Boiler or heat source runs continuously even when all Danfoss Ally thermostats show no heat demand.

Safety first: Isolate power to the boiler and control circuits before inspection.

Steps:

• Identify control path: Determine which device (Ally thermostat, boiler interface, or other controller) is actually switching the boiler.
• Inspect relay contacts: If using an external relay or contactor controlled by Ally, check for welded contacts and replace the faulty relay.
• Check wiring: Ensure there is no permanent live feed bridging the boiler’s control input.
• Test with thermostat disconnected: Temporarily disconnect the thermostat control wires at the boiler. If the boiler still runs, the fault is in the boiler or another controller, not the Ally system.