HVACopediaTrane · Furnace troubleshooting
Freeze protection for vent pipe in unheated spaces
What is going on
Vent pipe through unheated space gets insulation.
Likely causes
- Vent passes through an unheated space
- Condensate freezing in uninsulated vent pipe and blocking flow
- Unprotected domestic water pipes, which means the space is assumed to be unheated
Check in this order
- Insulate the vent pipe with 1/2 in (22.7 mm) thick Armaflex-type insulation or equal where it passes through unheated spaces.
- If the space is heated enough to prevent freezing, insulation is not required.
- If domestic water pipes in the space are not protected from freezing, treat the space as unheated.
- Check that the insulation covers the full run, including fittings.
Applies to: Horizontal and exposed vent runs
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Source: Trane AUH1B080A9421B installer's manual, p. 24. 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.