HVACopediaTrane · Furnace troubleshooting
Freeze protection and drain pipe sizing
What is going on
Frozen condensate lines block drains and shut the furnace down. Freeze protection and pipe size rules apply.
Likely causes
- Condensate drain line installed in an unconditioned space
Check in this order
- Use 1/2 in or larger PVC or CPVC pipe and fittings for drain connections.
- Use a corrosion-resistant condensate pump if the system needs one.
- If the drain runs in an unconditioned space, apply UL-listed heat tape rated 5 or 6 watts per foot at 120 V, self-regulating preferred, and install per the heat tape maker's instructions.
- Where manifolded with evaporator drains, run a primary drain vent stack that ends below the secondary heat exchanger drain outlet.
- If the furnace is over a finished ceiling, route the stack overflow into an auxiliary drain pan.
Applies to: All condensate drain piping
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Source: Trane installer's guide, p. 28. 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.