17
ODWR Series Outdoor Woodburning Fireplaces
87D1502
WARNINg: HeARTH eXTeNSION MUST Be IN-
STALLeD IN ACCORDANCe WITH FIgURe 25 AND
MUST NOT COVeR THe BOTTOM FRONT OPeNINg
OF THe CIRCULATINg MODeL.
Alternate noncombustible materials may be used pro-
viding the (total) thermal resistance (Rt value) of the al-
ternate 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.
Factors 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).
example of Determining Hearth extension equiva-
lents
To determine the thickness required for any
new
mate-
rial:
NEW
K of new material (per inch) Thickness
required =
X of listed
thickness K of listed material (per inch) material
example for Common Brick
T (new) = 5.0/0.458 x 0/50 in. =
5.46 in.
(new required
thickness).
COMMON MATERIALS AND FACTORS
MATERIAL
K*
R
MINIMUM
THICKNESS
EH2416
Common Brick
0.458
5.0
1.09
0.50
in.**
0.10 5.46 in.**
(MHSC)
R Value is for 1/2 inch.
* Units of K = BTU/SQ FT/HR
/˚F/IN
** Thickness of Listed Material
FP533ADD
Addendum
6/1/99 djt
8/4/99 changed .2 to .1
one inch to 1/2 inch djt
FP533ADD
Fig. 25
Hearth extension material factors.
FP550
Fig. 26
Sealing gaps.
FP550
BR/BC - SEALING
DETAILS
9/29/97
Wall Covering
Noncombus-
tible Decorative
Facing
2 x 4 Header
(Do not notch
at standoffs)
Seal all cracks
between fireplace sur-
round and wall materi-
als with noncombus-
tible material
Noncombustible
Decorative Cov-
ering
Hearth Extension
Insulation
Safety Strips
Must be overlapped 1/2"
minimum
Seal crack between
fireplace and hearth
extension with noncom-
bustible material
Side View
