Water pressure switch: what it is, how it works + how it is adjusted

Nikolay Fedorenko
Checked by a specialist: Nikolay Fedorenko
Author: Elena Pykhteeva
Last update: March 2019

Automation of independent water supply is impossible without the use of a pressure sensor. A sensitive device will almost instantly respond to a drop or increase in pressure in the network, start and stop pumping equipment without the participation of the owners.

You can use an autonomous water supply system equipped with automation devices as an urban system. It's incredibly convenient, isn't it?

We offer you complete information on how a water pressure switch works, what type of device is best to choose for installation in an independent system. Here you will find a detailed analysis of the technological nuances of various types of sensors.

The presented article has valuable information about the features of the installation of devices and the configuration of the pressure switch. For a better perception, the text is supplemented with photos, diagrams and video reviews.

The principle of operation and types of pressure switches

Electromechanical models of pressure switches have been used for a very long time. They are not complicated, therefore they are reliable and easy to use. Inside the device there is a flexible plate, the position of which changes under the influence of the flow of water. The more active the flow, the greater its bend.

This element is connected to two springs that respond to a change in position of the plate. As a result, the contacts of a pair of electrical circuits operating at user-specified pressure limits are closed and opened.

One spring is set to the maximum pressure value in the autonomous network, the second - to the difference between the upper and lower pressure limits. The device is connected to accumulator.

When the pressure reaches the minimum value set for the relay, the membrane inside the hydraulic tank weakens, the contact under the second spring is activated, and the pump turns on. Gradually, the pressure rises, reaches the upper limit, after which the contact opens under the first spring, which turns off the pump.

Mechanical relay device
The mechanical relay device is not too complicated, having understood the location of its main parts, even a not too experienced master will be able to connect and configure (+)

The springs that control the contacts are equipped with adjusting nuts. With their help, you can change the compression ratio of these springs. To ensure that the device operates at a higher pressure, they are tightened more tightly, but if you need to reduce the performance - on the contrary, the element should be weakened.

This is the principle of operation of the electromechanical version of the pressure switch; newer electronic models also exist.

Pressure Switch Benefits
Using a pressure switch, you can significantly reduce the number of pump starts and maintain the optimal pressure in the system, which will positively affect the state of its other elements

Electromechanical models of sensors

The operation of the pressure switch is closely connected with the accumulator, without which the inclusion of the device in the water supply network becomes meaningless. Instead of the already familiar electromechanical device, electronic options and automation units with the dry-running protection function are often used now.

If there is a risk of draining the source during the pumping process, the pressure switches are simply supplemented with an automation unit.

However, in a number of electromechanical devices, there are switch devices that can only be used with a pump. They also reduce the number of equipment starts and protect against operation when there is no water flow inside the pumping equipment.

Shutting down will help protect the motor from serious damage. In addition, using such a relay can be maintained in the water supply network. comfortable pressure.

The main characteristic of the device is the rated working pressure. It can vary from 1.5 - 6.0 bar.

When choosing a suitable relay, you should also pay attention to such indicators as:

  • sizes of connecting threads;
  • level of protection against dust and moisture;
  • weight and dimensions of the device;
  • contact voltage;
  • rated current parameters;
  • type of sensor, etc.

The pressure sensor can be installed directly on the hydraulic tank or mounted separately from it. It should also be noted that relays are designed to operate in a variety of environments. For household use a device designed for water.

Do not buy a relay designed for use with refrigerant or other liquids. You need to pay attention to the temperature of the working environment for a particular model.

Pressure switch instruction
Before installing or adjusting the device, you should carefully study the instructions with a description of its design, technical specifications, installation, operation, etc. (+)

Most often, for the needs of home water supply, the standard model RDM-5 is used. Such a device must first be connected to the accumulator of the water supply system, then to the contacts connected to the pump on / off mechanism. Then you need to provide the device with power.

How to choose a pressure switch
When choosing a suitable pressure switch, it is necessary to take into account such characteristics as the size of the nozzles, voltage, temperature of the working medium, etc.

Usually with pumping station a pressure switch is also supplied. If it is supposed to use an electronic model at the same time, then the shut-off pressure will be set using the electromechanical option. To connect to the water supply, use a triple fitting with suitable thread sizes.

Usually take a quarter inch element. If there is even a little experience in plumbing, this operation will take place without difficulty. Of course, all threaded connections should be sealed with FUM tape, linen thread, or other suitable material.

Complete the mechanical part of the installation of the pressure switch with the installation of a pressure gauge in order to obtain relevant information about the current state of the water supply.

Pumping station
To connect the relay to the pump contacts, remove the protective cover of the device. Under it are four contacts. Two of them are needed for entry, through them they provide power supply. Two more contacts are an output, they are connected to the pump

During the installation of the device, you must correctly select the cable cross-section, and also ensure its grounding, using three-pin socket. If it is necessary to protect against dry running, it is necessary to ensure the correct position of the pump. It must be installed above the check valve.

After installation, adjust the water pressure switch. For this, as mentioned above, there are two screws with springs. They are under the cover that needs to be removed. In production, the device is usually set up. The standard values ​​are from 1.4 atmospheres (minimum) to 2.8 atmospheres.

Connecting the relay to the mains
The relay should be correctly connected to the mains and to the contacts of the pump. Mandatory safety requirement - grounding of the device

Even if these data correspond to those necessary for a particular pump, they should be checked. During storage and installation, the settings might go a little wrong. Here is the procedure for setting up a relay connected to a system with a hydraulic accumulator.

First you should measure the pressure in the tank using an automobile pressure gauge that connects to the nipple connection. The nipple is located on top on vertical models of hydraulic tanks, on the side - on horizontal, but always from the side opposite to the location of the flange.

It is better to take devices with a sufficiently high gradation of the measuring scale. Cheap Chinese models do not always meet this requirement. The tank must be left empty, the pump or station does not need to be connected to the power supply.

Tank pressure
Before starting the adjustment, you need to measure the air pressure in the empty accumulator and adjust it to the values ​​recommended by the manufacturer

Normal pressure in an empty tank is set depending on its volume. Small containers (less than 25 l) should be inflated to 1.4-1.7 bar. Tanks for 50-100 liters need to be pumped up to 1.7-1.9 bar. If the pressure in the new tank does not match these parameters, you need to correct the situation, i.e. pump in the missing air or vent excess air.

Monthly it is recommended to check the condition of the accumulator, monitoring and, if necessary, adjusting the air pressure. These simple measures will not only help to maintain the required pressure level in the tank, but also prevent the rapid wear of the rubber membrane.

Before setting up, carefully read the documentation that came with the pump.

It is necessary to take into account such indicators as:

  • ultimate pressure;
  • operating pressure;
  • water consumption rate.

This data must be used when setting up the relay, the set pressure values ​​must be within these parameters.

The tank data is also taken into account. The power of a household pump is usually not enough to pump a conventional accumulator, but do not risk it and knowingly set incorrect settings.

Pressure switch springs
Relay adjusting screws are designated as P and ΔР, to get to them, you need to remove the protective cover from the device

Remove the cover from a relay installed in a suitable location. To do this, unscrew the fasteners. There are two springs. Next to the one that is larger, is the designation P, the one that is smaller is designated as ΔР. Now you can connect the pump or pump station to the mains, and begin the process of filling the tank with water.

When the pressure in the tank reaches the upper value, the relay will turn off the pump. The pressure gauge readings at this point should be determined. If the data obtained is different from the recommended, you need to adjust their value using a large spring.

To increase the limit, it is necessary to rotate the nut clockwise, if necessary, reduce the settings - against.

Now you should open the water and empty the hydraulic tank. Over time, the relay will trip and turn on the pump. It is necessary to again record the pressure gauge and adjust the relay settings, if necessary.To adjust the lower pressure limit, turn the small spring.

All manipulations with the adjustment springs must be carried out extremely carefully. These are very sensitive elements, you need to turn the screw gradually, to a small part of the circumference, do not make several full revolutions at once, so you can completely ruin the device.

Pump station pressure switch
Pressure switches can be used to control the operation of a surface pump station or a submersible pump system. The setting procedure is practically the same

In this case, the following important point should be taken into account: since a small nut regulates the difference between the limits, when adjusting the lower value, the data for the shutdown pressure will change.

Therefore, after adjusting the position of the large nut, wait until the tank is full and check the data for the upper limit again and change them if necessary.

When setting the upper limit settings for the relay, you need to remember that this indicator should be at least 10% lower than the pressure in the empty hydraulic tank, which was fixed and adjusted at the very beginning. Otherwise, the rubber membrane of the accumulator will be under unreasonably high pressure and will quickly wear out.

During operation, it may turn out that the recommended settings are not suitable for this particular water supply. Then you need to re-configure as described above. It should be remembered that the difference between the limits recommended by manufacturers varies between 1.2 - 1.6 bar.

Pressure switch circuit
To properly configure the mechanical version of the pressure switch, you need to rotate its adjustment screws. The condition of the device should be checked periodically, since over time the springs may weaken (+)

But you should not be too zealous, because the greater this difference, the greater the pressure fluctuations in the water supply. The shut-off pressure should be set lower than the maximum pump pressure.

If this moment is not taken into account, the equipment will work continuously, because it will not be able to provide the level of pressure necessary to turn off the device. This situation makes using relays pointless.

Checking the settings is recommended every three months. The same operations must be performed after pump station repairreplacing the tank, etc.

Adjusting the settings is not recommended by manufacturers of systems for pumping water, but if necessary, it is better to carry out the adjustment after each new filling of the system with water, for example, at the cottage after the systems were re-milled in the spring.

For more information on adjusting the pressure switch for the pump, see this article.

Electronic relay options

Electronic models of pressure switches are an order of magnitude more expensive than electromechanical counterparts, but these costs are well worth it. Such devices are easier to configure, and the limit values ​​can be set much more accurately.

Each such model is equipped with a flow controller, which instantly turns off the pump when there is no water. This reliably protects the pump from working in a dangerous “dry running” mode.

Electronic pressure switch
Electronic models of pressure switches are more accurate, reliable and easier to operate than mechanical devices, but they are much more expensive

Typically, an electronic pressure switch is equipped with a small hydraulic tank, the volume of which is only 400 ml. It is not much, but in this way the system is reliably protected from possible water hammer network. If an expensive high-quality pump is used for the well, it makes sense to invest in a good electronic pressure switch.

Such models look quite attractive, they are highly reliable and have a long service life. But they can be sensitive to the quality of the water entering the plumbing system. To protect the relay from damage, you need to take care of the installation necessary filters.

Pressure switch for pump
If the well is serviced by an expensive and powerful pump, it makes sense to buy an electronic relay to protect the device from overload

Such devices do not have adjustment springs, so you do not have to periodically reconfigure the device due to the fact that they are weakened. And the setup itself is much simpler to perform. First you need to study the instructions.

After the first connection to the network, some models turn on with a delay of 15 seconds. This is not a breakdown, just the device is configured.

In the future, the pump can also be turned off with a delay of about 7-15 seconds. This is necessary so that the pump switches off less frequently if the pressure rises again in this short period. The electronic model of such a controller can be used in conjunction with a pump station that already has a pressure switch.

Here the upper limit is set on this built-in device. And the switching pressure is set by adjusting the electronic relay. The power is connected first to the electronic device, then the contacts are transferred to the station relay, and then the pump is powered.

If an electronic relay is connected to the accumulator, the setup is easier to perform. The lower limit is set on the relay, which should be slightly higher than the similar data indicated on the pump casing. The water flow is switched off after the maximum pressure is reached in the system, which depends on the power of the pump.

The installation location of the electronic relay is chosen between the pump and before the first point of water intake from the system. The direction of water movement indicated by the arrow should be taken into account.

If the device is used with a pump with a capacity of more than 10 atm, it is recommended to place a pressure reducer in front of the electronic relay in order to save the device from unnecessary loads.

Electronic Relay Connection
When connecting an electronic relay to the station, you must first power up the device, then the mechanical relay, then turn on the pump

If the existing settings are not suitable, they can be changed. To do this, tighten the appropriate screw with a screwdriver or use other settings items described in the instructions. There should be a difference of at least 0.6 atmospheres between the maximum pressure that the pump can provide and the minimum indicator of the electronic relay.

To seal the threaded connection of such a device, it is best to use teflon tape. Electronic pressure switches typically have a built-in valve. This point should be considered when emptying the water supply.

Before starting the relay for the first time, you must first fill the supply line with water, then apply power to the device, then open the tap.

The activation of the “dry running” protection mode is usually signaled by the inclusion of a red LED on the case. To reboot the system, press the “reset” button, of course, having previously eliminated the causes of a dangerous situation.

Conclusions and useful video on the topic

Setting up a standard mechanical model is presented here:

This video describes in detail the setup procedure and operating features of the electronic pressure switch using the example of the BRIO 2000 model:

Pressure switch - an extremely useful device. Once you figured out how to configure it, you can regularly adjust the pressure state in the water system and reliably protect the pump and other equipment from possible breakdowns.

Do you have any questions or is there a desire to share your personal experience in choosing, installing and using a pressure switch? Please leave comments on the article and participate in discussions - the link block is located below.

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Visitors Comments
  1. Dmitry

    Water supply is organized from the well. I use an electromechanical type of relay with protection against “dry running”. There were no problems with it, but recently there have been doubts about the correspondence of the sensor to the set settings. The pump shuts off faster than usual, at a low pressure at the tapping points. The water source is in order, the whole system is working. I think the problem is in it, and so I decided to replace it. In this regard, there is a question: is it worth taking an electronic one from which, as I heard, such defects are not observed?

    • Alexander

      Dmitry, first of all, if the pump started to turn on / off often, I would check the pressure with a machine pressure gauge in the accumulator when it is completely empty, open the tap and turn off the pump. It must be on the passport or 10% less than the minimum pressure to turn on the pump itself.

  2. We often experience pressure interruptions in the pipeline, and as a result the water flows weakly or stops flowing altogether. In order to prevent the pressure drop from interfering, we use a special pressure regulator, namely an electronic relay with settings and with a display for easy monitoring. Recently purchased with an official guarantee. While it is working properly, water flows with the pressure set by us, without failures. Satisfied with the quality.

  3. Alexander

    “When setting the upper limit settings for the relay, remember that this indicator should be at least 10% lower than the pressure in the empty hydraulic tank, which was fixed and adjusted at the very beginning. Otherwise, the rubber membrane of the accumulator will be under unreasonably high pressure and will quickly wear out. ” - Something is wrong here. Air pressure in GA 10% less than the lower pressure limit in the system (on pump).

  4. Leonid

    I have had a Pedrollo hydrophore in my private house for over 7 years. Finally, the rubber membrane was torn and it began to turn on very often for 1 second. I decided to remove it all and put the electronic relay “Aquatica - 779556”. At the outlet of the relay into the internal pipeline there is a ball valve. With the valve closed, the relay holds pressure on the manometer for a long time (at least all night). However, when opening this faucet, but in the absence of water use, the pump runs for 6-8 seconds, the pressure on the pressure gauge rises to almost 4 bar and the pump turns off. But the pressure on the manometer begins to drop slowly in the absence of water use and after about 5 minutes the pressure drops to 1.5 bar and the pump turns on again. That is, it feels like my internal water supply is not sealed? But the pipes under the screed ... What should I do? Buy a hydrophore with an electromechanical relay and a bulb, or dig a pipeline and look for a leak? Tell me, please, since materially for me this is all very critical ...

    • Alexander

      Maybe the check valve does not hold, sometimes a grain of sand gets in and water oozes back.

  5. Denis

    Great article, thanks!

    • I put an additional pressure switch. Tried to adjust, but in vain. The engine continues to turn on and off periodically. Apparently, the matter is still in the electric relay, its circuit board (something burned out or warmed up), who faced such a problem, where to look for the cause? Thank.

  6. See the photo. With this assembly, by opening the water, the electronic relay will turn on and off at almost regular intervals. Is this a switch or is it necessary to install an additional pressure switch?

    Attached photos:
    • Alexei

      Hydraulic accumulator to help you.

  7. Sergei

    Good to you.The situation - a private house, an autonomous system, download from the well. Everything worked for several years, but the akvorobot died. I bought a new one, but of a different brand, installed (it seems like everything is necessary). The problem is this - it turns off only if you lightly hit it. Tell me if you know. THX!