What should be assessed first when a heating system is not producing heat?

When addressing a heating system that is not producing heat, the thermostat settings are the most logical first step to assess. The thermostat is the control mechanism for the heating system and directly influences its operation. If the thermostat is set incorrectly—whether it's set to "off," the temperature is too low, or the programming is incorrect—it can prevent the heating system from activating.

By checking the thermostat first, you can eliminate a simple and common issue that might lead to no heat production. If the thermostat settings are found to be appropriate, the next steps could include examining the furnace or boiler operation, the condition of the ductwork, and the insulation levels. However, starting with the thermostat saves time and effort, as it is often the root cause of heating issues.