Empire Comfort Systems VFHS-20/10T-4 Ventilation Air From Inside Building, Ventilation AIR

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 fireplace logs			BTU/Hr
Other gas appliances*	+		BTU/Hr
Total	=		BTU/Hr
Example: Vented gas heater		20,000	BTU/Hr
Vent-free heater +	18,000	BTU/Hr
Total	=	38,000	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:

25,600 BTU/Hr (maximum the space can support)

38,000 BTU/Hr (actual amount of BTU/Hr used)

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, Section 5.3 or applicable local codes.

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 Inside Building.

B.Vent room directly to the outdoors. See VentilationAir From Outdoors.

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: You must provide additional ventilation air in a confined space.

VENTILATION AIR

Ventilation Air From Inside Building

This fresh air would come from an adjoining unconfined space. When ventilating to an adjoining unconfined space, you must provide two permanent openings: one within 12" of the ceiling and one within 12" of the floor on the wall connecting the two spaces (see options 1 and 2, Figure 1). You can also remove door into adjoining room (see option 3, Figure 1). Each ventilation grill or opening shall have a minimum free area of one square inch per 1,000 BTUH of the total input rating of the gas equipment in the confined space.

Figure 1

WARNING: Rework worksheet, adding the space of the adjoiningunconfinedspace.Thecombinedspacesmusthave enough fresh air to supply all appliances in both spaces.

Ventilation Air From Outdoors

Provide extra fresh air by using ventilation grills or ducts.You must provide two permanent openings: one within 12" of the ceiling and one with 12" of the floor. Connect these items directly to the outdoors or spaces open to the outdoors. These spaces include attics and crawl spaces. In most cases for direct communication with the outdoors or direct communication through a vertical duct a free area opening of one square inch per 4,000 BTUH of heater input rating for each grill. If a horizontal duct is used, a grill free area or duct opening shall have a free area opening of one square inch per 2,000 BTUH for each grill. Follow the National Fuel Code NFPA 54/ANSI Z223.1, Section 5.3 Air for Combustion and Ventilation for required size of ventilation grills or ducts.

IMPORTANT: Do not provide openings for inlet or outlet air into attic if attic has a thermostat-controlled power vent. Heated air entering the attic will activate the power vent.

Figure 2

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