How to Fix / Troubleshooting

Safety first: Adjust only user-accessible controls unless you are a qualified technician.

Check thermostat location: Ensure the room thermostat is not near radiators, sunlight, or drafts. Relocate if necessary.
Adjust setpoints: Reduce flow temperature setpoint on the furnace to lengthen burner run times.
Enable modulation: If using an on/off thermostat, consider upgrading to a Saunier Duval modulating eBUS controller for better load matching.
Hydraulic adjustments: A heating engineer can adjust bypass valves and system design to reduce short cycling.

Furnace frequently cycles on and off, short burner run times, room temperature unstable

Possible Causes