Empire Comfort Systems VFCT25-3 Water Vapor A By-Productof Unvented Room Heaters

WATER VAPOR: A BY-PRODUCT OF UNVENTED ROOM HEATERS

Water vapor is a by-product of gas combustion.An unvented room heater produces approximately one (1) ounce (30ml) of water for every 1,000 BTU's (.3KW's) of gas input per hour.

Unvented room heaters must be used as supplemental heat (a room) rather than a primary heat source (an entire house). In most supplemental heat applications, the water vapor does not create a problem. In most applications, the water vapor enhances the low humidity atmosphere experienced during cold weather.

The following steps will help insure that water vapor does not become a problem.

1.Be sure the heater is sized properly for the application, including ample combustion air and circulation air.

2.If high humidity is experienced, a dehumidifier may be used to help lower the water vapor content of the air.

3.Do not use an unvented room heater as the primary heat source (an entire house).

PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR

This heater shall not be installed in a confined space or unusually tight construction unless provisions are provided for adequate combustion and ventilation air.

The National Fuel Gas Code, ANSI Z223.1 defines a confined space as a space whose volume is less than 50 cubic feet per 1,000 Btu per hour (4.8m3 per kw) of the aggregate input rating of all appliances installed in that space and an unconfined space as a space whose volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8m3 per kw) of the aggregate input rating of all appliances installed in that space. Rooms communicating directly with the space in which the appliances are installed, through openings not furnished with doors, are considered a part of the unconfined space.

The following example is for determining the volume of a typical area in which the VFCM-25 may be located and for determining if this area fits the definition of an unconfined space.

The maximum input of the VFCM-25 is 25,000 Btu per hour. Based on the 50 cubic feet per 1,000 Btu per hour formula, the minimum area that is an unconfined space for installation of the VFCM-25 is 1,250 cubic feet, 50 cubic feet x 25 = 1,250 cubic feet. To determine the cubic feet of the area in which the VFCM-25 is to be installed, measure the length, width and height of the area. Example: The area measures 16 feet in length, 10 feet in width and 8 feet in height, the area is 1,280 cubic feet. The VFCM-25 can be installed in this unconfined space with no requirement to provide additional combustion and ventilation air.

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.

Unusually Tight Construction

The air that leaks around doors and windows may provide enough fresh air for combustion and ventilation. However, in buildings of unusually tight construction, you must provide additional fresh air.

Unusually tight construction is defined as construction where:

a.Walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating of one perm or less with openings gasketed or sealed, and

b.Weatherstripping has been added on openable windows and doors, and

c.Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and at other openings.

If the heater is installed in a building of unusually tight construction, adequate air for combustion, ventilation and dilution of flue gases shall be provided in accordance with ANSI Z223.1/NFPA54.

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