Lennox Hearth GRANDVIEW GV230 - Manual (Page 8)

8
When the Grandview™ 230 is installed in an Alcove, the floor protection
must be a thermally rated non-combustible floor protector meeting or
exceeding a thermal rating of k=.47 or equivalent with a listed thickness
of 1/2" (12.7 mm) minimum in the USA and Canada. The thermal protec-
tion must extend 16” in front of the heater and 8” to each side (measured
from the door opening).
Using Alternate Material As Floor Protection
The floor protection or alternate material used as a floor protector must
be constructed of a durable noncombustible material having an equal or
better thermal conductivity value (lower k value) of k =.47 BTU/IN FT2 HR
°F or a thermal resistance that equals or exceeds r = 2.13 HR °F FT2 IN/
BTU with a minimum thickness of 1/2”. With these values, determine the
minimum thickness of the alternate material required using the formula(s)
and shown in Table 1.
Note: Any noncombustible material having a minimum thickness of
1/2”(12.7mm) whose k value is less than .47 or whose r value is more
than 2.13 is acceptable. If the alternate material used has a higher k value
or lower r value will require a greater thickness of the material used. In
some cases, if the k value is less or the r value higher, a thinner material
may be used.
Methods of determining floor protection equivalents:
To determine the thickness required for the alternate material when
either the "k" value or "r" value is known, use either the k formula or r
formula.
Example: If Micore 160 Mineral Fiber Board is to be used for the
floor protection, how thick must this material be?
k
M
= k value per inch of alternate material
r
M
= r value per inch of alternate material
T
M
= minimum thickness required for alternate material
T
S
= standard thickness of the alternate material
k
L
= k value per inch of listed material
r
L
= r value per inch of listed material
T
L
= minimum thickness of listed material
Note: An asterisk "*" indicates, it is a value taken from Table 1.
Using the k formula:
k formula:
Minimum k-value (per Inch) of Specified min.
thickness of = alternate material (k
M
) x thickness
alternate k-value (per inch) of listed
material (T
M
) of listed material (k
L
) material (T
L
)
T
M
(inches) = k
M
x T
L
*.47
T
M
(inches) = *.35 x .50"
*.47
.312 (inches)= .745 x .50"
Answer - The minimum required thickness of the Micore 160 is .372"
therefore round up to nearest standard thickness available which is
3/8” (.375”)
Minimum r-value (per Inch) Specified min.
thickness of = of listed material x thickness
alternate r-value (per inch) of listed
material of alternate material material
T
M
(inches) = r
L
x T
L
r
M
T
M
(inches) = *2.13 x .50"
*2.86
.312 (inches)= .745 x .50"
Answer - The minimum required thickness of the Micore 160 is .372"
therefore round up to nearest standard thickness available which is
3/8” (.375”)
Using the r formula:
Listed Material
k (per inch) r (per inch) Listed Min. Thickness
Listed Material .47
K
L
2.13
r
L
1/2 " (.50")
T
L
** Approved Alternate Materials for Floor/Hearth Protection
Alternative Materials Thermal Values Minimum Thickness
(rounded to nearest 1/8 inch)
k (per inch)
K
M
r (per inch)
r
M
Min. Thickness
T
M
Kaowool M Board .47 2.13 .5" (1/2")
Micore 160™
U.S. Gypsum
.35 2.86 .37" (3/8")
Micore 300™
U.S. Gypsum
.46 2.17 .49" (1/2")
Durock™ Cement Board
U.S. Gypsum
1.92 .52 2.04" (2-1/8")
Hardibacker™ 1.95 .51 2.07" (2-1/8")
Hardibacker 500™ 2.30 .43 2.45" (2-1/2")
Cultured Stone Hearth-
stone™
2.82 .35 3" (3")
Wonderboard 3.23 .31 3.44" (3-1/2")
Super Firetemp M
Johns-Manville
.61 1.64 .65" (3/4")
Super Firetemp L
Johns-Manville
.54 1.85 .57" (5/8")
Face brick 9.00 .111 9.57" (9-5/8")
Common brick 5.00 .20 5.32” (5-3/8")
Cement mortar 5.00 .20 5.32” (5-3/8”)
Ceramic tile 12.5 .08 13.30" (13-3/8")
Marble ~11 ~.09 11.70" (11-3/4")
Table 1 - USA AND CANADA REQUIREMENTS
** If the hearth extension material(s) that is intended to be used is NOT
listed on Table 1, the material can still be used if the material(s) is non-
combustible. However, the manufacturer of the material must provide
either the listed k-value per inch or r-value per inch with listed thickness
so that the minimum thickness required for the hearth can be calculated
(per instructions here or as specified in the NFI Certification Manuals).
Note: Also see NFI (National Fireplace Institute) Certification Manuals show-
ing other acceptable calculation methods and acceptable alternate materials
which can be used.
ALCOVE INSTALLATIONS - FLOOR PROTECTION