Nortek Reznor 120, Installation & Servicing Manual

Page: 13 / 68

• 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
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
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
30 139
40 206
60 274
85 409
120 567
135 717
180 822
205 987
235 1131
300 1410
375 1830
1.12 Air distribution system
All materials used within the construction of the delivery and
return air ducts must not represent a fi re hazard and should
be made from thermally inert materials. The selection of
materials must take account of the environment into which
the heater and its air delivery system is expected to work, it
must also take account of the stresses and loadings placed
upon it during its normal working life. Where interjoist spaces
are used to route ducting these must be lined with fi re
resistant insulation material.
In installations where forced recirculation is a feature, a full
and unobstructed return air path to the heater(s) must be
provided, with return air grilles connected by ducting directly
to the return air inlet on the heater.
The limit for recirculation should not be greater than 85%
re-circulated air to 15% fresh air.
Where the heater is installed within a compartment or plant
room the return air and discharge air arrangement must be