NOTE:
The boiler shall be installed in a space large
in comparison to the size of the boiler. Large space
is defined as having a volume at least sixteen (16)
times the total volume of the boiler.
181 to 401 514 to 824
926 to
1826
2100 to
4001
a.
Back
9
9
16
16
Right
9
5
16
16
Left
9
12
16
16
Vent
5
5
5
5
Indoor Top
39
36
24
24
Outdoor Top
NA
b.
Back
6
6
12
12
Right
6
3
12
12
Left
6
9
12
12
Vent
3
3
3
3
Indoor Top
30
24
16
16
Outdoor Top
NA
c.
Back
4
4
8
8
Right
4
3
8
8
Left
4
6
8
8
Vent
3
3
3
3
Indoor Top
24
18
12
12
Outdoor Top
NA
d.
Back
6
6
8
8
Right
6
6
8
8
Left
6
6
8
8
Vent
6
6
6
6
Indoor Top
39
36
24
24
Outdoor Top
NA
e.
Back
4
4
8
8
Right
4
2
8
8
Left
4
6
8
8
Vent
2
2
2
2
Indoor Top
24
18
12
12
Outdoor Top
NA
f.
Back
4
4
8
8
Right
4
3
8
8
Left
4
6
8
8
Vent
3
3
3
3
Indoor Top
24
18
12
12
Outdoor Top
NA
g.
Back
4
4
8
8
Right
4
3
8
8
Left
4
6
8
8
Vent
3
3
3
3
Indoor Top
24
18
12
12
Outdoor Top
NA
h.
Back
4
4
8
8
Right
4
3
8
8
Left
4
6
8
8
Vent
3
3
3
3
Indoor Top
24
18
12
12
Outdoor Top
NA
0.024 sheet metal with
ventilated air space.
1/2 in. thick insulation board
with ventilated air space.
0.024 sheet metal with
ventilated air space over
0.024 sheet metal with
ventilated air space.
1 in. glass fiber or mineral
wool batts sandwiched
between two sheets 0.024
sheet metal with ventilated air
space.
Boiler Size
Description
Location
Unobstructed
Unobstructed
3-1/2 in. thick masonry walls
without ventilated air space.
1/2 in. insulation board over 1
in. glass fiber or mineral wool
batts.
0.024 sheet metal over 1 in.
glass fiber or mineral wool
batts reinforced with wire on
rear face with ventilated air
space.
3-1/2 in. thick masonry wall
with ventilated air space.
Unobstructed
Unobstructed
Unobstructed
Unobstructed
Unobstructed
Unobstructed
Table D: Reduction of Clearances to Protected
Surfaces
Derived from National Fuel Gas Code, Table 6.2.3(b)
Outdoor Boilers
These boilers are design certified for outdoor installa-
tion. Boilers must not be installed under an overhang
within three (3) feet from the top on the boiler. Three
(3) sides must be open in the area under the over-
hang. Roof water drainage must be diverted away
from the boilers with the use of gutters.
The point from where the flue products exit the boiler
must be a minimum of four (4) feet below, four (4) feet
horizontally from or one (1) foot above any door, win-
dow or gravity inlet to a building. The top surface of the
boiler shall be at least three (3) feet above any forced
air inlet, or intake ducts located within ten (10) feet hor-
izontally.
High-Wind Conditions (Outdoor
Units Only)
In areas where high winds are frequent, it may be nec-
essary to locate the boiler a minimum of 3' from high
vertical walls, or install a wind break so the boiler is not
in direct wind current.
Combustion and Ventilation Air
(Indoor Units Only)
The boiler must have both combustion and ventilation
air. Minimum requirements for net free air supply
openings are 12 inches from ceiling for ventilation and
12 inches from the floor for combustion air as outlined
in Z223.1 - latest edition or the current CAN/CSA
B149, as well as any local codes that may have juris-
diction.
Fig. 3: Minimum Distances to Building Openings from
Where Flue Products Exit the Boiler
8
