PRE-INSTALLATION REQUIREMENTS
Combustion and Ventilation Air Requirement Worksheet (Vent Free only)
WARNING:
IF THE AREA IN WHICH THE HEATER MAY BE OPERATED IS SMALLER THAN THAT DEFINED
AS AN UNCONFINED SPACE OR IF THE BUILDING IS OF UNUSUALLY TIGHT CONSTRUCTION, PROVIDE
ADEQUATE COMBUSTION AND VENTILATION AIR BY ONE OF THE METHODS DESCRIBED IN THE NATIONAL
FUEL GAS CODE, ANSI Z223.1, SECTION 5.3. OR APPLICABLE LOCAL CODES.
This heater shall not be installed in a confined space or unusually tight construction unless
provisions are provided for adequate combustion and ventilation air.
The following formula can be used to determine the maximum BTU rating per the definition of unconfined space:
STEP ONE:
DETERMINE THE VOLUME OF SPACE IN CUBIC FEET.
LENGTH X WIDTH X HEIGHT = __________ cu. ft.
(Include adjoining rooms with doorless passageways or ventilation grills between rooms.)
Example:
24' (L) X 16' (W) X 8' (H) = 3,072 cu. ft.
STEP TWO:
MULTIPLY THE VOLUME OF SPACE BY 20 BTU/Hr. TO DETERMINE THE
MAXIMUM BTU/Hr. THE SPACE CAN SUPPORT.
Example:
3,072 cu. ft. X 20 BTU/Hr. = 61,440 BTU/Hr.
(Maximum BTU/Hr. the room can support)
STEP THREE:
ADD THE BTU/Hr. OF ALL THE FUEL BURNING APPLIANCES IN THE
SPACE.
VENT-FREE HEATER __________ BTU/Hr.
GAS APPLIANCE #1 __________ BTU/Hr.
GAS APPLIANCE #2 __________ BTU/Hr.
Total __________ BTU/Hr.
Example
: VENT-FREE HEATER 26,000 BTU/Hr.
GAS APPLIANCE #1 35,000 BTU/Hr.
Total 61,000 BTU/Hr.
NOTE: DO NOT INCLUDE DIRECT-VENT GAS APPLIANCES.
DIRECT-VENT IS SEALED COMBUSTION AND
DRAWS COMBUSTION AIR FROM THE OUTDOORS.
THE SPACE IN THE ABOVE EXAMPLE IS AN UNCONFINED SPACE BECAUSE THE 61,000 BTU'S AN
HOUR USAGE IS LESS THAN THE 61,440 BTU'S AN HOUR AVAILABLE. IF THE TOTAL BTU'S AN
HOUR USAGE IS GREATER THAN 61,440 BTU'S AN HOUR THEN THE SPACE WOULD BE A
CONFINED SPACE AND ADDITIONAL FRESH AIR MUST BE PROVIDED.
The National Fuel Gas Code defines a confined space as a space whose volume is less than 50 cubic feet per 1,000 Btu per hour
(4.8 m
3
per kw) of the aggregate input rating of all appliances installed in that space and unconfined space a s a space whose
volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8 m
3
per kw) of the aggregate input rating of all appliances installed
in that space. Rooms communicating directly with the space in which the appliances are installed, through openings not furnished
with doors, are considered a part of the unconfined space.
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