HVACopediaTrane · Furnace troubleshooting
Venting through a ceiling
What is going on
When a furnace vent passes through a ceiling, you need a proper firestop and a sealed support flange. I have seen vents just poked through a hole with nothing around them, and that is a fire and smoke path. Do the firestop right and seal everything that touches the flue.
Likely causes
- No firestop around the vent where it passes through the ceiling
- Unsealed flange, pipe or coupling letting flue gas into the space
- Clearance to combustibles not respected for the pipe material
Check in this order
- Build the firestop from galvanized sheet metal with a 3-7/8 in diameter hole for the support flange (12 in x 12 in panel, or 12 in diameter minimum).
- Seal the flange, pipe, coupling and metal panel with high-temperature RTV silicone sealant.
- Keep 0 in clearance for PVC vent pipe and 1 in clearance for Type 29-4C stainless vent pipe.
- Inspect the finished penetration from both sides for gaps.
Applies to: Vent through a finished ceiling
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Source: Trane installer's guide, 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.