Heater starts but shuts off after a few minutes; water is only slightly warm.

Safety first: Turn off power before accessing internal components.

• Monitor display: Watch the Nirvana display during operation for any brief error messages or temperature spikes.
• Check flow and filter: Ensure the pump is running properly and the filter is clean. Verify that the heater bypass (if present) is not diverting too much flow.
• Inspect high limits: Lightly tap the Nirvana high limit switches and check for loose connections. Replace if they trip at normal operating temperatures.
• Sensor comparison: Compare inlet and outlet temperature readings (if available). Unrealistic readings may indicate a bad sensor.
• Ventilation: Ensure the heater has adequate clearance and ventilation to prevent control board overheating.