34
IND GUIDE INST 10-11
HHIC REF T11/0027BRev8
The
use
of
fittings, elbows etc should be kept to a
minimum and any internal “burrs”
on cut pipework should be removed so that the internal pipe section is as smooth as
possible.
The customer/householder should be advised that even with the above measures this type
of installation could freeze, and that if this were to occur then boiler shutdown could result,
requiring remedial action - possibly involving a chargeable engineer call-out.
Where there are likely to be extremes of temperature or wind-chill, the use of a proprietary
trace-heating system for external condensate drainage pipework, incorporating an external
frost thermostat, should therefore be considered. If such a system is used then the
installation instructions of the trace heating manufacturer and any specific recommendations
regarding pipe diameter, insulation, etc. should be followed. All other relevant guidance on
condensate drainage pipe installation should also be followed.
Other cold weather protection methods approved or endorsed by boiler manufacturers
and/or service organisations may be adopted if these are considered suitable by the parties
involved.
If an external soil/vent stack is used as the external termination then the connection method
shown in Figure 4 should be used, together with the measures on insulation etc. as
described above and shown in the diagram.
When a rain water downpipe is used as the termination (
NB
only permissible if this downpipe
passes to a combined foul and rainwater drainage system
) an air break must be installed
between the condensate drainage pipe and the downpipe to avoid reverse flow of rainwater
into the boiler should the downpipe itself become flooded or frozen. Figure 5 shows a
suitable connection method.
Where the condensate drainage pipe is terminated over an open foul drain or gully, the pipe
should terminate below the grating level, but above water level, in order to minimise “wind
chill” at the open end. Pipe drainage will
be improved if the end is cut at 45
o
as opposed to a
straight cut. The use of a drain cover (such as those used to prevent blockage by leaves)
may offer further protection from wind chill. Figure 6 shows a suitable connection method.
Where the condensate drain pipe terminates in a purpose-designed soakaway (see BS
6798:2009 or boiler installation manual for soakaway design requirements) any above-
ground section of condensate drainage pipe should be run and insulated as described
above. Figure 7 shows a suitable connection method.
3. UNHEATED INTERNAL AREAS:
Internal condensate drainage pipes run in unheated areas such as lofts, basements and
garages should be treated as external pipe.
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