Boiler short cycles, turning on and off frequently without satisfying thermostat

Safety: Turn off power before adjusting internal controls.

Steps:

• 1. Check thermostat location: Ensure it is not near heat sources or in direct sunlight. Relocate if necessary.
• 2. Review aquastat settings: On boilers with adjustable aquastats, verify the high limit and differential are set per Slant/Fin recommendations. Increasing the differential can reduce cycling.
• 3. Confirm flow: Make sure all zones that should be open are calling for heat and that zone valves or circulators are operating correctly.

Professional evaluation: Persistent short cycling may require a technician to assess boiler sizing, control strategy, and possible buffer tank or control upgrades.