Lochinvar & A.O. Smith 100113144 Switch 321894-709 which means the contacts close

which means the contacts close at 28°F to signal the defrost board and open again at 70°F once the coil is sufficiently warmed

provided the connector matches

eliminating the guesswork during field installation

Built with industrial-grade relays and digital signal processing

Lochinvar & A.O. Smith 100113144 Switch 321894-709 which means the contacts closeThe Lochinvar & A. O. Smith 100113144 Blower Prover Switch is a critical safety component designed for high efficiency water heaters and commercial boilers. As a direct OEM replacement for NS2 1333 01, this pressure switch (often referred to as an air pressure switch or draft prover switch) monitors the differential pressure created by the inducer motor. By verifying stable airflow, it ensures the sequence of operation proceeds to ignition safely.