Application and principle of operation of a dry-running relay. Dry running relay - device, principle of operation, installation and connection features Deep pump dry running sensor

Dry running is incorrect functioning well pump for a water supply system, as a result of which the liquid stops pumping out. This mode of operation is unsafe because it can cause the equipment to malfunction at any time.

The downhole pump is designed so that the pumped water acts as a lubricant and cooling system in the device. If it does not reach the required level, then the equipment may overheat. In the case of operation in dry running mode for long term the main parts of the device are damaged, as a result of which the pump motor may be destroyed.

For this reason, it is necessary to monitor the functioning of the well pump during the operation of water supply equipment. Dry running protection is achieved by system automation. Special thermostats, relays and float controllers will be able to turn off the equipment when a dry run is detected.

The main factors of dry running

The main factor in the incorrect operation of the pump is the lack of fluid. It makes no difference which source is used when pumping water. An artificial reservoir, a large capacity, a drilled well, a well - in each of the listed sources, water ends and downhole device is above the liquid level.

Thus, the pump starts to run idle, and problems will soon arise in it. This may be due to the fact that the equipment for pumping water was not properly selected or placed inside the well. To exclude the possibility of idle operation, the installation of a borehole pump is usually carried out at the dynamic level of the well, that is, where the water never decreases.

Secondary pump idle factors are commonly seen with equipment that is designed to operate from the surface of the well. It is not uncommon for pipes for pumping liquid to become clogged, as a result of which water begins to flow poorly. Sometimes the pipe loses its tightness as a result of damage or deformation. As a result, air enters the water supply system and gets inside its main devices, disrupting their operation.

Machinery connected to the water supply system in country houses, most often installed as a water pressure booster. In this case, the idle operation of the device does not occur due to the lack of liquid, but due to reduced pressure in centralized system supplying the house with water.

Based on this, it can be confidently asserted that the dry run is manifested by factors similar to each other, that is, it is associated with the disappearance of the necessary liquid or the presence of air in the water supply system. If the device operates only with human intervention, it does not need to defense mechanism. Its need is also eliminated in the case of pumping water from permanent source which may be a natural reservoir. But if an automated water supply network is used, the pumping device needs constant monitoring and protection.

Pump protection against dry running

To protect the water pumping system from idle operation, it is necessary to equip it with special thermostats and relays designed to automatically turn off the power supply when the pump overheats. Device idle detection can be based on three factors:

well filling level;
pressure forces on the outer pipe of the pumping mechanism;
the pressure force of the water pumped out by the pump.

Float controllers and liquid level switches function by monitoring the degree required height water.

Since the controller is placed above the fluid transfer equipment, it allows it to function. If this level drops below normal, the controller circuit will be disconnected, as a result of which the power to the water supply will be turned off. Most controllers will require manual connection of the pumping mechanism.

The relay is the most advanced technological solution. It contains 2 controllers placed on the lowest and highest high levels wells. If there is a deviation from the norm, the equipment is turned off. In the case of backfilling and reaching the required level, the mechanism starts functioning again. The main advantage of the pressure switch is to turn off the system before the idle mode occurs.

The second factor is the force of pressure on the outer pipe of the pumping mechanism. If the pressure drops below the set rate, this means that the equipment does not pump out water. Accordingly, it needs to be disconnected from the power supply.

The third and final factor is the force of the fluid that flows through the pump through the flow controller. With a decrease in the level of pressure, a critical level is reached, which contributes to the instant shutdown of the device.

The second and third methods involve the operation of the paging mechanism in idle mode for some time, since the controller must detect incorrect operation of the equipment in order to turn it off. This is a small, but a disadvantage. It should be borne in mind that it will take at least 5-10 minutes for the mechanism to come into a faulty state.

Protection of the water supply network from idle operation will be required in country houses, but in most cases it is not used alone, but in combination with automated mechanisms, the installation of which is determined by the scheme water pipes and the presence of a water accumulator.

The “dry” running of the pump is called its idle operation, when water, for one reason or another, has ceased to flow to it. The fact that in this case there is a waste of energy is not the most the main problem: overheating and rapid wear of equipment are much more dangerous, because water plays the role of lubricant and coolant.

Incorrectly selected equipment. It often happens that a too powerful pump model was chosen to equip the well. Another possible variant problems - the device was mounted higher than the dynamic level of the well.

The suction line is clogged.

The pipeline has lost its tightness.

Decreased water pressure. If a running pump is not protected against dry running, it can quickly fail due to overheating.

Water is pumped from the tank. When the water in the tank dries up, the equipment goes to idle.

This is a control device that monitors the level of pressure inside the water supply. If it falls too low, the pump stops instantly by opening the supply circuit.

The design of the protective device includes:

Membrane. This role is performed by the wall of the inner chamber of the relay.

Contacts. They close or open the power supply network of the pump motor.

Spring. The level of its compression indicates the limit of the fuse operation (factory settings are in the range of 0.1-0.6 atm.).

Most often, the relay connection point is the ground surface (the place must be dry). However, on sale there are also devices in a sealed case, which are installed together with the pump in the well.

The dry-running relay operates on the following principles:

At normal pressure in the system, the membrane flexes, and it closes the contacts. This allows electricity to move freely through the circuit, ensuring the normal operation of the pump.

In the event of a weakening of the water pressure, or a complete cessation of its supply, the membrane straightens, opening the electrical circuit. As a result, the pumping unit instantly stops: the resumption of work is possible only in manual mode, before filling the apparatus with water.

Pressure sensors are characterized by a wider range of operation. They are able to respond to pressure drops from 1 bar. Usually, household appliances are completed in this way. pumping units central pipelines (more specifically, fire extinguishing and water supply systems).

Water pressure sensor: pressure gauge and pressure switch

To protect against idle operation of the pump, some other devices have also been developed:

"Float". A good option protection from idle move when water is pumped from another container or well. Here, it is not pressure that is monitored, but the water level inside the circuit. One of the types of floats reacts only to the filling level: the contacts open and the pump stops only after reaching the designated filling limit. Frankly, such a device rather protects against overflow, and not from dry running. A more suitable option are floats that fix the level of emptying. In this case, the opening of the contact occurs after the water in the tank or well drops below a certain level, which is oriented at the place where the float is mounted. The disadvantage of this solution is that the well or pipeline does not always fit such a sensor.

Level relay. A more modern modification of devices that respond to changes in water level are electronic sensors. They are equipped with a wellbore or well at several points: when the water drops below control device located immediately above the installation point of the pump, a command is sent to stop it. After the water level is restored, the equipment starts automatically. Such dry running control devices are highly reliable: they are often used when pumping water from a tank. In this case, the installation of the level switch itself is carried out indoors.

flow sensor. The main job of this device is to measure the flow of water through the pump. The device includes a valve and a switch. The valve is equipped with a spring and a magnet on one side. The water pressure sets the valve petals in motion, which provokes the contraction of the spiral and the activation of the magnet. The connected contacts provide an influx of electricity, and the pump starts. When the water flow dries up, the spiral expands and the magnet moves to its original position. As a result, the relay contacts open and the engine stops.

There is usually some delay in response after the flow is stopped, but pump performance is not particularly affected. As a rule, flow sensors are used to protect small power booster equipment from dry running. Their main advantage is compact dimensions and light weight. The range of fixed pressure here is from 1.5 to 2.5 bar.

They are equipped with single-phase devices to provide protection against idling and control: this is affected by the current parameters and the power of the device. The popularity of mini DCAs is due to their efficiency, ease of installation, low power consumption and reliability.

How to choose a dry run protection relay

Selection optimal view protection against dry running depends on the features of the equipment and the characteristics of the well or well. On sale are systems designed for a specific installation site of the pump - a well, a centralized line, wells with different depths. Much also depends on the performance of the source and the power of the pump. A noticeable influence on the choice of protection has the specifics of operating conditions - the diameter of the shaft, the installation location and technical specifications the pump being used.

To control the operation of the pump various models dry-running relays can be guided by different parameters- the force of movement of water in the pipes, its level or pressure. If a suitable pressure is present, the device turns on. After its disappearance or decrease below the boundary line, the station is switched off. It is important to understand that if the binding is made to pressure, then false alarms may occur : this is when water after pumping is immediately consumed by the consumer, due to which the pressure will not be able to gain the desired indicators. In this case, the relay will turn off the equipment, although there are no problems with water intake. Therefore, when buying a sensor, it is important to consider the maximum pressure developed by the pump.

Choice suitable option protection will facilitate the knowledge of the shortcomings of some of the above models:

By pressure. There are situations when the pressure in the circuit is created not by water, but compressed air. Under these conditions, the pump continues to idle until the pressure reaches the set threshold.

Contact with water. These models are designed to determine if there is water in the system. However, if the valve on the pump line is closed, it will run empty despite being filled with water. Therefore, it is better if there will be taps on the pump line at all: if they are necessary for carrying out Maintenance pump, it is recommended to use a flow switch.

By current consumption. Here the principle of response is based on the greater energy consumption of the pump, when it is idling. However, these types of devices have a high cost, and sometimes even professional plumbers cannot figure out their settings.

Flow switch. It is not effective when pressurizing the system by the pump itself.

In order for the dry-running relay to work normally, it is recommended to include a hydraulic accumulator in the water supply network (volume is not important). If the pump is installed in a deep well with a good flow rate with a constant water level, or if it is operated by an experienced user, then the dry-running relay can be omitted.

The process of installing a dry running relay consists of the following steps:

It is allowed to install the sensor only on a network with a pressure switch, thanks to which the electric pump can operate in automatic mode. The pressure switch is installed in strict accordance with the accompanying instructions.

Next, you need to decide where exactly to install the dry running relay. It is usually mounted on pressure pipe, near the pump outlet, immediately after the pressure switch.

The section of the water supply system where the installation will take place is freed from water. Before connecting, remove the cover from the device and unscrew the plastic insert. Further, using the opened pipe, it is connected to the desired fitting. Thread sealing is carried out with PTFE plumbing tapes or linen impregnated with special pastes.

The device is switched in series at the point where the power circuit is broken (it can be connected anywhere in relation to the pressure sensor (before or after). There are special terminals for entering the mains wire and the control wire. Before starting installation work network cable must be unplugged.

You can also watch a video on how to connect a dry-running protection relay to a pump:

The device is designed in such a way that its setting provides for changes in the level of communication between the surface that reacts to operating pressure, and the contact group that should work. For this purpose, the relay has screws that either compress or relax the springs. On almost all models, the factory settings set the lower limit of operation to 1.4 atm., The upper limit to 2.8 atm. The user has the opportunity to choose their indicators. To increase the lower limit of operation, the adjusting screw is rotated from right to left, to lower it, vice versa.

It is important to understand that with an increase in the lower limit, a natural increase in the upper one occurs (the difference of 1.4 atm remains). A prerequisite for setting is to set the switch off limit lower than the pump pressure. If this point is not taken into account, the pump will not respond to dry running at all, which will cause it to quickly fail.

Another adjusting nut allows you to change the difference between the extreme limits of the device response. As already mentioned, usually the factory setting corresponds to 1.4 atm. By tightening the nut, the difference can be increased up to 2 atm. In this case, the upper cut-off limit is also changed, which also follows the fate of the setting. It is very important that the level of the highest cut-off pressure does not exceed the value that the pump itself can deliver. Decrease lower level and boundary differences occur in direct opposite - by unscrewing the adjusting nuts.

You can also watch a video on how to set up a dry run protection relay:

Caveats:

If the minimum setting limit is too low, it may happen that an error of 0.3 bar will not allow the relay to turn off the voltage in time.

If the limit is too high, the same error can trigger the activation of the dry-running protection, and the pump will be turned off for no reason.

With a minimum dry running pressure, it will take longer to start the pump (you will have to drain the water from the accumulator).

An error of 0.2-0.3 bar can provoke the so-called. "rollback" of pressure. As a result, at large volume consumption, a sharp pressure drop of up to 0.4 bar can be observed. To avoid idle shutdowns, the idle pressure level must be lowered.

Modern pumping stations quite often they are equipped with either a full-fledged protective against dry running, 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.
As a source autonomous water supply a well or a well with a low debit is used. 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 summer time the water level is already falling, 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 slightly 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 drops 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.

Reliable operation of any device is possible only under the conditions set by the manufacturer. It is especially important to adhere to this rule for those who work with devices that use mechanical components, such as pumps. The work of most of them is undesirable to carry out "dry". In such expensive industrial and household equipment, there must be protection against dry running.

Dry running sensors

Reasons for installing protection

When it happens correct operation pump, then water passes through its cavity in a continuous stream. It performs several important functions at the same time:

lubrication of rubbing surfaces occurs, while the overcome force is reduced;
during friction, heating occurs, heat is picked up by water flows and carried away from the friction area.

Excessive overheating without a pump dry-running protection relay leads to rapid wear and tear of mating surfaces. The resulting heat during prolonged operation can deform the working parts, sometimes irrevocably. The electric motor also receives excess heat, and with significant overheating or the absence of a pump dry-running protection relay, it can burn out.

Hydraulic equipment with defective dry-running protection sensors must not be allowed to operate.

Design features

Let us consider in more detail the dry running sensor for the pump, the principle of its operation. The dry run protection relay is a block with several springs. It limits the operation of the entire device.

Everything is adjustable with a few nuts. The pressure force from the water is measured using a membrane. It either weakens the spring at low force or opposes its resistance at high load. The principle of operation of a dry-running relay is reduced to a force load on a spring, which is able to open the contacts that supply voltage to the pump.

Such protection against dry running of the pump during pressure reduction to the minimum indicated by the built-in algorithm closes the electrical circuit. The voltage during this action on the electric motor decreases, and it automatically turns itself off. The pump remains pressure sensitive. As soon as this works, the dry-running relay, according to the principle of its operation, will open the circuit and re-energize the motor.

You need to know that in most cases, the on / off interval of the relay is from one to nine atmospheres.

Water level switch

Often, pumps come factory-adjusted to a minimum of 1.2 atm and a maximum of 2.9 atm, when they turn off completely, without waiting for a drop to 1 atm.

Making adjustments

A direct mutual influence between the following quantities is derived:

pressure setting on the relay;
the volume of the accumulator;
water pressure.

Starting adjustment work, it is necessary to check the pressure level in the hydraulic accumulator.

The unit must be disconnected from the mains, it is also necessary to wait a few minutes for full discharge capacitors. Water from the cavity of the accumulator must be removed. We also dismantle the cover on it and measure the readings on the pressure gauge, which should be about 1.4-1.6 atm. If necessary, increase the air pressure.

VIDEO: Automation to protect pumps from dry running

Carrying out setup

The dry-running switch for the pump must be adjusted to the pressure of the running system. You should first start the pump to pump the level up to desired value. The system will automatically turn off the power supply, as the relay will trip.

Adjustment work is carried out with a pair of screws located under the cover of the machine. To clarify the drawdown limits, you must perform the following steps:

fix the switching pressure;
unplug the pump cable from the power supply;
remove the sensor cover and slightly loosen the clamping nut of the smaller spring;
setting the desired pressure parameter is performed by tightening / loosening the spring marked "P";
then we open the faucet, relieving pressure, monitor the start of the electric motor;
we fix the readings on the pressure gauge, repeat the operation several times and derive the most optimal pressure values empirically.

During adjustment work, it will be necessary to take into account the physical capabilities of the pump. With a passport value with all losses, there may be a manufacturer's limit of 3.5 bar, so we must go to 3.0 bar so that the pump does not burn out from overloads.

High quality dry run protection

Running the pump without water is the most common cause breakdown of this equipment with normal power supply. A popular material for the manufacture of pumps is thermoplastic, which can withstand long-term operation and has an affordable cost.

During load without water, the rubbing surfaces warm up. This happens the stronger, the more the device works without liquid. A natural consequence of heating is plastic deformation, and behind it, almost immediately, the motor jams and burns out from overload.

There are certain risk areas that are more likely to run dry:

wells or wells with a weak inflow of water. Also, the reason may be the excessive power of the apparatus, which does not correspond to the debit of the liquid. During dry periods, inflow per unit time also decreases for most sources;
large containers serving as spare collection tanks technical water. Care must be taken to ensure that the pump does not operate in an empty cavity without liquid;
network pipeline having an embedded pump to equalize the pressure in the system. During the dry season, there may be interruptions in the water supply, leading to a drop in pressure.

External elements for protection

The following external elements are used as protection against dry running:

float switch

The element refers to budget decisions. It is used to pump water from available containers. It only protects against overflows.

Pressure switch

Many devices have a contact opening when pressure thresholds are reached. Most of them have a low shutdown level and adjustment is not available in many models.

Flow switch with functions

In the absence of water pumping through the relay, automatic shutdown power supply. A small delay does not significantly affect the result.

Before purchasing additional protections, you should carefully read their threshold values.

VIDEO: How to protect the pump from running dry

The working process of water pumps is associated with numerous threats to the structure. These include pollution, engine overheating, breakdowns due to violations in the connections, etc. But even proper organization operating process in accordance with the instructions does not guarantee the exclusion of indirect threats. Dropping the pumped water level below the minimum value can lead to equally serious damage. To prevent this from happening, manufacturers recommend using a dry-running sensor for the pump, which captures the critical level of the working environment and decides to turn off the equipment.

General principle of operation of the device

Majority protective devices of this type are associated with control automation. The controller fixes the operating parameters for subsequent correction of the supply volumes, turning the unit on or off. In this regard, dry or idling sensors are only one of the signaling devices about the state of the working environment. Determination of water shortage can be made different ways depending on the type of dry running sensor used for the pump. The principle of operation of devices such as pressure gauges, for example, is based on fixing the pressure level. When the threshold level is reached, the detector sends a signal to the controller, which, in turn, automatically turns off the pumping equipment. Moreover, the sensor can continue its work as a pressure gauge. And when a sufficient pressure level is restored, it also resumes the pump function via the control controller. Again, the signs of water shortage can vary.

Multifunctional relays are connected to several types of detectors, which increases the accuracy of determining the level of the serviced medium.

Dry running sensor classifications

The simplest systems of this type provide protection, guided by the readings of mechanical signaling devices. These are models of float and flow type, which can be directly structurally connected with the target equipment. For the effective operation of such devices, even the introduction of automation is not necessary. More often mechanical protection used for borehole pump. In this case, the dry-running sensor should not even determine the critical level of shortage of the pumped medium, but its approach to the place of intake. For example, optimal height the water column for borehole pumps is on average 150-200 cm, and a decrease to 100 cm will be critical point. Automatic systems, as noted above, involve control through automation. The control relay cuts off the power supply and the equipment stops. But in both cases, the principles for determining the parameters of water supply may be different.

float switches

Such models are widely used in equipment that pumps water from wells, storage tanks or drainage systems. When the water level drops at the point of intake, a short circuit occurs and the sensor turns off the power. This occurs in parallel with the lowering of the float detector connected to the contacts in the phases of the power supply system. If we are talking For submersible systems, the dry-running protection sensor is placed above the nozzle protection grille or foot valve. The device can be integrated optionally, or, in the basic design, be part of the pump.

Flow switches with pressure sensors

In this case, press control is implemented. The normal mode of operation of the control system fixes temperature regime and pressure readings. The second parameter is considered as a target value for determining the risks of idling. By default, press control is set to a standard value of 1.5-2 atm. This is the threshold level, the achievement of which turns the system on or off, depending on the dynamics to increase or decrease. Of course, the user can set the dry running sensor for the pump to other peak values, taking into account the characteristics of the equipment and the conditions of the water supply in general. Some models of downhole units with such controllers do not provide for automatic activation. After stopping in the operating mode, they are entered only manually if the water level has risen to an acceptable level.

Level sensors

The principle of operation of electrical liquid level meters is most common in industry. Similar devices used to accurately control the level of technical media in production tanks, and in Lately they were also used in plumbing.

How does the dry running sensor work for this type of pump? The control relay includes an electronic board and several electrodes. Sensing elements are installed in different points the reservoir in which water is pumped out, and in the process of operation they exchange signals with each other. The liquid acts as a conductor for low-frequency currents, so the termination of the connection will mean that there is no water at a sufficient level. When the signal is interrupted, the circuit is opened and the power is turned off.

What to consider when choosing a sensor?

In addition to determining the appropriate operating principle of the device, it is important to consider the conditions in which it will be used. The control unit itself can be installed in the technical room. It does not have to be immersed in the working environment. But the sensor should be selected with an emphasis on temperature range and risks of physical damage. As for the first parameter, the spectrum from -1 to 40 ºС is considered optimal. In case of circulation pumps can be served and hot water, so the upper temperature bar increases to 70-90 ºС. From the point of view of the workflow, the pressure range that the dry-running sensor for the pump in a particular system can in principle be able to control is important. This indicator varies on average from 0.5 to 3 atm, and some versions reach a maximum of 10 atm. The protection class is also taken into account. The optimal solution For home use will be a model marked IP44.

Dry running relay connection

Installation of control valves is carried out at the stage of assembly of the pumping structure. First of all, a non-return valve with a filter is mounted on the suction line, after which you can proceed with the integration protective relay. Again, the controller and sensors are located at different points. The main thing is that physically the moment of registration of the critical level is ahead of the start of idling.

The electrical connection of the dry running sensor for the pump is carried out in the following sequence with a power supply of 200 V: socket - relay - pressure gauge - engine. Wiring loops usually operate with a current of about 10 A, while you should not forget about grounding and installing a stabilizing fuse.

Controller setup

The electrical circuit after installation will be an open two-contact relay. In this state, the pump cannot be started, as it will start to function at the same idle speed. Initially, the accumulator should be filled with water until the pressure reaches optimal level. For this technological period, the dry running sensor for the pump must be activated. The principle of its action on this stage is set to the service mode, in which idling is allowed, but without an alarm, followed by shutdown of the equipment. When the accumulator is able to maintain sufficient pressure, the relay with the sensor is switched to normal operation. But before that, it is necessary to set the threshold value of pressure at which electrical circuit will open again.

Pump controller manufacturers

High-tech relays with automation and the ability to prevent dry running are produced by Sturm, Elitech, Metabo, etc. The most successful developments come from the direct pump manufacturers. For example, Grundfos is working on a combination of centralized control panels, which include water fittings and a multifunctional package of protective automation. Domestic developers of controllers also succeeded in this direction. The dry running sensor of the Whirlwind 68/4/4 pump, for example, is distinguished by the support of a switching current of 12 A and maximum pressure at 10 atm. Its features include high class protection - IP65. Worthy offers in terms of price and quality are also produced by Belamos, Dzhileks and Zubr.

When should you not use dry run protection?

Not always the additional load in the form of sensors justifies itself. Obviously, pumping water from a lake, reservoir or pond does not involve the risks of dry running. Another thing is that a change in the position of the equipment itself can lead to a shift in the level of water intake, but such problems should be solved more reliable installation. It is also not recommended to use a pump controller in high flow wells. The dry running sensor in this case simply will not work, wasting energy in vain. At the very least, for wells and wells, a seasonal schedule can be established, when the risks of a sudden change in water level rise and fall. Accordingly, for these periods it is necessary to adjust the operating mode of the control equipment.

Finally

Underestimate the consequences of idling for pumping equipment not worth it either. For some models long work in this mode, it will make itself felt in the form of breakdowns of individual consumables, which can be replaced at minimal cost. But there are also whole groups of units that are directly dependent on water supply. In modifications with rotary units, the pumped liquid can be used as a technical lubricant or coolant. Therefore, a dry running sensor for the pump can prevent very significant engine damage. For the same reason, the manufacturers themselves in the basic configurations increasingly provide for the presence of control equipment. Moreover, refusal to use protective devices is a condition for the loss of warranty, since the instruction manual for the equipment is violated. These nuances should be taken into account even when developing a water intake scheme, evaluating the possibility of connecting the most effective means control.