Technical data
15% of the wall height
The low level natural ventilation opening
should be situated on an external wall and be
within 1000 mm of floor level for natural gas
and ideally at floor level for l.p.g gas
installations but in any event no higher than
250 mm.
2.4.2.4 Natural Ventilation Openings to
Enclosures for Flued Heaters
The table below provides specific data for
each heater model as -
Where the heater(s) is in an enclosure and in
flue only mode (ie without a positive
connection to atmosphere of combustion air
ductwork ) the minimum free area of
ventilation opening needs to be
At high level 5 cm
2
for each kW of
rated heat input
At low level 10 cm
2
for each kW of
rated heat input
The high level ventilation opening should be
sited on an external wall and positioned as
high as is practical and always within the top
15% of the wall height
The low level natural ventilation opening
should be situated on an external wall and be
within 1000 mm of floor level for natural gas
and ideally at floor level for l.p.g gas
installations but in any event no higher than
250 mm.
2.4.2.5 Mechanical Ventilation to a
Plant Room or Enclosure
The table below provides specific data for
each heater model as -
In the event that the installer prefers to
mechanically ventilate the plant room or
enclosure rather than provide ventilation
openings then -
The plant room or enclosure needs to
be mechanically ventilated at the rate
of 4.14 m
3
/h of fresh air per kW or
rated heat input.
It is a requirement that the mechanical
ventilation shall be of the ’input’ type
with either natural or mechanical
extraction. Where mechanical
extraction is selected then the
extraction rate should be 5%-10% less
than the input rate.
Systems of mechanical extraction with
a natural inlet shall not be used
It is necessary to provide an automatic
Minimum Free Area Of
Ventilation Opening
High Level Low Level
cm
2
cm
2
40 65 65
70 106 106
100 160 160
135 213 213
170 267 267
200 320 320
250 394 394
330 527 527
410 656 656
490 787 787
MODEL
Minimum Free Area Of
Ventilation Opening
High Level Low Level
cm
2
cm
2
40 65 130
70 106 212
100 160 320
135 213 426
170 267 533
200 320 640
250 394 788
330 527 1053
410 656 1312
490 787 1574
MODEL