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FIG. 4
12
ABOVE TOP OF
WARM AIR PLENUM
FROM THE
FRONT
FROM SIDES
AND BACK
FROM CHIMNEY
CONNECTOR
6 FT OF
PLENUM
6 FT OF
PLENUM
CLEARANCES TO COMBUSTIBLES
6” 48” 18” * 18” 6” 1”
! !
CAUTION
BE SURE TO INSTALL DUCT WORK
WITH CLEARANCES SHOWN
Floor Joist or Combustible Material
FURNACE
WARM AIR
PLENUM
6 Inches
6 Feet
Heat Supply
Ducts
1”
1” CLEARANCE TO
COMBUSTIBLES
BEYOND 6’ TO A
POINT WHERE
THERE IS A
CHANGE IN
DIRECTION OF
90 DEGREES OR
MORE.
Top View
Top View
Warm Air
Plenum
Cold Air
Plenum
18” MIN
18” MIN
8” Dia.
Flue Pipe
Combustible
Walls
NOTE:
DUCT AND PLENUMS SHALL BE
CONSTRUCTED ENTIRELY OF
SHEET METAL.
* Up to 50% less clearance between combus-
tible walls and chimney connector to furnace
and ducts is allowed if insulated according to
NFPA Standard 90B or your local building
code. This copyrighted book is available from
the National Fire Protection Association, Inc.,
PO Box 9101, Quincy, MA 02269-9101
SERVICE CLEARANCE OF 24 INCHES
MINIMUM REQUIRED TO SERVICE
BLOWER
FLOOR TO BE NON-COMBUSTIBLE MATERIAL