Keston C40 Installation And Servicing Instructions page 17

WD265/0/2002
exceptional recovery times with durable, long life stainless steel
construction and all associated controls. Contact Keston Boilers Ltd for
information
2.7.4 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 normally 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
to 20
must of the automatic type.
2.7.5 Balance Headers - Multiple Boiler Installations
Where multiple boilers are installed on a common distribution system
maintenance of balanced flow through each boiler is extremely important. The
implementation of a balance header, as detailed below, is recommended to
ensure adequate and balanced water circulation is maintained by each boilers
integral shunt pump, irrespective of system conditions.
The size of the balance header is dependant on the number of boilers serving the
header. A guide to sizing is given below:
Total Boiler Output (Max)
Up to 110kW
Up to 220kW
Up to 330kW
Up to 440kW
When assembling the balance header the following design considerations must
be observed:
A)
B)
C)
D)
2.7.6 Air Elimination
In the initial charge of
water
system
subsequent additions of
water to the system
some
dissolved in the water.
As the water is heated
the air is driven out of
the solution and will
collect in high spots in
the system. These air
Installation & Servicing Instructions
Chapter 2 - Boiler Location
C. To comply with the new Building Regulations Part L1 the bypass
Each boiler must have its own flow and return connections to the balance
header pipe. Common flow and return connections with the other boilers
will cause reverse circulation effects to occur.
The minimum distance between the system flow and return connections
is 600mm.
A drain off point should be fitted to the base of the header, along with
cleaning access, for sludge removal.
The top of the header should be vented.
to the boiler
and in all
air will be
Expansion
Vessel
The Keston C40, C40P, C55 & C55P
Header Diameter
3"
4"
4.5"
5"
C40/C55
Safety
AAV
Valve
42mm
Header
o
C
Additional system
pump.
Primary flow
Primary Return
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