Frequent start-stop of the system, unstable pressure, and excessive energy consumption are often related to the mismatch between the pressure switch and the working conditions. Timely adjustment of the pressure switch can solve these problems. This guide will show you how to adjust it the right way.
When might you need to Adjust a Pressure Switch?
Mismatch between Set Pressure and Actual Working Conditions
The factory settings of pressure switches are mostly generic standard values that are not optimized for specific application scenarios.
For example, in a water pump system, the original setting may cause insufficient water supply pressure or exceed the equipment pressure range. In pneumatic systems, the default value of the pressure switch may not meet the minimum pressure required for some pneumatic tools.
Adjusting the pressure switch can better meet your usage needs.
Short Cycling of Equipment
When the trigger point of a pressure switch is not set properly, the equipment will start or stop frequently, called short cycling. Short cycling will waste energy and accelerate the wear of internal components, increasing maintenance costs.
Properly adjusting the pressure range of the pressure switch can reduce unnecessary cycles, thereby extending equipment life and improving system efficiency.
Setpoint Drift
Mechanical components such as springs and diaphragms inside pressure switches can become fatigued, loose or corroded with use. This can result in a set point drift that can cause the device to miscontact or malfunction. Adjusting the set point of the pressure switch can restore its control accuracy without replacing the switch.
System Changes
After the device has been running for a period of time, your system may undergo structural adjustments, pipeline extensions, and other situations. These changes will affect the pressure distribution characteristics of the system. You need to adjust the pressure switch to match the pressure control with the new operating conditions.
Preparation of the Pressure Switch before Adjustment
Check the Equipment Status
Before opening the pressure switch casing, you need to inspect the overall appearance of the equipment. For example, confirm that the pressure switch has no obvious damage, the wiring is stable, and the connecting pipeline is not leaking or blocked.
If you find any aging, blockage or leakage of components, it is recommended to clean or replace them first.
Prepare Tools
Adjusting the pressure switch requires the use of professional tools to obtain accurate data. Therefore, a precise pressure gauge is necessary. In addition, you also need to prepare tools such as screwdrivers, sockets, wrenches, and insulation tape.
Clarify Target Pressures
You should refer to the equipment nameplate or technical manual to confirm the pressure range of the system, the maximum and minimum pressures allowed for the equipment, as well as the original set value of the pressure switch.
Make sure that the value you want to adjust is not outside the rated range of the system or safety valve.
Record Original Information
Before adjusting, you need to record the current setting value of the switch or the position of the nut. This can quickly restore the original pressure in case of debugging errors. It is also convenient for you to subsequently evaluate the effect of the adjustment.
Steps to Adjust the Pressure Switch
Step 1: Disconnect the Power Supply and Release the Pressure
Before starting the adjustment operation, cut off the power supply of the system. After disconnecting the power, completely relieve any residual pressure in the line. Verify that the pressure gauge reading returns to zero before proceeding.
Step 2: Identify Internal Adjustment Nuts
After opening the housing of the pressure switch, you will see two spring components with adjusting nuts.
Range Nut: It is usually located in the center and larger in size. The range nut is responsible for adjusting the overall pressure range, that is, simultaneously changing the cut-in and cut-out pressures.
Differential Nut: It is usually on the side of the range nut and is smaller in size. The differential nut is used to adjust the pressure difference, which is the difference between the cut-out and cut-in pressure. However, not all pressure switches will have differential nuts.
Remember, adjust the range nut first, then the differential nut.
Step 3: Adjust the Cut-In Pressure
You need to adjust the range nut. Using a socket to turn the range nut clockwise will increase both cut-in pressure and cut-out pressure. If you rotate counterclockwise, both of these values will decrease simultaneously.
For instance, your pressure switch was originally set at 30/50 psi. By increasing the range nut tension clockwise, the cut-in and cut-out pressures can be raised to 40/60 psi simultaneously. Conversely, decreasing the tension counterclockwise will bring the cut-in and cut-out pressures down to 20/40 psi at the same time. The 20 psi differential is always constant.
Step 4: Adjust Differential Pressure
By rotating the differential nut, the cut-out pressure can be changed to adjust the differential pressure.
Turning the differential nut clockwise will individually increase the cut-out pressure, and then the differential pressure will increase. If you rotate counterclockwise, the cut-out pressure will decrease and the differential pressure will become smaller.
Adjusting the differential nut won’t affect the cut-in pressure you just set at all.
Step 5: Test
After completing the setup, install the pressure switch housing back as it was. Make sure that the cover and fasteners are securely installed before reconnecting the device power.
Slowly restore the system pressure and observe whether the switch contacts actuate in time when the pressure rises to the set value. Then, gradually reduce the pressure and check whether the contacts can accurately reset at the preset pressure.
Usually, there will be a slight error during the first adjustment. You need to power off and make further fine-tuning until you achieve the desired pressure control effect.
Step 6: Record
After the adjustment is completed, you can promptly record the adjustment time, the pressure value before and after the adjustment, the system working condition and other information. A complete record can provide a reference for subsequent set point drift.
Precautions for Adjusting the Pressure Switch
Strictly Prohibit the Adjustment with Pressure and Electricity
The internal part of the pressure switch is usually connected to an electrical circuit. After removing the casing, the exposed metal parts are very easy to cause an electric shock accident in a small space. Also, the internal contacts of the switch may be damaged.
If the residual pressure in the pipeline is not released, the pressure medium may suddenly splash during the adjustment process, causing personal injury.
Control the Adjustment Range
Each time you rotate the nut, it is recommended to adjust it by “quarter turn” or “half turn”. Pressure switches are sensitive to the amount of adjustment. A significant rotation of the nut will cause a sudden change in pressure, and it may also cause the spring to trip or get stuck.
Test After Adjustment
Passing a single pressure cycle test does not mean that the switch performance is stable. You will need to repeat the pressurizing and relieving operation 3-5 times to see if the switch contacts act consistently at the cut-in pressure and the cut-out pressure.
Locking Adjustment Nut
After the pressure adjustment reaches the expected value, you should use a wrench to tighten and secure the locknut of the adjusting nut. Vibration during the operation of the device can apply periodic shocks to the unlocked adjusting nut, which can easily loosen it and cause the pressure setting to drift.
Avoid Interference from Environmental Factors
The adjustment of pressure switches should avoid harsh environments such as high temperature, high humidity, and high dust. High temperatures can affect the elasticity coefficient of pressure-sensitive components and cause deviations.
Moisture and dust can get inside the switch and corrode the contacts or block the voltage measurement channel. If you have to make adjustments on-site, you should cover the pressure switch with a dust-proof and waterproof cover. After the adjustment is completed, promptly clean the surface of the pressure switch.
Pressure Switch Adjustment for Different Devices
Well Pump Pressure Switch Specific Adjustment Requirements
In well pump systems, the pressure switch setting also should be matched to the pre-charge pressure of the pressure tank in order to make the system work properly.
In addition to the generic pressure switch adjustment procedure, you must also adjust the pressure tank. This is a unique adjustment step specific to the well pump system.
The pressure tank is partially pre-filled with gas inside and is used to maintain system pressure when the pump is not operating. This pre-charge pressure needs to be set slightly lower than the cut-in pressure of the pressure switch.
In this way, when water usage or pressure drops, the air in the pressure tank can properly compress the water, making the pressure switch promptly trigger the pump to start.
The general recommendation is to set the pre-charge pressure of the pressure tank to be about 2 psi lower than the cut-in pressure of the switch. For example, if the pressure switch is set at 30/50 psi, the pre-charge pressure will be about 28 psi.
After adjusting the cut-In pressure, you will need to empty the tank. Then, use the pressure gauge to check the pre-charge pressure. And use the air pump to increase or release air until it reaches the target pre-charge level.
Air Compressor Pressure Switch Specific Adjustment Requirements
Many air compressors incorporate an unload valve in their pressure switches. The unloading valve releases the pressure between the pump head and the check valve when the compressor stops, helping to make the next start easier.
Before and after adjusting the pressure switch, you should confirm whether the unloading valve is in normal condition.
Troubleshooting after Adjusting the Pressure Switch
The Switch does not Respond or the Pump/Compressor does not Start/Stop
If the system does not respond after adjusting the pressure switch, first check if there are any obstructions inside the pressure switch. This may be due to contamination, jamming, or poor wiring of the internal components of the pressure switch, which prevents it from sensing pressure changes.
You can check if the wires connected to the pressure switch are secure, if the pressure sensing path is blocked, and confirm if the switch itself is damaged. If necessary, clean the pressure sensing port or replace the switch component.
Unstable Pressure Readings or Abnormal Cyclic Behavior
After adjusting the pressure switch, if the pressure reading fluctuates greatly and the system starts and stops frequently, it often indicates that the differential pressure is inappropriate or there is a leak in the system.
You can first confirm whether the actual pressure value is stable through a pressure gauge, and then check if there are any leakage points in the pipeline and joints.
If the short cycle persists, you can consider increasing the differential pressure of the pressure switch appropriately or checking whether there are other pressure disturbance sources in the system, such as abnormal pre-charge pressure of the gas tank.
The Switch Trigger Point does not Correspond to the Measured Value
Sometimes the adjusted set value does not match the pressure gauge reading during on-site testing. This can be caused by calibration deviation of the pressure gauge itself or improper collection position of pressure readings.
You can first compare and test the pressure gauge with calibrated equipment to confirm its accuracy. Make sure the measurement point is close to the position of the pressure switch.
Blockages near the pressure-sensing port can also cause measurement errors. Therefore, during the troubleshooting, you can clean the connector and the filter.
FAQs
Can the Setting Value of any Pressure Switch be Adjusted?
No. Some pressure switches may have a fixed setting and you cannot change the trigger point by adjusting the internal nut. Attempting to force adjustments may damage parts.
Before adjustment, it is advisable to check the specifications and instructions of the pressure switch to confirm whether it can adjust the pressure set point.
How often does the Pressure Switch need to be Readjusted after the Initial Adjustment?
There is no set period for readjustment. It depends on the operating environment and the condition of the equipment wear.
Under stable operating conditions such as low vibration, normal temperature and humidity, you can check it every 6 to 12 months. Or readjust only when the pressure set point drift is detected.
In harsh environments such as high vibration, frequent changes in temperature and humidity, and corrosive media, you need to reduce the inspection period to 3-6 months.
In addition, you must re-adjust after replacing a pressure switch, pressure-sensitive element, or related system component.
Will Different Media Affect the Adjustment of the Pressure Switch?
Yes. Systems that use hydraulic oil need to take into account the viscosity of the oil. High-viscosity oil will delay the transmission of pressure. After the adjustment, it will take a longer time for the pressure to stabilize during the test.
The use of compressed air systems requires the removal of impurities from the air. This is to prevent the pressure tap from being blocked and causing inaccurate adjustment.
When regulating water supply systems such as well pumps, it is necessary to avoid water vapor intrusion that may affect electrical performance.
Why is it Difficult for Me to Read Accurate Pressure Values for Adjustment in Hydraulic or High-Frequency Pulse Systems?
The pressure of hydraulic equipment and high-frequency pulse systems changes rapidly and is often accompanied by strong mechanical vibrations. Many mechanical pressure gauges and conventional sensors are used to measure static or slowly changing pressure.
You can choose a high-frequency dynamic pressure sensor. Alternatively, install a pulsation damper in front of the measurement point to minimize the effect of pulsation on the reading.
Final Thoughts
A standardized adjustment process can enable the pressure switch to perform its best in the system. If you have any further questions regarding the pressure switch adjustment, please feel free to contact us for one-on-one guidance.
