What should be done first when troubleshooting a non-operational hydronic system?

When troubleshooting a non-operational hydronic system, the first and most critical step is to check the power supply to the system components. Ensuring that the system has power is fundamental because many issues can stem from a lack of electricity reaching the boiler, pumps, or other essential components. If there’s no power, the entire system will be non-functional, regardless of the condition of the thermostat settings, valves, or the need to bleed radiators.

If you were to start with the thermostat settings, although important, it rests on the assumption that the system is powered. Similarly, inspecting valves for leaks or bleeding radiators only addresses potential issues that would be relevant after confirming that the system is receiving power. Without addressing the power supply first, you could be overlooking the simplest and most likely cause of the system's failure to operate. Therefore, verifying the power supply lays a solid foundation for any subsequent troubleshooting efforts.