Procom WZN18TLA Owner's Operation And Installation Manual page 5

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 Fireplace logs
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.
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)
71,500 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 6.
B. Vent room directly to the outdoors. See Ventilation Air From Outdoors, page 6.
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 de-
fined 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, ANS Z223.1, Section 5.3 or applicable local codes.
Ventilation Air From Inside Building
This fresh air would come from adjoining unconfined space. When ventilating to an adjoining unconfined space, you
must provide two permanent openings:
one within 12" of the wall connecting the two spaces (see options 1 and 2, Figure 2). You can also remove door into
adjoining room (see option 3, Figure 2). Follow the National Fuel Gas Code NFPA 54/ANS Z223.1. Section 5.3, Air for
Combustion and Ventilation for required size of ventilation grills or ducts.
__________________ Btu/Hr
__________________Btu/Hr
__________________Btu/Hr
__________________Btu/Hr
__________________Btu/Hr
Example:
Gas water heater
Vent-free heater +
Total
5
40,000 Btu/Hr
31,500 Btu/Hr
= 71,500 Btu/Hr