Finishing; Hearth Extension - Heatilator A36C Owner's Manual

8 8

Finishing

A. Hearth Extension
A hearth extension must be installed with all fi replaces to
protect the combustible fl oor in front of the fi replace from
both radiant heat and sparks. See Figures 8.1 -8.3.
High temperature
(300°F min.) continuous,
non-combustible sealant
HX3 or 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 fl ooring.
This fi 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
• r = (foot 2 )(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 Mortor
Common Brick
Ceramic Tile
Armstrong Privacy Plus
Marble
26
Protective
Metal Hearth
Strip
2 in. (51 mm)
required
2 )(hour)(°F)
k per inch r per inch
thick thick
0.43 2.33
0.46 2.18
1.92 0.52
5.0 0.20
5.0 0.20
12.50 0.08
14.3-20.0 0.07-0.05
Heatilator • A36C & A42C • 28396 Rev Y • 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
Minimum thickness
required
Model #
1/2 in.
1/2 in.
2-1/4 in.
5-7/8 in.
5-7/8 in.
14-5/8 in.
Figure 8.3
16-5/8 in. - 23-3/8 in.
1 in. (25 mm) overlap
WARNING
Fire Risk
• Hearth extensions must be installed
exactly as specifi ed.
High temperatures or hot embers may ignite
concealed combustibles.
A
C
Hearth Extension Dimensions
A
in. 52
A36
mm 1321
in. 66
A42
mm 1676
Hearth Extension Dimensions
B
B C
16 8
406 203
20 8
508 203