Vermont Casting BC42 Common Materials And Factors, Majestic Fireplaces BR/BC Series, 7412944

WARNING: HEARTH EXTENSION MUST BE IN- STALLED IN ACCORDANCE WITH FIGURE 23 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. (Fig. 24)

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).

COMMON MATERIALS AND FACTORS

MATERIAL	K*	R	MINIMUM
			THICKNESS
EH2416	0.458	1.09	0.50 in.**
(CFM Corporation)
Common Brick	5.0	0.10	5.46 in.**

R Value is for 1/2 inch.

*Units of K = BTU/SQ FT/HR/˚F/IN ** Thickness of Listed Material

FP533ADD

Fig. 24 Hearth extension material factors.

Majestic Fireplaces® BR/BC Series

Wall Covering
Noncombustible	2x4" HEADER -
Decorative	Do not notch at
Facing	standoffs.

Seal all cracks
between fireplace
surround and wall
materials with
noncombustible
material.
Noncombustible
Decorative
Covering
Hearth	Seal crack
Extension	between fireplace
Insulation	and hearth extension
	with noncombustible
	material.

	Side View	Safety Strips -
		Must be overlapped
		¹⁄₂" minimum.
		FP550
Fig. 25 Sealing gaps.

Example of Determining Hearth Extension Equivalents

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).

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