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900573-00N/C
6
OPTIONAL OUTSIDE AIR KIT (MODEL AK4/AK4F)
The installation of an outside air kit should be performed during the
rough framing of the fireplace due to the nature of it's location. Outside
combustion air is accessed through a vented crawl space (AK4F) or
through a sidewall (AK4). See Figure 22 on page 13 for instruction of
operating air kit.
CAUTION: Combustion air inlet ducts shall not
terminate in attic space.
The maximum height for the air vent can not exceed
3 feet below the flue gas outlet of the termination.
HEARTH EXTENSION
A hearth extension projecting a minimum of 20" in front of and a
minimum of 12" beyond each side of fireplace opening is required
to protect combustible floor construction in front of fireplace. Fabri
-
cate a hearth extension using a material which meets the following
specifications: a layer of noncombustible, inorganic material having
a thermal conductivity of
k
= .84 BTU IN/FT
2
HR °F (or less) at 1"
thick. For example, if material selected has a k factor of 0.25, such
as glass fiber, the following formula would apply:
0.25 x 1.0" = 0.30" thickness required
0.84
Thermal conductivity
"k"
of materials can be obtained from manu-
facturer or supplier of noncombustible material. If hearth extension
is to be covered, use noncombustible material such as tile, slate,
brick, concrete, metal, glass, marble, stone, etc. Provide a means to
prevent hearth extension from shifting and seal gap between fireplace
frame and hearth extension with a non-combustible material such as
sand-cement grout (see Figure 3).
WARNING: Hearth extension is to be installed only
as shown in Figure 3.
Figure 3 - Hearth Extension
Seal Gap
Fireplace Front
Ember Protector
Fireplace Front
Raised Hearth
Fireplace Front
Elevated
Ember Protector
Ember Protector
Seal Gap
Hearth
Extension
MANTELS
A mantel may be installed if desired (see Figure 4). Woodwork such
as wood trims, mantels or any other combustible material projecting
from the front face must not be placed within 12" of the fireplace
opening. Combustible materials above 12" and projecting more than
1
1
/
2
" from the fireplace must not be placed less than 15" from the
top opening of the fireplace (NFPA 211, Section - Clearance from
Combustible Material).
Mantels or any other combustible material also may come up to the
side edge of the black metal face of the fireplace just as long as the
projection from the front face fall within the limit shown in Figure 4.
12
1
/
4
" Ref.
6"
Ref.
12" Min.
9" Min.
1
1
/
2
" Max.
3" Nom.
33°
Combustible
Material
Safe
Zone for
Projection of
Combustible
Materials
Fireplace Opening
Upper
Section of
Fireplace
Figure 4 - Mantel Clearances to Combustible Material
FIREBOX
SAFE ZONE
Top View of Fireplace
2" Max.
3.0"
Min. to
Perpendicular
Side Wall
12"
8.0"
33°
Combustible
Material Must
Not Overlap
Front Face
FIREPLACE INSTALLATION
Continued