Hearth and Home Technologies NorthStar-NT Indoor Fireplace User Manual


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Page 38
Heat & Glo • NorthStar EPA Fireplace • 480-1081C
September 1, 2008
September 1, 2008
September 1, 2008
8
Finishing
A. Hearth Extension
Ahearthextension mustbeinstalledwith allreplacesto
protectthe combustibleoorin frontof thereplacefrom
both radiant heat and sparks. See Figures 38.1 below, and
Figures 40.1 and 40.2 on page 40.
2 in. (51 mm)
required
Hi
g
h
temperature
(300°F min.) continuous,
non-combustible sealant
Tile, stone or other
non-combustible material
Floor constructed of wood or
o
th
e
r
co
m
bus
ti
b
l
e
m
a
t
e
ri
a
l
HX3 or HX4
Hearth Ext
or equivalent
insulation
(see Table below)
Fireplace
Protective
Metal Hearth
Strip
Figure 38.1 Hearth Extension Construction
Table 38.1
Hearth Extension Insulation Alternatives
Minimum R Value = 2.18
Material
k per inch
thick
R per inch
thick
Minimum
thickness
required
Hearth & Home HX3, HX4 0.49 2.18 1 in.
USG Micore 300™ 0.49 2.18 1 in.
USG Durock™ Cement Board 1.92 0.52 2-1/4 in.
Cement Mortor 5.0 0.20 5-7/8 in.
Common Brick 5.0 0.20 5-7/8 in.
Ceramic Tile 12.50 0.08 14-5/8 in.
Armstrong™ Privacy
Guard Plus 0.46 2.18 1/2 in.
Marble 14.3-20.0 0.07-0.05 16-5/8 in. - 23-3/8 in.
B. Calculating Alternate Floor Protection
Material
Thermal Conductivity: k value
Thekvalueindicatestheamountofheat(inBTU’s)thatwillow
in 1 hour through 1 square foot of a uniform material 1 inch thick
for each degree (F) of temperature difference from one side of
thematerialtotheother.TheLOWERthekfactormeansless
heat is being conducted through the non-combustible material
to the combustible material beneath it. The k value of a mate-
rial must be equal or smaller then the required k value to be
acceptable.
(BTU) (inch)
(foot
2
(hour) (
o
F)
Thermal Resistance: R value
The R value is a measure of a material’s resistance to
heat transfer. R value is convenient when more than one
material is used since you can add the R values together,
whereas you can not do this for k value. The HIGHER the R
factor means less heat is being conducted through the non-
combustible material to the combustible material beneath it.
The R value of a material must be equal or larger then the
required R value to be acceptable.
Converting k to R:
Divide 1 by k and multiply the results times the thickness in inch-
es of the material.
R=1/kxinchesofthickness
Converting R to k:
Divide the inches of thickness by R.
k=inchesofthickness/R
Calculations:
Example:Floorprotectionrequireskvalueof0.84and3/4inch
thick.
Alternativematerialhasakvalueof0.6andis3/4inchthick.
Divide0.6by.75=kvalueof0.80.Thiskvalueissmallerthan
0.84 and therefore is acceptable.
Fire Risk
• Maintainclearances.
• Use only non-combustible material below
standoffs, material such as cement board
is acceptable.
WARNING
• Framingornishingmaterialusedonthefront
of, or in front of, the appliance closer than the
minimums listed, must be constructed entirely of
noncombustible materials (i.e., steel studs, concrete
board, etc.).
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