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THE DIRECT EXTERNAL AIR SUPPLY
(DEAS) Ref BS8303 (2018)
Installer responsibilities
• All external air ducting as well as the inlet
grille must be fitted strictly in accordance with
these instructions which are intended to give
clear guidance to the installer on the safe
installation of the stove and its DEAS.
• The person installing the appliance takes
full responsibility for a safe installation (refer
to Approved Document J, BS8303 (2028) and
the relevant Hetas Technical Bulletins) and
must ensure that the installation complies
with all relevant Building Regulations.
• The installer must fully commission the
appliance, including undertaking appropriate
spillage tests and flue draught measurements,
to demonstrate and confirm the stove’s
safe operation with the room in its normal
state and also with doors and windows
closed and any mechanical extraction in the
room and the rest set of the dwelling set at
maximum operation i.e. worst case scenario
depressurisation conditions.
• As already required by Building Regulations
a CO detector(s) must be correctly fitted
and the householder made aware of the
importance of regularly testing it.
• The householder should also be made aware
that the stove should never be operated with
the door open except when refuelling and this
should always be kept to a minimum.
Direct air supply ducting requirements
• The external diameter of the DEAS inlet on
this stove is 90mm (internal dia approx 86mm).
• Ensure that the internal diameter of the direct
air ducting is at least the same size as the
internal diameter of the DEAS inlet pipe.
• Do not reduce the diameter of the ducting
as this will affect the safe operation of the
stove. For fire safety reasons only use the
appropriate metal or non-combustible ducting.
Never use plastic ducting.
• The maximum recommended ducting length
for the air supply to this stove is 1 metre. Longer
straight lengths may be considered provided
that the appropriate flue draught measurements
and spillage tests are undertaken by the
installer to ensure that this will not adversely
affect the safe operation of the stove.
• Keep bends in the ducting to a minimum
and avoid using bends greater than 60º.
Ensure that there is a good air-tight seal
between the ducting and the stove’s inlet
pipe. Use an appropriate weather-proof, non-
closable, external vent grille.
• When selecting the location of the external
vent grille you must ensure that it can be
easily accessed so that it can be regularly
checked for potential obstruction (eg foliage
growth, dead leaves or snow drifts etc). Never
use the stove if these conditions exist. Ensure
that the external grille will not be subject to
the adverse affects of prevailing wind which
will affect the stove’s performance.
IMPORTANT It may be, that despite
Installing with the DEAS, in order to
avoid depressurisation and to ensure
the safe operation of the stove, a
dedicated air vent, as prescribed in
Building Regulations Document J (or
its equivalent) is the only solution to
ensuring the necessary additional air
for the correct operation of the
stove where there is mechanical
extraction. It is strongly recommended
therefore that the installer makes the
householder aware of this before
any of the installation work proceeds.
