Lennox Hearth WHITFIELD 30 FS-2 - Manual (Page 5)

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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE
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Floor Protection - Profi le ® 30 FS-2
The fl oor protector must meet or exceed the minimum thermal require-
ments as defi ned on this page (see Floor Protection / Hearth Extension
Using Alternate Material As Floor Protector). If the fl oor protection is
to be stone, tile, brick, etc., it must be mortared or grouted to form a
continuous noncombustible surface. If a chimney connector extends
horizontally over the fl oor, protection must also cover the fl oor under
the connector and at least 2” (51 mm) to either side.
The fl oor protector must fully cover the area beneath the appliance and
extend 6” to the front, 6” to the sides, and 6” from the back as shown
in Figure 1 (Note: When installed at clearances less than 6”, the fl oor
protection is only required to extend to the wall).
Floor Protection / Hearth Extension Using Alternate Material As
Floor Protector - All Models
Note: Also see Floor Protection above for free-standing models and Hearth
Requirements, Page 7 for the fi replace insert model.
The hearth pad or alternate material used as a fl oor/hearth protector
must be constructed of a durable noncombustible material having an
equal or better thermal conductivity value (lower k value) of k = .84 BTU
/ IN FT
2 HR °F or a thermal resistance that equals or exceeds r = 1.19
HR °F FT 2 IN/BTU with a minimum thickness of 3/8”. With these values,
determine the minimum thickness of the alternate material required using
the formula(s) and the table shown here (see Table 1).
Note: Any noncombustible material having a minimum thickness of 3/8”
(10 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 fl oor 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 300 is to be used for the fl oor 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:
Minimum k-value (per Inch) of Specifi ed 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
*.84
T
M
(inches) = *.46 x .375"
*.84
.205 (inches)= .547 x .375"
Answer - The minimum required thickness of the Micore 300 is .205," there-
fore round up to nearest standard thickness available which is 1/4."
Minimum r-value (per Inch) Specifi ed 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) = *1.19 x .375"
* 2.17
.205 (inches)= .548 x .375"
Answer - The minimum required thickness of the Micore 300 is .205," there-
fore round up to nearest standard thickness available which is 1/4."
Using the r formula:
Listed Material
k (per inch) r (per inch) Listed Min.Thickness
Listed Material .84
K
L
1.19
r
L
3/8 " (.375")
T
L
** Approved Alternate Materials for Floor/Hearth Protection
AlternativeMaterials Thermal Values MinimumThickness
(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 .21" (1/4")
Micore 160™
U.S. Gypsum
.35 2.86 .16" (1/8")
Micore 300™
U.S. Gypsum
.46 2.17 .21" (1/4")
Durock™ Cement Board
U.S. Gypsum
1.92 .52 .86" (7/8")
Hardibacker™ 1.95 .513 .87" (7/8")
Hardibacker 500™ 2.30 .435 1.03" (1")
Cultered Stone Hearth-
stone™ 2.82 .355 1.26" (1-1/4")
Wonderboard 3.23 .31 1.44" (1-1/2")
Super Firetemp M
Johns-Manville
.61 1.64 .27" (1/4")
Super Firetemp L
Johns-Manville
.54 1.85 .24" (1/4")
Face brick 9.00 .111 4.02" (4")
Common brick 5.00 .20 2.23" (2-1/4")
Cement mortar 5.00 .20 2.23" (2-1/4")
Ceramic tile 12.5 .08 5.58" (5-5/8")
Marble ~11 ~.09 4.91" (4-7/8")
Table 1
** 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 noncombustible.
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 on this page and/or
as specifi ed in the NFI Certifi cation Manuals).
Note: Also see NFI (National Fireplace Institute) Certifi cation Manuals show-
ing other acceptable calculation methods and acceptable alternate materials
which can be used.