Page 4
506488-01
Issue 1008
Roof Curb Installation
If a roof curb is used, follow the manufacturer’s Installation
Instructions and be sure that all required clearances are
observed (see following Clearances section).
Clearances
All units require certain clearances for proper operation and
service. Refer to Table 1 for the minimum clearances to
combustibles as well as minimum clearances necessary for
servicing and proper unit operation.
In the U.S., units may be installed on combustible floors made
from wood or class A, B, or C roof covering material. In Canada,
units may be installed on combustible floors.
Service Access
Access to all serviceable components is provided by four
removable panels: filter compartment, blower compartment,
furnace compartment, and top panel.
Combustion Products Discharge
The unit must be positioned such that combustion products
discharged at the vent outlet will not result in building
degradation and must be consistent with the National Fuel
Gas Code, Z223.1 or CAN/CGA-B149.1 & .2.
The products of combustion are discharged through a
screened opening in the front mullion. The horizontal vent
system shall terminate at least 4' below, 4' horizontally from,
or 1' above any door, window, or gravity air inlet into the
building. The vent system shall terminate at least 3' above
any forced air inlet located within 10'.
The unit shall be installed in a manner such that snow
accumulation will not restrict the flow of flue products.
In addition to the above requirements, consideration must
be given to prevent unwanted ice buildup from the vent
condensate. The vent should not be located on the side of
a building where the prevailing winter winds could trap the
moisture, causing it to freeze on the walls or on overhangs
(under eaves). The vent location should not discharge over
Figure 3 shows the minimum clearances to combustibles
required above and below the vent hood. The minimum
clearance in front of the vent hood is 24".
Do not permit overhanging structures or shrubs to
obstruct condenser air discharge outlet or vent outlet.
Minimum Clearance to Combustibles
Above and Below the Vent Hood
Figure 3
Minimum Clearance
Above Vent Hood:
Distance from Top
of Vent Hood to Top
of Unit
Minimum Clearance
Below Vent Hood:
Distance from Bottom
of Vent Hood to Base
of Unit
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4
2
"
8
4
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3
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"
0
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4
2
"
3
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C
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0
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4
2
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0
"
0
3
"
0
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"
0
"
6
3
"
6
3
Minimum Clearance Requirements
Table 1
Roof Curb Assembly
Figure 2
