Heatilator ST42A Installation Manual page 28

B. Hearth Extension, Building and Fin-
ishing
WARNING! Risk of Fire!
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surfaces.
• Protective metal hearth strips MUST be installed.
• Hearth extensions MUST be installed exactly as
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alternatives.
WARNING! Risk of Fire!
Hearth & Home Technologies is not responsible for
discoloration, cracking or other material failures of
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Figure 7.3
28
High temperatures, sparks,
CAT. #
+; in
mm
Hearth Extension Dimensions
Heatilator • ST42A Installation Manual • 4012-051 • Rev O • 02/22
WARNING! Risk of Fire!
• Maintain clearances.
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closer than the minimums listed, must be constructed entirely
of non-combustible materials (i.e., steel studs, concrete board,
etc.).
WARNING! Risk of Fire!
Hearth extensions are to be installed only as illustrated to prevent
high temperatures from occurring on concealed combustible
materials.
Table 7.1
R = 1/k x inches of thickness
Table 7.2
Hearth Extension Insulation Alternatives, R Value = 1.03
Material
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C
B
A
A B
 
 
k per inch r per inch
thick thick
 
 
  
 
 
 
 2.18
14.3-20.0 0.07-0.05
C
12

Minimum
thickness
required
 LQ
 LQ
2 in.
  LQ
  LQ
  LQ
 LQ
14 5/8 in. - 20 3/8 in.