Справочник Пользователя для Empire Comfort Systems VFCM-25-3. VFCR-25-3

Page 6

16937-4-0806

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 (4.8m

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 (4.8m

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.