Product specifications
66
DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION
Determining if You Have a Conned or Unconned Space
Use this worksheet to determine if you have a conned or unconned space.
Space: Includes the room in which you will install heater plus any adjoining rooms with doorless 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 20ft. (length)×16ft. (width)×8ft. (ceiling height) =2560cu. 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
Gas water heater*
Gas furnace
Vented gas heater
Gas heater logs
Other gas appliances* +
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.
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 above example is a conned 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 unconned
space, remove door to adjoining room or add ventilation grills between rooms. See “Ventilation Air From
Inside Building”.
Vent room directly to the outdoors. See “Ventilation Air From Outdoors”.
Install a lower Btu/Hr heater if lower Btu/Hr size makes room unconned.
WARNING: If the area in which the heater may be operated is smaller than that dened as an unconned 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/NFPA 54, Air for Combustion and Ventilation, or
applicable local codes.
a)
b)
c)
Example:
Gas water heater 30,000 Btu/Hr
Vent-free heater + 26,000 Btu/Hr
Total = 56,000 Btu/Hr
Btu/Hr
Btu/Hr
Btu/Hr
Btu/Hr
Btu/Hr
Btu/Hr
Btu/Hr
Ventilation Air From lnside Building
This fresh air would come from an adjoining unconned space. When
ventilating to an adjoining unconned space, you must provide two perma-
nent openings: one within 12 inches of the ceiling and one within 12 inches
of the oor on the wall connecting the two spaces (see options 1 and 2,
Figure 2). You can also remove the door into adjoining room (see option
3, Figure 2). Follow the National Fuel Gas Code. NFPA 54/ANSI Z223.1,
Section 5.3, Air for Combustion and Ventilation
for required size of ventila-
tion grills or ducts.
Figure 1 - Ventilation Air from Outdoors