BENSON OUH 2 100, Installation And Operating Manual

Page: 12 / 44

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 2 cm2 for each kW of rated heat
input.
•
At low level 4 cm2 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 fl oor level.
The table below provides specifi c data for each heater model
as -
Minimum Free Area of ventilation
opening
Model High Level cm² Low Level cm²
40
88 176
60
128 258
70
166 332
90
192 384
100
230 460
1.11.2.2 Natural Ventilation Openings to Enclosures
For enclosure applications the minimum free area of
ventilation opening shall be:
• At high level 5 cm2 for each kW of rated heat
input.
•
At low level 10 cm2 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 fl oor level.
The table in the next column provides specifi c data for each
heater model as:-
Minimum Free Area of ventilation
opening
Model High Level cm² Low Level cm²
40
220 440
60
320 640
70
415 830
90
480 960
100
575 1150
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
It is necessary to provide an automatic means to safely inhibit
heater(s) operation should mechanical air supply fail for any
reason
The table to follow provides specifi c data for each heater
model as -
Mechanical Ventilation Rate
for Plant Room or Enclosure
Model M³/h
40
182
60
265
70
344
90
397
100
476