User Instructions

All components of the system including the heat exchanger of any calorifiers used
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.
2.6.3 Hot Water System (if applicable)
The hot water storage vessel must be of the indirect type). DIRECT CYLINDERS
MUST NOT BE USED. Further guidance is provided in BS 1394.
2.6.4 Balance Headers - Multiple Boiler Installations
Boiler water flows are critical to the operation of the boiler. If flow cannot be
maintained through the system pipework to meet the minimums required by the
boiler the boiler will “kettle” or even produce steam which can damage the heat
exchanger and invalidate the heat exchanger warranty. The implementation of a
balance header, as shown in the above schematics, is recommended to ensure
adequate water circulation is maintained through the boiler by the integral boiler
shunt pumps, 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 Header Diameter
up to 100kW 3”
up to 200kW 4”
up to 300kW 4.5”
up to 400kW 5”
When assembling a balance header the following design considerations must be
observed:
a) Each boiler must have its own flow and return connection to the balance
header pipe. Common flow and return connections with 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.
2.6.5 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.
Installation of air bleed valves at the high spot(s) in the system will allow for air
elimination when filling the system and will allow re-venting in a day or so after all
air has been driven out of solution.
2.6.6 Strainers
Debris in the heating system can cause noise if it enters the heat exchanger.
Fitting of a Y-strainer on the system return(s) will trap any debris left in the
system. The boiler guarantee does not cover heat exchanger failure due to debris
abrasion within the system.
WD53/0/1999 Chapter 2 - Boiler Connections The Keston 260 & 340 Condensing Boilers
Installation & Servicing Instructions Page : 8