EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE (Inlet Air from Crawl Space and Outlet Air to Ventilated Attic)
in the enclosure. See figures 4 and 5. When communicat- ing with the outdoors through horizontal ducts, each open-
ing shall have a minimum free area of 1 square inch (645
ROOF TERMINATED EXHAUST PIPE
SIDE WALL
TERMINATED EXHAUST PIPE (ALTERNATE LOCATION)
G61MP
VENTILATION LOUVERS
(Each end of attic)
| OUTLET |
| AIR |
| VENTILATION |
| LOUVERS |
INLET | (For unheated |
AIR | crawl space) |
mm2) per 2,000 Btu (.56 kW) per total input rating of all equipment in the enclosure. See figure 6.
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. If the design and free area of protec- tive covering is not known for calculating the size opening required, it may be assumed that wood louvers will have 20 to 25 percent 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
NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch per 4,000 Btu (645mm2 per 1.17kW) per hour of the total input rating of all equipment in the enclosure.
FIGURE 4
equipment operation.
EQUIPMENT IN CONFINED SPACE −
ALL AIR FROM OUTSIDE
EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
ROOF TERMINATED | VENTILATION LOUVERS | |
EXHAUST PIPE | ||
(Each end of attic) | ||
|
OUTLET
AIR
ROOF TERMINATED EXHAUST PIPE
SIDE WALL
TERMINATED EXHAUST PIPE (ALTERNATE LOCATION)
G61MP
OUTLET AIR 
INLET AIR
SIDE WALL | INLET AIR | |
(Ends 12" above | ||
TERMINATED | ||
bottom) | ||
EXHAUST PIPE | ||
| ||
(ALTERNATE | G61MP | |
LOCATION) | ||
|
NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch per 4,000 Btu (645mm2 per 1.17kW) per hour of the total input rating of all equipment in the enclosure.
FIGURE 5
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 mm) of the bottom. These openings must communi- cate directly or by ducts with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors or indi- rectly 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
NOTE−Each air duct opening shall have a free area of at least one square inch per 2,000 Btu (645mm2per .59kW) per hour of the total input rating of all equipment in the enclosure. If the equipment room is located against an outside wall and the air openings communi- cate directly with the outdoors, each opening shall have a free area of at least 1 square inch per 4,000 Btu (645mm2 per 1.17kW) per hour of the total input rating of all other equipment in the enclosure.
FIGURE 6
Installation − Setting Equipment
WARNING
Do not install the furnace on its front or its back. Do not connect the return air ducts to the back of the fur- nace. Doing so will adversely affect the operation of the safety control devices, which could result in per- sonal injury or death.
Select a location that allows for the required clearances that are listed on the unit nameplate. Also consider gas supply connections, electrical supply, vent connection, condensate trap and drain connections, and installation and service clearances [24 inches (610 mm) at unit front].
Page 8
