The LPS Low Pressure Switch electrically shuts off the booster pump if the feed water is interrupted. The LPS is designed to be mounted on the inlet side of the pump. Although the pump will not be damaged if operated without feed-water, pumping air into the membrane for extended periods can damage the module. We strongly recommend this device for applications where feed-water shut-off or interruption can occur. The LPS includes a wiring harness (not shown) that interconnects a pump and transformer. Specifications:Material: Wetted parts are FDA Approved or NSF listed Connection: 1/8" Male NPT thread Pressure Switch Closed: @ 5 PSI or more Pressure Switch Opened: 1 - 5, Preset @ 2.3 PSI Electrical: 125 - 250 VAC, 15A Max. Power: Compatible with 110V or 220V transformersSustained Operating Pressure: 50 PSI Max. Top Terminal: Common LeadMiddle Terminal: Normally Open LeadBottom Terminal: Normally Closed LeadAccessories: Wire Harness # 21-028 to connect to pump and transformer