Determining Fresh-Air Flow For Heater Location; Determining If You Have A Confined Or Unconfined Space - Procom FBD400T-C User Manual

DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION

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 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)
Example: 2560 cu. ft. (volume of space) ÷ 50 cu. ft. = 51.2 or 51,200 (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*+ _____________ BTU/hr
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 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 Outdoors,"
page 9.
b) Vent room directly to the outdoors. See "Ventilation Air from Outdoors", Page 9.
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.
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/NFPA 54, Air for Combustion and Ventilation, or applicable
local codes.
_____________ BTU/hr
_____________ BTU/hr
_____________ BTU/hr
_____________ BTU/hr
_____________ BTU/hr
= _____________ BTU/hr
Example:
Gas water heater
Vent-free heater + 26,000 BTU/hr
Total =
8
30,000 BTU/hr
56,000 BTU/hr