0108MLOOGBEN
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4.7 Type B Appliances
4.7.1 If the air heater is to be installed as a B type
appliance i.e. air for combustion to be taken from
within the space to be heated, figure 5, then it
must be ensured that an adequate air supply for
combustion and ventilation is provided, in
accordance with the regulations and rules in force.
4.7.2 A horizontal distance between air heater and flue
terminal and any combustion air intake duct, must
not be in excess of 16 m.
Note: 2 Meters of vertical rise negates the
resistance imposed by 1 meter of horizontal run.
Runs exceeding 16m may be subject to
condensation forming within the flue.
Equivalent lengths of flue fittings:
Elbow @ 45° = 1 m.
Elbow @ 90° = 1,5 m.
Flue terminal ≤ 3.0 m. (dependant on type)
4.7.3 To ensure that the allowable resistance is not
exceeded in the case of horizontal runs of flues, a
positive rise from the air heater of 1° i.e. 17 mm
per metre should be maintained.
4.7.4 If condensation is to be avoided, flues should be
insulated if they are installed in cold areas. The use
of twin wall flues should also be considered.
4.7.5 When mechanical ventilation is used, it shall be by
mechanical inlet with either mechanical or natural
extraction. Automatic means of control such as
interlocks must be provided. The function of other
ventilation systems in the heated zone must be
taken into account. At no time should a negative
pressure environment exist in the zone, this can
lead to a hazardous situation, whereby the air
heater flue may act as a pressure relief.
4.7.6 The terminal of a vertical flue must extend 1 m
above a roof surface, flues must not terminate
where combustion products might enter the
building. Terminals must be fitted to flues and
combustion air inlets. The combustion air inlet if
not used must be protected with an access guard.
Figure 4 FLUE SYSTEMS FOR TYPE C APPLIANCES
Reznor concentric flue system
Horizontal terminal arrangement Vertical terminal arrangement
Use "Burfix" Ø 80 mm or "Mugro" 2000 Ø 80 mm
Mugro 2000 system horizontal or burfix
80/125 horizontal
TYPE C12
Mugro 2000 system vertical or burfix 80
vertical
TYPE C32
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