Majestic Appliances EWF36A - Manual (Page 16)

16
Vermont Castings EWF36A
20005167
NEW
required
thickness K of new material (per inch)
K of listed material (per inch)
thickness
of listed
material
= x
COMMON MATERIALS AND FACTORS
MATERIAL K* R
MINIMUM
THICKNESS
EH2416
Common Brick
0.916
5.0
2.18 1.0 in.**
0.10 5.46 in.**
(Majestic Products
Company)
R Value is for ¹⁄₂ inch.
* Units of K = BTU/SQ FT/HR/ßF/IN
** Thickness of Listed Material
FP533ADD
Fig. 23 Hearth extension material factors.
The top of insulation must be covered with a non-
combustible decorative covering or a piece of .018”
minimum sheet metal, to protect hearth extension
material. (Fig. 25)
Secure the hearth extension to the floor to prevent
shifting, using trim molding or other similar means at
three (3) outer edges. Seal crack between the fireplace
hearth and hearth extension with a noncombustible
material. (Figs. 24 and 25)
WARNING: Hearth extension must be installed in
accordance with Figure 24. Top of hearth extension
must be level with bottom of fireplace.
Alternate noncombustible materials may be used
providing the (total) thermal resistance (Rt value) of the
alternate material employed is greater than or equal to
R = 1.09 Thermal resistance (R) or thermal conductiv-
ity (K), may be obtained from manufacturer of the
material. Factors are related by the formula K = 1/R.
(Fig. 23)
T = given thickness
R = thermal resistance for a given thickness (T)
K = thermal conductivity
Noncombustible material with a lower R value may be
used, provided thickness of material is sufficiently
greater to maintain an equivalent (total) thermal resis-
tance (Rt).
Example of Determining Hearth Extension
Equivalents
To determine the thickness required for any new
material:
Example for Common Brick
T (new) = 5.0/0.458 x 0.50 in. = 5.46 in. (new required
thickness).
Wall Covering 2 x 4 Header - Do not
notch at standoffs
Noncombustible
Decorative
Facing
Seal all cracks
between fireplace
surround (steel) and
wall materials with
noncombustible
material.
Cast Front
Noncombustible
Decorative
Covering
Safety Strips - Must be
overlapped 1/2” minimum
FP1202
Fig. 24 Sealing gaps.
NOTE: No
material
may cover
black cast
face.