Honeywell Discontinued: Valve proving system A4021
Kromschroeder alternatives for A4021/A8041 Valve Proofing System. Replaces both the control unit and gas pressure switch. Only needs extra tube connection upstream the first valve.

Functional replacement for A4021A1002 (220/240Vac). Replaces the gas pressure switch that monitors the pressure between valve 1 and 2. Additional tube is needed to measure the pressure upstream of the first valve.