Installation Guide

6
DETERMINING FRESH-AIR FLOW
FOR APPLIANCE LOCATION
Determining if You Have a Confined
or Unconfined Space
Use this work sheet to determine if you have a confined
or unconfined space.
Space: Includes the room in which you will install appli-
ance 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 22 ft. (length) x 18 ft. (width) x
8 ft. (ceiling height) = 3168 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. Multiply the space volume by 20 to determine the maxi-
mum Btu/Hr the space can support.
_______ (volume of space) x 20 = (Maximum Btu/Hr
the space can support)
Example: 3168 cu. ft. (volume of space) x 20 = 63,360
(maximum Btu/Hr the space can support)
3. Add the Btu/Hr of all fuel burning appliances in the
space.
Vent-free log set _______________ Btu/Hr
Gas water heater* ______________ Btu/Hr
Gas furnace ___________________ Btu/Hr
Vented gas heater ______________ Btu/Hr
Gas fireplace logs ______________ Btu/Hr
Other gas appliances* + ________ Btu/Hr
Total = ________ Btu/Hr
* Do not include
direct-vent gas appliances. Direct-vent
draws combustion air from the outdoors and vents to
the outdoors.
Example:
Vent-free log set ______________ Btu/Hr
Gas water heater* _____________ Btu/Hr
Total = ________ Btu/Hr
4.
Compare the maximum Btu/Hr the space can support with
the actual amount of Btu/Hr used.
____ Btu/Hr (max. the space can support)
____ Btu/Hr (actual amt. of Btu/Hr used)
Example: 63,300 Btu/Hr (maximum the space can sup-
port)
73,000 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 work sheet, 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 5.
B. Vent room directly to the outdoors. See Ventilation Air
from Outdoors, page 5.
C. Install a lower Btu/Hr appliance, 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.
39,000
40,000
79,000
AIR FOR COMBUSTION
AND VENTILATION
WARNING: If the area in which the
heater may be operated does not meet the
required volume for indoor combustion
air, combustion and ventilation air shall be
provided by one of the methods described
in the National Fuel Gas Code, ANSI Z223.1/
NFPA 54, the International Fuel Gas Code,
or applicable local codes.
CONTINUED