Noritz water heater cycles on and off rapidly when a small hot water demand is present (e.g., handwashing).

Safety first: Water temperature may spike during cycling; use caution.

Steps to check and correct:

• Increase flow: Open the hot tap more fully or run an additional fixture to keep flow above the minimum required by the Noritz unit.
• Upgrade fixtures: Replace extremely low-flow showerheads or faucets with models that provide adequate flow for tankless operation.
• Adjust mixing valves: Reduce excessive mixing at point-of-use valves that may be throttling flow through the heater.
• Consider recirculation: For chronic low-flow issues, consult a Noritz installer about adding a recirculation system compatible with your model.