Pressure switches are commonly used across many aerospace, defense, and industrial applications to provide systems with an on or off capability–either towards the rise or fall of pressurized fluids. Understanding how to properly manage and control these switches can be helpful when choosing a solution for a given operation. The following guide will cover best practices and steps for troubleshooting the latest pressure switch designs.
How To Wire A Pressure Switch
Wiring a pressure switch is a fairly simple process, and it only takes a few tools to get the job done. Before we learn how to wire a pressure switch, it’s important to identify the basic parts. We’ve included a wiring diagram to further illustrate the frame and design of each component. 
The model shows our 6900GE and 6900PE aluminum-gage pressure switches, made specifically for hazardous environments. Switches are often used as a primary mode for opening and closing an electrical circuit. The wiring can change from single make and break circuits to multi-makes and break circuits. While the mechanics are pretty straightforward, the proper circuit must be chosen for the right application. Let’s take a closer look at each circuit style and how it can be used in a system.
Single Pole Double Throw Switch Wiring
Single pole double throw (SPDT) pressure switch contacts are used for feeding power from one source into two separate connections. Normally open (NO) switches make an open circuit in its normal or default connection, while normally closed (NC) switches do the opposite. Microswitches are typically in the original state of a normally closed connection, which means a red wire is connected to a brown wire. But when the pressure switch is actuated, the microswitch will change from an NC, red-brown frame into an NO or blue-brown connection. Once the switch deactuates, it will return to its original state of an NC connection.
Double Pole Double Throw Switch Wiring
Additionally, double-pole, double-throw (DPDT) switch contacts have one input and four outputs. This type of configuration allows the input to have two corresponding outputs that it connects to. When the pressure switch is in its original state, the NC has one common, one red-brown wire connection along with the normally closed two common, two black-yellow wire connections. The pressure switch will actuate when the microswitch changes to a NO one common, one blue-brown connection to a NO two common, two yellow-purple connection. Just like an SPDT, the pressure switch will return to its original status when it deactuates.
How To Install A Pressure Switch
After wiring the pressure switch, you will then screw it on the pressure line using a wrench on the hex nut connection (which sits at the top of the process connection threading). Remember to tightly squeeze the male pipe using applied force. Here are some other things to consider when installing your pressure switch.
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- The units can be set up in any position on a flat surface using two mounting holes and M5 screws that are at least 50 mm long.
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- Most of these units are made with female ports, which are suited for connections to National Pipe Tapered (NPT) nipples or channels with a limited installation torque of 12 ft. We also recommend using either a union or bendable tubing for this process.
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- Be sure to avoid extreme rotation on all threaded connections.
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- A pipe joint sealing compound is the preferred method over Teflon tape. However, both ways are acceptable–as they prevent sealing material from entering into pressure switches or plumbing.
How To Test A Pressure Switch
Testing your pressure switch is a critical step in ensuring the operational quality and safety of your equipment. You will be following the same steps from the pressure switch installation process, with the exception of a testbed.
Setup & Testing
Step 1: Connect the pressure switch to a source. The most common types of pressure sources come from a pump, compressor, or an air tank. If you are using a compressor or pump, turn it on to release pressure through the piping that is connected to a series of manifold outlets leading to the pressure reader or gauge and switch. The gauge will provide a read-out of the same pressure that is being applied to the switch, confirming its actuation and deactuation points. At this stage, no air or oil is being released into the environment. Step 2: Install the pressure switch by wiring it to a lightbox with an electrical connection. When your switch is attached to the lightbox and accuates, it will turn from red to green. After de-actuation, the switch will go back from green to red. Step 3: Once everything is set up, you are ready to apply pressure to the switch. Next, turn the valve to allow air or oil to reach the system. Just like the previous step, you’ll know when it actuates when you see the light turn from red to green. The pressure gauge should then be checked to record its reading and confirm actuation. Lastly, close the valve to stop the switch from receiving any pressure. As the pressure decreases, it will cross a deadband period and attain full deactuation. The pressure gauge should be monitored to record its reading and confirm deactuation. By this time, the pressure is released to an ambient level.
Replacing & Adjusting The Pressure Switch
Replacing a pressure switch is very similar to its installation method, except it is in reverse. Simply, dewire the connection and screw the pressure switch off of its line. Although pressure settings are internally adjustable, this is not applicable if units are fixed setpoint units. If the electrical circuit can’t be used for testing, disconnect electrical power and use a suitable circuit tester or lightbox. To adjust a pressure switch, loosen its access cover and turn the adjustment screw using a screwdriver slot as illustrated. You can then turn it clockwise to increase settings or turn counterclockwise to decrease the setting. After you’ve finished adjusting the switch, re-tighten the access cover, reconnect the electrical circuit, and return power to the unit. To learn more about CCS pressure switches and how they operate in your industry, take a look at our product page or contact us directly.