Vermont Castings BR36 Homeowner's 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 providing
the (total) thermal resistance (Rt value) of the alternate
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 resistance (Rt).
COMMON MATERIALS AND FACTORS
MATERIAL
EH2416
Micor 300
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
6/1/99 djt
Noncombustible
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
K* R
THICKNESS
1.09 0.50 in.**
0.458
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 o
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
m a t e -
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
f
33"
17