k.
The boiler is supplied with an integral expansion vessel of 8l capacity. This is
suitable for systems of up to 125 Litres system volume. Table 3.7 Expansion
Vessel Selection provides guidance for the correct additional expansion vessel
size to use for systems with a water content larger than 125 Litres. Any additional
vessel must be fitted on the boiler primary return.
l
A filling point must be fitted, in accordance with local water authority
requirements. An approved filling loop is supplied loose with the boiler installation
jig. There must be no permanent connection to the mains water supply. The filling
loop must therefore be left isolated at both ends and disconnected after the
system is filled.
m
The installation must be designed to work with flow temperatures of up to 110
o
C.
All components of the system must be suitable for a working pressure of 3 bar
and a temperature of 110
o
C. Care should be taken in making all connections that
the risk of leakage is minimised.
n
The pipe from the safety discharge valve must not discharge above an entrance,
window or any type of public access area. The boiler safety discharge valve pipe
must be extended using not less than 15mm pipe to discharge, in a visible
position, outside the building, facing downwards, preferably over a
drain.
The
pipe must have a continuous fall and be routed to a position so that any discharge
of water, possibly boiling, or steam cannot create any danger to persons, damage
to property or external electrical components or wiring. To ease future servicing it
is advisable to use a compression type fitting to extend the safety discharge valve
pipe.
3.7.1
Boiler By-pass Piping
Boiler water flows are critical to the operation of the boiler. If flow cannot be maintained
through the system piping to meet the minimums required by the boiler, insufficient water
flows through the boiler will cause the boiler to "kettle" or even produce steam which can
damage the heat exchanger and will invalidate the heat exchanger warranty. In addition,
an open circuit is required after boiler shutdown to permit circulation during the boilers 2
minute pump overrun sequence.
It is advisable to incorporate a boiler by-pass in the system, especially if thermostatic
radiator valves are used. The flow/return differential should be 10
o
C to 20
o
C.
To comply
with the Building Regulations Part L1 the bypass must of the automatic type.
3.7.2
Air Elimination
In the initial charge of water to the boiler system and in all subsequent additions of water
to the system some air will be dissolved in the water. As the water is heated the air is
WD388/0/2004
Chapter 3 - Boiler Location
The Keston C36 Combi & C36P Combi Boilers
Installation & Servicing Instructions
Page : 14
COMBI
KESTON
Expansion
Isolating Valve
HEATING CIRCUIT
FLOW
RETURN
(disconnected
after filling)
Flex Hose
Isolating & Dbl Chekc Valve
By-pass
(if required)
Drain
Cock
(if required)
D
O
M
E
S
T
IC
W
A
T
E
R
D
O
M
E
S
T
IC
H
O
T
W
A
T
E
R
C
O
L
D
W
A
T
E
R
S
U
P
P
L
Y
Vessel
Figure 3.7 : CH & DHW Sealed Systems Diagram
