This 117U1021 relay replaced 117U1001 and functions as a current-operated switch to manage the start winding circuit during the initial torque phase

making it a critical stock item for maintaining system uptime

making it versatile for various regional equipment setups

this replacement knob retains the same physical dimensions and stem attachment for both the original series and the newer Lead-Free (LF) versions of the Watts 70A valves

Leak Prevention: Maintains a secure seal to prevent water damage to the combustion chamber and burner tray

Modine 5H0730570003 Block Vent Switch This 117U1021 relay replaced 117U1001The Modine 5H0730570003 Blocked Vent Switch is a critical safety component engineered to monitor flue gas temperatures and prevent hazardous operating conditions. This genuine OEM replacement part is specifically designed for Modine PD400 and BD400 unit heaters, serving as the direct functional successor to the legacy 5H73057 3 model. Operating as a manual reset safety switch, it is calibrated to trip when vent temperatures reach 200F (93C),