A boiler that keeps shutting off may be completing unusually short normal cycles or entering a lockout because of pressure, temperature, flow, ignition, or venting. The key is distinguishing short but controlled cycling from a shutdown with a fault code. Note when it happens and what the display shows before resetting.
Distinguish short cycling from a fault lockout
If the flame stops at setpoint and returns later without an error, demand or system sizing may be involved. If a code appears and a reset is required, treat the event as a fault rather than normal operation.
Check accessible pressure and circulation clues
Pressure outside the manufacturer range, too many closed emitters, or air in the circuit can affect operation. Check accessible controls and visible leaks; do not remove the casing or work on energized internal pumps or valves.
Note whether shutdown happens only on hot water or heating
A combi boiler that fails only during showers points to a different path than one that locks out only while heating radiators. Duration, fault code, pressure, and operating mode are more useful service information than repeatedly resetting it.
Repeated lockout needs professional diagnosis
Do not bypass sensors or defeat temperature or combustion limits. If you smell gas, leave and call from outside. Otherwise, stop using the unit when the same fault keeps returning, especially with overheating, unusual noises, or pressure loss.
Sources
- U.S. Department of Energy — Energy Saver — Practical information on home heating, cooling, thermostats, maintenance, and efficiency.