Monessen Hearth BWBC400MHB User Manual

Page of 40
61D0087 
11
16"min. - 400 unit
20" min. - 500 unit
8
"
8
"
Figure 9 - Installing Hearth Extension and Metal Safety Strip 
Only  install  metal  safety 
strip  horizontal  to  the 
fireplace. 
W
ARNING
Fireplace
Metal 
Safety Strip 
*HEARTH EXTENSION EQUIVALENTS
Hearth extensions are made of a 
1
/
2
" thick piece of **MICORE CV230 fiberboard covered with a sheet of 26 gauge galvanized 
steel. You may purchase these materials locally to fabricate hearth extensions. You can construct hearth extensions from any 
noncombustible material that is 
1
/
2
" thick with a “K” value (thermoconductivity) of 0.43 or lower. 
For example, an insulating material 
1
/
2
" thick with a “K” value of 0.35 would be acceptable. A hearth extension made from 
materials 
1
/
2
" thick with a “K” value of 0.43 or lower is equal to the H1652 or H2066 hearth extensions. See Figure 8, page 
10.
**MICORE CV230 is manufactured by U.S. Gypsum Corporation.
The following relations could be useful:
C = K divided by the material thickness
(Example C = .43 divided by 1/2 (.50)
        C = .86)
K = C multiplies by the material thickness
(Example K = .86 multiplied by 1/2 (.50)
        K = .43)
R = The material thickness divided by K
(Example R = 1/2 (.50) divided by .43
        R = 1.16)
C = Thermal Conductant
R = Thermal Resistance
FIREPLACE INSTALLATION