Submersible dry run sensor. Dry running protection for a pumping station

What is a "dry running" pump? This is an emergency mode of operation, in which the electric motor rotates, but water does not enter the pump or it does not enter in sufficient quantities. The design of the pump is such that the pumped medium plays the role of lubricating and cooling liquid in it. No cooling and lubrication - the electrical components of the engine overheat, moving parts are subject to increased wear. Without water, a running pump can fail in just a few minutes, a breakdown will be very expensive to repair. To exclude the possibility of functioning in emergency mode, it is necessary to protect the well pump from dry running.

For submersible pumps, dry running is due to the absence or insufficient amount of water at the level of the pump intake holes in the well or well. We list the reasons that can cause it:

• Drop in water level below the critical level as a result of an incorrect choice of the height of the pump suspension in the work string. An appropriate calculation of the dynamic level was not carried out or the well flow rate was incorrectly measured. With active water intake, the pump begins to “pick up” air.

The submersible pump must be located below the dynamic water level

• Degradation of a previously normally functioning well, as a result of which the amount of water that it can produce has decreased (the flow rate of the source has fallen).

If the source has not dried up completely, the water level temporarily drops, then it is restored and the owners may not always notice that the equipment periodically operates in emergency mode.

If the well or well is shallow (up to 10 m), a surface pump can be used to supply water. In this case, a dry run may occur not only due to a drop in the water level. The cause may be a leak in the suction pipe or its blockage.

Equipment protection and financial costs

A little about money:

• Downhole vibration pump "Brook" or its equivalent costs about 3,000 rubles. Its protection against dry running will cost approximately the same amount if you do all the installation and connection work yourself. Does it make sense to invest in additional equipment with such a cheap pump?

The domestic "Brook" is cheap, so it's hardly worth spending money on protecting it

• Expensive borehole pumps are initially equipped with protection, and often multifunctional. For example, all Grundfos models have protection not only against dry running, but also against overload, overheating, power surges and reverse axial displacement. The cost of high-quality equipment from a good manufacturer includes the necessary automation to prevent its operation in emergency mode. Separately, there is no need to worry about protection, when mounting to the calculated depth, additional sensors are not needed - "all inclusive".

High-quality equipment is already equipped with the necessary automation, it does not need additional protection

• Mid-range equipment can also be protected from running without water. Dry running sensors can be located inside the housing or be remote. For wells, this does not matter, but for a narrow well, the built-in option is preferable, there is less risk of damage. As for the lower price category, here you need to carefully study the package, read the product passport. The cheaper the pump, the higher the chance that protection will be absent in it. It is available as an option for many models. In any case, before buying, you need to find out exactly from the seller whether there is protection against dry running in a particular model. If not, add the price of additional equipment and its installation to the cost of a cheap pump - you get the amount of real costs.

• Most complete waterworks, where a surface pump is used, have protective automation. However, here you should also be interested in the configuration of a particular model.

When is a well pump protected against dry running?

There are no regulatory requirements for private developers regarding the protection of equipment for individual water supply. It's up to you whether you spend money on it.

For those who can afford it, we recommend purchasing high-quality equipment, initially equipped with all the necessary automation. Entrust the installation to competent installers and sleep peacefully in the future, without encountering any problems.

For those who are forced to save, we suggest approaching the issue rationally. Do you always need additional protection for a downhole pump that is not originally equipped with it?

In our opinion, in the country, where the pump is used for watering and washing in manual mode, and the owners always have the opportunity to notice that the water has stopped flowing from the pipe or hose, the protection of well pumps is not a strictly mandatory function. The power supply can be turned off by unplugging the power plug. Not very convenient, but free.

Another thing is if the water supply system operates in automatic mode. The automatic watering of the garden turns on when the owners are not at home, the large bathtub is filled, the washing machine or dishwasher is running at a time when all family members are watching TV. For those who want to have a comfortable residential building and not have problems with water supply, we advise you not to save money and install protection.

Expensive engineering equipment of a full-fledged individual residential building must be protected from emergency operation

Dry run protection

Perhaps one of our readers decides to select and install water supply equipment on their own. Do-it-yourself protection of a well pump from dry running can be performed using various technical solutions. Protection is provided by sensors (relays) that cut off the power supply before or after the emergency mode occurs. Let's see what dry running sensors are, how they work and how they are installed:

Water level measurement

The first group of sensors measures the water level in a well or well:

• Pressure switch that measures the dynamics of changes in the water level in the well. It consists of two sensors located at different levels. One monitors the minimum possible water level for the operation of the pump and turns off the power when it drops. The other is located at a level that guarantees a stable flow of water into the water intake. When the water rises to this mark, the pump will automatically turn on.

The electrical circuit of the dry-running protection relay, the signals come from two sensors located in the working string of the well

• A float sensor that measures the water level in a well. The sensor is located in a sealed air-filled casing (float), fixed on the body of the submersible pump. It floats in the water column above the water intake. When the water level drops, it goes down. When the mark overcomes the lower permissible limit, the water pressure on the float disappears, the relay opens the electrical circuit. If the equipment does not include additional automation, the pump with float protection must be turned on manually after it is triggered.

Float switches are practically non-existent on modern well pumps: there is simply no room for a float in a narrow casing pipe. But submersible pumps for wells, where there are no size restrictions, are very often equipped with float sensors.

Sensors and relays that measure the water level directly in the well and well are good because the pump is turned off even before the critical drop in water level. Thus, dry running is completely excluded and the equipment always operates in normal mode.

Pressure and flow sensors

Sensors that respond to the characteristics of the flow created by the pump are inferior to the water level control system in terms of efficiency. Flow and pressure sensors turn off the pump after the pumping of water has stopped. True, the period of work in emergency mode is short. However, this is not the best solution. But such protection of pumps for wells is cheaper, besides, their installation, repair and replacement, if such a need arises, is easier.

• Pressure sensor installed on the outlet pipe (supply pipe) after the pump. In general, the sensor is set to a value of 0.5 bar, a lower pressure with the pump motor running is considered critical. If the pressure value drops below, the electrical circuit opens. To control the pump (on-off) paired with a hydraulic accumulator, in any case, it is necessary to install a pressure switch. Often, the pressure switch is combined with a protection sensor in one device, which reduces the cost of automation.

Pressure sensors to turn on the pump and protect it from dry running are connected to the outlet pipe and the circuit supplying the electric motor in series

The pressure sensor has an adjustable spring design

• The flow sensor is also placed on the outlet pipe. The flow rate of water when the pump is running drops below the permissible value - it turns off.

The flow sensor determines the speed of water movement along the bend of the membrane (plate)

Pressure and flow sensors are not installed in the well, but in front of the entrance to the accumulator. Can be used with both submersible and surface pumps.

Dry running protection according to the electrical parameters of the pump

The sensors and relays listed above must be in direct contact with the pumped medium. There is a technical solution in which there is no need to mount measuring instruments in the working string or install them in the pipeline. Such well pump protection is based on reading the electrical parameters of the pump motor. When liquid enters the suction hole, the electric motor operates in normal mode and its power factor cos φ tends to the nominal value of 0.7 ... 0.8. Water stops flowing, pumping stops - cos φ drops to the level of 0.25 ... 0.4.

Graph of cos φ change depending on the pump operation mode

A special control relay, based on the parameters of voltage and current, calculates the power factor of the electric motor and switches it off if the value of cos φ drops below the critical one. Depending on the power of the pump motor and the relay model, the automation is connected directly or through a transformer. The reliability of this method of protection is quite high, but not all experts consider it 100%.

Motor power factor relay TELE G2CU400V10AL10 can be used in both single-phase and three-phase networks

How to choose the right dry run protection, which sensor or relay to install? There is no single answer to this question. Each of the technical solutions has its pros and cons. The depth of the well, the parameters of the pump, the presence of a hydraulic accumulator, the type of control automation, and equipment compatibility should be taken into account. It is possible and even desirable to duplicate the dry-running protection function in one system by various devices, provided that they are built on different principles for measuring parameters.

Video: 100% pump dry running protection

The video will be useful to those who plan to install water supply equipment on their own.

If you are not ready to study in depth the features of individual water supply yourself, we recommend entrusting the calculation of the necessary equipment parameters, its selection and installation to specialists. In this case, you can be sure that the protection of the well and expensive equipment is done at the proper level.

The water supply system of a private house is impossible without a pump. But it must somehow be turned on and off, to ensure that it does not work in the absence of water. The water pressure switch is responsible for turning the pump on and off, and protection against dry running of the pump should monitor the presence of water. How to implement this protection in different situations and consider further.

What is a dry running pump

Wherever the pump pumps water, sometimes a situation arises that the water is over - with a small flow rate of a well or well, you can simply pump out all the water. If water is pumped from a centralized water supply, its supply can simply be stopped. The operation of the pump in the absence of water is called dry running. Sometimes the term "idling" is used, although this is not entirely correct.

In order for the water supply at home to work normally, you need not only a pump, but also a dry water protection system, automatic on-off

What's wrong with dry running, besides wasting electricity? If the pump runs without water, it will overheat and burn out - the pumped water is used to cool it. No water, no cooling. The engine will overheat and burn out. Therefore, protection against the dry running of the pump is one of the components of automation that will have to be purchased. There are, however, models with built-in protection, but they are expensive. Cheaper to buy automation.

How can the pump be protected from running dry?

There are several different devices that will turn off the pump in the absence of water:

• dry run protection relay;
• water flow control devices;
• water level sensors (float switch and level control relay).

All these devices are designed for one thing - turn off the pump in the absence of water. They just work differently and have different applications. Next, we will understand the features of their work and when they are most effective.

Dry run protection relay

A simple electromechanical device controls the presence of pressure in the system. As soon as the pressure drops below the threshold, the power circuit breaks, the pump stops working.

The relay consists of a membrane that reacts to pressure and a contact group that is normally open. When the pressure drops, the membrane presses on the contacts, they close, turning off the power.

This is what dry running protection looks like.

When is it effective?

The pressure to which the device responds is from 0.1 atm to 0.6 atm (depending on factory settings). This situation is possible when there is little or no water at all, the filter is clogged, the self-priming part is too high. In any case, this is a dry running condition and the pump must be turned off, which is what happens.

An idle protection relay is installed on the surface, although there are models in a sealed housing. It works normally in an irrigation scheme or any system without a hydraulic accumulator. Works more effectively with surface pumps when a check valve is installed downstream of the pump.

When it does not guarantee shutdown in the absence of water

You can put it in a system with GA, but you will not get 100% protection against dry running of the pump. It's all about the features of the structure and operation of such a system. They put a protective relay in front of the water pressure switch and the accumulator. In this case, there is usually a check valve between the pump and the protection, that is, the membrane is under pressure created by the accumulator. This is the usual pattern. But with this method of switching on, a situation is possible when a running pump, in the absence of water, does not turn off and burns out.

For example, a dry running situation has been created: the pump has turned on, there is no water in the well / well / tank, there is some water in the accumulator. Since the lower pressure threshold is usually set on the order of 1.4-1.6 atm, the protective relay membrane will not work. After all, there is pressure in the system. In this position, the membrane is pressed out, the pump will run dry.

It will stop either when it burns out or when most of the water supply is used up from the accumulator. Only then will the pressure drop to critical and the relay will be able to work. If such a situation arose during the active use of water, nothing terrible will happen in principle - a few tens of liters will run out quickly and everything will be fine. But if it happened at night, they let the water out of the tank, washed their hands and went to bed. The pump has turned on, there is no signal to turn off. By the morning, when the analysis of water begins, it will be inoperative. That is why in systems with hydroaccumulators or pumping stations it is better to use other devices to protect against the dry running of the water pump.

Water flow control devices

In any situation that causes the pump to run dry, there is insufficient or no water flow. There are devices that monitor this situation - relays and water flow controllers. Relays or flow sensors are electromechanical devices, controllers are electronic.

Relay (sensors) of the flow

There are two types of flow sensors - petal and turbine. Flap has a flexible plate that is in the pipeline. In the absence of water flow, the plate deviates from the normal state, contacts are activated that turn off the power to the pump.

Turbine flow sensors are somewhat more complicated. The basis of the device is a small turbine with an electromagnet in the rotor. In the presence of a flow of water or gas, the turbine rotates, an electromagnetic field is created, which is converted into electromagnetic pulses read by the sensor. This sensor, depending on the number of pulses, turns on / off the power to the pump.

flow controllers

Basically, these are devices that combine two functions: protection against dry running and a water pressure switch. Some models, in addition to these features, may have a built-in pressure gauge and check valve. These devices are also called electronic pressure switches. These devices cannot be called cheap, but they provide high-quality protection, serving several parameters at once, providing the pressure required in the system, turning off the equipment when there is insufficient water flow.

Name	Functions	Parameters of operation of protection against dry running	Connecting dimensions	Producing country	Price
BRIO 2000M Italtecnica	Pressure switch + flow sensor	7-15 sec	1" (25mm)	Italy	45$
AQUAROBOT TURBIPRESS	Pressure switch + flow switch	0.5 l/min	1" (25mm)		75$
AL-KO	Pressure switch + check valve + dry running protection	45 sec	1" (25mm)	Germany	68$
Dzhileks automation unit	Pressure switch + idle protection + pressure gauge		1" (25mm)	Russia	38$
Aquario automation unit	Pressure switch + idle protection + pressure gauge + check valve		1" (25mm)	Italy	50$

In the case of using an automation unit, a hydraulic accumulator is an extra device. The system works perfectly on the appearance of a flow - the opening of a tap, the operation of household appliances, etc. But this is if the headroom is small. If the gap is large, both a GA and a pressure switch are needed. The fact is that the pump shutdown limit in the automation unit is not adjustable. The pump will only turn off when it reaches maximum pressure. If it is taken with a large margin of pressure, it can create excess pressure (optimal - no more than 3-4 atm, anything higher leads to premature wear of the system). Therefore, after the automation unit and the accumulator. This scheme makes it possible to regulate the pressure at which the pump is turned off.

Water level sensors

These sensors are installed in a well, borehole, tank. It is advisable to use them with submersible pumps, although they are compatible with surface pumps. There are two types of sensors - float and electronic.

float

There are two types of water level sensors - for filling the tank (protection against overflows) and for emptying - just protection against dry running. The second option is ours, the first is needed when filling out. There are also models that can work this way and that, and the principle of operation depends on the connection scheme (included in the instructions).

The principle of operation when used to protect against dry running is simple: as long as there is water, the float sensor is pulled up, the pump can work as soon as the water level has dropped so much that the sensor has dropped, the contactor opens the pump power circuit, it cannot turn on until until the water level rises. To protect the pump from idling, the float cable is connected to a break in the phase wire.

Level control relay

These devices can be used not only to control the minimum water level and dry running in a well, well or storage tank. They can also control overflow (overflow), which is often necessary when there is a storage tank in the system, from which water is then pumped into the house or when organizing water supply to the pool.

Electrodes are lowered into the water. Their number depends on the parameters they track. If you only need to monitor the presence of a sufficient amount of water, two sensors are enough. One - falls to the level of the minimum possible level, the second - the base - is located a little lower. The work uses the electrical conductivity of water: while both sensors are immersed in water, small currents flow between them. This means that there is enough water in the well / well / tank. If there is no current, it means that the water has dropped below the minimum level sensor. This command opens the power supply circuit of the pump and it stops working.

These are the main ways in which protection against dry running of the pump is organized in the water supply systems of a private house. There are also frequency converters, but they are expensive, so it is advisable to use them in large systems with powerful pumps. There they quickly pay off due to energy savings.

Dry running is the operation of a pump without liquid. For most models, this mode is highly undesirable and can lead to failure. We figure out how to protect the pump from dry running.

The pump is a necessary part of the water supply system of a private house. But in order for the pump to work for a long time, it must be periodically turned on and off, preventing operation without water. To protect the pump from dry operation, several technical solutions have been devised. Let's get acquainted with their advantages and disadvantages and choose the best way to protect against dry running.

What is a dry run

Most models are not designed to operate the pump in the absence of water. Such work is called a dry (sometimes idle, which is not entirely correct) move.

Most manufacturers explicitly indicate in the instruction manuals that dry running is unacceptable.

Let's figure out what causes this phenomenon and why it should not be allowed.

Wherever the water comes from, periodically there is a situation when the water runs out. For example:

• If the well flow rate is small, with a large analysis, it can simply be emptied. It will take some time for the well to fill up again.
• If the pump is located on the surface, the pipe through which water is pumped from the well may become clogged.
• If water is supplied centrally, it may dry up in the mains due to pipe breaks or technical work on the line, associated with a temporary interruption of supply.

Why is dry running unacceptable in the operation of the pump? The fact is that in most models, the water pumped out of the well plays the role of a coolant. In the absence of water, the parts begin to rub against each other more intensively, as a result they heat up. Then the process develops as follows:

• Heating parts expand, increase in size. Heat is conducted by the metal to neighboring nodes.
• Details begin to deform.
• The mechanism jams due to changes in the shape and size of parts.
• In the electrical part, due to a sharp voltage surge, when the mechanical part stops, the motor windings burn out.

In order for the pump to break down irreversibly, five minutes of running “dry” is enough. Therefore, dry-running protection is a necessary component of any pumping station.

When contacting the service, the masters easily diagnose dry running as the cause of the breakdown - because of this, a number of characteristic distortions of parts occur in the mechanism.

Dry running is in most cases grounds for denial of service under warranty.

How to protect the pumping station from running dry

Today, several solutions have been developed that will protect the pump from dry running by turning it off when the water supply is interrupted. Each of these solutions has its own strengths and weaknesses, so several protection systems combined together give the best effect.

But in order to determine how to create effective dry-running protection for your pump, you must first find out what features are characteristic of individual components.

Protection relay

This is a fairly simple mechanism in design. It reacts to the water pressure in the system. As soon as the pressure drops below the permissible norm (this is a signal that the water has stopped flowing into the pump), the device closes the electrical contact, and the pump power circuit is broken. When the pressure is restored, the circuit closes again.

Depending on the model and the settings that the manufacturer has set, the relay is able to operate from a pressure drop from 0.6 (most sensitive) to 0.1 (least sensitive) of the atmosphere. Usually this sensitivity is enough to determine the occurrence of an idle situation and turn off the pump.

The most common such mechanism for pumps located on the surface. But some models have a housing protected from water ingress and can be mounted on deep pumps.

Such a device is not recommended to be installed if a hydraulic accumulator (GA) is provided in the system. The fact is that usually in this case the installation of the protection device looks like this: "pump - check valve - protective relay - water pressure switch - GA". Such a scheme does not give 100% certainty that the pump will turn off during a dry run, since the water contained in the accumulator can create a pressure of 1.4 - 1.6 atmospheres, which will be taken as the norm.

And then, if, for example, at night someone flushed the water in the tank and washed their hands, this will turn on the pump, but will not empty the GA. And if for some reason water does not come from the well, then by morning the pump will already burn out due to dry running. Therefore, for hydraulic accumulator systems, it is better to look for other solutions to provide protection.

Water flow control

To determine if there is water flow through the system, two types of sensors are used:

• The most simple in design are petal relays. In them, the flow of water bends the plate, which, in the absence of pressure, will unbend and bridge the relay contacts. Then the circuit that supplies electricity to the pump will turn off.
• The turbine relay is more perfect, but more complicated in design. Its main element is a small turbine mounted on a shaft. The flow makes it spin, and the sensor reads the pulses generated by an electromagnet attached to the axis of the turbine. If the number of pulses falls below the reference value, the circuit is switched off.

There are also combined water flow controllers. They may additionally include a pressure gauge, a check valve, a membrane switch to protect against a drop in water pressure, and other components.

Such blocks are the most reliable, but due to the technical complexity, the cost of such a block can be quite significant.

Water level sensors

The water level sensor is placed in the shaft. It is most often installed with a submersible pump, but there are models designed for use with ground pumping stations.

There are two types of construction:

In addition to the mechanisms described, there are many other systems to prevent dry running, for example, frequency converters. But these solutions are not used on domestic plumbing because they are too expensive, bulky or consume too much electricity.

Necessary tools and materials

To connect a pressure switch and a dry-running protection relay, you will need to prepare:

• the relay itself.
• Tools for working with electrical wires: a knife for stripping contacts, screwdrivers.
• Wires to create an electrical circuit.
• Keys for mounting the relay on highways.
• Means of sealing connections: sealants, rubber gaskets (usually come with the relay).

Having prepared everything you need, you can get to work.

Do-it-yourself installation of protection against dry running of the pump. Step-by-step instruction

You can see the connection diagram of the pressure switch and protection against falling dry running in the figure:

The installation order is as follows:

After that, it remains only to test the system, make sure that the relay does not interfere with the normal operation of the pump and properly turns it off after going dry.

Despite the fact that connecting any dry-running protection relay is not particularly difficult, there are some nuances, the understanding of which comes with the accumulation of practical experience. Therefore, it is especially important to listen to the recommendations of specialists in each case. Here is what professionals advise about the selection, installation and configuration of protective mechanisms against dry operation:

• Before buying, carefully study the passport of the selected relay and make sure that its sensitivity and other characteristics are at the proper level for your well and pump. You can examine the passport directly in the store or find it on the page of the manufacturer of the protective device and download it in pdf format.
• Make sure that all wires and elements of the created circuits are sufficient for the power used. Otherwise, there is a risk that the conductor or relay will burn out.
• The most perfect protection system can be powerless if used ineptly. If any of the components have tripped, do not turn on the pump again until the cause of the malfunction is found and you are sure that it has been completely eliminated.
• Remember that each relay requires periodic verification and replacement. Replace expired protective system components in a timely manner.

In addition, we offer several videos so that you can see with your own eyes how to connect the relay:

Dry running protection is a precaution that should not be neglected when connecting the pump.

Although the purchase and installation of the necessary devices requires some time and money, these costs are much lower than the losses that will have to be incurred if the pump burns out.

Therefore, it is simply unreasonable to refuse to install protection in most cases.

Pumping equipment serving pipeline systems through which a 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 liquid pumped by it is not supplied to the pump, it is equipped with automatic sensors - a dry-running relay. Various types of such devices can be used for a pumping station.

Why pumping equipment must be protected from dry running

From whatever source the electric pump pumps water, this equipment may be in a situation where the liquid stops flowing into it. It is these situations that lead to the fact that the pumping station starts to idle (or, as they often say, dry) running. The negative consequence of the operation of 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 borehole pump (or circulation pump) is almost mandatory. Most modern models of pumping equipment have built-in relays. However, these pumps are very expensive. For this reason, users often purchase dry-running relays separately.

Basic Remedies

To protect the pump from dry or idling, various types of devices are used, 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:

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

The differences between all of the above devices are both in their design and principle of operation, and in their areas of 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

The dry running sensor for the pump refers to electromechanical type devices that control whether there is pressure in the system through which water is transported. If the pressure level is below the regulatory threshold, such a relay automatically stops the operation of the pumping equipment, opening the circuit of its electrical power.

The dry running relay for the pump consists of:

• 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).

The main elements of the "dry run" 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 is supplied to the pump motor, and the latter operates normally.
• If there is not enough water pressure or it does not enter the system at all, the membrane returns to its original state, opening the electric power supply circuit of the pumping unit and, accordingly, turning it off.

Situations when the fluid pressure in water supply systems drops sharply (which means that the pump needs protection from dry running) are caused by various reasons. Among such reasons are depletion of the natural water source, clogged filters, too high location of the self-priming part of the system, etc.

Pump dry running protection relays are 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 with pumping equipment in the well.

The relays that prevent the dry running of the pump work more effectively when they are installed in systems that are not equipped with a hydraulic accumulator that are served by a surface circulation pump. Of course, it is 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. In this case, the relay connection diagram looks like this: it is placed in front of the water pressure sensor and the hydraulic accumulator, and immediately after the pumping station, a check valve is installed that prevents the water from moving in the opposite direction. With this connection, the dry-running relay membrane is constantly under water pressure created by the accumulator. This can lead to the fact that the pump, which will not receive water from the source, simply does not turn off.

Effective protection of the pump against 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 the flow of water

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

Relays or water flow sensors

There are two types of electromechanical water flow sensors:

• petal;
• turbine.

The main working element of sensors of the first type is a flexible plate installed in their internal cavity, which has a cylindrical cross section. In the event that the fluid flow in the system is present and has sufficient pressure, such a plate equipped with a magnetic element is as close as possible to the reed switch, 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 shutdown of the pumping unit.

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

Automatic pump control sensor "Turby"

Electronic water flow controllers

An even more complex design is distinguished by electronic water flow controllers, 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 they are not cheap, replace several control and control devices at once. Installed in water supply systems, electronic pressure switches not only protect the pumping system from dry running, but also allow you to control the pressure and fluid flow parameters. When such system operation parameters do not meet the standard values, the electronic sensor automatically turns off the pumping equipment.

If a pump with a small headroom is used to service water systems, then they can only be equipped with an electronic relay. When the system uses a pump with a large margin for the pressure it creates, a hydraulic accumulator and a separate pressure sensor are required, 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 excess pressure is created in the system, the pumping station simply does not turn off.

Sensors that control the water level in the system

To prevent the occurrence of situations when the pump of the water supply system is idling, water level sensors are also capable, which are installed mainly in the source of water supply - a well, a well or a tank. Thus, by means of such devices, the well pump is protected from dry running (or a pumping unit that pumps water from a well). By design, level control sensors can be float and electronic.

float switches

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

The principle of operation of the float switch for monitoring the water level is quite simple. While there is liquid in the water supply, the float connected to the contact group is pulled 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 the protection of the pump-pump from dry running with the help of a float sensor for controlling the water level is the most affordable and the most common way.

Electronic relays

Electronic water level sensors are able to simultaneously solve two problems: to protect pumping equipment from dry (idle) running when the water level in the water supply source decreases and to prevent cases of liquid overflow when filling containers.

Equipping your source of water supply, any owner should think about its additional protection. In addition, not only the well itself or the well needs to be prevented from malfunctions, but also the equipment that performs the work: the so-called drainage systems and external pumps.

In order to avoid the operation of the Grundfos pump in a dry run, specialized devices are installed on the water pipes, which, first of all, should be chosen correctly.

Dry running pump - what is it?

Wherever the pump pumps water, sometimes a situation is formed, when the water ran out. With a small flow rate of the well, the water can simply be pumped out. In the event that water is pumped from the central water supply, its supply can be easily interrupted. The operation of the Grundfos pump in the absence of water will be called dry running. Sometimes the word "idling" is used, but this is not entirely correct.

What is wrong with the appearance of a dry run, besides the fact that electricity is wasted in vain? If, in the absence of water, the pump operates, it will overheat and then burn out - the pumped water is used to cool it. Therefore, the protection of pumps from dry running is one of the elements of automation that needs to be bought in addition. There are, however, modifications with integrated protection, however, they are not cheap. It is more economical to buy automation.

How can the pump be securely protected?

There are several different devices that will turn off the pump when there is no water.:

All these pumping devices are designed for one thing - turn off the unit without water. Only they function differently, have a different area of ​​​​use. Next, we will understand the distinctive features of their work and when they are most effective.

Dry running protection relay

Pump relay to protect the unit against dry running - a simple electromechanical device that controls the presence of pressure in the system. Its price is acceptable. As soon as the pressure drops below the threshold, the power line breaks, and the pump stops working.

The relay consists of a membrane that reacts to pressure and a contact group that is normally open. When the pressure drops, the membrane presses on the contacts, they close, turning off the power.

Pressure to which the fixture responds - from 0.1 atm. up to 0.6 atm. (depending on factory settings). A similar situation is likely if there is not enough water or it is completely absent, the filter is clogged, the suction part is very high. In each case, this is a situation with the appearance of a dry run and the pump must be turned off, which is what happens.

They install with the connection a protective relay against dry running on the surface, although there are modifications in a sealed case. Naturally, it functions in the irrigation scheme or any other system without a hydraulic accumulator. Works most productively with shallow pumps if a check valve is installed after the pump itself.

In a system with GA it can be installed, however, you will not get 100% protection of the unit against dry running. There is a problem in the quality of the structure and operation of such a system. Install a safety relay in front of the water pressure switch itself, as well as the built-in hydraulic accumulator. At the same time, as a rule, there is a check valve between this pump and the protection, in which case there is also a membrane, which is under pressure formed by the accumulator. This is a common scheme, however, with this method of administration, the situation is likely if a functioning pump without water eventually turns off and burns out.

For example, a dry running situation has been created: the pump is connected, there is no water in the well, there is a certain number in the accumulator. Since the lower pressure limit is set, as a rule, at about 1.4-1.6 atm., The safety relay membrane will not turn on - there is pressure in the system. In this state, the diaphragm is pressed out and the dry running pump will operate. Will it stall or in this case if it burns out? When most of the water supply is used up from the accumulator, a breakdown may occur. Only in this case will the pressure drop to the limit and the relay can affect.

If such a situation appeared during the period of intensive use of water, nothing terrible will happen in principle - a certain number of tens of liters will run out quickly and everything will be fine. However, if it happened at night- flushed the water in the tank, washed their hands and went to rest. The pump is connected, there is no signal to turn off. By morning, when there is a water intake, the unit will be inoperative. That is why in systems with hydraulic accumulators or pumping stations it is more correct to operate other dry-running protection devices.

Water flow sensor

To measure the flow of water passing through the pump, a submersible flow sensor with connection was created. The price for it in Moscow is affordable. The downhole regulator consists of a valve (“petal”) located in the flow path and a microswitch. The "petal" is spring-loaded and has an integrated magnet on one side.

The working diagram of the dry-running protection pump sensor is as follows:

The pump submersible flow sensor is inserted into booster stations with low capacity. Functions in establishing two values ​​of the degree of pressure and flow. The device stands out for its compact dimensions (light weight and size).

At a pressure level whose range is 1.5-2.5 bar (depending on the modification of automation) in the pump there is a command to start its work. The pump performs its own functions until the water intake stops. Due to the flow meter integrated into the relay, the pump is stopped. The downhole regulator very quickly detects the occurrence of a "dry run", which makes it possible to exclude a long stay in the working "waterless" mode.

Situations when it is allowed not to use protective devices

It is possible to do without mounting a downhole dry-running sensor only in some cases:

• continuously monitoring the water supply from a well or a well (you need to be close in order to respond in a timely manner to a change in the water stream);
• pumping is carried out from an inexhaustible source;
• the well has a high flow rate;
• the person checking the operation of the Grundfos station has experience, understands the principle of operation of the pump system.

If the state of the pump has become intermittent or it has turned off completely, it cannot be started again without disclosing and eliminating the malfunction factors.

What safety device to choose?

The choice of a protective device against dry running is determined by modification of the pump itself and problems which he needs to deal with. A suitable view is when a dry-running sensor in the form of a float and a protective pressure switch is used. Connecting these devices to the pipeline will make it possible to absolutely reduce the risks of malfunctioning pump equipment.

The use of safety elements is optional if:

• the depth of the well or tank is quite large;
• maintenance of the unit is carried out by an experienced specialist;
• the water level of the system does not change - it makes no sense to connect with protective devices.

The operation of a Grundfos pump requires a high level of user attention. As soon as the water disappears or the relay operates and the engine turns off, it is necessary to immediately find out the root cause and eliminate it, and only after that it is possible to resume the operation of the unit.