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C. Constructing the Appliance Chase
A chase is a vertical box-like structure built to enclose the
gas appliance and/or its vent system. In cooler climates
the vent should be enclosed inside the chase.
NOTICE: Treatment of ceiling fi restops and wall shield
fi restops and construction of the chase may vary with the
type of building. These instructions are not substitutes
for the requirements of local building codes. Therefore,
you MUST check local building codes to determine the
requirements to these steps.
Chases should be constructed in the manner of all out-
side walls of the home to prevent cold air drafting prob-
lems. The chase should not break the outside building
envelope in any manner.
Walls, ceiling, base plate and cantilever fl oor of the chase
should be insulated. Vapor and air infi ltration barriers
should be installed in the chase as per regional codes for
the rest of the home. Additionally, in regions where cold
air infi ltration may be an issue, the inside surfaces may be
sheetrocked and taped (or an equivalent method may be
used) to achieve maximum air tightness.
To further prevent drafts, the wall shield and ceiling fi re-
stops should be caulked with caulk with a minimum of
300ºF continuous exposure rating to seal gaps. Gas
line holes and other openings should be caulked with
caulk with a minimum of 300ºF continuous exposure rating
or stuffed with unfaced insulation. If the appliance is being
installed on a cement surface, a layer of plywood may be
placed underneath to prevent conducting cold up into the
room.
NOTICE: Install appliance on hard metal or wood surfaces
extending full width and depth. DO NOT install directly
on carpeting, vinyl, tile or any combustible material other
than wood.
WARNING! Risk of Fire! Maintain specifi ed air space
clearances to appliance and vent pipe:
• Insulation and other materials must be secured to prevent
accidental contact.
• The chase must be properly blocked to prevent blown
insulation or other combustibles from entering and
making contact with fi replace or chimney.
• Failure to maintain airspace may cause overheating and
a fi re.
Heatilator • NBV3630I-B, NBV3933I-B, NBV4236I-B, NBV4842I-B Installation Manual • 2376-980 Rev. F • 7/16
D. Hearth Extension/Floor Protection
WARNING! Risk of Fire! Hearth extension required to
protect combustible fl oors in front of appliance.
Elevated Hearth Systems
Some hearth systems will elevate the appliance off the
fl oor at a given dimension. The elevation will also have
to be added to the rough opening height (header height)
referenced in Figure 3.7. Note: Finished fl oor thickness
should also be considered when determining installation
dimensions.
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