10
HEAT RECOVERY VENTILATION
Where a stove is to be installed in a dwelling with
Heat Recovery Ventilation
(HRV) a number of
precautionary 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
atmospheric, 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.
EXTERNAL DUCTED AIR
Where required the primary air supply can be
ducted from outside. An aluminium flexible duct is
available to order for connection to the stove.
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.
Fig.6
Note: When Installing
outside air pipe adhere
to ‘Clearance to
Combustible’ Section.
‘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.’
Where such an installation exists, a test for spillage
should be made with the fan or fans and other appli-
ances using air in operation at full rate, (i.e.extraction
fans, tumble dryers) with all external doors and win-
dows closed.
If spillage occurs following the above operation, an
additional air vent of sufficient 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 5m
3
/ (h.m
2
) (nor-
mally newer properties built from 2006), then a per-
manent ventilation must be fitted to provide 550mm
2
of ventilation for each kW of rated output. If a
draught stabiliser is also fitted then the requirement
is 850mm
2
per kW of rated output.
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 appli-
ance/flue while the fan is in operation. Refer to B.S.
8303 Part 1.
As wind effects can create suction and pressure
zones on
opposite sides of the dwelling it is
recommended 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.6.
