Heater does not heat:

— Check the breaker in the fuse panel box.

— Check for adequate water flow.

— Check the voltage at the heater terminals.

— Measure the amps on the elements.

— Turn the heater off and check the heating elements for the proper resistance. If not correct, inspect the heating element.

— Check the heater’s sizing: it may be too small.

Contactor failure – caused by dirty filter, inadequate water flow or undersized field wiring: — Backwash filter, clean skimmer, ensure proper water level.

— Ensure adequate water flow.

— Check for closed valves.

—Check contactor for proper voltage.

— Check for a weak contactor coil.

— Ensure there is no source of chlorine fumes, which can damage electrical components.

Elements were dry—fired:

— Check for closed valves.

— Purge all air from the system before starting the heater.

— Leave the system on for 5 minutes to ensure that the air is completely purged before starting the heater.

— Check for a defective flow switch.

Freeze damage:

— Water left in the heater that was allowed to freeze will cause the tank to crack.

If the pool will be shut down, the heater should be drained.