507715-01
Page 35 of 61
Issue 1716
Exhaust through Crawl Space Vent Option
All 33” condensing gas furnaces (92%+) are now approved
to be vented down through a crawl space. The following
diagrams show the approved methods. Ensure a sanitary
tee is used as directed for condensate control.
Consult the vent tables for vent lengths and approved
materials.
2” or 3”
Sanitary Tee
1/2” PVC
Drain Stub
Drain Trap
Assembly
Rubber Boot
Clamp
From
Furnace
To Vent
Termination
Drain Trap
(assembled)
Figure 49.
Kit 51W18 Parts Identification and
Assembly
Exhaust from
Furnace
To Termination
Exhaust from
Furnace
To Termination
Figure 50. Kit 51W18 Trap Assembled Incorrectly
Figure 51.
Upflow or Downflow Furnace with Exhaust through Crawl Space
KIT 51W81
Basement Floor
To Termination
1/2” PVC to
Code-Approved
Drain
24” max.
Downflow Furnace
Exhaust
NOTE:
Upflow furnaces exhaust from the left side. All dimensions shown are typical for upflow or downflow furnaces.
NOTE:
All horizontal runs of exhaust pipe must slope back toward the kit a minimum of 1/4” (6mm) for each 12” (305mm) to ensure drainage.
