Square D - 9013GSG2J21 - Pressure Switch 575VAC 5HP G +Options - Allied Electronics & Automation, part of RS Group

What’s a Pressure Switch? A well water pressure switch helps to control a well pump system which helps provide water to a household or business. The pressure switch has a spring on the inside that’s connected to electrical contacts. As time goes on, the spring becomes weak and the electrical contacts wear out which can make it seem that your pump isn’t working quite right. It is used with submersible well pumps and jet pumps. What does 20/40, 30/50, 40/60, 50/70, and 60/80 mean? These numbers represent the pressures that your pressure switch is tuned to in the water line. The first number is what tells the pressure switch to send a signal down to your pump to turn on. The second number tells the pressure switch to send a signal down to your pump to turn off. You may hear the terms “cut-in pressure” and “cut-off pressure” = cut-in pressure / cut-off pressure. When you open up a faucet the pressure drops. For example on a 40/60 pressure switch (most popular option) a home’s water pressure sits at 60 psi. When someone opens up a faucet, it goes from 60 psi down to 40 psi. The pressure switch senses the drop to 40 psi and that’s when it sends an electrical signal down to the pump to turn on. When you turn the faucet off, the pump will continue to pump until the pressure gets back to 60 psi and that’s when the pressure switch will send a signal to your pump to turn off. Side Note: Your water pressure tank should be set to 2 psi below the cut-in pressure (low number). For example 40/60 psi, the tank should be set to 38 psi.