Carrier 58PAV Operations Instructions download pdf (Page 5)

Step 2—Air For Combustion and Ventilation

Provisions for adequate combustion and ventilation air must be

provided in accordance with Section 5.3 of the NFGC, Air for

Combustion and Ventilation, or applicable provisions of the local

building codes.

Canadian installations must be installed in accordance with NSC-

NGPIC and all authorities having jurisdiction.

Air for combustion must not be contaminated by halogen

compounds, which include fluoride, chloride, bromide, and

iodide. These elements are found in aerosol sprays, deter-

gents, bleaches, cleaning solvents, salts, air fresheners, and

other household products.

All fuel-burning equipment must be supplied with air for combus-

tion of the fuel. Sufficient air MUST be provided to ensure there

will not be a negative pressure in the equipment room or space. In

addition, a positive seal MUST be made between the furnace

cabinet and the return-air duct to prevent pulling air from the

burner area and blocked vent safeguard opening.

The operation of exhaust fans, kitchen ventilation fans,

clothes dryers, or fireplaces could create a NEGATIVE

PRESSURE CONDITION at the furnace. Make-up air MUST

BE PROVIDED for the ventilation devices, in addition to that

required by the furnace.

The requirements for combustion and ventilation air depend upon

whether the furnace is located in an unconfined or confined space.

UNCONFINED SPACE — An unconfined space must have at

least 50 cubic ft for each 1000 Btuh of input for all the appliances

(such as furnaces, clothes dryer, water heaters, etc.) in the space.

If the unconfined space is of unusually tight construction, air for

combustion and ventilation MUST come from either the outdoors

or spaces freely communicating with the outdoors. Combustion

and ventilation openings must be sized the same as for a confined

space as defined below. Return air must not be taken from the

room unless an equal or greater amount of air is supplied to the

room.

CONFINED SPACE — A confined space is defined as a space

whose volume is less than 50 cu ft per 1000 Btuh of total input

ratings of all appliances installed in that space. A confined space

MUST have provisions for supplying air for combustion, ventila-

tion, and dilution of flue gases using 1 of the following methods.

(See Fig. 3, 4, and Table 2.)

NOTE: In determining free area of an opening, the blocking

effect of louvers, grilles, and screens must be considered. If free

area of louver or grille design is unknown, assume that wood

louvers have a 20 percent free area and metal louvers or grilles

have a 60 percent free area. Screens, when used, must not be

smaller than 1/4-in. mesh. Louvers and grilles must be constructed

so they cannot be closed.

The size of the openings depends upon whether air comes from

outside of the structure or an unconfined space inside the structure.

1. All air from inside the structure requires 2 openings (for

structures not usually tight):

a. Each opening MUST have at least 1 sq in. of free area per

1000 Btuh of total input for all equipment within the

confined space, but not less than 100 sq in. per opening.

(See Fig. 3 and Table 2.) The minimum dimension of air

openings shall not be less than 3 in.

b. If building is constructed unusually tight, a permanent

opening directly communicating with the outdoors shall be

provided. See item 2 below.

c. If furnace is installed on a raised platform to provide a

return-air plenum, and return air is taken directly from

hallway or space adjacent to furnace, all air for combustion

must come from outdoors.

2. Air from outside the structure requires 1 of the following

methods:

a. If combustion air is taken from outdoors through 2 vertical

ducts, the openings and ducts MUST have at least 1 sq in.

of free area per 4000 Btuh of total input for all equipment

within the confined space. (See Fig. 4 and Table 2.)

b. If combustion air is taken from outdoors through 2 hori-

zontal ducts, the openings and ducts MUST have at least 1

sq in. of free area per 2000 Btuh of total input for all

equipment within the confined space. (See Fig. 4 and Table

2.)

c. If combustion air is taken from outdoors through a single

opening or duct (horizontal or vertical) commencing within

12 in. of the top of the confined space, opening and duct

MUST have at least 1 sq in. of free area per 3000 Btuh of

the total input for all equipment within the confined space

and not less than the sum of the areas of all vent connectors

in the confined space. (See Fig. 4 and Table 2.) Equipment

clearances to the structure shall be at least 1 in. from the

sides and back and 6 in. from the front of the appliances.

When ducts are used, they must be of the same cross-sectional area

as the free area of the openings to which they connect. The

minimum dimension of ducts must not be less than 3 in. (See Fig.

4.)

AIR DUCTS

Step 1—General Requirements

The duct system should be designed and sized according to

accepted national standards such as those published by: Air

Conditioning Contractors Association (ACCA), Sheet Metal and

Air Conditioning Contractors National Association (SMACNA) or

American Society of Heating, Refrigerating and Air Conditioning

Engineers (ASHRAE). Or consult factory The Air Systems Design

Guidelines reference tables available from your local distributor.

The duct system should be sized to handle the required system

design airflow CFM at the design external static pressure.

When a furnace is installed so that the supply ducts carry air to

areas outside the space containing the furnace, the return air must

also be handled by a duct(s) sealed to the furnace casing and

terminating outside the space containing the furnace.

Secure ductwork with proper fasteners for type of ductwork used.

Seal supply- and return-duct connections to furnace with code

approved tape or duct sealer.

Example of unconfined spaces:

58PAV FURNACE

INPUT BTUH

MINIMUM SQ FT WITH

7-1/2 FT CEILING

44,000 293

66,000 440

88,000 587

110,000 733

132,000 880

154,000 1026

1 2 3 4 5 6 7 8 9 10 ... 19 20

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Carrier 58PAV Operations Instructions Page 5

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