Installation Guide
507052-04 Page 31 of 53Issue 1727
Exhaust through Crawl Space Vent Option
All 33” condensing gas furnaces (92%+) are now approved
to be vented down through a crawl space. Ensure a vent
pipe drain kit, 51W18 (USA) or 15Z70 (Canada), is used as
directed through the oor joists and into the crawl space.
See the following gures.
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 (51W18)
Drain Plug (15Z70)
Clamp
(51W18 Only)
From
Furnace
To Vent
Termination
Drain Trap
(assembled)
Figure 43. Kit 51W18 (USA) / 15Z70 (Canada) Parts
Identication and Assembly
Exhaust from
Furnace
To Termination
Exhaust from
Furnace
To Termination
* Kit 51W18 is shown.
Figure 44. Crawl Space Vent Pipe Drain Trap
Assembled Incorrectly
Figure 45. Upow or Downow Furnace with Exhaust through Crawl Space
KIT 51W18 (USA)
Basement Floor
To Termination
1/2” PVC to
Code-Approved
Drain
24” max.
Downflow Furnace
Exhaust
KIT 15Z70 (Canada)
* Kit 51W18 is shown.
NOTE: Upow furnaces exhaust from the left side. All dimensions shown are typical for upow or downow 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.