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COMBUSTIBLE CONSTRUCTION CLEARANCES
The water heater should be positioned to provide the minimum clearances from combustible surfaces and to
provide sufficient space for servicing the unit as follows.
MINIMUM CLEARANCES: PROTECTED SURFACES
Clearances to surfaces installed
in rooms which are large (2) in
comparison with size of heater.
Rear 12" 9 6 4 6 4 4 4 4
Left Side 12" 9 6 4 6 4 4 4 4
136 Right Side 6" 5 3 3 6 2 3 3 3
Indoor Top 42" 42 42 42 42 42 42 42 42
Rear 12" 9 6 4 6 4 4 4 4
Left Side 12" 9 6 4 6 4 4 4 4
181-399 Right Side 12" 9 6 4 6 4 4 4 4
Indoor Top 39" 39 39 39 39 39 39 39 39
Outdoor Top(1)
Rear 12 9 6 4 6 4 4 4 4
Left Side 18 12 9 6 6 6 6 6 6
512-825 Right Side 6 5 3 3 6 2 3 3 3
Indoor Top 36 36 36 36 36 36 36 36 36
Outdoor Top (1)
Rear 24 16 12 8 8 8 8 8 8
Left Side 24 16 12 8 8 8 8 8 8
926-1826 Right Side 24 16 12 8 8 8 8 8 8
Indoor Top 24 24 24 24 24 24 24 24 24
Outdoor Top (1)
(1) Unobstructed.
(2) Large rooms are defined as having a volume at least 16 times the total volume of the heater.
(3) Installation clearances for heaters in rooms not large in comparison with the heater size shall be as listed
under combustible surfaces and shall not be reduced by the protection methods.
SERVICING CLEARANCES: 24" in front of heater for removal of burner tray.
18" on side opposite water connection for deliming of Heat Exchanger on
Models 181-1826 only.
Combustible Surfaces
(a) 3 1/2-in. thick masonry wall with-
out ventilated air space
(b) 1/2-in. insulation board over 1-in.
glass fiber or mineral wool batts
(c) 0.024 sheet metal over 1-in. glass fiber
or mineral wool batts reinforced with wire
on rear face with ventilated air space
(d) 3 1/2-in. thick masonry wall with venti-
lated air space
(e) 0.024 sheet metal with ventilated air
space
(f) 1/2-in. thick insulation board with
ventilated air space
(g) 0.024 sheet metal with ventilated
air space over 0.024 metal with
ventilated air space
(h) 1-in. glass fiber or mineral wool
batts sandwiched between two sheets
0.024 sheet metal with ventilated air
space
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