20 • Residen al Gas Tankless Water Heater Use and Care Guide
INSTALLATION
Combus on Air Supply Op ons
Gable vent
to outdoors
Install above
ŝŶƐƵůĂƟŽŶ
Outlet air to
ĂƫĐϭŝŶ
2
;ϲ͘ϱĐŵ
2
)
per 4,000 btu/h
/ŶůĞƚĂŝƌĨƌŽŵ
ƚŚĞĐƌĂǁůƐƉĂĐĞ
KƉĞŶĨŽƵŶĚĂƟŽŶǀĞŶƚ
ŽŶĮŶĞĚ
^ƉĂĐĞ
Alternate
Air Inlet
ϭŝŶ
2
;ϲ͘ϱĐŵ
2
)
per 4,000 btu/h
Figure 9 -
Direct to Outdoors Openings
Two permanent
Openings
1 in
2
(6.5 cm
2
)
per 4,000 btu/h
12” (305 mm)
maximum
12” (305 mm)
maximum
ŽŶĮŶĞĚ
Space
Figure 10 -
Direct to outdoors openings. Two
permanent openings.
Outlet air to
ĂƫĐϭŝŶ
2
;ϲ͘ϱĐŵ
2
)
per 4,000 btu/h
/ŶůĞƚĂŝƌĚƵĐƚ
ϭŝŶ
2
;ϲ͘ϱĐŵ
2
)
per 4,000 btu/h
ŽŶĮŶĞĚ
^ƉĂĐĞ
ϭϮ͟;ϯϬϱŵŵͿ
ŵĂdžŝŵƵŵ
'ĂďůĞǀĞŶƚ
ƚŽŽƵƚĚŽŽƌƐ
/ŶƐƚĂůůĂďŽǀĞ
ŝŶƐƵůĂƟŽŶ
Figure 11 -
Ver cal Duct Openings
1 in
2
(6.5 cm
2
)
per 2,000 btu/h
ŽŶĮŶĞĚ
Space
Outlet
Inlet
KƵƚĚŽŽƌ
Air Ducts
1 in
2
(6.5 cm
2
)
per 2,000 btu/h
Figure 12 -
Horizontal Duct Openings
ŽŶĮŶĞĚ
^ƉĂĐĞ
1 in
2
(6.5 cm
2
)
ƉĞƌϯ͕ϬϬϬ
btu/h
ůƚĞƌŶĂƟǀĞ
KƉĞŶŝŶŐ
>ŽĐĂƟŽŶ
Figure 13 -
Single Opening
Two permanent
Openings
1 in
2
per
1,000 btu/h
12” (305 mm)
maximum
12” (305 mm)
maximum
ŽŶĮŶĞĚ
Space
Figure 14 -
Two permanent openings
Table 6:
Minimum Free Area of Permanent Openings for Ven la on and Combus on Air Supply – Air from outdoor or indoor spaces.
Based on the total BTU/hr input ra ng for all gas burning appliances within a con
fi
ned space.
Opening Source
Minimum Free Area
Direct to outdoors*
1 in
2
(6.5 cm
2
) per 4,000 BTU/hr (See Figure 9 & Figure 10)
Ver cal ducts
1 in
2
(6.5 cm
2
) per 4,000 BTU/hr (see Figure 11)
Horizontal ducts
1 in
2
(6.5 cm
2
) per 2,000 BTU/hr (see Figure 12)
Single Opening
1 in
2
(6.5 cm
2
) per 3,000 BTU/hr (see Figure 13)
Two permanent openings
to another room**
1 in
2
(6.5 cm
2
) per 1,000 Btu/hr (see Figure 14)
Opening: 100 in
2
(645 cm
2
) Min
Minimum dimension of air openings: no less than 3 in (76 mm)
*These openings connect directly with the outdoors through a ven lated a c, a ven lated crawl space, or through an outside wall.
**United States: For direc on on combining spaces in di
ff
erent stories within the structure, refer to the current edi on of the Na onal Fuel Gas Code ANSI
Z223.1/NFPA 54. In Canada, refer to the current edi on of B149.1 Natural gas and propane installa on code.
