Sears 153.336801, 153.336701, 153.336432, 153.336431 Allair from Inside Buildings, 1Figure 3

Combustion Air and Ventilation

for Appliances Located in

Unconfined Spaces

-UnconfinedSpaceis a spacewhose volume is not lessthan 50 cubic feet per 1,000 Btu per hour of the aggregateinput rating of all appliances installed in that space. Roomscommunicating directly with the space in which the appliances are installed, through openings not furnished with doors, are considered a part of the unconfined space

in unconfined spacesin buildings, infiltration may be adequate to provide air for combustion, ventilation and dilution of flue

gases.However, in buildings of tight construction (for example, weather stripping, heavily insulated, caulked, vapor barrier, etc.), additional air may need to be provided usingthe methods described in Combustion Air and Ventilation for Appliances Locatedin Confined Spaces.

Combustion Air and Ventilation

'for Applia_ncesLocated in

Confined Spaces

Confined Spaceis a spacewhose volume is lessthan 50 cubic feet per 1,000 Btu per hour of the aggregateinput rating of all appliances installed in that space.

a.ALLAIR FROM INSIDE BUILDINGS:

(SeePage8 Figure 1, and Figure.2 below)

The confined spaceshall be provided with two permanent openings communicating directly with an additional room(s) of sufficient volume so that the combined volume of all spaces meetsthe criteria for an unconfined space. The total input of all gas utilization equipment installed in the combined space shall be considered in making this determination. Eachopening shall have a minimum free area of one square inch per 1,000 Btu per hour of the total input rating of all gas utilization equipment in the confined space, but not less than 100 square inches. One opening shall commencewithin t2 inchesof the top and one commencing within 12 inchesof the bottom of the enclosure.

FUR._.F. I WAT_II (LOUVERS,_._F.F_S. Er¢._

b. ALLAIR FROM OUTDOORS: (see Figures 3-5)

The confined space shall be provided with two perma- nent openings, one commencing within 12 inches of the top and one commencing within 12 inches from the bot- tom of the enclosure. The openings shall communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.

If

1Figure 3 I

1.When directly communicating with the Outdoors, each opening shall have a minimum free area of I square inch per 4,000 Btu per hour of total input rating of all equipment in the enclosure. (See Figure 3.)

2.When communicating with the outdoors through vertical ducts, each opening shall have a minimum free area of 1 square inch per 4,000 Btu per hour of total input rating of all equipment in the enclosure. (See Figure 4.)

Q'_" CHIMNEY OR GAS VENT

iJ_,_ VE_T,U_IONLOU'._RS

each end ol atilt)

U'rLET

!l = Yi 4t4fl WATERH_a_

II ]1=,_ _cE

11-4 I ILlllA_RIN_T

Jti IEND_ 1" ABOVE FLOOR)

Figure 4 1

3.When communicating with the outdoors through horizontal ducts, each opening shah have a minimum free area of 1 square inch per 2,000 Btu per hour of total input rating of all equipment in the enclosure. (SeeFigure 5.)

I_EY OR GAS VENT

INLET

4.When ducts are used, they shall be of the same cross-sec- tional area as the free area of the openings to which they connect. The minimum short side dimension of rectangular air ducts shall not be less than 3 inches. (See Figure 5.)

5.Louvers and Grilles: In calculating free area, consideration shall be given to the blocking effect of Iou_,ers, grilles or screens protecting openings. Screens used shall not be smaller than ¼ inch mesh. ff the free area through a design of louver or grille is known, it should be used in calculat- ing the size opening required to provide the free area spec- ified. If the design and free area is not known, it may be assumed that wood louvers will be 20-25percent free area and metal louvers and grilles will have 60-75 percent free area. Louvers and grilles shah be fixed in the open position or interlocked with the equipment so that they are opened automatically during equipment operation.

6.Special Conditions Created by Mechanical Exhausting or Fireplaces: Operation of exhaust fans, ventilation systems, clothes dryers or fireplaces may create conditions requiring special attention to avoid unsatisfactory operation of installed gas utilization equipment.