2.7.3
Hot Water System (if applicable)
The hot water storage vessel must be of the indirect type (certain direct cylinders
can be used provided they are suitably adapted by fitting an immersion calorifier).
DIRECT CYLINDERS MUST NOT BE USED. Further guidance is provided in BS
1394. It is advisable to fit a locksheild valve on the cylinder return to enable
balancing of the flow rate through the cylinder.
The Keston Spa range of stainless steel unvented cylinders are an ideal
option for use with the Keston range. The Keston Spa range combine
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
C
to 20
o
C. To comply with the new Building Regulations Part L1 the bypass
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)
Header Diameter
Up to 110kW
3”
Up to 220kW
4”
Up to 330kW
4.5”
Up to 440kW
5”
When assembling the balance header the following design considerations must
be observed:
A)
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.
B)
The minimum distance between the system flow and return connections
is 600mm.
C)
A drain off point should be fitted to the base of the header, along with
cleaning access, for sludge removal.
D)
The top of the header should be vented.
2.7.6
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 driven out of the solution and will collect in high spots in the
system. These air bubbles can interfere with pumping and heat transfer and
must be eliminated.
WD536
Chapter 2 - Boiler Location
The Keston C45, C40P, C55 & C55P
Installation & Servicing Instructions
Page : 13