Constructing The Appliance Chase - Majestic MERCURY Series Installation Manual

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 firestops and wall shield
firestops 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.
NOTICE: Where required by code, install only sprinkler

heads with a sprinkler activation temperature classified
as Extra High.
•
Sprinklers inside of chase: Keep sprinkler head away
from vent and chimney.
•
Heat Management applications: Maintain 36 inches of
clearance to openings from which heat is discharged
such as heat zone registers, etc. Refer to Section 6.B
for Heat Management options allowed for this appliance.
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 floor of the chase
should be insulated. Vapor and air infiltration barriers
should be installed in the chase as per regional codes for
the rest of the home. Additionally, in regions where cold
air infiltration 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 fire-
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 in-
stalled 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 specified 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 fireplace or chimney.
• Failure to maintain airspace could cause overheating
and a fire.
12 Majestic • MERC32IN, MERC32IL Installation Manual • 2401-980 Rev. L • 1/21