Protection against dry running of the pump: what are, installation. Automatic pumping station: implementation of protection against "dry running"

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

In pumps for household needs thermoplastic (high-strength wear-resistant plastic) is most often used as the main material for impellers and diffusers, which, being highly technological and low-priced, has been doing its job well for many years. But when working without water, which under normal conditions works both as a lubricant and as a source of heat removal, internal details pump start to touch, heat up and deform. In extreme cases, the pump shaft may jam and the 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 simply identified by a specialist when disassembling the pump and does not apply to warranty cases!

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

Typically, this is the following:

• Pumping water from wells or wells with a low flow rate. This may be due to an incorrectly selected pump (with a very high performance) or natural phenomena (in a dry summer, the water level in many wells or wells drops and the flow rate of the well / well, in other words, the amount of water that feeds the well / well from underground sources per unit time, below the performance of the pump itself).
• Pumping water from tanks. It is imperative to ensure that the pump does not pump out all the water from the tank 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 in the network.

Without dry-running protection, the pump "does not understand" that it needs to turn off when there is no water in the suction pipe. It will continue to work on until it breaks, or until it is turned off by forgetful owners.

The main types of protection against "dry running":

(float) - a fairly inexpensive and reliable assistant in the protection against "dry running" when pumping water from tanks or wells. There are floats that work only to fill the tank. That is, the contacts inside the float will open and the pump will stop when the tank is filled to a certain level. This type of floats is more likely to be needed to protect against overflow, and not from “dry running”. The second type of floats, which works for emptying, is just our case. The float cable is connected to a break in one phase of the supply pump. The contacts inside the float will open when the liquid level in the tank/well falls below a certain level, thus stopping the pump. The required level of operation is set by the place where the float is installed. The float cable must be fixed at a fixed level so that when the float is lowered, water will still remain in the container along with the general water level at the moment the contacts open. In the case of pumping water from the well with a submersible / surface (self-priming) pump, it must be fixed so that when the contacts open, the water is above the suction grate / bottom valve of the pump. It should be noted that this principle of protection against "dry running" is implemented in almost all well pumps. various manufacturers(for DAB, these are pumps of the PULSAR series).

Unfortunately, the float is not universal. In a well or a network pipeline, he simply does not have enough space. We must look for other forms of protection.

Pressure switch with dry run protection. This device is a conventional pressure switch with additional function opening contacts when the pressure drops below the threshold level. Usually this level is set by the manufacturer at the level of 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 a "dry run", opens the contacts supplying the pump. It will be possible to start the pump again only manually, having previously established and eliminated the cause of the "dry run". The pump, before a new start, will again have to be filled with water.

It should be noted that the use of a pressure switch with "dry run" protection is possible only if automatic operation pump (together with a hydraulic tank), otherwise the use of this relay loses its meaning. It is mainly used together with a downhole 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 gives 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 is turned off after the withdrawal of water is stopped, due to the lack of fluid flow through the relay. Protection is “dry running” and is carried out thanks to the flow sensor built into the relay, which registers the actual flow rate of the liquid through the relay. The pump is switched off with a short time delay after a dry run is detected, which does not affect the pump's performance. In addition, the press control performs other protective functions, such as current and voltage protection. The main advantage of press control is its very small dimensions and weight. Unfortunately, there are now a large number of press controls produced in an unknown place. Average term the service life of such devices does not exceed 1-1.5 years, and then, if you're lucky. Certified and high-quality press control (as in 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 the relay with a conventional single-core electrical wire, and serve only to send 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, a signal from it is transmitted to the level switch and a command is given to stop the pump. After the water rises above the control sensor, the pump will automatically start. This method of protection is very reliable, however, a little more expensive than the 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 specific task and preferences. From experience, we can say the following: when pumping water from tanks / tanks / wells by a pumping station, almost 100% guarantee of protection will be the use of both a pressure switch with “dry run” protection and a float installed in the tank. They will just duplicate each other. At a price, this option will come out no more than installing one flow switch. When defending well pump most often use a pressure switch with "dry run" protection. But it is better to use a slightly more expensive, but also more reliable way protection, using a level switch.

Note that if you have drilled a deep well with a good flow rate (confirmed well certificate) or if you have significant experience in operating pumps in your well / well and know that the water level practically does not decrease during continuous operation of the pump, you can protect against "dry running" ' and don't 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 do not need to immediately try to start it again, first try to establish the cause of the malfunction, and only then start the pump again.

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

The most common emergency situation associated with the failure of a household pump or a pumping station for a domestic water supply is the operation of the unit idly, that is, without pumping water or with pumping from weak pressure. This situation is called "dry running". It should be noted that this species emergency is not covered under warranty. Because the manufacturer is not guilty of this, and he is not responsible for this. Improper operation of the pumping station is to blame for everything.

What is the danger of dry running

During idle operation, the so-called zone of stable cavitation occurs. That is, under the influence of the emerging elevated temperatures, the design of some components and parts of the pump itself changes. That is why such a term as dry running protection for a pumping station is increasingly heard.

Deformed pump impeller

The thing is that the pumped water is a cooling medium for such parts. pumping equipment, as an impeller (impeller), sealing cuffs and guide vanes (nozzle, inlet pipe). By the way, it should be noted that the impeller is a rather expensive part, and it is not so easy to replace it. It is very important to understand that the impeller itself is located in a separate compartment. And the gap between its edges and the body of the compartment is not very large. Under thermal stress, the impeller expands and begins to come into contact with the housing. This is the emergency. By the way, it is she who can disable the electric motor, which is much worse and more expensive.

Therefore, regardless of the local water supply device, purchased as a whole or, it is recommended to install a dry-running relay. An exception may be in some cases: in case of intermittent operation of the pump, for example, in the country, when constantly monitoring the device, water is taken from an inexhaustible source, the consumer has extensive experience in operating the device. But even in these cases, many experts still recommend installing a safety relay in order to completely eliminate the possibility of a breakdown.

Causes

If we talk about the external reasons for the appearance of a dry run, then we can say that there are a lot of them. But all of them are concentrated on one thing - this is the complete or partial absence of water in the working compartment of the pump. As for the partial absence, as a result of this, inside working chamber air bubbles appear. It is in them that the zones are formed elevated temperature. Experts note that the critical performance of the pumping station, at which we can talk about dry running, is 5 l / min. What might affect it.

• Lack of water in the hydraulic structure.
• Depressurization of the supply hose or pipeline, due to which the pump begins to suck in air inside the system.
• clogged up check valve.
• The voltage in the power supply network has dropped.

Pump parts after running dry

By the way, it should be noted that the friction of rotating parts leads to an increase in temperature. This is from the course. school curriculum in physics. An insufficient amount of water that flows inside the working chamber of the pump causes it to boil. It is good if the impeller is made of metal, but today many manufacturers have switched to plastic, which reduces the cost of the product. But precisely polymer material reacts negatively to saturated steam, which deforms the plastic impeller.

Purpose of the dry running relay

As you can see, an emergency situation can lead to irreparable losses. The pumping station not only stops working, but after long-term operation her in dry running mode, it simply fails. After that, you will have to do either an expensive repair, or a complete replacement of the unit. To prevent this from happening, manufacturers began to install a dry-running relay for a pumping station in the design of the device. Its main task is to turn off the power to the pump motor if the water pressure in the supply pipeline of the water supply system has fallen below critical. That is why the device is mounted on the pipeline after the pumping station.

Attention! The dry-running relay is not installed separately from the pressure switch. Both devices complement each other, working in pairs.

Installation location of the dry-running relay

True, it should be noted that a dry-running relay is just a device that responds to a specific signal from a sensor that responds to changes in water parameters within the local water supply network. For example, protection against dry running of a borehole pump consists of a relay and a float switch. The latter monitors the water level in the hydraulic structure, sends a signal to the dry-running relay, which interrupts the supply of electricity to the pump motor. Instead of a float switch, you can use a liquid flow sensor that will control the speed of water in the pipeline. That is, you can always find a certain option that would track a certain water parameter and react to its change.

The principle of operation of the relay

Currently, manufacturers offer various models of dry-running relays. But they all work on the same principle. In principle, this device works like a conventional two-contact relay. That is, it is an intermediate device between the mains supply and a device that consumes electricity. The last in this case is the pump of the pumping station. Therefore, the relay itself is installed in the network in series.

Device LP-3

This is how the Italian model Italtecnica LP3 works.

• In the initial state, the relay contacts are always open.
• To turn on the pump, you must press the red button on the relay housing and hold it in this state a little.
• That is, the contacts close, through which an electric current begins to flow to the electric motor.
• As soon as the pressure in the water supply system drops to 0.5 bar, the contacts simply open.

Attention! The presence of water in the plumbing system creates the conditions for its splashing. Therefore, all dry-running relays, regardless of the manufacturer's brand, are manufactured with electrical safety requirements. Therefore, their electrical protection class is IP44.

To respond to the pressure in the water supply, a spring is installed inside the relay, which is adjusted to certain low and high critical values ​​\u200b\u200bof a given water parameter. It is with its help that the contacts are opened and closed inside the device.

Installation method

How to install correctly

As mentioned above, a dry running sensor for a pumping station is installed in conjunction with a pressure switch and mounted on the supply pipeline.

• First of all, it should be noted that the entire installation process is carried out with an empty pipeline and pumping station.
• The dry-running relay itself must be connected to the water supply line through a fitting, usually a tee. Installation must be carried out according to all the canons of plumbing, that is, with complete sealing of the joints.
• It is very important to make the electrical connection of the devices correctly. As already mentioned, in this system the connection must be serial. By the way, you can see it in the photo below.
• It remains only to connect through the terminal box ( contact group) wires, which are necessarily carried out through pressure seals. It is clear that it is necessary to work with electrical wiring only when the unit is powered off.

Scheme electrical connection dry run relay

It should be noted that the diagram shown above is not standard. That is, it is not necessary to install a dry-running switch before the pressure switch. These devices can be interchanged. The main condition is the consistent installation of both in the electrical supply circuit. Moreover, many models of pumping stations are already equipped with a pressure switch at the factory, which is installed directly on the outlet inlet pipe of the pumping unit.

New generation relay

Currently, manufacturers have begun to offer new devices, which include a check valve and an electronic plateau. But the control of the device is fixated on a micro switch and a magnetic relay. The latter are contacts sealed in a glass tube, and they respond well to a changing magnetic field.

On the check valve, which is spring-loaded, is installed permanent magnet. With increasing pressure, the valve moves towards the glass bulb, where, under the action of magnetic field contacts close. That is, the circuit is closed, and current is supplied to the pump motor. As soon as the pressure in the pipe drops, under the action of a spring, the valve moves back, dragging the magnet along with it. That is, inside the flask, the contacts open. This is how the power supply to the motor is disconnected, which immediately stops, interrupting the dry run of the pumping station.

Relays of the new generation of the Brio series

There are several useful options in this dry-running relay model.

• In order for the check valve with a magnet to connect the relay itself, it is necessary to create pressure inside the pipeline. Therefore, the start of the electric motor occurs without a relay, the action time is 7-8 seconds. It is during this time that he can pump water into water supply network to create pressure.
• After the water supply stops, that is, the formation of a dry run, the relay turns off. But after a certain time, it will turn on automatically. And if there is no pressure, then it will turn off again. And this can be repeated several times. If after all attempts the water pressure in the plumbing system has not increased, the relay will turn off completely. It can only be restarted manually.

This is how the dry-running relay works, which is the protection of pumping stations from emergencies associated with the lack of water in the plumbing system. A small device that increases the duration of trouble-free operation of pumping units.

Dry running of the pump is the operation of the unit in the absence of the required amount of pumped liquid. If water or other liquid runs out, then the pump protection against dry running is activated. It can be represented as several different devices, the most common of which is considered a dry running relay for a pump.

Dry running sensor for a pump - principle of operation and device

There are several most common devices, the main task of which is to protect pumps from running dry. These include:

• Dry running protection relay;
• The sensor of control of volume of the pumped-over liquid;
• Water quantity sensor - float.

Each of the listed devices is used in various pumps with different tasks and functions. The most commonly used in the manufacture of pumps is the dry-running protection relay. It has a fairly simple design, but it shows high efficiency when operating centrifugal, vortex and other types of equipment.

The relay is a simple electromechanical device designed to control the pressure inside the pipeline. As soon as the pressure falls below the minimum allowable limits, electrical circuit immediately opens and the unit switches off.

The relay device includes a sensitive membrane that reacts to pressure fluctuations and a group of contacts, which, in normal condition is in the open position. With the pressure burning, the membrane begins to put pressure on the contacts, which leads to their closure and the interruption of the supply of electricity to the pump motor.

Each dry running sensor for the pump is designed to work in an environment with a certain pressure. Depending on the manufacturer's settings, the equipment can operate in the range from 0.1 to 0.6 atmospheres. As a rule, the relay is mounted on a surface outside the pump housing, however, there are devices mounted inside the device.

Installing a protective relay in a system with a hydraulic accumulator - is it worth the risk?

The protective relay will function normally with any pipeline that does not have a hydraulic accumulator in its design. On the other hand, you can install a relay in tandem with a hydraulic accumulator, however, such an installation will not provide full protection against dry running.

The reason for this lies in the principle of operation and structural features of the sensor: the protective relay should be mounted in front of the hydraulic accumulator and the fluid pressure switch. In this case, a dry-running valve is installed between the protective device and the pumping unit.

In this case, the relay membrane will be under the influence of constant pressure created by the accumulator. This is a fairly typical circuit, but in most cases it is not able to help protect the pump. For example, consider the following case: when the pump is turned on, which pumps out liquid from an almost empty tank, the remaining liquid remains in the accumulator. Since the lower pressure threshold is set by the manufacturer within 0.1 atmospheres, there is actually pressure, but the pump will run idle.

As a result of this, the pump motor will stop working only when the accumulator becomes completely empty, or when the engine itself burns out. As a conclusion, it can be said that systems with hydraulic accumulators are better equipped with other protective devices.

How to connect a dry running sensor - the correct procedure

The connection of the relay can be performed by anyone who has the slightest idea of ​​\u200b\u200bwork electrical appliances. First of all, you need to remove the protective cover of the device. Under it are 4 contacts - two for input and two for output. The connection diagram to the input "L1" and "L2" and to the output "M" of the pump itself is shown in the image below:

It should be remembered that the cross section of the wires supplying the pump must correspond to the power of the unit. The socket must be grounded.

Setting the connected safety relay

Dry running relay for pumping station or domestic pump you need to not only connect, but also correctly configure. This should be understood as an adjustment of the dependence and rigidity between the switched contacts and the platform, which is subject to the operating pressure. You can adjust these characteristics by changing the stiffness of the spring, which must be weakened or compressed by turning the nuts. Below, as an example, the location of these nuts in the RDM-5 relay is shown. Most other modern protective devices have a similar design, and the adjusting nuts on them are located in the same way.

According to the factory settings, the minimum pressure for the relay to operate is 1.4 atm. The maximum pressure, in this case, is 2.8 atmospheres. If you want to change the minimum pressure threshold, then for this the nut "2" must be tightened clockwise. In this case, the upper pressure threshold will also increase. The difference between them will always be 1.4 atmospheres.

If you want to adjust the difference between the lower and upper pressure threshold, then for this you need to turn the nut "1". Turning it clockwise will increase this value, while turning it counterclockwise will decrease it.

Protective relays LP 3 - description and characteristics

The device of this model of the hydrostop type is used in water supply systems, and is intended for shutting down wells and surface pumps in automatic mode. The devices are switched off openly immediately after the liquid level falls below the permissible limits. To the main technical specifications relay applies:

• The maximum level of switched current is 16 A;
• Pumped water temperature range – from 1 to 40 °C;
• Pressure range during operation - from 0.5 to 2.8 atmospheres;
• Electrical protection class IP44.

The manufacturer provides a 1-year warranty for this relay model. The device shows reliability and effective protection pumps during operation.

In domestic pumps, the main material of the impellers is thermoplastic (plastic, which is durable). It is characterized by great potential of work and low cost. The material has served its purpose well for many years. But if it works without water, which acts as a lubricant and a source of heat removal, then the internal components of the pump are deformed. In the most extreme cases, the shaft may jam and the motor may fail. Usually, after this, the pump cannot supply water, or it supplies it with very poor quality.

Who can diagnose a breakdown?

Dry running can be easily diagnosed by a specialist when disassembling the pump. It does not apply to warranty damage.

Rules to follow

Any manufacturer of the device indicates that it is impossible to use the pump without water. Therefore, it is important to observe certain norms, especially in places with increased level risk.

The main reasons for the breakdown of the unit include the following:

• Wells and wells with a low flow rate. The fault of dry running may be the selection of an unsuitable pump configuration, which is distinguished by a high power level. Or the cause may be natural phenomena. For example, in hot summers, the water level in wells and wells drops, and their flow rate becomes lower than the pump performance level.
• The process of pumping water from containers. It is recommended to carefully monitor that the device does not pump out absolutely all the water, and turn it off in time.
• When pumping water from a network pipeline, the pump is embedded directly into it. It helps increase blood pressure. Since the pressure in the system is low, this is a fairly common application. It is very difficult to determine the moment when there will be no water in the network.

The pump must be protected against dry running. When the container is empty, the device is not able to automatically turn off. It will continue to function until it breaks or until inattentive users turn it off.

Float

The pump is protected from dry running when pumping water by means of a float. The cost of such a switch is low.

There are the following types of device:

• Devices that are designed only for filling the container. Raising the water level to a certain limit causes the contacts inside the unit to open, and the pumping system stops its work. This type of floats serves as protection against overflow, but not against dry running.
• Another modification involves work on emptying containers. This is exactly what is required. The cable of the device is connected to a break in one of the phases that feeds the pump. The contacts inside the device open, and if the liquid level in the tank drops to a certain level, the pump will stop. The required response limit is determined by the place where the float is mounted. The cable of the device is fixed at a fixed level in such a way that when the float is lowered, at the moment the contacts open, there is still water in the tank. If water is pumped out of the well by a pump with a surface (self-priming) design, then the fastening should be carried out in such a way that when the contacts open, the water level is above the grate that sucks in water.

It should be noted that such protection of the pump against dry running is used in almost all wells with pumps. Devices are produced by various companies.

Unfortunately, the float is not universal. It simply does not fit in a well or network pipeline. Here are other types.

Using a pressure switch with dry-running protection

The pump dry-running protection relay is an ordinary device equipped with an additional contact opening function when the pressure drops below the extreme level.

This level is usually set by the pump manufacturer and is between 0.4 and 0.6 bar. This indicator is not regulated. At correct operation the pressure in the system will not drop below this mark, since all pumps used for private needs operate at high pressure.

A drop to the limit threshold can only be observed if there is no water in the pump. Without water, there is no pressure, and the relay, reacting to a dry run, opens the contacts that power the device. The pump can only be started manually. Before doing this, the cause of the failure must be identified and eliminated. The pump is refilled with water before it is switched on again.

What type of construction is this pump protection intended for? Dry running of the pressure switch will help to avoid only automatic configuration (together with a hydraulic tank). Otherwise, the operation of the device loses its meaning.

As a rule, the relay is designed for a deep pump configuration, as well as for surface system or stations. There is also protection submersible pump from dry running.

Flow switch equipped with pressure function

Many manufacturers offer to replace the hydraulic tank and pressure switch with another compact device - a flow switch, or a press control. This device sends a command to start the pump when the pressure in the system drops to 1.5-2.5 bar. After the water supply stops, the pump turns off, since the liquid no longer passes through the relay.

Protection of the pump against dry running is provided by a sensor built into the relay. The shutdown of the system occurs after fixing the dry run, which takes a little time and does not affect the functionality of the pump. In addition, press control provides protection against increased voltage in the mains.

The main advantage of the unit is its small size and weight. Unfortunately, the market is overflowing with devices that are produced by unknown countries. Understanding the quality of a particular model can sometimes be very difficult.

On average, the device works for about 1.5 years, provided that the assembly is done at a high level. A device that has been certified and has high rates, manufactured by ACTIVE. Its cost is about $100.

Using a level switch

The basis of the level switch is electronic board, to which the dry running protection sensors of the pump are connected. As a rule, the design of the device involves three electrodes, one of which performs a control function, and two - a working one. They are connected to the device through an ordinary single-core electric wire. The electrodes serve to give a signal.

The principle of operation of the device

Protection against dry running of the borehole pump is carried out when the sensors are immersed in the tank at different levels. When the water drops below the control sensor, which is installed a little higher than the installation of the pump itself, the electrode sends a signal to the level switch, and the pump stops.

After raising the water above the control sensor, the automatic pump is activated. Dry running protection is different high level reliability, but the cost of such a relay is much higher than that of other devices. Also, the device is used for pumping water from wells and wells. The level switch itself is installed indoors or in any place where there is no moisture.

Which device to choose?

The use of the device depends on the pump model and the taste of the user. Experts note the following.

Protection against dry running of the borehole pump, as well as devices located in tanks or wells, will be fully implemented with the simultaneous use of a pressure switch and a float. These devices will complement each other. At a cost, this option will not be more expensive than installing an expensive level switch.

It should be noted that in order to protect a pump intended for operation in wells, they often resort to the use of a pressure switch. It is better to use models of an expensive segment, as well as a level switch, which is distinguished by a high degree of reliability.

Note that the application protective equipment optional if:

The well is deep, and it has a good flow rate, indicated in the technical data sheet;
. you have the proper experience in using pumps in a well or well;
. you are sure that the water level in the system practically does not fall.

When operating the pump, be extremely careful. As soon as you notice that the water has disappeared or that it has worked that caused the pump to turn off, try to find out the cause of what happened, and only then put the pumping system into action.

Electrical modifications

Despite the fact that protective means have been developed that operate on elementary principles and understandable criteria, it should be remembered that in addition to mechanical components (pipes, pressure switches, receivers, valves and stop valves), there are configurations that operate on electricity.

Do-it-yourself protection of the pump from dry running can be carried out using relays, transistors and resistors. The process is not particularly difficult.

But there are currently a wide range of electronic devices and this makes the task much easier. There are even special automatic units that combine the function of a protection relay and a pressure relay. Some models perform a smooth restart of the pump.

For example, reviews indicate that the LC-22B model can cope with all the problems that arise in the pumping system quickly.

Users note the EASYPRO pressure controller from Italian manufacturer Pedrollo. It provides constant maintenance automatically starts and stops the pump. The pressure regulator in this device is supplemented expansion tank and the function of changing the outlet pressure in the range from 1 to 5 bar. In addition, the display of the device shows the entire the necessary information About work pumping system.

Conclusion

Applying your knowledge and skills to implement a pumping system protection scheme is not that difficult. Any mechanical configuration is simple.
With not only a theoretical base, but also knowledge of several options for solving this problem, you can ensure the smooth functioning of your pumping system.

Modern pumping stations are often equipped with either a full-fledged dry-running protection, or at least protection against engine overheating. The benefit of having such elements in the design is obvious: where necessary, protection can prevent pump failure.

But the presence of protective modules leads to an increase in the cost of the structure. That is why it is worth considering in advance how important dry run protection is for you, and whether it is worth spending money on a more expensive station - such as.

The presence of a device that will turn off the pump when water stops flowing into the system is highly desirable in such cases:

• The pump is used to increase pressure by tapping the pumping station into the mains water supply. This is done quite often, and in order to insure the equipment in case of a water supply shutdown, protection is installed.
• The station is used to draw water from a reservoir. Here, the relevance of protection against “dry running” is obvious: as soon as the container is emptied, the pump will begin to “grab” air, and if it is not turned off in advance, it will quickly fail.
• A well or a well with a low debit is used as a source of autonomous water supply. Here, too, there is a risk that the hose with which the intake is carried out will be above the water level, and this will lead to breakage.

The latter case is relevant for almost all private households. In the summer, the water level drops anyway, but it is additionally lowered due to intensive selection for irrigation. So a pumping station pumping water from a well or a shallow well must be tediously protected.

Ways to implement protection

Dry running protection can be implemented in different ways. Here are the most common patterns.

float switches

A float is the simplest device that is used when equipping autonomous water supply systems based on tanks or wells:

• The float is fixed in such a way that the system works when the water is just above the level of the intake pipe.
• When the water level drops, the float opens the contacts.
• When the contacts open, the phase supplying the pump is broken, and the pump stops working.

Pressure/flow switch

Another device (example -), which is equipped with many pumping stations. It works quite simply:

• The manufacturer sets a certain pressure level at which the relay is activated. Usually this value does not exceed 0.5 -0.6 bar and cannot be changed by the owner of the pump.
• As soon as the pressure in the system falls below this level (and this does not happen even with intensive simultaneous water withdrawal), the relay registers a “dry run” and the pump is de-energized.

Note! Restart must be carried out in manual mode, after the cause of the relay operation has been eliminated and the system has been filled with water.

A prerequisite for effective work the pressure switch is the presence of a hydraulic accumulator. However, automatic alluvial stations are completed initially.

If there is no accumulator, then a compact flow switch can be used instead of a pressure switch. But it works on a similar principle, but turns off the system when water passes through the device. The response time of such devices is short, so the pump receives effective protection.

Level switch

If the water source is a well, then a level switch can be used to protect the pump from "dry running":

• The relay is a board to which the electrodes are connected (usually two working and one control).
• The electrodes are lowered into the well and fixed in such a way that the control electrode is located just above the level of the well pump installation.
• As soon as the water level in the well drops, the control sensor is activated and the pump is turned off. After the water level rises, the system automatically starts on a relay signal.