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Trane · Furnace troubleshooting

Air for combustion and ventilation in non-direct vent installs

UH1/DH1

What is going on

On non-direct vent UH1/DH1 installs the furnace draws combustion air from the room, so the air openings have to stay open and clear. Starving a furnace of air can cause poor combustion, flame rollout or carbon monoxide, so confirm the supply before leaving, and have a licensed installer size anything in doubt.

Likely causes

  • Not a fault call. Combustion air requirement for non-direct vent installs.

Check in this order

  1. Confirm combustion air openings are free of anything that restricts airflow.
  2. Plan for future remodels so the furnace room keeps free airflow and openings do not get blocked.
  3. Size and provide air per the National Fuel Gas Code, ANSI Z223.1 / CAN/CGA B149.1, or local code.
  4. Consider mechanical exhaust fans and fireplaces, which can disturb furnace operation by pulling air out of the room.
  5. After the install, check draft and flame behaviour with the exhaust fans running.
  6. Test for carbon monoxide at the vent and in the living space.

Applies to: Non-direct vent UH1/DH1 furnaces

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Source: Trane installer's guide 18-CD29D1-11, p. 6. 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.