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6.2
Type B appliances
6.2.1
Flues for power vented installations
If the air heater is to be installed as a type B appliance,
air for combustion will be taken from within the space
where the heater is installed.
Single wall flue seamless aluminium or stainless steel
pipes are required. All joints must be sealed to prevent
products of combustion from leaking into the building. If
the flue passes through a combustible element of the
building it must be enclosed by a sleeve of non-
combustible material and separated from the sleeve by a
minimum of 25 mm air break. The temperature of any
combustible material near to the flue must not exceed
65°C when the heater is in operation. The flue must be at
least 150 mm away from any combustible material.
Single wall flue pipe exposed to cold air or run through
unheated areas should be insulated. Where
condensation is unavoidable, provision must be made for
the condensation to flow freely to a point to which it can
be released, i.e. a drain or gully. The condensation drain
from the flue must be constructed from non-corrodible
material not less than 20 mm diameter. Copper or copper
based alloys must not be used for condensation drains.
For testing, the flue pipe should include a sealable test
port. The port must be at least 450 mm away from the air
heater flue connection socket.
Follow the flue pipe manufacturer’s installation
instructions for making joints, including connections to
the air heater, for passing through a building element
and for support requirements.
6.2.2 Air
supply
Ensure that an adequate air supply for combustion and
ventilation is provided within the building in accordance
with BS6230/BS5440 plus other relevant regulations &
rules in force.
It is important to ensure that there is an adequate air
supply at all times for both combustion and heating
requirements.
Modern buildings involve greater use of insulation,
improved vapour barriers, and weather proofing. These
practices mean that buildings are sealed much tighter
than in the past.
Proper combustion air supply for a power vented Type B
installation requires ventilation of the heated space.
Natural infiltration of air may not be adequate. Use of
exhaust fans aggravates this situation. It is important to
ensure that there is adequate combustion air supply at
all times. Reliance on doors and windows is not allowed.
Ensure that the air combustion inlet opening at the side of
the unit cannot be obstructed (cfr. fig 7b).
When these air heaters are installed in type B
applications, designed to take air for combustion
from the space in which it is installed. Do not
restrict the combustion air intake.
Figure 7a : Approved appliances type B
B52/B22* – Roof
* : only Belgium
B52/B22* – Wall
Figure 7b : Type B appliances – Combustion air and
flue pipe sockets
1 Combustion air inlet opening
2 Flue pipe outlet collar
