A.O. Smith Flow Modulation / Minimum Flow Issue

A.O. Smith tankless water heater cycles on and off during use, causing temperature swings.

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

Flow rate below minimum activation, Clogged inlet filter, Oversized unit for low-flow fixtures, Temperature set too high causing short-cycling

Safety: Turn off both electrical power and gas supply before cleaning any filters.

1. Increase flow: Open the hot water tap further or use a higher-flow showerhead to maintain the flow rate above the heater's minimum activation threshold.
2. Clean inlet filter: Remove and thoroughly clean the cold water inlet filter screen on the tankless unit.
3. Adjust temperature: Lower the set temperature to reduce the need for cold water mixing, which can help stabilize the flow.
4. Descale: If mineral scale restricts internal passages, perform a descaling procedure according to the manufacturer's instructions.

Medium 3/5

Cold Water Inlet Filter Screen

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