though a failing internal relay in the control board can also be the culprit

Optional Purification: Available with integrated filtration for applications requiring oil-free and particulate-free air delivery

Designed for professional HVACR control applications

it will not generate the vacuum needed to close the pressure switch

Lochinvar & A.O. Smith 100271315 Limit Switch 30067439-890 though a failing internal relayThe Lochinvar & A. O. Smith 100271315 Limit Switch is a critical safety component engineered for high performance hydronic and water heating systems. As a veteran technician knows, maintaining the integrity of the safety loop is non negotiable. This OEM high limit switch is designed to monitor outlet water temperature and provide a positive safety shutdown by interrupting the electrical circuit if temperatures exceed the factory set threshold,