HVACopediaGoodman · Furnace troubleshooting
Direct vent (dual pipe) routing and terminations
What is going on
Direct vent uses separate combustion air intake and vent pipes, run horizontally through a side wall or vertically through the roof.
Check in this order
- Run the intake and vent pipes both horizontally or both vertically.
- Pipes run through an unused chimney must extend at least 12 in above the chimney top.
- Close the space between the pipes and chimney with weather tight, corrosion resistant flashing.
- Keep intake and vent terminations in the same atmospheric pressure zone.
- For an alternate horizontal termination, keep at least 12 in between intake and vent and keep 3 to 24 in between the pipes.
- Use 90 degree elbows for the alternate termination, as shown in the figures.
- Intake may be snorkeled to get 12 in minimum ground clearance.
- If the intake runs above a finished ceiling or where condensate drip is a problem, insulate it with 1/2 in thick closed cell foam (such as Armaflex or Insultube).
Applies to: Direct vent installations
More furnace guides
- Airflow lower than demanded, furnace runs on low stage when high stage is expected
- Alternate combustion air opening (upflow or horizontal)
- Alternate vent/flue location (upflow or horizontal left)
- Annual inspection checklist
- Auxiliary limit control (location and purpose)
- Auxiliary limit switch open (blower compartment)
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Source: Goodman GMVC96 service manual, p. 16-17. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.