Homemade dry running sensor. Dry running protection: selection, connection, configuration, principle of operation

First, let's go over the theory, answer the question: “why do you need a dry-running protection relay for well pump?”, and then we’ll look at the principle of operation and how this relay is connected.

Dry running of a pump is a condition in which the pump runs idle, without water. In this state, the pump quickly overheats and can fail in a matter of minutes. To ensure safe work pump, a dry-running protection relay was invented.

Let's take a quick look at what can cause a pump to run dry:

When the pump power is incorrectly selected - for example, a high-capacity pump is selected that pumps out all the water from the well.
When the water level in the well naturally drops.
Leaking water pipe.

Operating principle of the dry running relay

Now let's look at how the dry running relay works. If we disassemble the relay, then under the cover we will see: a safety button, a group of normally open contacts for turning off the pump and two springs for regulating the shutdown pressure.

When the water in the water pipe disappears, the pressure in the water supply system drops sharply. At this moment, the relay, under the action of a spring, opens the contact group, which in turn turns off the supply of electric current to the pump.

The relay is reactivated by pressing the safety button. The contacts close, thereby assembling a circuit to turn on the pump, which creates the necessary pressure in the system, which is within 1 - 1.5 atmospheres. At this pressure in the system, the contacts of the dry running relay will be constantly closed.

Adjusting the relay operation

At the factory, the dry running relay is set to a pressure of 0.5 - 0.8 atm. At this pressure, the contacts will open and turn off the pump.

Let's consider the process of adjusting the shutdown pressure using the LP/3 relay as an example. To do this, you need to do a number of operations:

Disconnect the power supply to the pump.
Open the relay protective cover.
Turn the nut clockwise on the small spring, thereby increasing the initial activation pressure.
On the large spring, tightening the nut clockwise will raise the pump shutdown pressure.
After adjusting the relay, we need to determine the shutdown pressure: to do this, it is necessary to analyze the water in the system, for example, open the faucet in the sink; as the water supply system empties, the water pressure will decrease. Use a pressure gauge to track at what pressure the relay contacts open. There should be a click and the safety button will come out of the housing.

With these simple manipulations we can set the shutdown pressure we need.

How to connect a dry running relay

The dry-running protection relay is mounted in the water supply system through the so-called five-pin, this is a fitting that has five connection pins:

Supplying water to the system
Exit to hydraulic accumulator
Pressure gauge output
Output for connecting a dry running relay
Water exiting the system.

This can be clearly seen in the following figure:

Since the dry running relay works in tandem with pressure relay That electrical diagram The connection of these relays is as follows.

A dry-running protection relay is required to be installed, as it guarantees long term pump service. If the pump fails due to dry operation, it is considered out of warranty!

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Pumping equipment serving piping systems, through which the liquid medium is transported, especially needs protection at the moment when the pressure of the liquid drops or it stops flowing altogether. To provide such protection in situations where the pump is not supplied with the liquid it pumps, it is equipped with automatic sensors - dry-running relays. Various types of such devices can be used for a pumping station.

Why pumping equipment must be protected from dry running

Whatever source the electric pump pumps water from, this equipment may find itself in a situation where liquid stops flowing into it. It is precisely such situations that lead to the fact that the pumping station begins to operate at idle (or, as they more often say, on dry) running. Negative consequence operating the pump in this mode is not even a waste of electricity, but intense heating of the equipment, which ultimately leads to deformation of its structural elements and rapid failure. Water simultaneously acts as a lubricant and coolant, so its presence inside the pump is simply necessary.

For this reason, the presence of a relay that provides protection against dry running of a well pump (or circulation pump) is almost mandatory. Majority modern models pumping equipment has built-in relays. However, such pumps are very expensive. For this reason, users often purchase dry-running protection relays separately.

Basic protection

To protect the pump from dry or idling, devices are used various types, the main task of which is to stop the operation of the equipment at the moment when water stops flowing into it. These include, in particular:

dry running pump protection relay;
water flow sensor;
pressure switch with dry run protection option;
sensors that monitor the liquid level in a water supply source, which can be float switches or level control relays.

The differences between all of the above devices lie both in their design and operating principle, as well as in the areas of their application. To understand in what situations the use of one or another type of relay that protects pumping equipment from dry running is most appropriate, you should get to know each of them in more detail.

Characteristics of the pump dry running protection relay

A dry running sensor for a pump is an electromechanical type device that monitors whether there is pressure in the system through which water is transported. If the pressure level is below the standard threshold, such a relay automatically stops the operation of the pumping equipment, opening its electrical supply circuit.

The dry-running relay for the pump consists of:

a membrane, which is one of the walls of the inner chamber of the sensor;
a contact group that provides closing and opening of the circuit through which electric current flows to the pump motor;
springs (the degree of its compression regulates the pressure at which the relay will operate).

Main elements of the dry-running relay

The principle by which such a dry-running protection relay works is as follows.

Under the pressure of the water flow in the system, if its level corresponds to the standard value, the membrane of the device bends, acts on the contacts and closes them. Electric current in this case, it goes to the pump motor, and the latter operates normally.
If the water pressure is insufficient or does not enter the system at all, the membrane returns to its original state, opening the electrical power supply circuit of the pumping unit and, accordingly, turning it off.

Situations when the liquid pressure in water supply systems decreases sharply (which means the pump requires protection from dry running) are caused by for various reasons. Some of these reasons include exhaustion natural source water, clogged filters, the location of the self-priming part of the system is too high, etc.

A pump dry running protection relay is usually installed on the surface of the earth, in a dry place, although there are models made in a moisture-proof housing that can be mounted together with pumping equipment in a well.

Relays that prevent the pump from running dry work more effectively when they are installed in systems that are not equipped with a hydraulic accumulator and are served by a surface pump. circulation pump. It is, of course, possible to install such a relay in a system with a hydraulic accumulator, but in this case it will not be able to provide one hundred percent protection of the pumping unit from dry running. The relay connection diagram looks like this: place it in front of the water pressure sensor and hydraulic accumulator, and install it immediately after the pumping station check valve, preventing water from moving in the opposite direction. With this connection, the dry-running relay membrane is constantly under water pressure created by the hydraulic accumulator. This can lead to the fact that the pump, which will not receive water from the source, simply will not turn off.

Effective protection of the pump from dry running in cases where it serves systems in which a hydraulic accumulator is installed is also possible, but other types of devices are used to solve this problem.

Sensors that control water flow

In situations where an undesirable phenomenon such as dry running occurs, the fluid flow that enters the pump either has insufficient pressure, or is absent altogether. In order to monitor the presence of flow and its operating parameters, special devices are used, which are called water flow sensors. By design and the principle of operation they can be electromechanical (sensors) or electronic (controllers).

Water flow relays or sensors

There are two types of electromechanical water flow sensors:

petal;
turbine

The main working element of the first type of sensors is a flexible plate installed in their internal cavity, which has a cylindrical cross section. If there is a fluid flow in the system and has sufficient pressure, such a plate, equipped with a magnetic element, is as close as possible to the reed switch type, and its contacts are in a closed state. If the pressure of the fluid flow decreases or it disappears altogether, the flexible plate moves away from the switch, its contacts open, which leads to the pumping unit being turned off.

Turbine-type flow sensors differ more complex design. Its basis is a small turbine, in the rotor part of which an electromagnet is installed. The operating principle of such a sensor, which is also capable of protecting the pump from idling, is as follows. The fluid flow rotates a turbine, in the rotor of which an electromagnetic field is created, which is then converted into electromagnetic pulses read by a special sensor. The sensor makes the decision whether to turn on or off the pumping equipment servicing the system depending on how many pulses the turbine sends to it per unit time.

Sensor automatic control pump "Turbi"

Electronic water flow controllers

Electronic water flow controllers have an even more complex design, which combine the functions of both a pressure switch and a device that protects pumping equipment from dry running. Such controllers, also called electronic pressure switches, although not cheap, replace several monitoring and control devices at once. Installed in water supply systems, electronic pressure switches not only provide protection pumping system from dry running, but also allow you to control the pressure and fluid flow parameters. When such system operating parameters do not correspond to standard values, an electronic sensor automatically turns off the pumping equipment.

If a pump with a small head reserve is used to service water supply systems, then they can only be equipped with an electronic relay. When the system uses a pump with a large margin of the pressure it creates, a hydraulic accumulator and a separate pressure sensor are needed, since the electronic relay is not regulated by the maximum shutdown pressure of the pumping unit. Using only an electronic relay in such cases can lead to the fact that when creating overpressure in the system the pumping station simply will not turn off.

Sensors that monitor the water level in the system

Avoid situations where the pump plumbing system works at idle, water level control sensors, which are installed mainly in the water supply source - a well, a well or a container, are also capable. Thus, through such devices, the well pump is protected from dry running (or a pumping unit pumping water from the well). By design, level control sensors can be float or electronic.

Float sensors

Among float sensors, there are two main types. Some of them control the filling of containers with water, preventing cases of overflow, and the second, which protect the pump from dry running, regulate the emptying of water containers, wells and wells. In addition, there are combined models that, depending on the connection diagram to the system, can perform both functions.

The operating principle of the float relay for water level control is quite simple. As long as there is liquid in the water supply source, the float connected to the contact group is raised up. The work process will not be interrupted until the water level in the source decreases to such an extent that the float drops and thereby opens the contacts through which electric current flows into the phase wire of the pump motor.

It should be noted that protecting the pump from dry running using a float sensor for water level control is the most affordable and most common method.

Electronic relays

Electronic water level control sensors are capable of simultaneously solving two problems: protecting pumping equipment from dry (idle) running when the water level in the water supply source decreases and preventing cases of liquid overflow when filling containers.

Dry running of the pump (operation without water) is one of the most common causes of pump failure. In addition, such a malfunction is not covered by the manufacturer's warranty. That is, the service department will refuse you warranty repairs if the examination shows signs of prolonged idle operation of the device. To avoid such problems, the system autonomous water supply protection must be provided against dry running of the well pump, which turns off the power supply if there is insufficient water in the well.

IN modern devices Wear-resistant plastic is most often used as a material for working elements. Its advantage is high strength and relatively low price. This material copes with its task perfectly, provided that the operational requirements are met. One of these conditions is the constant presence of lubrication and cooling, the function of which is performed by the working medium, that is, water.

In the absence of coolant, plastic parts overheat greatly, and the plastic gradually deforms. The consequences for the electric pump can be very dire: from reduced performance to a jammed shaft and a burned out motor.

Important to know! In the equipment passport, any manufacturer emphasizes that dry running is an unacceptable mode of operation of a well pump.

Deformation of parts is clearly visible during disassembly of the device, so it will not be possible to hide the cause of the breakdown from the service department. In this case, the equipment warranty is void.

Dry running protection: operating principle

The main task of protecting a well pump from dry running is to block the operation of the device in the event of a low level or complete absence of water in the well. The most common means of such protection are:

float switch;
pressure switch;
level relay.

Float switch

The operating principle of such a device is quite simple. The contacts of the float switch (float) are connected to the open circuit of the motor power supply. The float itself monitors the water level in a well or well. When the water drops below normal, the contacts open, thereby stopping the supply of voltage to the electric pump. The correct trigger level is determined by where the float is installed. It is very important that the body of the device is still in the water when the power is turned off.

Pressure switch

During normal well operation, the pressure in autonomous system The water supply cannot drop below 1 bar. To monitor this parameter, a pressure relay (sensor) is used, the contacts of which break the electric motor circuit. Typically, the sensor response threshold is set within 0.4-0.6 bar.

A type of pressure sensor is a flow switch. In this case, control is carried out over the flow of water in the system. As soon as the flow rate drops below the set value, the pump stops working. Such devices are usually used in automated system water supply

Flow control on water pipe

Level relay

As in the case of a float switch, the operating principle of this device is based on monitoring the water level in a well, with the only difference being that such a relay is a more technologically advanced and complex device. One or more sensors are lowered into the water to a control depth. As soon as the level drops below normal and there is a risk of idling, a signal from the sensor is sent to an electronic device, which gives the command to turn off the electric pump. This method of control is very reliable, although more expensive compared to other types of protection.

Water supply system based electronic sensor level

What type of protection to choose for the pump

The choice of type of pump protection against dry running depends on the size of the well, the type of pumping equipment and the financial capabilities of the owners. The simplest and cheap way protect the device from idle operation - float switch. However, it has one significant flaw. The float cannot be used in small diameter wells. It simply cannot perform its function in a narrow water pipe. Although for wells this option would probably be optimal.

For submersible equipment, the most suitable means is a level switch. You will have to pay more for such a device, but you will be sure that the pump is reliably protected from a decrease in the water level in the well. But for pumping stations, such protection is not very suitable, since the hose in the water riser pipe may become clogged, and water will not flow into the device, although the level in the well will correspond to the norm. In this case, it is better to use a pressure sensor or flow switch.

Important! Without dry running control, the pump simply will not understand that it needs to turn off when the well is empty. Therefore, it is better to prevent its breakdown than to purchase a new device.

If you have difficulty choosing optimal protection borehole pump from dry running, you can always consult with specialists who will help you choose the most suitable option for your water supply system.

Video: how to protect the pump from dry running

It is often used in home water supply systems. But in order for it to function fully and, most importantly, uninterruptedly, it is important to protect the device as much as possible from possible overheating, etc. This can be achieved using certain protective elements(sensors) that prevent the pump from running dry. It is important to understand the operating principle of these elements, as well as their connection diagrams. This will be discussed further (video instructions are attached for clarity).

“Dry running”: what is it, the reasons for its occurrence

“Dry running” is usually called the operating mode of the pump without water. It is considered emergency and, accordingly, very dangerous for the device pumping out water. The fact is that the lack of water is a threat to the functional elements of the pump, because it is a kind of cooler and performs a lubricating function. Even a short run of the pump “dry running” (regardless of its type) is enough for it to fail ahead of schedule.

Advice. Some owners of water pumps are in no hurry to install protective elements that prevent the device from running dry (without water), but it would be worth it, because breakdowns that occur as a result of running “dry” are not included in the warranty cases. This means that you will have to do the repairs at your own expense.

First, it’s worth understanding why insufficient water supply may occur:

Poor choice of pump. Typical problem when operating the device in a well. Lack of water is possible if the pump’s performance “interrupts” the well’s flow rate or the installation level of the device is located above the dynamic water level.
Blockage in the pump out pipe.

Dry running relay

Loss of water pipe seal.
Low water pressure. If this problem occurs and the pump is not equipped with a dry-running protection system, it will continue to operate until it fails or is manually turned off.
Lack of control over the water level in a drying source.

Dry running protection devices: types, principle of operation

To prevent the possibility of “dry running”, several devices were created that differ in design and operation scheme:

Dry running sensor: connection diagram

The sensor is connected in two stages: mechanically and by connecting to the electrical network. First, the sensor is physically attached to the pump. Usually the device has a special socket.

Advice. Some pumps do not have such a socket. As a replacement, you can use a brass tee, to which, by the way, you can connect a pressure gauge and even a hydraulic accumulator.

Before screwing the relay onto a tee or onto a socket, it is necessary to seal the threads. This can be done either using a special (and rather expensive) thread or flax.

Advice. To securely fix the thread, it is wound towards the end in a clockwise direction.

After winding the thread, you can begin to tighten the relay. This must be done very carefully. When things get tight, you need to tighten the relay with a wrench.

Now you can connect the sensor to the power supply. First of all, find two groups of contacts on the sensor. In each group of wires, find the free ends and screw the wire strand to them. We connect the ground separately, attaching it to the screw on the relay.

Connected dry running sensor

Now you can connect the relay directly to the pump. A regular wire will do. We connect one end of it to the free relay wires, the other to the pump wires. Do not forget that the colors of the connected wires must match each other.

All that remains is to check the system in action. We connect the pump to the power supply and observe. If during operation of the pump the indicator on the pressure gauge increases, and when the maximum permissible indicator on the sensor is reached, the pump turns off - the installation was carried out correctly. The device can be used in real conditions.

This concludes our review existing varieties protective devices for the water pump, as well as their connection diagrams. Be careful when installing the device. Good luck!

How to connect a dry running sensor: video

"Dry run", namely the operation of a pump without water, along with the problem of a stable and high-quality energy supply, is one of the most common causes of failure of both the pump part and the entire pump as a whole. This applies equally to both surface and submersible well pumps.

In pumps for domestic needs, thermoplastic (high-strength wear-resistant plastic) is most often used as the main material of impellers and diffusers, which, characterized by high manufacturability and low price, has been doing its job perfectly for many years. But when working without water, which is normal conditions works both as a lubricant and as a source of heat removal, the internal parts of the pump begin to touch, heat up and deform. In extreme cases, the pump shaft may jam and the electric motor may burn out. As a rule, after such a test, the pump either completely stops supplying water, or supplies it without giving out its passport characteristics.

“Dry running” is quite easily identified by a specialist when disassembling the pump and does not apply to warranty cases!

Any pump manufacturer indicates that operating the pump without water is unacceptable. Therefore, it is so important to provide protection against dry running, especially in places that are potentially dangerous from this point of view.

Typically this is the following:

Pumping water from wells or wells with low flow rates. This may be due to an incorrectly selected pump (with very high performance) or natural phenomena(in dry summers, the water level in many wells or wells drops and the flow rate of the well/well, or simply put, the amount of water feeding the well/well from underground sources per unit time is lower than the productivity of the pump itself).
Pumping water from containers. It is imperative to ensure that the pump does not pump out all the water from the container and turn it off in advance.
Pumping water from network pipelines. In this case, the pump cuts directly into the network pipeline and serves to increase the pressure in the system. Since the pressure in the network pipeline, especially in summer, is often insufficient, this is a fairly common scheme for using pumping stations. It is very often not possible to track when water disappears from the network.

Without dry-running protection, the pump “does not understand” that it needs to turn off if there is no water in the suction pipe. It will continue to work until it breaks down, or until its forgetful owners turn it off.

Main types of protection against dry running:

(float) is a fairly inexpensive and reliable assistant in protecting against “dry running” when pumping water from containers or wells. There are floats that only work to fill the container. That is, the contacts inside the float will open and the pump will stop when the container is filled to a certain level. This type of float is more likely to be needed to protect against overflow, rather than against “dry running”. The second type of float, which works for emptying, is exactly our case. The float cable is connected to the break of one phase supplying the pump. The contacts inside the float will open when the liquid level in the tank/well drops below a certain level, thereby stopping the pump. The required response level is determined by the location of the float. The float cable must be secured at a fixed level so that when the float is lowered along with the general water level, there is still water in the container at the moment the contacts open. In the case of pumping water from a well with a submersible/surface (self-priming) pump, it must be secured so that when the contacts open, the water is above the suction grid/bottom valve of the pump. It is worth noting that this principle of protection against “dry running” is implemented in almost all well pumps from various manufacturers (for DAB these are PULSAR series pumps).

Unfortunately, the float is not universal. There is simply not enough space for it in a well or network pipeline. We need to look for other types of protection.

Pressure switch with dry-running protection. This device is a conventional pressure switch with additional function opening contacts when pressure drops below a threshold level. Typically this level is set by the manufacturer at 0.4-0.6 bar and cannot be adjusted. Under normal operating conditions, the pressure in the system cannot fall below these values, since all pumps used for private needs operate at significantly higher pressures (from 1 bar and above). The pressure can drop to 0.4-0.6 bar in almost only one case - if there is no water in the pump. No water - no pressure, and the relay, registering “dry running”, opens the contacts supplying the pump. It will be possible to restart the pump only manually, after first identifying and eliminating the cause of the “dry running”. Before starting again, the pump will have to be filled with water again.

It is worth noting that the use of a pressure switch with dry-running protection is only possible if automatic operation pump (together with the hydraulic tank), otherwise the use of this relay becomes meaningless. It is mainly used in conjunction with a borehole submersible (deep) pump, but can also be used with surface pumps(or pumping stations).

Flow switch with pressure switch functions(press control). Many manufacturers suggest using a compact device instead of a hydraulic tank and a pressure switch - the so-called “flow switch” (or press control). This relay sends a command to turn on the pump when the pressure in the system drops to 1.5-2.5 bar, depending on the setting. The pump turns off after the water intake stops, due to the lack of liquid flow through the relay. Dry running protection is carried out thanks to a flow sensor built into the relay, which records the actual fluid flow through the relay. The pump switches off with a short time delay after dry running is detected, which does not affect the performance of the pump. In addition, press control also performs other protective functions, such as current and voltage protection. The main advantage of press control is its very small dimensions and weight. Unfortunately, now a large number of press controls have appeared on the market, manufactured in unknown places. Average term The service life of such devices does not exceed 1-1.5 years, and only if you are lucky. Certified and high-quality press control (like pumping units ACTIVE) costs about 100 USD.

It is an electronic board to which several sensors (electrodes) are connected. Usually there are three of them, one control and two working. The sensors are connected to regular single-core relays electric wire, and serve only to provide a signal. The principle is as follows: the sensors are lowered into the well for different levels and when the water level drops below the control sensor, which should be located slightly above the installation level of the pump itself, the signal from it is transmitted to the level relay and a command is given to stop the pump. Once the water rises above the control sensor, the pump will automatically start. This method of protection is very reliable, but also a little more expensive than others. It can also be used in the case of pumping water from containers. The level switch itself is located in a house or other place protected from moisture.

Which protection method to choose depends on the specific task and preferences. From experience we can say the following: when pumping water from containers/tanks/wells pumping station An almost 100% guarantee of protection will be the use of both a pressure switch with dry-running protection and a float installed in the tank. They will simply duplicate each other. In terms of price, this option will be no more expensive than installing one flow switch. When protecting a well pump, a pressure switch with dry-running protection is most often used. But it is better to use a slightly more expensive, but also more reliable way protection using a level relay.

Note that if you have drilled a deep well with a good flow rate (confirmed by the well passport) or if you have significant experience in operating pumps in your well/well and know that the water level practically does not decrease during prolonged operation of the pump, you can protect against “dry running” " and do not use it. The most important thing is to be careful - as soon as you see that the water has disappeared in the pressure pipe or the thermal relay has tripped and the pump has turned off, you should not immediately try to start it again, first try to determine the cause of the malfunction, and only then start the pump again.

2007 website Setting the pressure switch and adjusting the air pressure in the accumulator.