18
Example: Given that the required “R value” for a suitable hearth extension used must be equal to or greater than:
“R” = r x TL = 3.70 x 1" = 3.70.
If it is desired to elevate a marble hearth exten- sion to a level of 5" or more above the floor surface. What combination of noncombustible materials can be used to accomplish this?
If common brick is used so that the 3 ¹⁄₂" dimension is the height, “R” for the common brick becomes:
“R”M = r x TM = 0.20 x 3 ¹⁄₂" = .70
Using ¹⁄₂" of mortar to set the brick, “R” for the mortar is calculated as follows:
“R”M = r x TM = 0.20 x ¹⁄₂" = .10
A ³⁄₄" marble slab set in ¹⁄₂" mortar covers the brick, “R” for the marble and mortar becomes:
“R”M = r x TM = 0.09 x ³⁄₄" = .068 “R”M = r x TM = 0.20 x ¹⁄₂" = .10
The sum of all “R values” is:
.70 + .10 +. 068 + .10 = .968
This would not be an acceptable combination of material for the hearth extension since the total calculated “R value” of the materials used is under the required “R value” of 3.70. An additional layer of insulating materials must be used.
WARNING: THE CRACK BETWEEN THE FIREPLACE AND THE HEARTH EXTEN- SION MUST BE SEALED WITH A NON- COMBUSTIBLE MATERIAL.
WARNING: WHEN INSTALLING HEARTH EXTENSION IN FRONT, THE FIREPLACE MUST BE RAISED IF HEIGHT OF HEARTH EXTENSION EXCEEDS 7 ¹⁄₂" ABOVE THE BOTTOM OF FIREPLACE (FIGURE 45 ).
7¹⁄₂"
Max. Thickness Of Hearth Extension When
Figure 45
Secure the hearth extension to the floor to prevent possible shifting.
FINISH TO YOUR TASTE
There are a wide variety of “finished looks” for these fireplaces, from formal wall decor with elaborate mantels to rustic wood paneling or warm brick facings.
Only noncombustible materials like stone, tile, brick, etc., may overlap the black front facing. Do not extend these materials beyond the black facing and into the firebox area. Be sure not to interfere with the installation and operation of glass doors or block the upper or lower grilles. Seal all joints between the black facing and wall surrounds to prevent air intrusion. Use non- combustible caulking material only to seal the black metal facing to the surround material on the finished wall.
Combustible materials may project beyond the sides of the fireplace opening as long as they are kept within the shaded areas illustrated in Figure 46.
Combustible
Materials
Allowed In
Shaded AreaFireplace
“Safe Zone”
14" | 1" |
| |
45° |
|
20" | Min. Distance To |
| |
14" | Protected Side Wall |
20" | Min. Distance To | |
Unprotected Side Wall | ||
|
Figure 46
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
INSTALLATION COMPONENTS
The following items are available for use in the installation of this appliance.
Outside Combustion Air Kits |
| |
(with duct) | 81L87 | FOAK |
(without duct) | 81L88 | |
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Firestop Spacer (30° ) | 63L37 | |
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Offset/ Return |
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Package (30° ) | 63L23 |
Combination |
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Offset/Return Elbow | 63L34 |