NOTE:
There must not be an extractor fan fitted in the same
room as the stove as this can cause the stove to emit
smoke and fumes into the room. All materials used in
the manufacture of air vents should be such that the
vent is dimensionally stable, corrosion resistant, and
no provision for closure. The effective free area of
any vent should be ascertained before installation.
The effect of any grills should be allowed for when
determining the effective free area of any vent. Air
vents should be positioned so that they are not liable
to blockage.
Air vents direct to the outside of the building should
be located so that any air current produced will not
pass through normally occupied areas of the room.
An air vent outside the building should not be locat-
ed less than the dimensions specified within the
Building Regulations and B.S. 8303: Part 1 from any
part of any flue terminal. These air vents must also
be satisfactorily fire proofed as per Building
Regulations and B.S. 8303: Part 1.
Air vents in internal walls should not communicate
with bedrooms, bedsits, toilets, bathrooms or rooms
containing a shower. Air vents traversing cavity walls
should include a continuous duct across the cavity.
The duct should be installed in such a manner as not
to impair the weather resistance of the cavity. Joints
between air vents and outside walls should be
sealed to prevent the ingress of moisture. Existing air
vents should be of the correct size and unobstructed
for the appliance in use.
If there is an extraction fan fitted in adjacent rooms
where this appliance is fitted, additional air vents
may be required to alleviate the possibility of spillage
of products of combustion from the appliance/flue
while the fan is in operation. Refer to B.S. 8303 Part
1. Where such an installation exists, a test for
spillage should be made with the fan or fans and
other appliances using air in operation at full rate,
(i.e. extraction fans, tumble dryers) with all external
doors and windows closed. If spillage occurs follow-
ing the above operation, an additional air vent of suf-
ficient size to prevent this occurrence should be
installed.
Especially Airtight Properties:-
If the stove is being fitted in a property where the
design air permeability is less than 5m3/ (h.m2) (nor-
mally newer properties built from 2006), then a per-
manent ventilation must be fitted to provide 550mm2
of ventilation for each kW of rated output. If a
draught stabiliser is also fitted then the requirement
is 850mm2per kW of rated output.
9
EXTERNAL DUCTED AIR
Where required the combustion air supply can be
ducted from outside.
It is recommended to bring the air supply for the
stove into the house using a 4” plastic pipe. Where
the pipe meets the outside wall make sure a vent
cover is fitted properly to ensure no rodents can
enter via the vent pipe.
The vent pipe should be located to prevent the
ingress of moisture and in a location where it will not
get blocked with leaves or any other debris.
As wind effects can create suction and pressure
zones on opposite sides of the dwelling it is recom-
mended to run the air vent from opposite poles
(North, South, East & West) of the dwelling and tee
off for the air supply to the stove. This should negate
the effect of suction and pressure zones. See Fig.8.
‘HETAS product approval covers this appliance
when installed in accordance with the manufactur-
er’s instructions and relevant standards. As there is
currently no standard for Ducted Combustion Air
Supply this does not fall within the remit for HETAS
product approval. Responsibility for the specification
of this and for appropriate manufacturer’s instruc-
tions is carried by the appliance manufacturer, as
allowed for under the Building Regulations.’
HEAT RECOVERY VENTILATION
Where a stove is to be installed in a dwelling with
Heat Recovery Ventilation (HRV) a number of pre-
cautionary measures must be undertaken:
Should for example the delivery fan in the HRV unit
fail and the extraction fan in HRV fan continue to run
the HRV may create a pressure less than atmos-
pheric, this low pressure will effect the flue pressure
which is required to safely evacuate the products of
combustion from the stove.
1. Fit an adequately sized vent in the room to pre-
vent pressure less than atmospheric occurring.
The size should be established by closing all
windows and doors and then creating the
possible failure situation. Then open a window
in the room where the stove is fitted, slowly
until the pressure reaches atmospheric. The
size of the window opening should be measured
and a vent of the corresponding size installed.
2. Fit a CO Alarm which has been approved to
EN 50291.