 146.5 164.0 201.5 232.0 266.0 289.9 317.1:
Gas m3/hr. 5.0 5.5 6.8 7.9 9.0 9.8 10.7
Rate ft3/hr 176 197 242 280 320 “| 349 ‘| 382
Flue Gas , m3/hr 5.0 5.6 6.9 7.9 9.1 9.9 |. 10.6
Volume * f£t3/hr 141 158 195 233 257 | 280 305
Main Burner mbar 13.8 15.0 15.2 13.1 14.6 14.6 12.8
Pressure in. W.g. 5.5 5.9 6.1 5. 5.9 5-9 ST.
Main Burner No. off 6 6 7 9 11 12 14
Injector Size @mm 2.30 2.40 2.40 2.40 2.30 2.30 2.30
Pilot Burner | No. off 1 1 1 1 1 1 1
Injector Size 2 Holes mm 0.29 0.29 0.29 0.29 0.29 0.29 0.29
Pilot Burner | KW 0.21 0.21 | 0.21 0.21 | 0.21 | 0.21 | 0.21
Input Btu/hr 730 730 730. 730 730 730 730
* Volumés are given at STP and are for the secondary flue with dilution assuming
a minimum of 1 mm.w.g. (0.04 in.w.g.) negative draught at the boiler socket.
These figures are given as a guide for flue design purposes only and should be
used with secondary flue conditions of approximately 4% CO. and 180°C gross flue
gas temperature.
No. of Sections 9 10 12 12 16 18 20
Flow Position See Fig. 1 page 2. | See Fig.2 page 2.
Tapping Size in BSP 12" | 12" | 14" | 1" 15" | 15" | 15"
Return Position See Fig.l page 2. See Fig.? page 2.
Tappings Size in BSP | 14" | 12" 115 | 14 14" | 18" 12"
Max. Working PSI 56 56 56 56 56 56 56
Water Head Bar 4.0 4.0 4.0 4.0 4.0 4.0 4.0
Gas Inlet Position ~ Left or Right Side Casirig Panel
Connection Size in BSP =" аи an gu an аи E
Minimum Gas mbar 17.5 17.5 17.5 17.5 17. 17.5 17.5
Inlet Pressure *, in. w.g. 7:0 7.0 7.0 | 7.0 7.0 7.0 7.0
Electrical Supply 240 V MW 50 Hz. Isolator & 5 A Fuse Required
Nominal Flue mm 175 175 200 200 250 250 250
Size to BS 835 in. T 7 8 8 10 10 10
Diverter Socket mm 213 213 238 238 288 288 288
Internal Diameter in. 8.4 8.4 9.4 9.4 11.3 11.3 11.3
High Level in? 42 42 44 51 55 58 64
Ventilation cm? 270 270 300 325 353 | 373 395
Low Level in? 84 84 88 | 101 | 110 | 116 | 123
Ventilation cm? 540 540 600 650 706 745 790
Dry Weight kg 148 | 162 | 191 | 220 | 248 | 276 | 301
1b 326 356 420 484 546 607 | 669
Water Content Litre 13.3 14.7.1 17.5 20.3 23.1 | 25.9 28.7
Gallon 2.9 3.3 | 3.9 | 4.5 | 5.1 5.8 | 6.1
Wet Weight ke 161 | 177 | 209 | 240 | 271 | 302 | 333
| 1b 355 389 459 | 529 597 665 733
Water t 25°C mbar 2T 33 45 59 28 35 38
Resistance t 20°C mbar 42 51 70 93 Hy 54 60
t 11°C mbar 139 168 231 307 145 178 198
t 10°C mbar 168 203 279 371 175 215 239
Water Flow t 25°C 1/s 0.41 0.46 | 0.56 | 0.65 | 0.74 | 0.81 0.88
t 20°C 1/s 0.51 0.57 0.70 0.81 0.93 1.02 1.11
t 11°C 1/s | 0.93 | 1.04 | 1.28 | 1.47 | 1.69 | 1.84 | 2.01
t 10°C 1/s 1.02 1.14 1.40 1.62 1.86 2.02 2.21
Maximum” Flow °С 90 90 90 90 90 90 90
This pressure to be measured at the inlet to the multi-functional valve when the
appliance is running under full operating conditions.
Potterton Diplomat HE gas fired boilers are
available in seven sizes with outputs ranging from
43 kW (147,000 Btu/hr) to 93 kW (137,000 Btu/hr).
They are approved by British Gas for use on open
vented systems, however, they are suitable for use
on sealed systems with a maximum operating pressure
of 4 bar (56 p.s.i.). Refer to relevant British
Standards and Codes of Practice re installation of
Diplomat HE boilers on sealed systems.
The Diplomat HE 9 and 10 section boilers are
intended for use as commercial appliances and are
not tested by British Gas for use in domestic
applications. ;
For ease of installation all boilers are delivered
fully assembled with the casing and draught diverter
fitted. The boilers are delivered on a single
pallet with a frame work of wood around them to
protect them and they are shrink wrapped over.
For sites with restricted access a fully assembled
boiler will pass through a standard 30" door. With
the draught diverter removed the boiler will pass
through a 21" gap. If the draught diverter is
removed the mastic sealing material may be damaged
and this should be inspected and replaced if
necessary before the diverter is refitted.
The flow and return connections are made to the
right hand side of the boiler casing and the gas
supply can be made to the left or right hand side
of the casing. ; -
The boiler sections are cast iron with pips to aid
heat transfer and the sections are joined by steel
nipples and hydaulically assembled.
The control system includes an on/off switch, a
multi-functional valve, boiler thermostat, overheat
cut out device and permanent pilot.
The boiler sections are insulated with fibre glass
"insulation and Rockwool. The case is finished in
- white and covered with a protective film to prevent
any minor damage. This protective film should be
removed when the boiler is commissioned.
The installation should comply with relevant British
Standard - Specifications, Codes of, Practice and
‘current Building Regulations, together with any
special regional requirements of the Local Gas
~ Undertaking, Local Authorities and Insurance
- Company. All electrical wiring must comply with
I.E.E. Regulations for the Electrical Equipment of
The installation of the boiler must be in accordance
with the relevant requirements of the:-
Gas Safety (Installation and Use) Regulations: 1984
Health & Safety at Work Act 1974. |
CP331:3 Low Pressure Installation Pipes.
ES 6644: 1986 Installation of Gas Fired Boilers.
CP341:300-307 Central Heating by Low Pressure Hot
CP342:2 Centralised Hot Water Supply.
Also the following British Gas publications:-
IM/11 Flues for Commercial and Industrial Gas Fired
Boilers and Air Heaters.
IM/2 Purging Procedure for Non-Domestic
IM/5 Soundness Testing for Non-Domestic
In the event of a gas booster being necessary
refer to:- ©
IM/16 Guidance Notes on the Installation of Gas
Pipework, Boosters and Compressors in Customers
The Gas Act 1972, Schedule 4, Paragraph 18.
Manufacturers notes must not be taken, in any way,
as overriding statutory obligations.
The minimum clearance required for access, erection
and maintenance are:-
Front - 600mm to allow for burner removal.
Rear - 50mm (rear of flue hood).
Left Hand Side - 130mm (gas supply pipe to be no
closer than 100mm to casing panel).
Right Hand Side - 200mm (to make flow and return
If the gas supply pipe runs down the left hand:
side of the boiler it should run no closer than
4' to the left hand casing panel. This is so that
if the casing panel ever has to be removed to
replace the overheat cut out device, the casing
can be slid along and up to this pipework.
Top - 1000mm for cleaning.
The electrical supply should be 240V NV 50 Hz
single phase and must be connected to the boiler
through a suitable two pole isolator and a SA
fuse. ;
All on site wiring shall conform to I.E.E.
Typically 0.22 KVA for all sizes.
The boiler should be sited in accordance with
BS 6611: 1986 with respect to protecting the
boiler from damage, air for combustion and’
ventilation, access, discharge of products of / 8
combustion, clearance, temperature, noise levels, *
the disposal of boiler water and the effects of
flooding of the boiler house or seepage from a
roof top boiler house. A level non-combustible
floor capable of supporting the weight of the
boiler filled with water, see Table 2 page 4,
together with any additional weight bearing down
on the base from connections, etc must be provided.
This will typically be a 50mm concrete plinth with
an area equal to that of the plan of the boiler.
Safe, efficient and trouble-free operation of
conventionally flued gas boilers is vitally
dependent on the provision of an adequate supply
of fresh air to the room in which the appliance is
installed. Account must also be taken of any
other fuel burning appliance existing or to be
fitted when designing the ventilation and
combustion air systems.
Air Supply by Natural Ventilation
Ventilation by grilles communicating directly with
“ the outside air is required at both high and low
levels. 9 .
The minimum free area of the grilles for a single
boiler are given in Table 2 page 4, and are based
on:- :
Low Level - 540 cm? plus 4.5 cm? per kilowatt in
excess of 60 kW total rated input.
High Level - 270 em? plus 2.25 cm? per kilowatt in
excess of 60 kW total rated input.
Position ventilation grilles to avoid accidental
obstruction by blockage or flooding.
Further guidance on ventilation is provided in
BS 664: 1986.
Air Supply by Mechanical Ventilation
Ihe supply of air to a space housing the boiler by
mechanical means should be by mechanical inlet with
natural or mechanical extraction.
ventilation with natural inlet must not be used.
Where a mechanical inlet and a mechanical extract
system 1s applied the design extraction rate should
be 0.45 m3/sec per 1080 kW heat input and the inlet
rate should be 1.1 m*%/sec per 1000 kW heat input.
The requirements for air supply by mechanical
ventilation are given in BS 6644: 1986.
For mechanical ventilation systems, an automatic
control should be provided to cut off the supply of
gas to the boiler(s) in the event of failure of air
flow in either inlet or extraction fans.
The use of an extract fan in the same room as the
boiler (or on an adjacent room in communication)
can, in certain conditions, adversely effect the
safe operation of the boiler. Where such a fan is
already fitted (or if it is intended to fit an
extractor fan after installation of the appliance)
the advice of the Gas Region should be obtained.
Contaminated Combustion Air
1t is essential that fresh and uncontaminated air
is introduced to the boiler for combustion. ;
Air ‘contaminated with chlorine vapours and CFC
gasses must not be allowed to enter boiler
combustion chambers or formation of chlorine gas
and hydrochloric acid will create severe and rapid
boiler corrosion. There is also a danger that
toxic chlorine gas will be emitted from the boiler
“In areas where such products are used, and these
include degreasants, dry cleaning fluids,
refrigerants and aerosol propellants, steps must be
taken to isolate the boiler from the area by
situating it in a separate area where fresh air can
be introduced. Care should be taken in positioning
extract ducts from contaminated areas in relation
to boiler house grilles to ensure that cross
contamination will not occur.
Where there is an existing primary gas meter, the
appropriate gas supplier/undertaking must be
consulted to ensure that the service/meter supply
capacity is adequate for the proposed installation.
To ensure safe and satisfactory operation the
chimney system, which may be individual or common
in the case of modular boiler installations, shall
be capable of the complete evacuation of combustion
products at all times. The effective height of
the chimney terminal(s) above the boiler(s) flue
outlet shall ensure sufficient buoyancy to overcome
the resistance of the bends, tees and runs of the
flue pipe involved and shall terminate in a down
draught free zone. The number of bends and lengths
of horizontal flue pipe used should be kept to a
minimum in order to comply with the recommendations
made in BS 6644: 1986, British Gas publication
IM/11 "Flues for Commercial and Industrial Gas
Fired Boilers and Air Heaters", the third edition
of the 1956 Clean Air Act Memorandum and the
Building Regulations should be strictly observed
where applicable.
A flue system should be no nearer than 50mm to
combustible material except where it passes through
it enclosed in a sleeve of non-combustible material
with an annular (air) space of 25mm. The chimney
design should avoid the formation of excessive
quantities of condensate and for this reason it is
recommended that all chimneys are insulated and
lined. In the case of brick or similar structures,
a stainless steel rigid or flexible flue liner
(Grade 304/316) may be used backed up with a 50mm
minimum thick layer of vermiculite or perlite
granules between the liner and the inner skin of
the chimney body. Liners should be sealed at both
top and bottom.
A terminal should be used for flues upto 200mm
diameter. For other flues effective protection is
necessary to prevent entry of rain, snow, leaves,
birds, etc while having minimum resistance to the
egress of flue products. The flue termination
should be at least 1m above the roof surface and
away from any wind pressure areas where the flue
products could re-enter the building, eg. near an
openable window, mechanical air inlet, etc.
As the Diplomat HE boilers are supplied with an
integral draught diverter, no other draught
diverter should be fitted in the system. The
integral draught diverter is not load bearing and
the flue should be supported by other means.
Facilities should be included in the flue systems
to disconnect the boiler flue hood from the flue
should it ever be necessary for maintenance,
repair or inspection of the flue system. A flue
header which connects into the main flue or chimney
should be independently supported and the
connection soundly made. |
Drainage points positioned at the bottom of all
vertical chimney sections should be provided.
Drain pipes should be no less than 25mm I.D. and
should be manufactured from acid condensate
resistant material such as stainless steel and
positioned so that pipe runs and discharge points
are not subject to the effects of frost. These
runs should fall with a gradient of at least 3%
and at no point must the drain pipe rise above the
level of the drainage point connection.
The dimension of the nominal flue size and boiler
flue outlet socket are given in Table 2 page 4. A
draught of 1 mm.w.g. (0.04 in.w.g.) should be
provided at the flue socket under full load running
conditions. The flue should be designed to
evacuate the products of combustion when all
boilers are firing.
The Diplomat HE is suitable for use on fully
pumped water systems only.
The water circulation system should be indirect and
installed in accordance with the relevant parts of
British Standards Code of Practice CP 342 and
BS 6644: 1986.
The maximum and minimum temperature differential
across the boiler should be 25°C and 10°C. The
volume flow and pressure drop across the boiler at
25%, 20%, 11° and 10°C are given in Table 2 page 4.
The maximum and minimum working head are 4 bar (136
ft.w.g.) and 0.1 bar (3 ft.w.g.). Care is needed
in siting the pump relative to the cold feed and
open vent connections.
The boiler flow and return connection sizes are
given in Table 2 page U4 and they are located as in
Fig.1 page 2.
If the return water temperature is likely to fall
below 55°C under normal running conditions then a
shunt pump should be fitted, sized to handle the
minimum water flow rate through the boiler, see
Table 2 page 4.
The provision of pump overrun by a time delay
system or a thermostat situated in the flow pipe
close to the boiler is essential to remove residual
heat from the boiler, see Fig.12.
It is essential that all systems are thoroughly
flushed through to remove all debris and scale
prior to fitting the boilers. Cleaning systems
with descaling agents is not generally recommended
as , if incorrectly used, the scale and deposits
may continue to break up after the system has been
flushed and the boiler installed.
The fitting of sludge traps and/or strainers is
strongly recommended, see page 8.
"The system should be checked to ensure that there
is no raw water make-up. The raw water hardness
must not exceed 100 p.p.m. hardness nor must the
TDS (salinity) be excessive. A specialist water
treatment company should be consulted if in doubt.
The boiler and system should be protected by
~ suitable frost thermostats and unions and isolating
“valves should be fitted to the flow and return
manifolds so that the boiler can be isolated from
. the system if the need arises.
. Water Flow Switch
“If the boiler is to be operated at flow settings
above 85°C than a water flow switch should be
fitted in the return connection to the boiler and
wired in series with the control thermostat so that
it is not possible to fire the boiler with no water
The water flow switch and pump overrun should be
fitted to all boilers operating above 85°C in order
that residual heat can be removed from the boiler
which could cause nuisance shut down of the overheat
thermostat and boiling over of the unit.
Safety Valves
Each boiler, whether in single or multiple
installations, shall be fitted with an individual
safety valve.
In the case of modular boiler installations each
bank of boilers shall be fitted with a safety valve
in the common flow unless each boiler is fitted
with a safety valve.
The safety valve or common safety valve shall be
sized to suit the total rated output of the boiler
or bank of boilers and shall be located between the
boiler or bank of boilers and the water isolating
valve. The size of the valve will be based on the
following table:-
Safety Valve Sizes |
Rated Output Minimum Clear Valve Bore \
Diameter . Area
kW mm mm?
45 to 264 19 284
264 to 352 25 491
352 to 440 32 802
440 to 528 38 1135
528 to 732 51 2050
732 to 1142 64 3210
1142 to 1640 76 4540
Over 1640 1 x 102 | 8180
or 2 x 76
The safety valve shall be fitted in the flow pipe
work between the boiler and the next valve in line
and the safety valve shall not be more than 1m
from the boiler measured along the flow pipe.
The safety valve fitted shall have a maximum
setting pressure not greater than 4.7 bar (68.15
Safety valves shall be of the direct spring Loaded)
type or dead weight type and shall be set according”
to the following equation:-
NB: 1 bar = 33.5 ft head or 14.5 1b/in2.
Spring loaded valves are recommended where the
static head exceeds 2.5 bar and/or where the
boiler may be affected by external vibrations.
The size of the connecting pipe or fitting shall
be not less than the nominal size of the valve
inlet, or the cross sectional area shall not be
less than the aggregate cross sectional area of
the valves mounted on it.
The discharge pipe from the safety valve shall
terminate in a visible position where discharge
will not result in hazard to the user or plant.
The size of the discharge pipe shall not be less
than the nominal size of the valve outlet.
For further information on safety valves see
BS 6644: 1986.
Open Vented Systems À
A cold feed pipe should be provided and taken
directly from a feed and expansion cistern which
shall not supply water for any other purpose.
It shall not be smaller than as specified below
and shall be connected to the boiler or boiler
side of any valve on the return pipe. The cold
feed pipe shall be situated within the building
and shall be insulated along those parts of its
length where freezing conditions or condensation
on the pipe may be expected to occur.
For multiple and modular boiler installations the
cold feed connection shall be either to the common
return pipe upstream of the individual boiler
isolating valves or to each individual boiler
return pipe downstream of the isolating valve. The
cold feed to a multiple or modular boiler
installation shall be provided with a lockable
isolating valve.
For a single boiler installation an open vent pipe
shall be fitted to the flow pipe and sized according
to the table below. It shall rise continuously by
the shortest practical route to the venting point.
The open vent pipe shall discharge into the feed
and expansion cistern above the over flow level
and for a single boiler installation the pipe shall
not be fitted with valves (apart from a 3 way type
such that when closed to the common vent pipe the
boiler is open to atmosphere through the third port
and shall incorporate means of indicating the
position of the open port and the nominal bore of
the valve shall not be less than that of the open
vent pipe in which it is fitted) nor shall there be
any obstruction which could prevent safe venting of
the boiler. The vent pipe shall be insulated along
those parts of its length where freezing conditions
may be expected and shall be situated as far as
practicable inside buildings to reduce freezing
Multiple boiler installations shall have an open
vent pipe or pipes of the size given below as
appropriate. Indivigual open vent pipes shall be
either routed independently to the venting point or
be connected to a common open vent pipe of
appropriate sizes for the total rated heat input of
the installation.
For modular boiler installations, each bank of
boilers in a module shall be fitted with an open
vent pipe on the common flow pipe. This vent pipe
shall be sized to suit the total capacity of the
bank and shall be connected between the boiler bank
and the safety valve. Any individual boiler fitted
with a water isolating valve shall be provided with
an open vent pipe as for a multiple boiler
For modular boiler installations vent pipes shall
be sized on the table below.
Cold Feed Pipe Sizes
Rated Output | Minimum Bore Nominal Bore
kW mm in*
Below 60 19 2
60 to 150 25 1
150 to 300 | . 32 1#
300 to 600 | - 1-38 13
Above 600 50 2
* Steel pipe sizes complying with medium or
heavy quality of BS 1387.
A boiler vent pipe connection is provided as an
equal tee on the flow manifold.
For further details see BS 6644: 1986.
Water Pressure Gauge (Head Gauge)
The boiler shall be fitted with a gauge that
indicates the pressure in metres of water. or bars.
The gauge shall be fitted on the flow pipe and
sited so that it can be easily read and can be
easily replaced without draining the boiler/system.
Sludge Traps and Strainers
When new boilers are connected to old systems the
fitting of sludge traps and/or strainers is
strongly recommended to protect the boiler from
migrating system debris which could have a
detrimental effect on the boiler.
System Filling
When filling the boiler system with water care
should be taken that water does not backwash system
debris into the boiler via the flow connection
and by-passing any sludge traps and strainers that
may have been fitted.
Fig.3 Diplomat HE Casing Fig.5
9-14 Sections
Diplomat HE Feet
9-14 Sections
I -
Fig.6 Diplomat HE Feet
16-20 Sections
Fig.4 Diplomat HE Casing
- 16-20 Sections
foma, —— ——
9 527 421
10 589 183
12 713 607
14 837 731
16 982 358
18 1104 420
20 1226 180
Please check the installation and clearance
requirements given on page 5.
The boiler is delivered fully assembled with the
casing fitted. ' To remove the boiler from its
wooden pallet, remove the casing as illustrated in
Fig.3 for 9-14 section boilers and Fig.4 for 16-20
section boilers. The drain valve is a 3" BSP and
is threaded into the sections and the return
manifold is connected by unions onto stub pipes
into the sections. Once the unions have been
released the plastic capping into the casing should
be removed with a screwdriver and then the casing
panel can be lifted over the male part of the
The boiler is sécured to the wooden pallet by Ц
screws through brackets on the bottom of the
combustion chamber and these should be removed.
' +
The boiler may be lifted by the carrying handles on’
the cast iron sections to its position.
The boiler is supported on its wooden pallet by 6
plastic feet for the 9-14 section boilers and 5
nlastic strips for the 16-20 section boilers.
25e feet should be positioned as shown in Fig.5
‚ur the 9-14 section boilers and Fig.6 for the
16-20 section boilers, on the boiler base and the
boiler positioned on then.
Replace the casing and the ancillaries removed.
The casing is protected by shrink wrap plastic and
this should be peeled off at the time of
Connecting the Gas Supply
The gas connection should be made into the female
elbow fitted by an '0' ring and screws to the main
gas valve.
The elbow should be positioned to the left or right
to suit the incoming gas supply. The appropriate
knock out in the side casing panel should be removed
to allow entry of the gas supply.
The elbow on top of the gas valve can be released
to allow withdrawal of the burner assembly and
therefore an additional union within the casing for
this purpose is not necessary.
An isolating valve should be fitted by the installer
“ the pipework adjacent to the boiler to allow it
be isolated for maintenance and also to test up
LO the seat of the gas valve for gas soundness.
A union should also be provided between the gas
cock and the boiler.
If the gas supply is made to the left hand side,
the gas pipe inner edge should run no closer than
4" to the left hand casing panel. This is to allow
the left hand casing panel to ‘be moved away from
the side of the boiler to replace the overheat cut
off device phial should it ever be necessary.
The size of the gas supply to the boiler ‘should
never be made-. in a size smaller than the gas
connection size, ie. 2" BSP, and should be sized
for the rate of gas needed, see CP331 Part 3.
Always ensure that all dirt and swarf are removed
from the gas supply pipe system before connecting.
Connecting the Water System
The flow and return connections are made to the
right hand side of the boiler.
On the 9-14 section boilers the return connection
s made into a 12" BSP female connection into the
sing (see Fig.1 page 2).
The female connection is a socket welded to ‘a
sparge pipe which runs into the sections. A
sparge pipe is a tube with holes in it which
directs the water into the sections. The female
socket has a pip on it and after connecting the
return connection the socket should be checked to
make sure that the pip is pointing directly upwards
and this will ensure that the holes in the sparge
pipes are pointing in the right direction. If not
it should be adjusted, see Fig.8.
The 16-20 section boilers have the two return
connections made to the 14" BSP female socket in
the return manifold. The female socket should be
securely held whilst connecting to the return to
avoid damaging the internal flexible pipe. These
sizes of boiler also have sparge pipes fitted but
their positions are pre-set during assembly.
The flow connection is made to a 11" BSP tee as
shown in Figs.1 and 2, see page 2. No sparge pipe
is fitted to this connection.
The unions and isolating vaives should be fitted
to the flow and returns so that the boiler can be
isolated from the water system if required. The
drain off cock is supplied loose and should be
connected as shown in Figs.1 and 2, page 2.
Electrical Connections
All electrical wiring must be installed in
accordance with I.E.E. Regulations. Care must be
taken that all wiring is kept clear of sharp edges
and hot surfaces.
A 5 Ampere fuse and a suitable 2 pole isolator
having a contact separation of at least 3mm in all
poles has to be provided by the installer for
isolation of the boiler and should be installed.
close to the boiler.
The incoming electrical connections should be made
through the conduit provided on the left or right
hand side of the boiler running from back to .
The 240 volts Vv AC single phase supply should
be connected to the live and neutral terminals in
the junction box and the earth connection should
be connected to the earth bar in the junction box
via a cable entry gland. The length of the
conductors between the cord anchorage and the
terminals must be such that the current carrying
conductors become taut before the earth conductor
if the cable or cord slips out. of the . cord
anchorage. Access to the junction box is made by
removing the screws holding the lid in position.
A wiring diagram is fixed inside the lid of the
junction box and is also included in this manual.
If the left hand conduit is used the incoming wire
should be run across the front of the boiler in
the conduit provided.
Connecting the Flue System
A flue adaptor socket is provided with each boiler
for use with flues to BS 835, for flues to BS 715
this flue adaptor socket can be discarded. The
flue system should be made in accordance with the
notes given on page 6. The flue pipe should be
supported so that no weight is transferred to the
boiler draught diverter. Facilities for
disconnecting the flue system from the boiler
should be provided.
Boiler Controls
The operation of the boiier is under the control
of its own boiler thermostat and high limit
In addition the boiler should be controlled by a
time switch, frost thermostat, pump overrun
facility and for multiple boiler installations a
boiler sequence controller.
Before commencing to commission the boiler ensure
that the shrink wrap plastic is removed from the
casing panels then check the following:-
1. Electrical supply is switched off. All
electrical connections are sound and correctly
2. Electrical system and the boiler are correctly
3. Gas supply is tested for soundness and purged
of air.
y. Test .for gas soundness of gas trains as
described on page 13.
5. Appliance gas cocks are all turned off.
6. Gas supply is turned on at meter.
T- Boiler and system are filled with water.
8. Flow and return valves are open.
9. Any external controls and the on/off switch
are in the 'ON' position.
10. The circulation pumps are operational. Check
that the pump is scheduled to run and not on
pump overrun if the boiler has previously been
For boiler houses with natural ventilation, the
4 Press and hold in fully the
ea of the grilles should be checked against the
tes given on 'Ventilation' on page 6.
r boiler houses with mechanical ventilation , the
itability of the ventilation and extract system
ould be checked against the notes given under
echanical Ventilation' on page 6.
addition the installer must check that it is not
ssible for the boiler to operate if either the
ntilation or extract fans are not running.
.1 Check that the electricity supply to the
boilér is’ off, the on/off switch is off and
that ‘the boiler thermostat is at the 'OFF'
position marked with a white dot.
.2 Check that ancillary contróls such as time
clocks and external thermostats are off or at
their lowest settings.
.3 Ensure that the gas supply to the boiler is
square button
marked " <> "on the gas control valve and
press the Piezo ignitor two or three times to
light the pilot. Keep the button held in for
20 seconds after the
release the square button.
If the pilot flame goes out, push in and
release the button marked '0'. Wait for 3
minutes then repeat from step 1.4.
.5 With the pilot flame established turn on the
electricity supply, on/off switch, time switch,
external thermostats and turn the boiler
thermostat to its required setting.
e boiler will now light.
6 Refit the boiler front casing.
2.1 Temporarily - turn the boiler thermostat to
the 'OFF' position. Turn the on/off switch
and the time switch, if fitted, off.
To bring the boiler on again, turn on the
time switch and on/off switch and turn the
boiler thermostat to the required setting.
2.2 Long Periods - turn off the time switch,
electricity supply and on/off switch and turn
the boiler thermostat to the 'OFF' position.
Push the square OFF button marked 'O' on the
gas control valve and the pilot will go out.
Turn off the gas cock.
After lighting the boiler the operation of the
above mentioned controls, eg. clock and
thermostats, should be checked.
pilot has lit, then
WARNING - If the pilot light is extinguished
either intentionally or unintentionally, no
attempt should be made to re-light it until at
least 3 minutes have elapsed.
Main Burner
Fit a pressure test gauge to the outlet pressure
test nipple on the valve as shown in Fig.7.
Check that the burner pressure is as given in
Table 1, page 3, and if necessary adjust the
pressure regulator. The posiiton of the adjuster
is shown in Fig.7.
After the burners have stabilised for 30 minutes,
check the gas pressure and if needed re-adjust it
again and measure the gas rate at the meter. The
, gas rates are given in Table 1, page 3.
With the boiler hot and cold check for spillage of
combustion . products with a smoke bomb or smoke
wand. Check that air is moving into the front of
the boiler, that combustion products are not
spilling out of the front or spilling out of the
draught diverter at the back. The flue draught
should be checked with a draught gauge and should
be measured at a suitable test point in the flue
above the flue adaptor socket.
For boiler houses with natural ventilation the
area of the grilles should be checked against the
notes given on ventilation.
For boiler houses with mechanical ventilation, the
suitability of the. ventilation and extract system
should be checked against the notes given under
"Mechanical Ventilation". In addition, the
installer must check that the flow switches on the
ventilators are interlocked with the turner
controls so that it is not possible for the boiler
to operate if either the ventilation or extract
fans are not running.
Whilst the boiler is operating, check for gas
soundness in the main gas line and the pilot line
downstream of the multi-functional control using a
soap solution or other approved method.
Switch the boiler off, remove the pressure gauge
and re-tighten the test point sealing screw.
Pilot Burner
When correctly set the pilot flame must be
sufficient to heat the thermocouple so that the
pilot safety device is held in, but must not cause
the thermocouple to overheat.
This can be detected by observing the thermocouple
tip and the pilot flame as shown in Fig.9.
The pilot flame should be about 20mm long and
should cover the thermocouple tip. If the
thermocouple is bright red it is too hot and the
pilot gas rate should be reduced by use of the
adjuster screw as illustrated in Fig.7. Turn the
screw clockwise to reduce and anti-clockwise to
increase the pilot flame.
The iginition electrode gap should be as illustrated
in Fig.9.
The action of the flame failure device should be
checked by turning the pilot off and making sure
that the flame failure device cuts out. This will
be heard as an audible click within 60 seconds.
Water Flow Switch
For boilers fitted with a water flow switch, the
installer should check that it is not possible for
the boiler to fire when there is no water flow.
This may be done by checking that the boiler closes
down when the pumps are switched off or the water
flow is gated off. Adways restore the water flow
before completing commissioning.
WARNING - Always isolate the electrical supply and
the gas supply to the boiler before commencing
maintenance or component replacement.
Always replace the electrical junction box cover
after maintenance.
The frequency of servicing depends upon the usage
and application of the boiler. This is likely to
be at least once a year,
At every service visit the boiler should be cleaned
as detailed below and the soundness of the safety
shut off valve within the multi-functional valve
checked as described under "Commissioning" and the
gas control assembly must be checked for leakage
with a soap solution or other approved method. The
boiler should be fully re-commissioned as described
under "Commissioning" and attention also paid to:-
1. The effectiveness of natural and mechanical
ventilation and in particular the safe
operation of an air flow switch on a mechanical
ventilation system.
2. That the chimney is sound and adequately
evacuating the products of combustion and that
there is no spillage of flue products.
3. That the burner gas pressure is correct and
that the boiler is still on rate.
4. That the water flow switch,
operating correctly.
if fitted, is
5. That the low pressure switch on a booster
system, if fitted, is operating correctly.
Remove the front casing panel, the large top
casing panel which is secured by 4 screws and the
bottom front strip secured by 2 screws.
Remove the plastic terminal cover on the main gas
valve secured by a screw and disconnect the
electrical supply made by push on connections and a
screw on spade terminal. Disconnect the overheat
cut off device by removing the two push on female
connections to it.
Isolate the gas supply at the gas cock and release
the gas supply by removing the 4 screws from the
elbow on top. of the multi-finctional valve and
breaking the connection. Take care not to lose the
'0' ring or to get foreign matter into the pipe or
Remove the 4 headed screws securing the burner
assembly and withdraw it.
Remove the Rockwool covering the flue hood clean
out cover and unscrew the screws securing it and
remove the cover, paying attention not to damage
the seal.
Remove the flueway baffles and clean the flueways
from the top and bottom with the brush provided
with the boiler and sweep away the debris from the
bottom of the combustion chamber.
Replace the flueway baffles and the flue hood
cover taking care to position it on the seal and
secure it by replacing the screws. Replace the
Rockwool insulation cover and refit the large top
casing panel with the 4 screws.
While the burner assembly is removed from the
boiler check the condition of the burner front
plate and insulation and replace if necessary.
Check the condition of the Vermiculite blocks
lining the combustion chamber and replace them if
Lightly brush the burners and remove. any fluff
which may have accumulated.
Inspect the thermocouple, ignition electrode and
pilot burner head. See Fig.9 for the correct
position of the thermocouple and ignition
Remove and clean the main burner injectors in
cleaning fluid. When replacing the injectors use
an approved thread sealant.
Replace the burner assembly - taking care not to
damage the Vermiculite lining and the burner front
plate insulation and re-fit the 4 Hex head screws.
Re-connect the gas line, thermocouple interrupter
and the electrical connection to the
multi-functional valve.
Check for gas soundness of the safety shut off
valve within the multi-functional valve and check
the control assembly for gas leakage with a soap
solution or any other approved method as described
under "Commissioning".
Re-fit the front casing panel.
Boiler Thermostat
This is a Honeywell thermostat range 25-90°C and is
graduated in degrees Centigrade and there is an off
position marked with a white dot.
The thermostat has been calibrated by the
manufacturers and no attempt should be made to
re-calibrate it on site.
When the boiler reaches a suitable temperature,
turn it to a lower setting to check that the main
burner shuts down.
Overheat Cut Off Device
This is a Landis & Gyr RAK 21.4/2756 which acts as
a thermocouple interrupter.
Tt has been set by the manufacturers to 98°C and no
attempt should be made to re-calibrate it on site.
When a temperature of 98°C is reached the device
will shut down the pilot. Brefore re-lighting the
pilot, investigate the cause and rectify the reason
for overheat condition being reached. Re-set the
device by pressing the green button on it and then
re-light the pilot 3 minutes after the last attempt
to light the pilot.
The operation of the overheat cut off circuit
should be checked by disconnecting a female push on
connection to the overheat cut off device and
checking that the boiler shuts down.
Location of Thermostat Phials
The boiler thermostat phial is located in the
thermostat pocket behind the Homeywell boiler
thermostat and the thermostat body is clamped to
the thermostat pocket by a single screw.
The overheat cut off device phial is located in a
thermostat pocket in the left hand side of the cast
iron boiler sections.
Fig.T Multi-Functional Control
To Test Gas Soundness of the Safety Shut Off
Valve Within the Multi-Functional Control
The soundness of the safety shut off valve should
be checked at every service visit.
Fit a manometer to the inlet of the
multi-functional valve and light the pilot in the
normal way and bring on the main burners.
Turn the multi-functional valve off by pressing
the square 'OFF' button marked '0'.
Listen for the click as the safety shut off valve
closes and pressurise up to this valve seat by
closing the gas cock.
Observe the manometer for a period of 3 minutes.
If the valve loses less than 1% in.w.g. (3.8 mbar)
in 3 minutes the valve is satisfactory.
If any loss of pressure is observed then check the
assembly and pipework for leaks with a soap
solution and rectify if a leak is found.
If no external leaks are found the safety shut off
valve seat is letting by and the valve should be
6 >
Л — ey -
® ||
Overheat Cut Off Device
Remove the front casing panel, the front bottom
strip secured by 2 screws and the small top panel
secured by 2 screws. Lift these panels away and
then lift away the left hand side panel. If the
gas connection is made through the left hand side
panel, the panel should be slid along the pipe
which should have been positioned 4" away from the
Remove the thermostat pocket retaining clip and
remove the thermostat phial from its pocket and
then the 2 wires connected to the overheat cut off
device by female push on connections.
Remove the 2 screws securing the device to its
mounting bracket and replace with a new one supplied
by the manufacturer and calibrated to 98% only.
Position the new phial fully into the pocket and
secure with the retaining clip.
Replace the two wires to terminals 1 and 2 as
removed and replace the casing panels.
Boiler Thermostat Replacement
Remove the front casing panel and unscrew the
plastic cover plate on the front of the thermostat
body, pull down the plastic lower protion of the
thermostat and disconnect the electrical
connections. Remove the electrical wire through
the cable entry gland and release the screw securing
the thermostat body to the head of the thermostat
Re-fit a complete new unit, secure the thermostat
to the thermostat pocket, re-make the electrical
connections. tighten up the cable entry gland and
re-fit the plastic cover over the connections.
Check the operation of the thermostat as described
under "Commissioning" and re-fit the front casing
On/Off Switch Replacement
Remove the front casing panel and the front of the
Junction box which is secured by screws. Disconnect
the push on connectors to the on/off switch. Push
the body of the switch through the junction box lid
and replace with a new one and re-connect the push
on connectors. Check that the connectors are made
to the correct terminals.
Re-light the boiler and check that the switch
closes down the main burner.
Pilot Assembly/Thermocouple/Ignition Electrode
Disconnect the high tension ignition lead from the
ignition electrode and unscrew the thermocouple
from its fitting on the pilot burner assembly.
Release the pilot bundy tube from both the
multi-functional control valve and the pilot
assembly taking care not to lose the injector from
the pilot burner.
Remove the 2 screws securing the pilot burner to
the burner assembly and replace with new pilot
burner assembly if necessary.
To replace the thermocouple, unscrew it from its
connection into the side of the multi-functional
gas valve and replace with a new one as necessary.
The ignition electrode is secured by 2 self tapping
screws into the pilot burner assembly. This is a
non-serviceable item and if necessary the complete
pilot burner should be replaced.
Replace the pilot assembly and secure with the 2
Screws. Care should be taken that the pilot
assembly is mounted the correct way up. Looking
at the pilot from the front of the boiler, the
thermocouple should be on the left hand side and
the ignition electrode on the right hand side.
See Fig.10.
Re-connect the pilot line taking care to make sure
that the pilot injector is included. If the pilot
bundy tube does not align this may be because the
pilot burner is upside down. See above.
Re-connect the thermocouple to the pilot burner
and to the slot on the side of the multi-functional
gas valve. Care should be taken that the
thermocouple is screwed into this slot which also
fixes the wire to the overheat cut off device and
that the thermocouple is not screwed directly into
the pilot solenoid connection. See Fig.8 and 9.
Re-connect the high tension ignition electrode
lead to the ignition electrode.
Check the position of the pilot burner,
thermocouple and electrode as given in Fig. 10.
Replace the burner assembly, check for letby of
the safety shut off valve as described under
"Commissioning" and check the control assembly for
gas leaks with soap solution or other approved
Adjust the pilot rate as described under
Check that the thermocouple is holding in the
flame failure device within the multi-functional
valve and then turn the pilot to the 'OFF' position
and make sure that the flame failure device cuts
out with an audible click within 60 seconds.
Check that the overheat cut off circuit is
operational by disconnecting one female push on
connection to the device and checking that the
boiler closes down.
Main Gas Valve Replacement
Remove . the burner assembly as described under
Release the pilot bundy tube, the thermocouple and
the two thermocouple interrupter wires from the .
multi-functional valve.
Disconnect the high tension ignition lead from the
Piezo ignitor.
Release the 8 screws securing the valve to its
flanges and replace with a new valve and new '0'
ring seals.
When these 8 screws are released it is possible to
remove the Piezo ignitor and its bracket from the
old valve.
Re-fit the Piezo ignitor and its bracket to the
new: valve.
Reassemble the thermocouple, the pilot bundy tube
and the 2 overheat cut off device wires into the
multi-functional valve. Care should be taken that
the thermocouple is screwed into the slot on the
side of the multi-functional valve into the
overheat cut off device wire and not directly into
the pilot solenoid magnet.
Replace the burner assembly. Check for letby of
the safety shut off valve within the
multi-functional valve as described under
"Commissioning" and also check for gas soundness
of the control assembly with soap solution or any
other approved method. |
Re-commission the main burner and pilot as
described under "Commissioning".
Piezo Ignitor
To replace the Piezo ignitor, disconnect the high
tension ignition lead
from it and unscrew the
plastic lock nut on the body of the ignitor and
remove it from its bracket.
Replace with a new unit
and the ignition lead.
Section Replacement
Each section is joined
, refit the plastic lock nut
together on the water side
by steel push nipples and strips of Tapperil sealing
mastic between the sections to form a gas tight
Tapperil is also used to seal the flue hood to the
top of the heat exchanger and fire cement 18 used
to seal the sections to
the combustion chamber.
The sections are held to the combustion chamber by
4 Taptite screws passing through lugs at the base
of the section into
combustion chamber.
fixing brackets on the
» .
The flue hood and draught diverter are fixed to the
cast iron sections by
bolts and washers securing
the flue hood to lugs on the top of the sections.
If a section leaks, the
boiler must be drained down
and the heat exchanger containing the leaking
section removed.
To do this the casing
When the heat exchanger
and combustion chamber Vermiculite lining for °°
must be stripped away, the
.—.——nsulation-and--the-flue-hood........ ..- em ео) = =
is removed check the burners
damage and replace where necessary.
Once the heat exchanger is removed, remove the
sparge pipe on the 9-14 sections models and the
two sparge pipes on the
14-20 section models. _
Remove all plugs and the thermostat pockets if end
sections are to be replaced.
Remove the two tie
together. The sections
sharp chisel between
easing apart.
rods holding the sections
can be split by inserting a
the sections and carefully
When re-assembling, use new nipples, clean the
nipple port with wire
jointing compound. F
wool and use a proprietiary
it new strips of Tapperil
jointing mastic along the edges of the section.
Fit the sections together and pull up so that they
come metal to metal around the nipple ports. The
sections should be pulled up using a set of pulling
up tools available from the Parts Department of
Potterton International Ltd. Alternatively, the
thermostat pockets and all plugs can be removed and
3 threaded bars passed
all sections and with
can be used to pull the
through the nipple ports in
a suitable end plate these
sections up together.
Refit the two tie rods and carrying handles and the
thermostat pockets and
Jointing compound.
Pregsure test the block
operating pressure, le.
After pressure testing
the 9-14 section boile
plugs using a proprietary
of sections to 11 times the
6 bar.
refit the sparge pipes. On
rs the pip on the 1i" BSP
female socket should point upwards and it will be
seen that with the sparge pipe in this position the
holes in the pipe direct water up into the legs of
the section.
Or the 16-20 section
sparge pipe fittings s
that the holes in the p
legs of the sections.
models the indent on the
hould also point upwards во
ipe direct water up into the
Refit thé heat exchanger to the combustion chamber
using new fire cement and secure with the 4 screws.
Refit the flue hood to the heat exchanger using
new strips of Tapperil jointing mastic.
Refit the insulation and the casing panels and
recommission the boiler.
If a section has failed it may be due to scale and
deposits within the boiler. If : this is the case
then it is generally recommended that the complete
bank of sections be replaced as the other sections
may also contain scale and deposits and they may
have a shortened life.
For this reason it is strongly recommended that
sludge traps and strainers be fitted to a system
to prevent system debris entering the sections and
the Technical Department of Potterton Commercial
Products, address given on the back page of this
manual, will be pleased to receive and examine any
failed sections to help identify the cause.
Fig.8 Sparge Pipe 9-14 Sections
Pip pointing
to top
Fig.9 Diplomat HE Pilot Assembly
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Fig.10 Diplomat HE Wiring Diagram
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Fig. 11 Block Diagram of Gas Control Assembly
GAS IN > —
. - 7 N
Fig.12 Pump Overrun Using Changeover Pipe Thermostat
— | >
50 Hz TO
с 7
O wo
NOTE: The electrical loading of the pump should not +
exceed the contact rating of the pipe thermostat. 7
©. Pilot will not light
Air in gas line.
Faulty gas control valve.
No spark at electrode tip.
Blocked pilot injector.
Over heat cut off device tripped.
Loose connection on leads to overheat
cut off device.
Loose thermocouple connection.
Faulty thermocouple.
Faulty over heat cut off device.
. Faulty gas control valve.
Pilot partially blocked or needs
Pilot does not remain
alight when knob released.
YI MU uu
a + + L)
. No electrical supply to burner.
. On/off switch is in 'OFF' position.
Pilot established - main 1
3. Boiler thermostat set too low.
burner does not light.
. Faulty thermostat or connections.
. Faulty gas control valve.
Main burner remains alight 1. Faulty thermostat.
when thermostat satisfied. 2. Faulty gas control valve.
Main burner remains alight 1. Faulty on/off switch.
. when on/off switch in 'ОРР' 2. Faulty main gas valve.
position. 3. Incorrect control circuit.
Potterton Part Number
a 1. Honeywell VA4400C 2" gas valve (9-20 sections) 402852
= 75, Honeywell Q309 thermocouple 40225701
| N Piezo ignitor Honeywell Q635 358024
4. Ignition electrode 358026
5. On/off switch Arco Electric 358023
6. Pilot assembly complete Polydoro 511 358204
7. Pilot injector 2 holes @ 0.29 - 358027
8. Boiler thermostat Honeywell Aquastat 30-90°C 358020
9. Over heat cut off device Landis & Gyr RAK 21.4 2756 358022
10. Over heat cut off device connection wires 358031
11. Main burner injector ¢ 2.4mm 358030
12. Main burner injector @ 2.3mm 358240
13. Ignition electrode lead 358046
NB: Early boilers were fitted with a Honeywell LS 8C97A over heat cut off device. The landis & Gyr
RAK 21. 4/2756 should be used for spares purposes. The Landis & Gyr device is fitted to a mounting bracket
(Potterton Part No.358050) by two M3 x 6 screws (Potterton Part No. 633931). This bracket has a slot in
1t which fixes: under the head of the hex head screw securing the front inner panel to brackets on the
block of sections. The bracket also has a 5mm hole in it and a number 6B by 12m self tapping screw
Of ‘Potterton Part No. 613434) or one of the original fixing screws should be used to fix the bracket to the
LE en] hole in the front inner panel used for mounting the original cut off device.
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