When the return water temperature is below 54
o
C, part of the water vapour in the
combustion products will condense inside the heat exchanger, thus increasing the boiler
efficiency 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 50mm muPVC pipe to the outside. The temperature of the
flue gases are usually around 10
o
C above the temperature of the return water. The flue
pipe should be terminated outside the building from where they cannot re-enter the
building or any other adjacent building.
The heating level may be controlled by room thermostats, hot water cylinder thermostats,
programmer time clocks and energy management systems.
1.3
RELATED DOCUMENTS
The Keston Condensing Boiler must be installed in accordance with the current issue of
the
Gas Safety (Installation and Use) Regulations
, current
IEE Wiring Regulations
,
Building Regulations
,
Building Standards (Scotland) Consolidation
, and the
Bye Laws of
the local Water Undertaking
.
In addition, due account must be taken to the following Codes Of Practice:
BS 6891
:
Gas Supplies
BS 6798
:
Installation Central Heating Boilers
BS 5449
:
Installation Pumped Central Heating
BS 5546
:
Installation Domestic Hot Water
BS 5440.1
:
Flues
WD51/2/1997 Chapter 1 : General Instruction
The Keston 170 Condensing Boiler
Installation & Servicing Instructions
Page : 2
