Operating Guide

8
DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION
Use this worksheet to determine if you have a confined or unconfined space. Space: Includes the room in
which you will install heater plus any adjoining rooms with door less passageways or ventilation grills
between the rooms.
1. Determine the volume of the space Length × Width × Height = cu. ft. (volume of space)
Example: Space size 20 ft. (length) × 16 ft. (width)×8 ft. (ceiling height) =2560 cu. ft. (volume of space) 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) ÷ 50 cu. ft. = (Maximum BTU/hr the space can support)
3. Add the BTU/hr of all fuel burning appliances in the space.
Vent-free heater BTU/hr
Gas water heater* BTU/hr
Gas furnace BTU/hr
Vented gas heater BTU/hr
Gas heater logs BTU/hr
Other gas appliances* + BTU/hr
Total = BTU/hr
Example:
Gas water heater 30,000 BTU/hr
Vent-free heater + 26,000 BTU/hr
Total = 56,000 BTU/hr
*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
BTU/hr (maximum the space can support)
BTU/hr (actual amount of BTU/hr used)
Example: 51,200 BTU/hr (maximum the space can support) 56,000 BTU/hr (actual amount of BTU/hr
used)
The space in the prior 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:
Rework worksheet, adding the space of an adjoining room. If the extra space provides an unconfined
space:
a) Remove door to adjoining room or add ventilation grills between rooms. See “Ventilation Air From
Inside Building” on next page.
b) Vent room directly to the outdoors. See the following “Ventilation Air from Outdoors” for details.
c) Install a lower BTU/hr heater if lower BTU/hr size makes room unconfined. If the actual BTU/hr
used is less than the maximum BTU/hr the space can support, the space is an unconfined space.
You will need no additional fresh air ventilation.