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With all clearance reduction systems using ventilated air space there shall be at least 1" clearance
between the reduction systems using ventilated air space.
Mineral wool batts, blanket or board shall have a minimum density of 8lb/ft
temperature of 1500
Insulation material used as part of a clearance reduction system shall have a thermal conductivity of
2
1.0(Btu/In)/ (Ft
/Hr/
Type of protection applied to and
covering all surfaces within the distance
specified as the required clearance with
no protection
3½" thick masonry wall without
ventilated air space
½" insulation board over 1" glass fiber
or mineral wool batts
24 gauge sheet metal over 1" glass fiber
or mineral wool batts reinforced with
wire on rear face with ventilated air
space
3½" thick masonry wall with ventilated
air space
24 gauge sheet metal with ventilated air
space
½" insulation board with ventilated air
space
24 gauge sheet metal with ventilated air
space over 24 gauge sheet metal with
ventilated air space
1" glass fiber or mineral wool batts
sandwiched between 2 sheets 24 gauge
sheet metal with ventilated air space
If the furnace is to be installed in a residential garage, the furnace must be a minimum of 18" above
the garage floor and located so it cannot be damaged by a moving vehicle
6
0
F.
0
F).
Table 2 Allowable Clearances with Specified Protection
Where the Specified Clearance with No Protection from the Appliance or
Chimney Connector
18"
Above
N/A
12"
9"
N/A
9"
9"
9"
6"
12"
Rear &
Above
Rear &
Sides
Sides
12"
N/A
9"
9"
9"
6"
6"
6"
4"
6"
N/A
6"
6"
6"
4"
6"
6"
4"
6"
6"
4"
6"
6"
4"
3
and a minimum melting
9"
Above
Rear &
Above
Sides
N/A
6"
N/A
6"
5"
4"
5'
3"
3"
N/A
6"
N/A
5"
3"
3"
5"
3"
3"
5"
3"
3"
5"
3"
3"
6"
Rear &
Sides
5"
3"
3"
6"
2"
3"
3"
3"
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