specifically the AT-11-399 and AT-21-403 series

check the ignitor resistance (ohms)

Engineered for universal refrigerant compatibility

the B250 is specifically engineered for chilled or hot water and glycol solutions

While sized at 1/2"

Sterling 11J11R06778-002 Pressure Switch Els PW 17895 specifically the AT-11-399 and AT-21-403The Sterling 11J11R06778 002 Pressure Switch is a critical safety and operational component designed for high performance HVAC system pressure monitoring. This OEM replacement part, which is technically identical to model J11R06778 002, ensures that your furnace or air handler operates within precise atmospheric parameters. Built to withstand the rigorous demands of industrial and commercial heating applications, this switch facilitates accurate