Plan Your Installation
CLEARANCES TO COMBUSTIBLES
ABOVE TOP OF | FROM THE | FROM SIDES | FROM CHIMNEY | 6 FT OF | 6 FT OF |
WARM AIR PLENUM | FRONT | AND BACK | CONNECTOR | PLENUM | PLENUM |
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6” | 48” | 18” * | 18” | 6” | 1” |
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Floor Joist or Combustible Material
! CAUTION !
BE SURE TO INSTALL DUCT WORK
WITH CLEARANCES SHOWN
6 Inches
WARM AIR
PLENUM
FURNACE
6 Feet
1”
Heat Supply
Ducts
1” CLEARANCE TO COMBUSTIBLES BEYOND 6’ TO A POINT WHERE THERE IS A CHANGE IN DIRECTION OF
90 DEGREES OR MORE.
8” Dia.
18” 
MIN
Combustible
NOTE:
DUCT AND PLENUMS SHALL BE CONSTRUCTED ENTIRELY OF
Flue Pipe
Top View
Cold Air
Plenum
Top View
Warm Air
Plenum
Walls 
18” MIN 
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
SERVICE CLEARANCE OF 24 INCHES MINIMUM REQUIRED TO SERVICE BLOWER
FIG. 4
FLOOR TO BE | 12 |
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