SFS2
Raypak
Secondary Stack Flue Sensor Fault
Display shows 'SFS2' and heater locks out; indicates secondary flue temperature fault.
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Failed secondary flue sensor, Loose sensor wiring, Localized hot spot in flue collector, Incorrect sensor installation depth
How to Fix / Troubleshooting
Safety first: Turn off power and gas. Allow flue components to cool.
Steps to address SFS2 error:
- Locate secondary flue sensor: Identify the additional sensor in the flue collector or vent collar. Check mounting and ensure it is fully seated.
- Inspect wiring: Look for heat‑damaged insulation or loose connectors. Reseat plugs at the control board.
- Test sensor resistance: With power OFF, disconnect and measure resistance. Compare to Raypak’s chart. Replace if out of range.
- Check for localized blockage: Inspect the area around the sensor for soot buildup or partial blockage that could cause localized overheating.
Warning: Do not operate the heater with a known flue sensor fault until the cause is corrected.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Secondary Stack Flue Sensor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements