Keston C36 Combi - Page 9

system and burns with
a blue flame just off
the surface of the
burner. As the hot
products of
combustion pass
downwards, they are
cooled by exchanging
heat with the
circulating water which
enters the heat
exchanger at the
bottom of the heat
exchanger. The
optimum heat input is
detected by monitoring
flow and return
temperatures and is
adjusted by controlling
the speed of the fan.
The optimum pump
speed is also detected
and automatically
selected by the boiler.
When the return water temperature is below 55
o
C, part of the water vapour in the
combustion products will condense inside the heat exchanger, thus increasing the boiler
efficiency further by releasing
the latent heat of
condensation. This
condensate falls to the
bottom of the heat exchanger
where it is separated from
the flue gases and exits from
the boiler through the
condensate drain. Any
condensate formed in the
flue runs back down the
flueway and is drained at the
base of the flue connection
to the heat exchanger or
drain points within the flue.
The condensate is very
slightly acidic (about the
same acidity as vinegar) and
should be piped in a plastic
pipe. It is not harmful to the
waste disposal system and
may be disposed of as
normal waste water.
The flue gases are piped in a
50 mm muPVC (BS5255
and/or BSEN1566-1 and
BSEN1329) plastic or,
alternatively, 75mm Keston
composite plastic pipe to
outside. The temperature of
the flue gases are usually
WD388/0/2004 Chapter 2 : General Instruction The Keston C36 Combi & C36P Combi Boilers
Installation & Servicing Instructions Page : 4