A wall shield is required where a continuous perpendicular side wall is within 12" of the fireplace opening (Figure 49 ). Use a 36" W x 36" H wall shield constructed of a durable, noncombustible material having an equal or better (lower k value) insulating value than k =
.54 BTU IN/FT2 HR ° F. At no time may a perpendicular side wall be located closer than 9" from the fireplace opening.
If fireplace is installed diagonally across a 90° corner; no wall shields are required.
Side Wall
12" (305 mm) Min. to Fireplace Opening
C
B
D 
C 
A
Figure 49
Calculating Minimum Thickness if Multiple Materials are Used
At times it is important to know what combination of materials are acceptable for use as floor protection. The “R values” are used to determine acceptable combinations of materials because “R values” are additive where r and k values are not.
“R value” = 1/k = “r” x thickness of material used
Example: Given that the required “R value” for a suitable floor protector used must be equal to or greater than:
“R” = rL x TL = 1.19 x 1” = 1.19.”
If it is desired to elevate a marble hearth extension 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:
brick
“R”M = rM x TS = 0.20 x 3 1/2" = .70
Using 1/2” of mortar to set the brick, “R” for the mortar is calculated as follows:
mortar
“R”M = rM x TS = 0.20 x 1/2" = .10
Next, a 3/4" marble slab set in 1/2" mortar covers the brick, “R” for the marble and mortar becomes:
marble
“R”M = rM x TS = 0.05 x 3/4" = .038
mortar
“R”M = rM x TS = 0.20 x 1/2" = .10
The sum of all “R values” is: .70 + .10 +. 038 + .10 = .938
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 1.19. An additional layer of insulating materials must be used.
Note: Also see NFI Certification Manuals for expanded explanation on calculating “R val- ues” when multiple materials are used.
WARNING: THE CRACK BETWEEN THE FIREPLACE AND THE HEARTH EXTENSION MUST BE SEALED WITH A NON- COMBUSTIBLE MATERIAL.
WARNING: WHEN INSTALLING HEARTH EXTENSION IN FRONT OF THE FIRE- PLACE, THE FIREPLACE MUST BE RAISED IF HEIGHT OF HEARTH EXTENSION EXCEEDS 8" ABOVE BOTTOM OF FIREPLACE (FIGURE 50 ).
8"
(203 mm)
Max.
Maximum Thickness of Hearth Extension when Fireplace is on the Floor.
Figure 50
FINISH TO YOUR TASTEThere are a wide variety of “finished looks” for your LS43ST fireplace from formal wall decor with elaborate mantels to rustic wood paneling or warm brick facings.
Only noncombustible materials like marble, stone, tile, brick, etc. may overlap the black front facing, but be careful not to interfere with the operation of the glass doors.
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
Seal all joints between the black facing and wall surrounds to prevent cold air intrusion. Use noncombustible caulking material only to seal the black metal facing to the surround material on the finished wall. Combustibles may also project beyond the sides of the fireplace opening as long as they are kept within the shaded areas (refer to Figure 5 ).
ACCESSORY PARTS AND COMPONENTS LIST FOR THE LS43ST
The accessory parts and components shown on pages 19 and 20 are to be used only with your LS43ST fireplace system. Separate installation instructions are packaged with all combustion air kits and chimney terminations.
If you encounter any problems or have questions concerning the installation or application of this system, please contact your distributor. For the name of your nearest distributor call:
LENNOX HEARTH PRODUCTS
1110 West Taft Avenue
Orange, CA 92865
INSTALLATION COMPONENTSThe following items are available for use in the installation of this appliance.
Outside Combustion Air Kits |
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(with duct) | 81L87 | FOAK | ||
(without duct) | 81L88 | |||
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Combination |
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Offset/Return Elbow | 63L35 |
Model | Part Number | Weight |
LS43ST | 23M92 | 400 lbs. |
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