MHSC BR36 Installation And Operating Manual page 17

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
EH2416
(CFM Corporation)
Common Brick
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR/˚F/IN
** Thickness of Listed Material
Fig. 24 Hearth extension material factors.
FP533ADD
Wall Covering
Addendum
Noncombustible
6/1/99 djt
Decorative
8/4/99 changed .2 to .1
Facing
one inch to 1/2 inch djt
Seal all cracks
between fireplace
surround and wall
materials with
noncombustible
material.
Noncombustible
Decorative
Covering
Hearth
Extension
Insulation
Side View
FP550
Fig. 25 Sealing gaps.
7412944
MINIMUM
R
K*
THICKNESS
0.458 1.09 0.50 in.**
5.0 0.10 5.46 in.**
FP533ADD
2x4" HEADER -
Do not notch at
standoffs.
Seal crack
between fireplace
and hearth extension
with noncombustible
material.
Safety Strips -
Must be overlapped
" minimum.
FP550
BR/BC - SEALING
DETAILS
9/29/97
BR/BC Series Woodburning Fireplaces
example of Determining Hearth extension equiva-
lents
To determine the thickness required for any new mate-
rial:
NEW K of new material (per inch)
required = --------------------------------------- X of
listed
thickness K of listed material (per inch)
rial
example for Common Brick
T (new) = 5.0/0.458 x 0.50 in. = 5.46 in. (new required
thickness).
Recessed Installation - BR/BC36 Only
Noncombustible
Material
Minimum
(if desired)
36" (914 mm)
Insulation
with Minimum
R Value
of 2.75
2"
(51 mm)
Hearth Extension
Minimum .030 Thick Stain-
less Steel Plate
Maximum
10"
(254 mm)
Maximum
14"
(356 mm)
Hearth
Extension
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.
thickness
mate-
A
6"
(152 mm)
Minimum
Minimum
(838 mm)
2"
(51 mm)
A
Insulation with Minimum R
Value of 2.75
Minimum .030
Thick Stainless
Steel Plate
FP1608
View A
33"
17