Martin Fireplaces 400BWBIA - Manual (Page 12)

12 61D0008
52" (400 Models)
66" (500 Models)
Safety Strip
3"x36" Min. (400 Unit)
3"x42" Min. (500 Unit)
16" Min.
(400 Unit)
20" Min.
(500 Unit)
21"
21 1 /
2
"
40 1 /
2
"
40 1 /
8
" (400 Unit)
46 1 /
8
" (500 Unit)
16"min. - 400 unit
20" min. - 500 unit
8 " 8 "
INSTALLING FIREPLACE ON COMBUSTIBLE FLOOR
(CONTINUED)
This hearth extension must be either 6" (minimum) thick stone or brick; a H1652 (400 units) or H2066 (500 units) Hearth
Extension Kit; or a locally constructed hearth that has a “K” factor less than .43 and at least ½" thick. For other non-com-
bustibles, the total thickness minimum is 1.16 times its thermal conductivity (K).
The following relations could be useful —
Minor shifting of the supporting floor or
expansion and contraction may eventually
cause a crack to develop between the hearth
extension and the face of the fireplace with
either type hearth extension. To help prevent
the cracking, firmly fasten the hearth extension
materials in place. Screw wall ties to the face of
the fireplace. Imbed the wall ties in the mortar
joints of brick, stone, or other non-combustible
materials.
Place metal safety strip packed with the
fireplace beneath the fireplace. Extend metal
safety strip under the hearth extension or into
a mortar joint of the hearth. See Figures 6
through 9. If a crack does eventually develops,
the metal safety strip will prevent sparks or
embers from falling from the fireplace onto
combustible flooring materials.
FLOOR PROTECTION
Figure 8 - Installing Hearth Extension
(Circulating Model Shown)
Figure 9 - Installing Hearth Extension and Metal Safety Strip
Only install metal safety
strip horizontal to the
fireplace.
W
ARNING
Gas
Opening
Junction
Box
Opening
Floor
Level
Fireplace
Hearth
Metal
Safety Strip
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