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For equipment of this type, National Fire Protection Agency (NFPA) Standard No. 90B specifies the minimum
standard clearances to combustible surfaces as summarized below:
Above Top of Plenum ........................................
From the Front .................................................. 48"
From Sides and Back .......................................
From Flue Pipe .................................................. 18"
From Back ......................................................... 10"
DUCT CLEARANCES FOR SOLID FUEL
DEVICES WITH BLOWER ASSEMBLY
FLOOR JOIST OR
COMBUSTIBLE
6"
MATERIAL
SUPPLY
AIR
3"
PLENUM
FURNACE
CLEARANCE TO
COMBUSTIBLES
10"
MINIMUM
COLD AIR
RETURN
6" DIAMETER
FLUE PIPE
RECT.
DUCT
FLOOR TO BE
NON-COMBUSTIBLE MATERIAL
Figure 2
BOX 422 • TOWER, MN 55790 • USA • Tel (218) 753-2330 • www.lamppakuuma.com
1"
HEAT SUPPLY
DUCTS
1" CLEARANCE TO
COMBUSTIBLES
BEYOND 6' - 0"
6"
SIDE VIEW
COMBUSTIBLE
WALLS
6"
MINIMUM
WARM AIR
DUCT
6"
From Horizontal Warm Air Duct:
Within 3 feet of Plenum .....................................
6"
Within 3 to 6 feet of Plenum .............................
Beyond 6 feet of Plenum ..................................
Area between the furnace and combustible ducts
are insulated according to NFPA Bulletin 90B. This
copyrighted book is available from National Fire Pro-
tection Association, 60 Batterymarch Street, Boston,
Massachusetts 02110.
5
Figure 34
U-BRICK
RETAINERS
GRATE
6"
6"
1"
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