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3.3.1 Flues for power vented installations
(Type B appliances)
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. Ensure that an adequate air supply for
combustion and ventilation is provided within the building in
accordance with the regulations & rules in force.
Table 5 shows flue pipe sizes and maximum vent lengths. The
minimum flue length is 0.5 metres.
Table 5 Flue pipe diameters & maximum lengths
Single wall flue pipes are required. All joints must be sealed to
prevent products of combustion from leaking into the building.
An approved flue terminal is required.
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 at least a 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 50 mm away from any combustible
material.
Single wall flue pipe exposed to cold air or run through
unheated areas must 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.
3.3.2 Combustion air inlet pipe & flue pipe for balanced
flue installation (Type C appliances)
Balanced flue air heaters are designed to be fitted with a
combustion air inlet duct that obtains outdoor air and a flue
pipe that exhausts flue products to outdoors.
Air heaters if fitted with a power venter permitting either a
vertical or horizontal combustion air inlet/flue pipe system.
The
heaters must be installed with a concentric vertical or
horizontal flue/air inlet. The heaters are only approved for
use when installed with the appropriate approved
concentric vent terminal.
See table 6.
Both the flue and combustion air pipes must be sealed. Use
gasket sealed seamless aluminium pipe or equivalent.
The flue pipe must include a re-sealable test port to allow good
average sampling of the flue gas mixture for testing, the port
must be at least 450 mm away from the air heater flue
connection socket.
Follow any flue pipe manufacturers installation instructions for
making joints, including connections to the air heater, for
passing through a building element and for support
requirements. If more than one air heater is being installed in
the same place each heater must have a separate flue system.
Figure 2b : Combustion air and flue pipe sockets
Type C
Legend :
¬
combustion products flue outlet socket for
flue pipe
-
Combustion air inlet opening
®
Inlet blocking bracket for combustion air inlet
pipe
SCA
45,60,
75,100,
125
150,200,
250,300
Heater socket &
mm
pipe f
80
100
130
Maximum straight
m
length
9
Equivalent length
m
of 45° elbow
0.75
Equivalent length
m
of 90? elbow
1.5