354/254 Clearance Diagram
Minimum Clearances to Combustible Materials and Floor
Protection
Model 354
Model 254
A
Sides of Unit to Combustibles
18”
18”
B
Back of Unit to Combustibles
24”
18”
C
Floor Protection – Unit to Front
16”
16”
D
Floor Protection – Unit to Side
8”
8”
E
Chimney Connector to Combustible Wall or Ceiling
18”
18”
F
Floor Protection – Unit to Back
8”
8”
Floor protection
must be listed to UL 1618 and provide insulation of at least 3/8” thick millboard having
an insulation Factor of K - 0.84 (R - 0.45) and must extend a minimum of 8 inches on the non-flue side
and back, 12 inches
or 2” beyond the flue connector on the flue side of the ash door, and 16 inches in
front of ash door. An easy means of determining if a proposed alternate floor protector meets
requirements listed in this manual is to follow this procedure:
1) Convert specifications to R-value:
a. R-value given
– no conversion needed.
b. k-factor given with required thickness (T) in inches: R = 1/k x T
c. C-factor given: R = 1/C
2) Determine the R-value of the proposed alternate floor protector.
a. Use the formula in step (1) to convert values not expressed as “R”
b. For multiple layers, add R-values of each layer to determine the overall R-value.
3) If the overall R-value of the system is greater than the R-value of the specified floor protector, the
alternate is acceptable.
Example:
The specified floor protector should be 3/8-inch thick material with a k-factor of 0.84. The proposed
alternate is 4” brick with a C-factor of 1.25 over 1/8” mineral board with a k-factor of 0.29.
Step (a): Use formula to convert specification to R-value. R = 1/k x T = 1/.84 x .375 = .446
Step (b): Calculate R of proposed system
4” brick of C = 1.25, therefore Rbrick = 1/C = 1/1.25 = 0.80
1/8” mineral board of k = 0.29, therefore Rmineral board = 1/.29 x 0.125 = 0.431
TotalR = Rmineral board = 0.8 + 0.431 = 1.231
Step (c): Compare proposed system R of 1.231 to specified R of .446. Since the proposed system
R is greater than required, the system is acceptable
Front
A
B
Front
Floor Protection
C
E
D
F
Clearance to Combustibles
