What is the main cause of a primary control relay chattering?

The primary cause of a primary control relay chattering is low voltage. When the voltage supplied to the relay is below the required threshold, the relay cannot maintain a stable connection. This results in the relay repeatedly opening and closing, or "chattering," which can lead to erratic operation of the heating system.

Low voltage can be caused by various factors such as voltage drops due to long wire runs, inadequate wire sizing, or issues with the power supply. Ensuring that the voltage is within the specified range is crucial for the reliable operation of the control relay and the overall system.

Other factors like high fuel pressure, mechanical failure, or incorrect wiring can contribute to operational issues, but they do not typically cause chattering in the relay itself. Understanding the relationship between voltage levels and relay operation is key for troubleshooting and maintaining efficient heating systems.