Boiler cycles on and off rapidly when only domestic hot water is used (combi models)

Safety first: Turn off power and close water valves before removing any DHW components.

• 1. Observe flow conditions: Note if cycling occurs only at very low hot water flows (e.g., handwashing). This may be normal to some extent.
• 2. Clean inlet screens: Check and clean any cold water inlet screens or filters on the combi boiler.
• 3. Exercise flow sensor: Some models use a turbine or paddle flow sensor. If accessible, remove and clean debris or scale from the sensor.
• 4. Descale DHW heat exchanger: If hot water output is also reduced, professional descaling of the plate heat exchanger may be required.