Keston 50 - GC Installation And Servicing Instructions page 15

WD50/2/1997 Chapter 2 - Boiler Connections
2.7.5 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.
Installation of an automatic air vent will ensure that any air, even minute
amounts, which subsequently enters the system will be automatically removed.
2.7.6 Strainers
Debris in the heating system
can cause noise if it enters the
heat exchanger. Fitting of a
Y-strainer ahead of the
circulating pump will trap any
debris left in the system and
will protect the pump from
damage.
2.7.7 Pump Selection
The Keston boilers have low
water content heat exchangers
with a high resistance to flow,
when compared with cast iron
heat exchanger boilers. As a
result selection of the correct
pump is essential in order to
avoid localised boiling within
the heat exchanger. The
selected pump must be
capable of maintaining the
required flow rate for the boiler
against the pressure losses
contributed by the boiler and
the rest of the system.
Refer to the pressure loss/flow
rate Table 2.7.7 to determine
the pressure loss from the
boilers. Add this to the
pressure loss caused by the
rest of the system and select a
pump capable of meeting the
flow rate required at the total
pressure loss generated by the
boiler and the rest of the
system. The selected pump
must comply with BS 1394.
Installation & Servicing Instructions
The Keston 50, 60 & 80 Condensing Boilers
Y-Strainer will
collect any loose
debris in the piping.
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Figure 2.7.7 : Pressure Loss Graph
Page : 12
5 10 15 20
Water Flow - L/min
Figure 2.7.6 Strainers
Keston 80
Keston 50
Keston 60
25 30 35