User Guide

507716-01 Page 33 of 58Issue 1717
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 Identication and
Assembly
Exhaust from
Furnace
To Termination
Exhaust from
Furnace
To Termination
Figure 50. Kit 51W18 Trap Assembled Incorrectly
Figure 51. Upow or Downow Furnace with Exhaust through Crawl Space
KIT 51W81
Basement Floor
To Te rmination
1/2” PVC to
Code-Approved
Drain
24” max.
Downflow Furnace
Exhaust
NOTE: Upow furnaces exhaust from the left side. All dimensions shown are typical for upow or downow 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.