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Encore 1450 Non-Catalytic Woodburning Stove
30002425
How to Determine if Alternate Floor
Protection Materials are Acceptable
All floor protection must be noncombustible (i.e. met-
als, brick, stone, mineral fiber boards, etc.). Any organic
materials (i.e. plastics, wood paper products, etc.) are
combustible and must not be used. The floor protection
specified includes some form of thermal designation
such as R-value (thermal resistance) or k-factor (ther-
mal conductivity).
Procedure:
1. Convert specifications to R-value:
i. R-value given - no conversion needed.
ii. k-factor is given with a required thickness (T) in
inches:
iii. K-factor is given with a required thickness (T) in
inches:
iv. r-factor is given with a required thickness (T) in
inches: R = r x T
2. Determine the R-value of the proposed alternate
floor protector:
i. Use the formula in Step 1 to convert values not
expressed as R.
ii. For multiple layers, add R-values of each layer to
determine overall R-value.
3. If the overall R-value of the system is greater than
the R-value of the specified floor protector, the alter
-
nate is acceptable.
EXAMPLE: The specified floor protector should be 1/2-
inch thick material with k-factor of 0.84. The proposed
alternate is 4” brick with an r-factor of 0.2 over 1/8”
mineral board with a k-factor of 0.29
Step a: Use formula above to convert specification to
R-value:
Step b: Calculate R of proposed system.
4” brick of r = 0.2, therefore:
R
brick
= 0.2 x 4 = 0.8
1/8” mineral board of k = 0.29, therefore
R
mineralboard
= x 0.125 = 0.431
R
total
= R
brick
+ R
mineralboard
= 0.8 + 0.431 = 1.231
Step c: Compare proposed system Rtotal of 1.231 to
specified R of 0.59. Since proposed system Rtotal is
greater than required, the system is acceptable.
Definitions
R = x T
1
K x 12
R = x T = x 0.5 = 0.59
1
k
1
0.84
1
0.29
r = =
(ft
2
)(hr)(°F)
(Btu)(in)
1
k
(Btu)(ft)
(ft
2
)(hr)(°F)
K =
k = = K x 12
(Btu)(in)
(ft
2
)(hr)(°F)
R =
(ft
2
)(hr)(°F)
Btu
R = x T
1
k
Floor Protection for Fireplace Installations
Do not assume that your fireplace hearth is completely
noncombustible.
Many fireplace hearths do not meet the “completely
noncombustible” requirement because the brick or
concrete in front of the fireplace opening is supported
by heavy wood framing. (Fig. 13) Because heat passes
through brick or concrete readily, it can easily pass
through to the wood. As a result, such fireplace hearths
can be a fire hazard and are considered a combustible
floor.
Keep in mind, also, that many raised hearths will extend
less than the required clearance from the front of the
heater when it is installed. In such cases, sufficient
floor protection as described above must be added in
front of the hearth to satisfy the minimum floor protector
requirement from the front of the stove: 16” (406 mm)
from the front in the United States and 18” (450 mm)
from the front in Canada.
Hearth rugs do not satisfy the requirements for floor
protection.
Fireplace installations also have special clearance
requirements to the side walls, side decorative trim, and
fireplace mantel. This information follows in the section
on Fireplace and Mantel Trim Shields.
D
E
A
B
A
E
C
ST500
Encore
floor protection
2/23/01
E
F
E
F
U.S. Canada
A. 39” 43” (1092 mm)
B. 45” 49” (1245 mm)
C. 12” 12” (305 mm) 8” Connector
10” 10” (255 mm) 6” Connector
D. 6” 8” (200 mm)
E. 6” 8” (200 mm)
F. 16” 18” (450 mm)
ST500
Fig. 12 Required floor protector dimensions for both top-and
rear-exiting stove.
Required thermal protection: 1/2” (13 mm) mini-
mum noncombustible material with an R-value
of at least 0.59.