Boiler runs but room temperature overshoots or undershoots setpoint significantly.

Safety: No special hazards; do not open the boiler casing for control adjustments.

Steps:

• Check that the room thermostat is not near heat sources, draughts, or direct sunlight.
• Verify that the thermostat is correctly configured for the heating system type (e.g. on/off vs. modulating).
• If using a Bosch modulating controller, review the heating curve and room influence settings and adjust gradually.
• Replace batteries in wireless thermostats and ensure good signal.

If control remains poor, a heating engineer should review system controls and wiring.