Circulating AIR Requirements

WARNING:

Do not allow combustion products to enter the circulating air supply. Failure to prevent the circulation of combustion products into the living space can create potentially hazardous conditions including carbon monoxide poisoning that could result in personal injury or death.

All return ductwork must be secured to the furnace with sheet metal screws. For installations in conﬁned spaces, all return ductwork must be adequately sealed. The joint between the furnace and the return air plenum must be air tight.

The surface that the furnace is mounted on must provide sound physical support of the furnace with no gaps, cracks or sagging between the furnace and the ﬂoor or platform.

Return air and circulating air ductwork must not be connected to any other heat producing device such as a fireplace insert, stove, etc. This may result in ﬁre, explosion, carbon monoxide poisoning, personal injury, or property damage.

Return Air Connections

U.S.A. home manufacturers shall comply with all of the following conditions to have acceptable return air systems for closet installed forced air heating appliances:

•The return air opening into the closet shall not be less than speciﬁ ed in the appliance’s listing.

•The cross-sectional area of the return duct system leading into the closet, when located in the ﬂ oor or ceiling shall not be less than 235 square inches (or 390 square inches for 5 ton ready M1/M5 Furnaces).

CAUTION:

HAZARD OF ASPHYXIATION: Do not cover or restrict return air opening.

•Means shall be provided that prevent inadvertent closure of ﬂ at objects placed over the return air opening located in the ﬂ oor of the closet (versus the vertical front or side wall).

•The total free area of openings in the ﬂ oor or ceiling registers serving the return air duct system must be at least 235 sq. in. At least one register should be located where it is not likely to be covered by carpeting, boxes and other objects.

•Materials located in the return duct system must have a ﬂ ame spread classiﬁ cation of 200 or less. This includes a closet door if the furnace is in a closet.

•Noncombustible pans having 1” upturned

ﬂanges are located beneath openings in a

ﬂoor duct system.

•Wiring materials located in the return duct system shall conform to Articles 300-22 of the National Electrical Code (ANSI C1/NFPA-70).

•Gas piping is not run in or through the return duct system.

CAUTION:

HAZARD OF ASPHYXIATION: Negative pressure inside the closet, with closet door closed and the furnace blower operating on high speed, shall be no more negative than minus 0.05 inch water column.

•Test the negative pressure in the closet with the air-circulating fan operating at high speed and the closet closed.The negative pressure is to be no more negative than minus 0.05 inch water column.

•Air conditioning systems may require more duct register and open louver area to ob- tain necessary airflow. Use NORDYNE’s certiduct program to determine proper duct size for A/C.

Supply Air Connections

For proper air distribution, the supply duct system must be designed so that the static pressure measured external to the furnace does not exceed the listed static pressure rating shown on the furnace rating plate.