Hearth Protection - Lennox Hearth Products Elite E260 Installation And Operation Manual

HEARTH PROTECTION

The hearth and/or floor protection must be a thermally rated non-com-
bustible hearth/floor protector meeting or exceeding a thermal rating
of k=.84 or equivalent with a listed thickness of listed thickness of 3/4"
(19 mm) minimum in the USA and Canada. The covering must extend
USA-16"/Canada-18" (C260) and 22" (E260) in front of the heater and
8" to the side (measured from door opening in the USA and measured
from the side of the unit in Canada).
Using Alternate Material As Floor / Hearth Protection
The hearth extension or alternate material used as a floor/hearth protec-
tor must be constructed of a durable noncombustible material having
an equal or better thermal conductivity value (lower k value) of k =.84
BTU/IN FT2 HR °F or a thermal resistance that equals or exceeds r = 1.19
HR °F FT2 IN/BTU with a minimum thickness of 3/4". With these values,
determine the minimum thickness of the alternate material required using
the formula(s) and shown in Table 2.
Note: Any noncombustible material having a minimum thickness of
3/4"(19 mm) whose k value is less than .84 or whose r value is more
than 1.19 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 = k value per inch of alternate material
M
r = r value per inch of
M
T = minimum thickness required for alternate material
M
T = standard thickness of the alternate material
S
k = k value per inch of listed material
L
r = r value per inch of
listed
L
T = minimum thickness of
L
Note: An asterisk "*" indicates, it is a value taken from Table 2.
Using the k formula:
Minimum
thickness of =
alternate
material (T )
M
T (inches) =
M
T (inches) =
M
.12 (inches)=
Answer - The minimum required thickness of the Micore 160 is .312"
therefore round up to nearest standard thickness available which is 3/8"
(.375")
8
material
alternate
material
material
listed
k-value (per Inch) of
alternate material (k ) x
M
k-value (per inch)
of listed material (k )
L
k
x
M
*.8
*.5 x
*.8
.1 x
Using the r formula:
Minimum
thickness of
alternate
material
T (inches)
M
T (inches)
M
.12 (inches)=
Answer - The minimum required thickness of the Micore 160 is .312"
therefore round up to nearest standard thickness available which is 3/8"
(.375")
Listed Material
Alternative Materials
Kaowool M Board
Micore 10™
U.S. Gypsum
Micore 00™
U.S. Gypsum
Durock™ Cement Board
U.S. Gypsum
Hardibacker™
Hardibacker 500™
Cultured Stone Hearth-
stone™
Wonderboard
Super Firetemp M
Johns-Manville
Super Firetemp L
Johns-Manville
Face brick
Common brick
Cement mortar
Ceramic tile
Marble
Specified min.
Table 2 - USA AND CANADA REQUIREMENTS
thickness
of listed
material (T )
** If the hearth extension material(s) that is intended to be used is NOT listed
L
on Table 2, the material can still be used if the material(s) is noncombustible.
T
However, the manufacturer of the material must provide either the listed k-value
L
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
.5"
in the NFI Certification Manuals).
Note: Also see NFI (National Fireplace Institute) Certification Manuals show-
.5"
ing other acceptable calculation methods and acceptable alternate materials
which can be used.
r-value (per Inch)
= of listed material
r-value (per inch)
of alternate material
r
=
L
r
M
= *1.19
*2.8
.1
Listed Material
k (per inch) r (per inch)
.8 1.19
r
K
L L
** Approved Alternate Materials for Floor/Hearth Protection
Thermal Values
k (per inch) r (per inch)
r
K
M M
. 2.1
.5 2.8
. 2.1
1.92 .52
1.95 .51
2.0 .
2.82 .5
.2 .1
.1 1.
.5 1.85
9.00 .111
5.00 .20
5.00 .20
12.5 .08
~11 ~.09
Specified min.
x thickness
of listed
material
x T
L
x .5"
x .5"
Listed Min. Thickness
"
/ (.5")
T
L
Minimum Thickness
(rounded to nearest 1/8 inch)
Min. Thickness
T
M
.2" (1/2")
.1" (/8")
.1" (1/2")
1.1" (1-/")
1." (1-/")
2.05" (2-1/8")
2.52" (2-5/8")
2.88" (")
.5" (5/8")
.8" (1/2")
8.0" (8-1/8")
." (-1/2")
." (-1/2")
11.1" (11-1/")
9.82" (9-/8")