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5
Above Top of Plenum
........................................
6”
From the Front
.................................................. 48”
From Sides and Back
.......................................
6”
From Flue Pipe
.................................................. 18”
From Back
......................................................... 10”
From Horizontal Warm Air Duct:
Within 3 feet of Plenum
.....................................
6”
Within 3 to 6 feet of Plenum
.............................
6”
Beyond 6 feet of Plenum
..................................
1”
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.
For equipment of this type, National Fire Protection Agency (NFPA) Standard No. 90B specifies the minimum
standard clearances to combustible surfaces as summarized below:
DuCt CLearanCeS For SoLID FueL
DeVICeS WItH BLoWer aSSeMBLy
Figure 2
3”
6”
6”
10”
MInIMuM
1”
6”
MInIMuM
FLoor JoISt or
CoMBuStIBLe
MaterIaL
Heat SuPPLy
DuCtS
1” CLearanCe to
CoMBuStIBLeS
BeyonD 6’ - 0”
SIDe VIeW
FurnaCe
SuPPLy
aIr
PLenuM
CLearanCe to
CoMBuStIBLeS
CoLD aIr
return
6” DIaMeter
FLue PIPe
reCt.
DuCt
FLoor to Be
non-CoMBuStIBLe MaterIaL
CoMBuStIBLe
WaLLS
WarM aIr
DuCt
Figure 34
Grate
u-BrICk
retaIner
