FC
Hayward Pool Heater
Severity:What Does This Error Mean?
FC on a Hayward HD-series pool heater means the flue or condensate drain has detected a fault — usually a blocked vent, blocked condensate trap, or vent fan failure. Inspect the vent termination outside and check the condensate drain is not frozen or clogged.
Affected Models
- Hayward HDF400
- Hayward Universal H-Series HD
- Hayward Omni HD
- Hayward H400FDP
- Hayward HD400FN
Common Causes
- Vent termination outside blocked by leaves, snow, or insect nest
- Condensate drain trap clogged or frozen
- Inducer (vent) fan failed or running slow
- Vent pressure switch failed or tubing disconnected
How to Fix It
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Power off the heater.
Switch the heater off at the breaker. FC is a safety-critical fault — operating with a venting issue risks carbon monoxide release and fire. Confirm the heater is fully off before any inspection.
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Inspect the outside vent termination.
Locate the vent pipe exit on the outside of the equipment area. Check for leaves, snow, ice, insect nests, or anything blocking the vent. Clear any debris carefully.
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Check the condensate drain.
The condensate drain runs from the bottom of the heater to a drain or grade. Confirm it is not pinched, frozen, or clogged. Frozen condensate is a common winter cause of FC in colder climates.
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Look for visible damage to the vent piping.
PVC or stainless vent piping should be intact along its full length. Cracks, melted spots, or sagging sections all cause FC. Damaged vent piping is not user-repairable — book service.
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Book a gas-qualified technician.
Persistent FC after cleaning the vent and condensate path requires service. The technician will test the inducer fan, vent pressure switch, and condensate trap. Repair costs vary widely — USD 200–600 depending on the part.
When to Call a Professional
Flue and condensate work requires a gas-qualified technician on HD-series heaters. Do not attempt internal inspection — improper venting risks carbon monoxide release.
Frequently Asked Questions
Is FC dangerous to ignore?
Yes — a venting fault can cause carbon monoxide to back up into the equipment area instead of venting outside. While most pool heaters are outdoors and CO disperses, indoor or shed-mounted heaters with FC faults are a serious hazard. Resolve before reuse.
Can cold weather alone cause Hayward FC?
Yes — frozen condensate is a very common cold-weather cause. Hayward HD heaters condense large amounts of water vapour during operation, and the drain line can freeze in temperatures below -5°C (23°F). Insulate or heat-trace the condensate line in cold climates.