Boiler Size Selection; Gas Supply - Keston C40 Installation And Servicing Instructions

WD265/0/2002
The appliance must be connected to the 3A supply via a fused double-pole switch
having at least 3 mm (1/8 inch) contact separation in both poles, serving only the
boiler and the system controls.
The connection point to the mains supply should be readily accessible and
adjacent to the boiler, except for rooms containing a bath or a shower. Refer to
section 2.3 Position.
2.4.2 External Wiring & Controls
1.
2.
3.
4.
5.
V4043H1106
Zone Valve
Heating
V4043H1056
Zone Valve
DHW
2.4.4 Wiring Expample - Honeywell S-Plan for DHW and (Optional) Weather Compensated Heating Control
2.5

BOILER SIZE SELECTION

The C40 and C55 will automatically adjust heat output and pump speed to match the
system requirements at any given time. Efficiency and combustion levels are maintained
at optimum levels throughout the possible output range. The C40 and C55 are therefore
suitable for all systems with a total heat load within the maximum range of the boiler.
2.6

GAS SUPPLY

A gas meter should be connected to the service pipe by the local gas region or their
contractor. An existing meter should be checked preferably by the gas region to ensure
that the meter is adequate to deal with the rate of gas supply required. Installation pipes
should be fitted in accordance with BS 6891.
Minimum/Maximum Gas Pressure:
Natural gas pressure before the gas valve must be maintained at between 18 mbar (7.2 in
WG) and 22 mbar (8.8 in) while the boiler is running.
LPG pressure must be maintained between 31.5 mbar (12.4 in w.g) and 37.6 mbar (14.8
in w.g) while the boiler is running.
Gas pressures above or below these levels will lead to problems associated with the gas
valve's internal pressure regulator.
Supply pipes to the boiler must not be sized less than the boiler inlet connection
(22 mm). Due consideration must be given to the supply pressure to other gas
appliances in the premises. Reduction in dynamic gas supply pressure will result in
intermittent ignition failures. Ensure gas supply pipe work is adequately sized for
Installation & Servicing Instructions
Chapter 2 - Boiler Location
The boiler is designed so that all control wiring is external to the boiler.
A programmer may be used with zone valves to give independent control
of central heating and hot water.
A Keston Chronotherm controller may be used to provide room
compensation and optimum stop/start control on heating only systems
Control signal inputs must the 230VAC "switched live" type.
A Keston outside temperature sensor may be connected as an option.
The boiler will automatically detect this connection and will operate on a
"weather compensation" basis when receiving a signal on switched live 1.
Screened cable (80% density) must be used to connect the outside
temperature sensor.
Brown
5
Blue 2
Mains Supply
Grey 1
Fused @ 3A
Orange 9
230V
Green/Yellow
3
White N/U
Brown
8
Programmer
Blue 2
ST6300A
Grey 1
Orange
10
Green/Yellow 3
C
Cyl. Thermostat
1
L641A1039
2
The Keston C40, C40P, C55 & C55P
Room Thermostat
Live
1 T6360B1028
Neutral 2
Earth 3
KESTON
C55 / C40
L 1
2
N
1
6
3
4
4
Keston Spa
Cylinder Stat
6
OR
8
Keston Spa
Overheat Stat
1 4
3 5
2
2
L 1
N 2
E 3
9
SL1
SL2 10
EX1
To Keston
EX2
Ext. Sensor
[Optional]
6
C
1
2
C
8
1
2
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