LG 395CAV User Manual

Page 4

CAUTION:

Air for combustion must not be contami-

nated by halogen compounds, which include fluoride,
chloride, bromide, and iodide. These elements are found
in aerosol sprays, detergents, 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 draft safeguard opening.

CAUTION:

The operation of exhaust fans, kitchen ven-

tilation 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 constructed unusually tight, 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. A minimum opening with a total of at least 1 sq in. per 5000
Btuh of total input rating for all equipment must be provided.
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 has volume less than 50 cu ft per 1000 Btuh of
the total input rating for all appliances installed in that space. A
confined space MUST have 2 permanent openings, 1 within 12 in.
of the ceiling and the other within 12 in. of the floor. (See Fig. 2.)

NOTE:

In determining the free area of an opening, the blocking

effect of the louvers, grilles, and screens must be considered. If the
free area of a louver or grille design is unknown, it may be
assumed 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 the air comes from
inside or outside of the structure.

1. All air from inside the structure:

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

per 1000 Btuh of the total input for all equipment within
the confined space, but not less than 100 sq in. per
opening. (See Fig. 2.)

b. If the building is constructed unusually tight, a perma-

nent opening directly communicating with the outdoors
should be provided. This opening shall have a minimum
free area of 1 sq in. per 5000 Btuh of total input rating
for all equipment in the enclosure.

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

a return-air plenum, and return air is taken directly from
the hallway or space adjacent to the furnace, all air for
combustion must come from outdoors.

2. All air from outside the structure:

a. If combustion air is taken from outdoors through vertical

ducts, the openings and ducts MUST have at least 1 sq
in. of free area per 4000 Btuh of the total input for all
equipment within the confined space. (See Fig. 3.)

b. If combustion air is taken from the outdoors through

horizontal ducts, the openings and ducts MUST have at
least 1 sq in. of free area per 2000 Btuh of the total input
for all equipment within the confined space.

For Example:

395CAV 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

Fig. 2—Air For Combustion and Ventilation (Inside Air)

A89012

SUPPLY

AIR

″

MIN

(FRONT)

†

RETURN AIR

VENT THROUGH ROOF

1 SQ IN.
PER 1000
BTUH* IN DOOR

OR WALL

″

MAX

1 SQ IN.
PER 1000
BTUH* IN DOOR

OR WALL

″

MAX

INTERIOR

HEATED

SPACE

* Minimum opening size is 100 square in. with
minimum dimensions of 3-In.

†

Minimum of 3-In. when type-B1 vent is used.

UNCONFINED
SPACE

CONFINED