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12 81D0107
Measur
e
this
distance
Heater in
Fireplace or
Firebox
Heat
Resistant
Material
Figure 5 - Measuring Heat Resistant Material
Heat resistant material (minimum requirements) with no wooden mantel or other combustible projection:
To install the gas logs into a fireplace with no wooden mantel, shelf or other combustible projection above the fireplace
opening, measure the heat resistant material height, per Figure 5, then see TABLE A.
Heat resistant materials such as slate and marble must be at least 1/2” thick. Sheet metal should not be installed onto
combustible material.
IMPORTANT: If you cannot meet these minimum clearances you must operate the heater with chimney flue damper open.
Refer to “Installing Vented Applications” found on page 18.
TABLE A - Heat Resistant Material Requirements with no Mantel or Combustible Projection
CLEARANCES and HEIGHT REQUIREMENTS
HEAT RESISTANT
MATERIAL
MEASUREMENT
REQUIREMENTS FOR SAFE INSTALLATION
NB18 NB24
12" or more Hood not required. Hood not required.
8" to less than 12" Hood not required. Extend heat resistant material
to 12" OR install hood. See
Figure 5.
Less than 8" Extend heat resistant material
and 8” AND install hood. See
Figure 5.
Extend heat resistant material
to 8" AND install hood. See
Figure 5. OR, extend heat
resistant material to a height of
at least 12".