HVACopediaAllied · Furnace troubleshooting
Exhaust piping installation
What is going on
Exhaust runs under positive pressure and must be sealed completely to keep flue products out of the living space.
Check in this order
- Where pipe passes a joist or wall, make the hole large enough to clear the pipe on all sides.
- Support pipe 5 ft between hangers for schedule 40 PVC, 3 ft for other pipe.
- Isolate the pipe where it exits the wall or roof to stop vibration transfer.
- Route the pipe outside and follow the termination section.
- Slope all horizontal exhaust runs back toward the unit at least 1/4 in. per 12 in. of run.
- Check that there are no sags or low spots in the exhaust piping.
- Glue exhaust pipe to the furnace exhaust fitting.
- If the furnace is in a seasonal home, provide a way to drain condensate from the trap and lines.
Applies to: Exhaust venting on 92G1UH
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Source: Allied 92G1UH installation manual, p. 20-21 (PDF p. 20-21). 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.