Mendota GREENBRIAR M-50, Installation & Operating Instruction Manual

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HEARTH PROTECTION PAD REQUIREMENTS
Hearth Protection R Rating: MINIMUM R-1 IS REQUIRED. USE OF A ½” THICK (MINIMUM) CEMENT BOARD (Hardi-
backer, Wonderboard or other brand) plus ¼” thick mortar (ThinSet type) plus ¼” thick ceramic tile exceed the R-1 re-
quirement. Use this as a reference, if in doubt. Natural Stones of 1” or greater thickness also exceed R-1 rating.
All hearth pads must be non-combustible (metal, brick, stone,
or mineral fiberboard).
Do not use any combustible material
to protect the floor in front of this fireplace. For the M-50,
the hearth protection pad must be rated at R-1 minimum
AND it must extend 24 inches in front of the fireplace face
if the M-50 fireplace is installed at floor level.
Use the following procedure to determine if a hearth pad meets
the requirements listed in this manual. Find the available val-
ues, R, K or C and follow the formulae below to arrive at a R
value.
R-value = Thermal Resistance
K-value = Thermal Conductivity
C-value = Thermal Conductance
Convert the specification to R-value;
a. If R-value is given, no conversion is needed.
b. If K-value is given with for a thickness (t) in inches:
T
K
R
× =
1
...( 1 divided by K , then multiplied by thickness).
c. If C-value is given:
C
R
1
=
…(1 divided by C).
Determine the R-value of the proposed hearth pad. For mul-
tiple layers, add R-values of each layer to determine overall R-
value. If the overall R-value of the system is greater than R-1,
then the proposed hearth pad is acceptable.
Example:
Required minimum R value for hearth protection pad is R=1.
The proposed alternative is 1/4” tile with a C- factor of 1.25
over 1/8” mineral board with a K-factor of 0.29. Determine if
the proposed layers will provide the minimum R=1 rating.
Step A. Use formula to convert C-factor of the ¼” tile to R-
value.
R of the tile:
C
R
1
=
= 1/1.25 = 0.80
Step B. Use formula to convert K-factor of mineral board to
R-value.
R of mineral board:
T
K
R
× =
1
=1/0.29 x 0.125 = 0.431
Step C. Add R values of ¼” Tile and mineral board to get the
Total R-value of proposed alternative:
R
Total
= R
tile
+ R
mineral board
= 0.8 + 0.431 = 1.231.
Step D. Compare proposed system R = 1.231 to required R
of 1.0. Since R of proposed system is greater than
the required R=1, the proposed system is accepta-
ble.
This fireplace may be installed in an elevated position by created an elevated deck and an appropriate framed enclosure.
NOTE: This fireplace may be elevated but MUST allow a minimum of 72” distance between this fireplace’s floor level and
the ceiling.
NOTE: For every 1" this fireplace is raised off the floor,
the non-combustible hearth protection pad may be reduced
by 2". If this fireplace is raised off the floor more than 12",
No hearth protection pad is required.
24" min. R-1 Rated Non-combustible Hearth
protection required.
1
1
2
" HEARTH PAD HEIGHT
(MIN R-1 RATING)
IS REQUIRED
5/8" min. from unit front
edge to back edge of hearth
pad. Spacer is installed on fireplace.
Figure 8: HEARTH PROTECTION REQUIREMENT