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8 8
Finishing
A. Hearth Extension
A hearth extension must be installed with all replaces to
protect the combustible oor in front of the replace from
both radiant heat and sparks. See Figures 8.1 -8.5.
High temperature
(300°F min.) continuous,
non-combustible sealant
HX4 Hearth Ext
Tile, stone or other
or equivilent
non-combustible material
insulation
(see Table below)
Floor constructed of wood or
other combustible material
Figure 8.1
Hearth Extension Construction
WARNING
Fire Risk
•
Metal hearth strips MUST be installed.
Sparks or embers may ignite ooring.
This replace has been tested and approved for use with a
hearth extension insulated to a minimum R value of 1.16.
To substitute materials for the factory-available hearth ex-
tensions, see Figure 8.3 and calculate insulation alterna-
tives as per Table 8.1 and the following formulas:
•
Thermal conductivity per inch thickness = k
•
k = (BTU)(inch) / (foot
•
Required thickness = Rk
•
Thermal resistance per inch thickness = r
2
•
r = (foot
)(hour)(°F) / (BTU)(inch)
•
Required thickness = R / rB.
Table 8.1
Hearth Extension Insulation Alternatives, R Value = 1.16
Material
Hearth & Home HX3, HX4
USG Micore 300™
USG Durock™ Cement Board
Cement Mortar
Common Brick
Ceramic Tile
Armstrong™ Privacy Guard Plus
Marble
24
Protective
Metal Hearth
Strip
2 in.
[51 mm]
required
2
)(hour)(°F)
Minimum thickness
k per
r per
required
inch
inch
thick
thick
in.
0.43
2.33
1/2
0.46
2.18
1/2
1.92
0.52
2-1/4
5.0
0.20
5-7/8
5.0
0.20
5-7/8
12.50
0.08
14-5/8
.046
2.18
1/2
14.3 to
0.07 to
16-5/8 to
20.0
0.05
23-3/8
Heatilator • CI60 • 4013-031 Rev M • 10/06
Metal strips are placed 2 in. (51 mm) under the front
of the fireplace and must extend beyond the front
and sides of fireplace opening by 2 in. (51 mm).
Figure 8.2
Positioning the Protective Metal Hearth Strips
66 in.
(1676 mm)
mm
13
13
57
149
149
Figure 8.3
Hearth Extension Dimensions
371
13
422 to
594
1 in. (25 mm) overlap
WARNING
Fire Risk
•
Hearth extensions must be installed
exactly as speci ed.
High temperatures or hot embers may ignite
concealed combustibles.
12 in.
(305 mm)
See next page for ush installation.
20 in.
(508 mm)
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