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Combustion Air Options
ƽ CAUTION: Under no circumstances
should the mechanical room ever be under a
negative pressure. Particular care should be
taken where exhaust fans, attic fans, clothes
dryers, compressors, air handling units, etc.,
take away air from the unit.
1. Outside Combustion Air, No Ducts You can direct
outside combustion air to this unit using either one or two
permanent openings.
One Opening
The opening must have a minimum free area of one square
inch per 3000 Btu input (7cm
2
per kW). You must locate this
opening within 12" (30cm) of the top of the enclosure.
Figure 6 - Outside Combustion Air - Single Opening
Two Openings
The combustion air opening must have a minimum free area of
one square inch per 4000 Btu input (5.5cm
2
per kW). You must
locate this opening within 12" (30cm) of the bottom of the
enclosure.
The ventilation air opening must have a minimum free area of
one square inch per 4000 Btu input (5.5cm
2
per kW). You must
locate this opening within 12" (30cm) of the top of the
enclosure.
Figure 7 - Outside Combustion Air - Two Openings
2. Outside Combustion Air, Using Ducts
You can direct outside combustion air to this unit using two air
ducts to deliver the air to the boiler room.
Each of the two openings must have a minimum free area of
one square inch per 2000 Btu input (11cm
2
per kW).
Figure 8 - Outside Combustion Air Through Ducts
3. Combustion Air from Interior Space
You can direct combustion air to this unit using air from an
adjoining interior space. You must provide two openings from
the boiler room to the adjoining room.
Each of the two openings must have a net free area of one
square inch per 1000 Btu input (22cm
2
per kW), but not less
than 100 square inches (645cm
2
).
Installation and
Service Manual
9