Technical data

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.
2.4.2.2 Natural Ventilation Openings to
Plant Rooms for Flued Heaters
The table below provides specific data for
each heater model as -
Where the heater(s) is installed in a plant
room and in flue 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 2 cm
2
for each kW of
rated heat input
 At low level 4 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.
2.4.2.3 Natural Ventilation Openings to
Enclosures for Room Sealed Heaters
The table below provides specific data for
each heater model as -
For enclosure applications the minimum free
area of ventilation opening will also depend
upon whether the heater(s) is installed in
room sealed mode (ie with a positive
connection to atmosphere of both flue and
combustion air)
Or with flue only (ie without the positive
connection to atmosphere of a combustion
air duct)
Where the heater(s) is installed in a plant
room and in room sealed mode (ie with a
positive connection to atmosphere of both
flue and combustion air ) 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 5 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
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 26 52
70 43 85
100 64 128
135 86 171
170 107 214
200 128 256
250 158 316
330 211 422
410 263 525
490 315 630
MODEL