Navien Short Cycling During Demand

Navien water heater frequently shuts off and restarts while hot water is running, causing brief interruptions.

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.

Possible Causes

Oversized unit for low flow demand, Flow sensor reading unstable, Scale causing rapid temperature rise, Incorrect minimum firing rate adjustment (technician setting)

How to Fix / Troubleshooting

Safety: Be cautious of temperature swings during cycling.

Steps:

1. Increase flow: Test by opening an additional hot water tap. If cycling stops at higher flow, the issue is related to low demand versus unit capacity.
2. Clean flow sensor and inlet filter: Remove debris to stabilize flow readings.
3. Descale heat exchanger: Remove scale to reduce rapid overheating and shutdown.

If short cycling continues, a technician may need to adjust combustion parameters or recommend plumbing changes to maintain minimum flow.

Repair Difficulty

Medium 3/5

Required Part

Flow Sensor Assembly

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