Doc No. 20-45-159 Page 9 of 60
openings (sections 1.11.2.1 refers to plant room applications
and sections 1.11.2.2 refers to enclosure applications).
Alternatively the plant room or enclosure may be
mechanically ventilated (section 1.11.2.3 refers).
1.11.2.1 Natural Ventilation Openings to Plant Rooms
For plant room applications the minimum free area of
ventilation opening shall be:
• At high level 2cm2 for each kW of rated heat input.
• At low level 4cm2 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 oor level for
natural gas installations but no higher than 250 mm.
The table below provides specic data for each heater model
as -
Minimum Free Area of ventilation
opening
Model High Level cm² Low Level cm²
30 64 128
40 97 194
60 127 254
85 193 386
120 257 514
135 291 582
180 386 722
205 460 920
235 515 1030
300 623 1246
375 847 1694
1.11.2.2 Natural Ventilation Openings to Enclosures
For enclosure applications the minimum free area of
ventilation opening shall be:
• At high level 5cm2 for each kW of rated heat input.
• At low level 10cm2 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 oor level for
natural gas installations but no higher than 250 mm.
The table in the next column provides specic data for each
heater model as:-
Minimum Free Area of ventilation
opening
Model High Level cm² Low Level cm²
30 159 318
40 244 488
60 317 634
85 483 966
120 643 1286
135 726 1452
180 965 1930
205 1152 2304
235 1287 2574
300 1558 3116
375 2118 4236
1.11.2.3 Mechanical Ventilation to a Plant Room or
Enclosure.
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 m3/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
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