Installation Manual

Key to symbols and safety instructions
6 720 811 761 (2014/05)
4
Each appliance requires 9.950 cubic feet of available combustion air, or
a minimum of 1.243 square feet of space with an 8 foot ceiling to
operate. If this amount of air space is not available, provisions must be
taken to provide sufficient combustion air from the outside.
Always install the combustion air grill to prevent foreign objects from
falling into the unit.
If other appliances that draw in air or exhaust air share the same space,
their requirements must be taken into consideration when sizing the air
supply.
Always follow local codes and regulations if they are more stringent.
Appliances located in unconfined spaces
• a) An unconfined space is one whose volume is greater than 50 cubic
feet (1.42 cubic meter) per 1,000 BTU/Hr (292.81 Watts) of the
combined rating of all appliances installed in the space. That would
be 9.950 cubic feet (281.8 cubic meters) for the water heater alone.
• b) In unconfined spaces in buildings of conventional frame, masonry,
or metal construction, infiltration air is normally adequate to provide
air for combustion
Appliances located in confined spaces
The confined space must be provided with two permanent openings,
one commencing within 12 inches (304.8mm) of the top and one
commencing within 12 inches (304.8mm) of the bottom of the
enclosure. Each opening must have a minimum free area of one square
inch per:
• 1,000 BTU/Hr (292.81 Watts) if all air is taken from inside the
building
• 2,000 BTU/Hr (585.62 Watts) if all air is taken from the outside by
horizontal ducts
• 4,000 BTU/Hr (1171.24 Watts) if all air is taken from the outside by
direct openings or vertical ducts
Or the confined space must be provided with one permanent opening or
duct that is within 12 inches (304.8mm) of the ceiling of the enclosure.
This opening must have a minimum free area of one square inch per:
• 3,000 BTU/Hr (878.43 Watts) if all air is taken from the outside by a
direct opening or vertical duct
Louvers, grills and screens have a blocking effect, when used, increase
the sizes of your openings by 300% for wood louvers (as wood type will
reduce the free air by 75%) and 43% for metal louvers (as metal will
reduce the free air by 30%). Refer to the National Fuel Gas Code for
complete information. In buildings of tight construction all air should be
taken from outside.