F9
Peerless
Safety Limit Circuit Open
Boiler shows F9 and may indicate 'Limit String Open'
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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.
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Possible Causes
Open rollout switch, open blocked vent switch, tripped manual reset limit, broken safety wiring
How to Fix / Troubleshooting
Safety first: Turn off power and gas. Do not bypass safety switches.
Steps:
- Locate safety string: Follow the low-voltage safety circuit from the control through rollout switches, blocked vent switch, and high limits.
- Check each switch: Inspect for manual reset buttons (often on rollout or blocked vent switches). If tripped, investigate cause (flame rollout, vent blockage) before resetting.
- Inspect wiring: Repair any broken or disconnected wires in the safety loop.
- Test continuity: With power off, test each safety device with a multimeter. Replace any that remain open when conditions are normal.
- After repair: Reset the boiler and monitor operation closely.
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Repair Difficulty
Hard
4/5
Required Part
Flame rollout switch
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