Lennox International Inc G50UH-24A-070, G50UH-48C-110 WiTER/ Room, FIGURE Air from Inside

CHIMNEY

VENT

EQUIPMENT IN CONFINED SPACE ALL AIR FROM INSIDE

Air from Outside

If air from outside is brought in for combustion and ventila- tion, the confined space must have two permanent open- ings. One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305

	HEATER
FURNACE	1_

OPENINGS (To Adjacent

WiTER/ Room)

I II I

NOTE - Each opening shall have a free area of at least one square inch (645 mm 2) per 1,000 Btu (.29 kW) per hour of the total input rat- ing of all equipment in the enclosure, but not less than 100 square inches (64516 mm2).

FIGURE 2

Air from Inside

If the confined space that houses the furnace adjoins a space categorized as unconfined, air can be brought in by providing two permanent openings between the two spaces. Each opening must have a minimum free area of 1 square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of total input rating of all gas-fired equipment in the confined space. Each opening must be at least 100 square inches (64516 mm2). One opening shall be within 12 inches (305

mm)of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. See figure 2.

mm)of the bottom. These openings must communicate di- rectly or by ducts with the outdoors or spaces (crawl or at- tic) that freely communicate with the outdoors or indirectly through vertical ducts. Each opening shall have a minimum free area of 1 square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of total input rating of all equipment in the en- closure. See figures 3 and 4. When communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch (645 mm 2) per 2,000 Btu (.56 kW) per total input rating of all equipment in the enclosure. See figure 5.

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 dimension of rectangular air ducts shall be no less than 3 inches (75 mm). In calculating free area, the blocking effect of louvers, grilles, or screens must be considered. Ifthe design and free area of protective cov- ering is not known for calculating the size opening required, it may be assumed that wood louvers will have 20 to 25 per- cent free area and metal louvers and grilles will have 60 to 75 percent free area. Louvers and grilles must be fixed in the open position or interlocked with the equipment so that they are opened automatically during equipment operation.

CHIMNEY OR

GAS VENT

VENTILATION LOUVERS

EQUIPMENT IN CONFINED SPACE

ALL AIR FROM OUTSIDE

(Inlet Air from Crawlspace and Outlet Air

to Ventilated Attic)

(Each end of attic)

I ...... I

OUTLET

FURNACEAIRWATER

HEATER

VENTILATION	INLET
LOUVERS	AIR
(For unheated crawl	!

NO TE- The inlet and outlet air openings shall each have a free area of at least one square inch (645

mm2) per 4, 000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.

FIGURE 3

Page 7