Pressure switches are designed to sense changes in pressure automatically and are commonly used in systems with pressurized liquids. Many pressure switches can be adjusted on-site, while others require factory-set and calibrated configurations. This makes them an essential tool for keeping pressure-sensitive systems running at optimal levels.
Learning how to adjust your pressure switch properly can take time and effort. In this article, we will cover the basics of pressure switch adjustment, including how to properly modify a pressure switch to ensure the safety of you and your switch. With this knowledge, you can ensure that your equipment runs properly and efficiently.
What is a Pressure Switch?
A pressure switch is a handy and straightforward electromechanical device. It is triggered by pressure to turn an electrical circuit on or off. The pressure point which activates the switch is referred to as its set point, and the pressure threshold which deactivates the switch is known as the cutout point. With these two pressure points, you can easily control the power flow of an electrical circuit.
A pressure switch comprises several components that work together to ensure reliable operation. These components include a diaphragm, adjustment spring, auto/off lever, electrical contacts, and terminals.
- The diaphragmacts as a pressure detection element and is designed to be made of a pliable, pressure-sensitive material. This durable material offers superior responsiveness and accuracy, ensuring an accurate and reliable pressure detection experience.
- An adjustment springto differ the set or cutout points. Some switches have separate springs for controlling the set and cutout points.
- An AUTO/OFF leverto spark off the transfer or to manually flip it off. This lever helps deactivate the switch during installation or maintenance. Sometimes, it may be a knob instead of a lever, but the principle is the same.
- Electrical contactsthat permit modern-day from an outside energy supply to by skip thru them once they touch.
- Terminalsto attach the outside energy supply to the contacts.
There are 2 types of pressure switches: typically open (NO) and typically closed (NC). The open/closed nomenclature indicates the electrical contacts in the switch. In a NO switch, the connections remain open when the pressure is within the acceptable range and close when the pressure exceeds or falls below the allowable range. On the other hand, the NC switch functions the opposite; its contacts remain closed when the pressure is within the acceptable range and open when it exceeds or falls below the acceptable range.
For NC (Normally Closed) switches, the pressure threshold that triggers a change in the state of the contacts varies depending on the application. In some cases, it may be the set point, while in others, it may be the cutout point. To ensure optimal performance, selecting a switch with the appropriate pressure threshold for the application is essential.
HOW PRESSURE SWITCH WORK?
A pressure switch is a passive device that requires pressure to be present for it to function. When the pressure on the diaphragm compresses a calibrated spring, the spring tension will reach or exceed the set point and cause the contacts to move from open to close in a NO switch or closed to open in an NC switch. This makes it easy to configure pressure switches for various applications, as most pressure switches come with at least one pair of NO and one pair of NC contacts.
How to Properly Adjust Pressure Switch?
Cut-In and Cut-Out
Pressure switches offer two key operating points: the cut-in (Reset Point) and cutout (Trip Point) settings. The cut-in factor is for the falling pressure, and the cut-out factor is for the growing pressure. All switches also include a differential or range determined by the cut-in and cutout points. For example, if the cut-in is forty PSI and the cutout is 60 PSI, the differential is 20 PSI. Most switches can be adjusted to adjust the cut-in and cutout points to suit specific applications. So whether you’re looking to control pressure in a tank, pump, or other systems, a pressure switch can give you the precision you need for optimal performance.
Tips for Standard Switch Adjustment
- For optimal protection, disconnect the power to your switch from the power supply before making any adjustments. This will ensure that you and your switch remain safe during the process.
- Once the power is disconnected, measure and record the distance from the exposed thread at the top of the nut to the top of the stud that you are adjusting. Note this measurement in fractions of an inch or millimeters – this will help you return to the same spot if you need to start over.
- Making adjustments to your cut-in and cutout settings is the first step to ensuring the optimal performance of your mechanical system. To do this, use the larger nut to adjust the cut-in setting and the smaller nut to adjust the range. As shown in the picture, adjust the larger nut to increase the cut-in pressure and the smaller nut to change the range. Once you have made the necessary adjustments, you can adjust the differential as a secondary adjustment. This will allow you to fine-tune your system to its peak performance.
- To ensure maximum accuracy and safety when tightening nuts, only turn the nut three times, either up or down, each time. This will help ensure a secure fit and prevent damage to the threads.
Adjusting the Cut-In
Adjusting your switch’s cut-in or cutout settings can be quickly done with a 3/8″ nut driver or socket. Follow the steps below to change the switch while maintaining the same differential.
- Rotate the range nut clockwise to increase the cut-in pressure or counterclockwise to decrease it. Note: adjusting these settings will NOT affect the differential.
- When you adjust the cut-in pressure by a certain amount, the cut-out pressure will automatically adjust to the same amount. This makes it easy to keep the two values balanced, saving you the time and effort of changing the cutout value manually. For instance, if you increase the cut-in pressure by 10 PSI, the cut-out pressure will automatically increase by the same amount.
Monitoring is a Must
Once you have adjusted the pressure switch, monitor the system closely to ensure the pressure setting is correct. Remember that your adjustment to the pressure switch will only be read after the pump has reached its adjusted shutoff. The next cut-in and cut-off pressure is your new setting, so observe this closely to ensure that the unique setting works appropriately.
- Draining the water from your pressure system is easy! By opening the boiler drain or sediment faucet, you can reduce the pressure until it drops below the cut-in point, and your pump will start running again. This simple process ensures that your system runs smoothly and efficiently.
- You can then turn the faucet off.
- Monitor the system’s pressure closely as the pump builds pressure and fills the tank. Keep an eye on the pressure gauge to accurately determine the point at which the pump turns off. Doing so will help ensure that your system runs efficiently without any issues.
- Make sure to repeat adjustments if necessary and keep monitoring for a few more cycles until you reach the desired setting. This will help ensure that you get the precise settings you need.
- When adjusting the pressure setting on a bladder tank water system, it’s essential to keep two things in mind: first, the pressure should be set to 2 PSI below the cut-in point when the tank is empty. Second, the differential between the cut-in and cutout points can only be adjusted up to the minimum and maximum differential published by the switch manufacturer.
Following these guidelines will ensure your system is running safely and efficiently.
Is the Switch Tripping?
If you’re finding that the pressure switch is tripping the cut-in pressure, it’s likely because the tank pre-charge is too close to the switch cut-in. To ensure the switch won’t trip, you must keep a minimum difference of 2-5 PSI between them. So, for example, if the switch cut in is 40 PSI, the tank pre-charge should be no more than 35-38 PSI.
When purchasing a pressure switch, keep in mind that individual testing is not conducted, meaning the switch could be anywhere from 28-48 PSI instead of the advertised 30-50 PSI. Additionally, pressure switches can become stuck, resulting in the switch turning on at 1 or 3 PSI different from one cycle to the next. Lastly, be aware that the ambient pressure can raise the pre-charge in the tank. It’s important to factor these things into your purchase decision.
When adjusting a pressure switch, it’s essential to keep these tips and steps in mind. First, determine the type of pressure switch you have. Different switches have different adjustment steps, so it’s necessary to look into what switch you have and research its specific instructions. Ensure the switch is off before beginning any adjustments. Make sure you understand the switch’s settings and what each adjustment will do. When adjusting a standard pressure switch, refer to its manual for the exact steps. Make sure to change the switch slowly and carefully, as too much or too little pressure can damage the switch. After making adjustments, check the switch to ensure the setting is correct. Following these tips and steps ensures that your pressure switch is adjusted correctly and safely.
BCST has supplied pressure switches and other high-quality control devices for over 21 years. BCST provides these devices for many industries, found in pumps, HVAC and hydraulic systems. We have a large inventory of standard devices and we can custom-design parts for your specific needs.
Don’t hesitate to contact us for more information about our pressure switches or other products.