Heater shuts down with F05; water is hot but unit stops before reaching set temperature.

Safety first: Turn off power and allow the heater to cool before servicing. Hot water and surfaces can cause burns.

• Check water flow: Ensure the pool pump is running at full prime and that all valves to and from the heater are fully open. Clean the pool filter if pressure is high.
• Inspect bypass: If your system has a manual or automatic bypass around the Nirvana heater, verify it is adjusted correctly to allow sufficient flow through the heater.
• Bleed air: Some Nirvana models have a manual air bleed on the top of the heat exchanger. With pump running and heater off, carefully open the bleed screw to release trapped air until water flows steadily.
• Check high limit switches: Locate the Nirvana high limit thermostats on the water manifold. Inspect wiring and connections. If a limit is repeatedly tripping, it may be weak and require replacement, but also indicates an underlying flow or scaling issue.
• Descale (professional): Heavy scale inside the heat exchanger can cause localized overheating. A technician can chemically descale the Nirvana copper or cupronickel heat exchanger.