Finishing; Hearth Extension - Heatilator EL36 Series 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.
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 exten-
sions and calculate insulation alternatives as per Table 8.1
and the following formulas:
• K = Thermal conductivity per inch thickness. The lower
the K value, the less heat a material will transfer,.
• R = Thermal resistance per inch thickness. The higher the
R value, the less heat a material will transfer.
• To calculate the required thickness for the alternate
material, you need to know the K value for that material
and use the following formula:
K alt.
x .5 = thickness of alternate material
.43
Example: K of Brick = 5
5
.43
To determine the required thickness for an alternate mate-
rial, and if you know the R values of the materials you want
to use, add the values until the result is equal to or larger
than the R value required by your installation.
Example: Required R Value = 1.16
1 in. cement board (R = .52) + 3 in. brick (R = .60) + 1 in.
marble (R = .07).
Total R value = 1.19
26
x .5 = 5.81 in. of
Table 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
Heatilator • EL36/EL42 • 4044-132 Rev P • 02/07
Fire Risk
•
Sparks or embers may ignite fl ooring.
A
Model #
EL36
EL42
Figure 1 Hearth Extension Dimensions
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
0.46 2.18
14.3-20.0 0.07-0.05 16-5/8 in.-23-3/8 in.
WARNING
Metal hearth strips MUST be installed.
C
A B
in. 52 16
mm 1321 406
in. 66 20
mm 1676 508
Minimum
thickness
required
1/2 in.
1/2 in.
2-1/4 in.
5-7/8 in.
5-7/8 in.
14-5/8 in.
1/2 in.
B
C
8
203
12
305