Water pressure switch: what it is, how it works + how it is adjusted
Automation of independent water supply is impossible without the use of a pressure sensor. The sensitive device will almost instantly react to a drop or increase in pressure in the network, start and stop pumping equipment without the participation of the owners. It is possible to use autonomous water supply system equipped with automation devices as a city system. This is incredibly convenient, is not it?
We offer you full information on how the water pressure sensor works, what type of device is better to choose for installation in an independent system. Here you will find a detailed analysis of the technological nuances and technical specifics of the relay of all types currently in operation.
The article submitted for consideration has valuable information about the features of device installation and about changing settings if necessary.To optimize 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 are used for a long time. They are arranged simply, therefore are reliable and convenient in operation. Inside the device there is a flexible plate whose position changes under the influence of water flow. The more active the flow, the greater will be its bend.
This element is connected to two springs that respond to a change in the position of the plate. As a result, the contacts of a pair of electrical circuits that operate at user-defined pressure limits are closed and open.
One spring is set to the maximum pressure in the autonomous network, the second to the difference between the upper and lower pressure limits. The device is connected to the hydroaccumulator.
When the pressure reaches the minimum value set for the relay, the diaphragm inside the hydraulic tank weakens, the contact under the second spring is activated, and the pump is turned on. Gradually, the pressure increases, reaches the upper limit, then the contact opens under the first spring, which turns off the pump.
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 the operation of the device at a higher pressure, they are tightened tighter, but if it is necessary to reduce the performance - on the contrary, the element should be loosened. This is the principle of operation of the electromechanical version of the pressure switch, there are also newer electronic models.
Electromechanical sensor models
The operation of the pressure switch is closely connected with the hydroaccumulator, without which the inclusion of the device in the water supply network becomes meaningless. Instead of the already familiar electromechanical device, electronic variants and automatic units with the function of protection against "dry running" are often used now.If there is a risk of draining the source in the process of pumping water, the pressure switch is simply supplemented with an automation unit.
However, in a number of electromechanical instruments, there are dial gauges that can only be used with a pump. They also reduce the number of inclusions of equipment and protect against work in the absence of water flow inside the pumping equipment. Switching off will help protect the motor from serious damage. In addition, using such a relay, you can maintain a comfortable pressure in the water supply network.
The main characteristic of the device is the nominal operating pressure. It can vary from 1.5 to 6.0 bar. Choosing a suitable relay, you should also pay attention to such indicators as:
- connecting thread sizes;
- level of protection against dust and moisture;
- weight and dimensions of the device;
- contact voltage;
- current rating;
- sensor type, etc.
The pressure sensor can be installed directly on the hydraulic tank or mounted separately from it. It should also be noted that the relays are made to work in different environments. For household suitable device intended for water.You should not purchase a relay designed to work with refrigerant or other liquids. Pay attention to the temperature of the working environment for a particular model.
Most often for the needs of home plumbing using the standard model RDM-5. Such a device must be connected first to the hydroaccumulator of the plumbing system, then to the contacts connected to the pump on / off mechanism. After that it is necessary to provide the device with power supply.
Usually a pressure switch is supplied with the pumping station. If it is intended to use an electronic model at the same time, then a cut-off pressure will be established using the electromechanical variant For connection to the water supply, a triple fitting with suitable thread sizes should be used.
Usually take the item by a quarter of an inch.If there is at least some experience in plumbing, then this operation will take place without difficulty. Of course, all threaded connections should be sealed with FUM tape, linen thread, or other suitable material.
The mechanical part of the installation of the pressure switch is completed by mounting the pressure gauge in order to obtain current information on the current state of the water supply system.
During the installation of the device, it is necessary to choose the cable cross-section correctly, as well as to provide its grounding using a three-pin socket. If it is necessary to make protection against dry running, it is necessary to ensure the correct position of the pump. It must be installed above the check valve.
After installation, you need to adjust the water pressure switch. For this, as mentioned above, there are two screws with springs. They are under the hood that needs to be removed. In production, the device is usually set up.Standard indicators are considered from 1.4 atmospheres (minimum) to 2.8 atmospheres.
Even if these data correspond to those necessary for a particular pump, they should be checked. In the process of storing and installing the settings could be a little lost. Here is the procedure for setting the relay connected to the system with a hydroaccumulator.
First, measure the pressure in the tank using a car manometer, which is connected to the nipple connection. The nipple is located on top of the vertical models of hydraulic tanks, on the side - on horizontal ones, but always from the side opposite to the flange location.
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.
The normal pressure in an empty tank is set depending on its volume. Small containers (less than 25 liters) should be pumped to 1.4-1.7 bar. Tanks for 50-100 liters need to pump up to 1.7-1.9 bar. If the pressure in the new tank does not match these parameters, the situation needs to be rectified, i.e. pump up the missing air or bleed its excess.
It is recommended to check the condition of the hydroaccumulator on a monthly basis, monitoring and, if necessary, adjusting the air pressure. These simple measures will not only help maintain the required level of pressure in the tank, but also prevent rapid wear of the rubber membrane.
Before setting, you need to carefully study the documentation that comes with the pump. It is necessary to take into account such indicators as:
- ultimate pressure;
- operating pressure;
- water consumption rate.
These data should be used when setting up the relay, the set pressure values must be within these limits. The hydraulic tank data is also taken into account. The power of the domestic pump is usually not enough to pump the usual hydroaccumulator, but you should not risk and knowingly set incorrect settings.
Remove the cover from the installed relay. To do this, unscrew the fasteners. There are two springs. Next to the one that is greater, is the designation P, the one that is less, denoted as ΔP. 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 a high value, the relay will turn off the pump. It is necessary to determine the readings of the gauge at this point. 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 in a clockwise direction, if you need to make a decrease in settings - against.
Now you need to open the water and release the hydraulic tank. Over time, the relay will operate and turn on the pump. It is necessary to record the readings of the pressure gauge again and adjust the settings of the relay, if necessary. To adjust the lower pressure limit, turn the small spring.
All manipulations with the adjusting springs need to be done very carefully.These are very sensitive elements, you need to turn the screw gradually, on a small part of the circle, you should not do several full turns at once, so you can completely spoil the device.
In this case, the following important point should be taken into account: since the small nut adjusts 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 for the relay, it must be remembered 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 wear out quickly.
During operation, it may be that the recommended settings are not suitable for this particular water supply. Then you need to re-perform the configuration as described above.It should be remembered that the difference between the limits recommended by manufacturers varies in the range of 1.2 - 1.6 bar.
But overzealous is not worth it, because the greater this difference, the greater will be the fluctuations of pressure 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, since it will not be able to provide the level of pressure necessary to switch off the device. This situation makes the use of a relay meaningless.
It is recommended to check the settings every three months. The same operations should be performed after repair and replacement of the pump, hydraulic tank, etc. Adjusting the settings is not recommended by manufacturers of systems for pumping water, but if necessary, it is better to make adjustments after each new filling of the system with water, for example, at the dacha after the systems have been reopened in the spring.
Electronic Relay Options
Electronic models of the pressure switch are an order of magnitude more expensive than electromechanical counterparts, but these costs fully pay off. Such devices are easier to configure, and the limits can be set much more accurately. Each such model is equipped with a flow controller that instantly shuts off the pump when there is no water. This reliably protects the pump from working in the dangerous “dry running” mode.
Usually, an electronic pressure switch is equipped with a small hydraulic tank, the volume of which is only 400 ml. This is not much, but in this way the system is reliably protected from possible water hammer. If an expensive high-quality pump is used for a well, it makes sense to invest in a good electronic pressure switch.
Such models look quite attractive, they are distinguished by high reliability and 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 installing the necessary filters.
Such devices do not have adjusting springs, so it is not necessary to reconfigure the device periodically because they have weakened. Yes, and the configuration itself is much easier. 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 failure, just the device is configured.
In the future, the pump can be shut off also with a delay of about 7-15 seconds. This is necessary so that the pump is switched off less frequently, if during this short period the pressure increases again. 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 embedded device. And the switching pressure is set by adjusting the electronic relay. The power supply is first connected to the electronic device, then the contacts are transferred to the station relay, and then the pump is powered.
If the electronic relay is connected to the accumulator, the setup is easier.The relay sets the lower limit, which should be slightly higher than the similar data indicated on the pump casing. The water flow is turned off after the maximum pressure is reached in the system, which depends on the pump capacity.
The installation location of the electronic relay is chosen between the pump and before the first water intake point from the system. Consider the direction of water movement indicated by the arrow. If the device is used with a pump with a capacity of more than 10 atm, it is recommended to install a pressure reducer in front of the electronic relay to relieve the device from unnecessary loads.
If the existing settings are not suitable, you can change them. To do this, use a screwdriver to tighten the corresponding screw or use other settings 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 is best to use Teflon tape. Electronic pressure switches usually have a built-in valve.This point should be considered when emptying the water supply. Before the first start of the relay, you must first fill the supply line with water, then apply power to the device, then you need to open the tap.
The activation of the “dry run” protection mode is usually signaled by the inclusion of a red LED on the housing. To reset the system, click the “reset” button, of course, after eliminating 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 features of operation of an electronic pressure switch using the example of the BRIO 2000 model:
Pressure switch - the device is extremely useful. Once you figure out how to set it up, you can regularly correct the pressure state in the plumbing system and reliably protect the pump and other equipment from possible damage.