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15
WMC Series Woodburning Fireplace
20000583
Hearth Installation
A hearth extension is required to protect a combustible
floor in front of the fireplace. Refer to Figure 24 for
minimum dimensions and mounting detail.
NOTE: Hearth Extension must not cover the air
inlet/outlet opening of a fireplace.
The hearth extension described in Figure 24 must be a
durable noncombustible material with a minimum (to-
tal) Rt value of 1.09; refer to Figure 25 for examples.
The overall height (above a combustible floor), depth
and width must be as indicated, with the extension
centered to the fireplace opening.
The top of insulation must be covered with a noncom-
bustible decorative covering or a piece of .018” mini-
mum sheet metal, to protect hearth extension material.
(Fig. 24)
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 fire-
place hearth and hearth extension with a noncombus-
tible material. (Figs. 22 and 26)
WARNING: HEARTH EXTENSION MUST BE IN
-
STALLED IN ACCORDANCE WITH FIGURE 24 AND
MUST NOT COVER THE BOTTOM FRONT OPENING
OF THE CIRCULATING MODEL.
Alternate noncombustible materials may be used provid-
ing the (total) thermal resistance (Rt value) of the alter-
nate material employed is greater than or equal to R =
1.09. Thermal resistance (R) or thermal conductivity (K),
may be obtained from manufacturer of the material. Fac-
tors are related by the formula K = 1/R.
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).
Minimum Wall Clearances
WITH
Noncombustible
Surround Facing
WITHOUT
Noncombustible
Surround Facing
Minimum Hearth Extension Dimensions
(for On-Site Construction)
G
H
G
J
Seal cracks
between the
fireplace
and hearth
extension with
noncombustible
material
Safety strips
must overlap
" minimum
May install
noncombustible
decorative
covering
OR .018" min.
sheet metal
FIREPLACE
HEARTH
COMBUSTIBLE
FLOOR
MINIMUM
INSULATION
VALUE "R"
4" MIN.
FP594A
WMC combustible min.
1/29/99 djt
FIREBOX
OPENING
A - Min. clearance
to combustible
perpendicular wall
B - Min. clearance
to combustible
perpendicular wall when
using noncombustible wall shield*
SIDE
WALL
SIDE
WALL
F**
C**
E
E
D
4" BRICK
(Example material)
Combustible material permitted within shaded area.
*
Noncombustible wall shield requires 1" Majestic EH2416
insulation (minimum R Value = 1.85) between decorative
noncombustible rigid covering and combustible wall.
Minimum height and width is 40" x 40".
**
Dimension/degree of angle will vary depending on thickness
of noncombustible surround facing.
4"
Shaded area starts
1/2" away from
edge of unit
FP594A
Fig. 24 Combustible side wall protection and hearth extension dimensions.
A B C D E F G H J
WMC36 16" 12" 48° 41° 18" 14" 7³⁄₄" 16" 48"
406 mm 305 mm 457 mm 356 mm 197 mm 406 mm 1219 mm
WMC42 20" 12" 42° 35° 18" 14" 11
¹⁄₂" 20" 61¹⁄₂"
508 mm 305 mm 457 mm 356 mm 292 mm 508 mm 1562 mm