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WD53/0/1999
Chapter 2 - Boiler Connections
External wall faces and any internal faces of cavity walls must be made good.
2.8
AIR SUPPLY
The Keston is a room sealed appliance and therefore does not require purpose provided
ventilation to the boiler room for combustion air.
2.9
COMPARTMENT INSTALLATION
The casing temperatures of the Keston 260 and Keston 340 are very low. Due to this fact,
no compartment ventilation is required for cooling purposes.
2.10
CONDENSATE DRAINAGE
Being a condensing boiler, the Keston is fitted with a condensate trap at the base of the
heat exchanger and flue assembly, with facility to connect to a drain point underneath the
appliance.
Use only plastic piping and do not reduce below 28mm internal diameter within the
dwelling. Condensate should preferably be drained into the sanitary waste system or,
alternatively, the rainwater system of the property.
Termination of the pipe must be either at a branch or stack internal to the building, or
externally at an open gully. Alternatively, discharge into a purpose made condensate
soakaway can be considered. Existing or purpose built drains must use suitable corrosion
resistant material as condensate is mildly acidic.
A minimum slope downwards towards the drain of 1 in 20 is essential. Freezing of the
termination and pipework must be prevented. Any drainage pipes outside the property
must be at least 32 mm inside diameter.
2.11
UNDER FLOOR HEATING/WEATHER COMPENSATION
Both underfloor heating and weather compensating control demand reduced system
operating temperatures for some of all of the time the system is operating. Traditionally
this is achieved by used of mixing valves to reduce flow temperature by blending return
water.
The Keston Condensing Boiler provides increased operating efficiencies at low return
system temperature. Therefore, in the event the Keston boiler is serving only underfloor
heating or only weather compensated circuits at any time the boiler flow temperature
should be achieved by limiting the boiler temperature and dispensing with the use of a
mixing valve.
The low operating temperatures of this type of system lead to very good operating
efficiencies. In fact, under floor heating can produce in excess of 95% operating efficiency
from a Keston condensing boiler.
Installation & Servicing Instructions
The Keston 260 & 340 Condensing Boilers
Page : 12
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