USSC VFZC32L Owner's Operation And Installation Manual page 8

AIR FOR COMBUSTION AND VENTILATION
Determining if You Have a Confined or Unconfined Space
Use this worksheet to determine if you have a confined or unconfined space.
Space: Includes the room in which you will install the firebox plus any adjoining rooms with
doorless passageways or ventilation grills between the rooms.
1. Determine the volume of the space (length x width x height).
Length x Width x Height = _______________ cu. Ft. (volume of space)
Example: Space size
If additional ventilation to adjoining room is supplied with grills or openings, add the
volume of these rooms to the total volume of the space.
2. Divide the space volume by 50 cubic feet to determine the maximum BTU/Hr the space
can support.
_________ (volume of space)
Example: 3168 cu. Ft. (volume of space)
BTU/Hr the space can support)
3. Add the BTU/Hr of all fuel-burning appliances in the space.
Vent-free Firebox
Gas water heater*
Gas furnace
Vented gas heater
Gas firebox logs
Other gas appliances*
Total
Example: Gas water Heater
Vent-free firebox with log heater
Total
* Do not include direct-vent gas appliances. Direct-vent draws combustion air from
the outdoors and vents to the outdoors.
4. Compare the maximum BTU/Hr the space can support with the actual amount of
BTU/ Hr used.
______________
______________
Example: 63,300 BTU/Hr (maximum the space can support)
79,000 BTU/Hr (actual amount of BTU/Hr used)
The space in the above example is a confined space because the actual BTU/Hr used is
more than the maximum BTU/Hr the space can support. You must provide additional fresh
air.
Your options are as follows:
A. Rework worksheet, adding the space of an adjoining room. If the extra space provides
an unconfined space, remove door to adjoining room or add ventilation grills between
rooms. See Ventilation Air From Inside Building, page 9.
8
22 ft. (length) x 18 ft. (width) x 8 ft. (ceiling height) =
3168 cu. Ft. (volume of space)
50 cu. Ft. = (Maximum BTU/Hr the space can support)
BTU/Hr (maximum the space can support)
BTU/Hr (actual amount of BTU/Hr used)
CONTINUED
50 cu. Ft. = 63.3 or 63,300 (maximum
__________________ BTU/Hr
__________________ BTU/Hr
__________________ BTU/Hr
__________________ BTU/Hr
__________________ BTU/Hr
+ __________________ BTU/Hr
= __________________ BTU/Hr
40,000
+ 39,000
= 79,000
BTU/Hr
BTU/Hr
BTU/Hr