Majestic Appliances BC42 - Manual (Page 17)

17
Majestic Fireplaces
®
BR/BC Series
7412944
Example of Determining Hearth Extension Equiva-
lents
To determine the thickness required for any new mate-
rial:
NEW
K of new material (per inch) thickness
required = --------------------------------------- X of
listed
thickness K of listed material (per inch) mate-
rial
Example for Common Brick
T (new) = 5.0/0.458 x 0.50 in. = 5.46 in. (new required
thickness).
WARNING: HEARTH EXTENSION MUST BE IN-
STALLED IN ACCORDANCE WITH FIGURE 23 AND
MUST NOT COVER THE BOTTOM FRONT OPENING
OF THE CIRCULATING MODEL.
Alternate noncombustible materials may be used pro-
viding the (total) thermal resistance (Rt value) of the al-
ternate material employed is greater than or equal to R
= 1.09 Thermal resistance (R) or thermal conductivity
(K), may be obtained from manufacturer of the material.
Factors are related by the formula K = 1/R. (Fig. 24)
T = given thickness
R = thermal resistance for a given thickness (T)
K = thermal conductivity
Noncombustible material with a lower R value may
be used, provided thickness of material is sufficiently
greater to maintain an equivalent (total) thermal resis-
tance (Rt).
COMMON MATERIALS AND FACTORS
MATERIAL K* R
MINIMUM
THICKNESS
EH2416
Common Brick
0.458
5.0
1.09 0.50 in.**
0.10 5.46 in.**
(CFM Corporation)
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR/˚F/IN
** Thickness of Listed Material
FP533ADD
Addendum
6/1/99 djt
8/4/99 changed .2 to .1
one inch to 1/2 inch djt
FP533ADD
Fig. 24 Hearth extension material factors.
FP550
Fig. 25 Sealing gaps.
FP550
BR/BC - SEALING
DETAILS
9/29/97
Wall Covering
Noncombustible
Decorative
Facing
Noncombustible
Decorative
Covering
Seal all cracks
between fireplace
surround and wall
materials with
noncombustible
material.
Seal crack
between fireplace
and hearth extension
with noncombustible
material.
2x4" HEADER -
Do not notch at
standoffs.
Safety Strips -
Must be overlapped
��� " minimum.
Hearth
Extension
Insulation
Side View
2”
(51 mm)
2”
(51 mm)
Maximum
14”
(356 mm)
Maximum
10”
(254 mm)
A
A
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Minimum
33”
(838 mm)
Minimum
36” (914 mm)
6”
(152 mm)
Minimum
Minimum .030 Thick Stain-
less Steel Plate
Insulation with Minimum R
Value of 2.75
Minimum .030
Thick Stainless
Steel Plate
View A
NOTE: If noncombustible material is not used between the
stainless steel plate and fireplace opening, the steel must
be attached to the front of the unit a minimum of four (4)
places on each piece with sheet metal screws no longer
than 1/2".
NOTE: The size of the insulation and stainless steel
plate must be within limits stated above and covers all
combustible framing material.
Fig. 26 Recessed installation.
FP1608
Hearth
Extension
Hearth Extension
Noncombustible
Material
(if desired)
Insulation
with Minimum
R Value
of 2.75
Recessed Installation - BR/BC36 Only