Dry running pump protection: methods, features, step-by-step instructions and reviews. Application and principle of operation of a dry-running relay How a dry-running relay works

Equipping their own source of water supply, each owner is obliged to take care of its additional protection. In addition, not only the well or well itself needs to be prevented from breaking, but also the equipment that performs the work: the so-called drainage systems and external pumps. For safety reasons and to reduce the risk of overheating, a water flow sensor is used, which must first be properly selected.

Why is the pumping system running dry?

Incorrect operation of a pumping station installed to a reservoir may depend solely on the lack of fluid. There is absolutely no difference which body of water is used to pump water; dry running problems for the pump are relevant in any case.

Dry running float switch for pump

The reasons for idle operation often occur due to improper installation of the pump in the water supply source, as well as its incorrect selection for these purposes (non-compliance technical specifications and parameters of the well or well). To exclude overheating of the pump and its possible malfunctions, it is necessary to place the pumping device at a dynamic level, that is, in the place where the water does not decrease.

Also, the cessation of the liquid supply may occur due to a decrease in pressure in the pipeline, due to which the water flow decreases and a airlock, which penetrates into the working mechanism of the device, disables it. If the tightness of the hose or pipe is lost, similar problems may also occur.

Note! If your pump is set up for manual operation only and operates from a constant source (from a local pond, river or lake), then there is no need to use an automated flow sensor. In the event that the pump is connected to small wells and does not have circuit breakers, it is worth taking care to prevent breakage.

Types of dry running sensors for pumps

In practice, there are only a few types of sensors that perform protective function in relation to pumping equipment. Today they are divided into three main types:

pressure switch with functional protection equipment. The average cost of a domestic manufacturer of a water flow structure is about 250 rubles. A feature of the mechanism is the ability to turn off the motor when the pressure drops below the nominal level. Usually, the maximum allowable pressure is set at the factory and cannot be manually adjusted;

Disassembly of the dry running sensor for water

Some well-type pumping stations do not require special protective additions, since they have their own protection as factory parameters.

Dry running sensor diagram

The pressure control sensor or idle speed switch does its job using a separate principle. The flow device itself is a mechanism with switching contacts. Before installation, the relay has open contacts. To start the sensor, you need to press and hold the red button until the pressure level rises to the desired value. If the number of atmospheres is not enough, the sensor will be disabled.

Some installations have special nuts on springs in the design, which allow you to adjust the pressure values \u200b\u200bwhen the mechanism is triggered. Pay attention to how the diagram below depicts the entire process of action.

The layout of the dry running sensor in the water supply system

To connect water flow sensors for borehole pumps, you will need to place them in series in the power grid along with pumping equipment. When a drop in atmosphere is detected, the pump protection against dry running is activated, thereby opening the electrical network.

Attention! The installation of a flow movement relay for pumping substations in an autonomous source of water supply occurs strictly according to the concept diagram. There should not be any deviations from the specified values, since the probability of the device malfunctioning and the protection failing increases.

How to choose a device and install it at home?

Be sure to select a flow movement device taking into account the various characteristics of your pumping equipment and possibilities of the source of water supply. Before buying and directly installing a protective relay with your own hands, be sure to get the advice of an experienced specialist.

An important step after selecting the installation of the movement of the flow is its correct installation. Be sure to ensure that the pressure switch is installed before the first start-up of the water supply system. In this case, you can provide possible malfunctions and prevent their consequences.

How to connect a dry running sensor to a pump

In order to perform a mechanical type of connection for a pressure switch, you will need skills in working with fittings. You need to cut the thread, if it is not there, and seal the structure with linen or fum tape. A special adjustable wrench will help to embed the device in the pipe. After we are engaged in connecting the electricians in the mechanism. Please note that the conductors on the sensor must be suitable in terms of power to the pump in their cross section.

Typical mistakes of masters

When arranging the pipeline with your own hands, it is important that the flow control equipment is properly connected. But unfortunately, not quite an experienced user can introduce violations into the stability of the work. To eliminate all troubles you need to know about common mistakes, which allow the wizard to connect the relay.

The device is connected incorrectly. It also happens when the sensor is connected to the water flow meter, due to which the principle of operation becomes incorrect.
Leakage of joints occurs when special seals are not used or materials of inadequate quality are selected.
The equipment for the water supply system itself is not exactly matched, and there is a discrepancy with the technical characteristics of the pump.
Schema is missing correct connection, as a result of which there may be a parallel connection of the device.
The owners are trying to change the pressure sensitivity in those mechanisms that are not provided for this.

Due to this neglect of water flow protection designs, you will not achieve a perfect working result. Most likely, the protection of the pumping station will work halfway, so there is no guarantee of the durability of the device.

Choosing a dry running sensor for well pump

The choice of a dry-running sensor for a pump and its connection is best done according to a strict scheme, so as not to subsequently observe errors in the operation of the equipment.

Dry running sensor

Significantly reduces the life of the pump, emergency operation without water, the so-called "dry running". Water performs both lubricating and cooling functions. Without fluid, the pump quickly overheats, deformation of parts occurs, and the engine may burn out. A short dry run adversely affects the performance of the equipment, regardless of the type of pump (drainage, submersible or surface).

To prevent breakage, automation is used:

float switch;
dry running sensor for the pump;
dry run relay.

Protection must be provided in a timely manner, since the cost of repairs after a "dry run" is not included in the list of warranty cases. Having disassembled the pump, the specialist will quickly determine the cause of the breakdown. The operating instructions indicate that the operation of the pump without water is prohibited.

Possible causes of "dry running"

Consider the main situations of insufficient water supply:

1. Wrong choice of pump. More often occurs in cases with wells if:

pump performance exceeds well flow rate;
the dynamic level of the well is below the level of the pump installation.

2. Clogging of the pumping pipe (typical for surface models).

3. Violation of the tightness of the pipe through which water enters.

4. With low water pressure (or lack thereof) in the water supply to which the pump is connected. Without automatic devices, the pump itself will not turn off and will continue to “idle” work until it is turned off, or it breaks down.

5. When water is supplied from a source (tank) to be cut off, it is necessary to constantly monitor the level of the incoming liquid.

Ways to protect pumps from running without water

Protection against "dry running" of the pump is provided by automation - sensors and relays that block the power supply at the time of the appearance of a "waterless" mode or in advance. The operation occurs in different devices, and depends on the definition of the following quantities:

water level;
pressure in the outlet pipe;
water flow;
combined scores.

Let us consider in more detail the individual types of automatic protection.

Water level switch and float

Tracking the water level, the level switch and the float sensor work. The level control switch regulates the operation of the water control valves and pump starters. It is one of the most reliable, but also expensive ways of protection. The main advantage is that it turns off the pump before a “dry run” appears.

The relay includes an electronic board, sensors (three electrodes: two working, one control) and single-core connecting wires.

Scheme of work: the control sensor is installed above the pump, the working sensors - on different levels wells; when the water level drops to the control sensor, the pumping unit stops. When the water reaches the level of the control sensor again, the pump will automatically turn on.

The main sensor board is located in a dry place, usually in the house.

The float sensor (switch) is able to effectively solve the problem of "dry running" in wells and water supply from containers. It is mounted above the pumping unit. The level of operation is regulated by the length of the float cable and the specified location of the sensor.

The switch cable is connected to the phase supplying power to the pump. When the water level drops below the float sensor, the electrical circuit opens and the pump stops.

The fixed float level is selected taking into account the presence of water in the tank at the time the sensor is triggered. For submersible and surface pumps, the “critical” water level must be above the bottom valve or suction grate of the pump.

You can use a float switch to protect drainage and well pumps. For guard pumping units operated in a network pipeline or wells, other automatic installations must be used.

Relay and pressure sensor

To determine the pressure level at the outlet pipe, a pressure switch and a pressure sensor function. The minimum allowable pressure is set in the relay - usually 0.5 bar. You cannot adjust the pressure limit yourself. It is possible to use a pressure switch as protection if the pump operates with a hydraulic accumulator.

When the pressure switch is operating, the contacts open if the pressure has dropped to the set limit. It should be noted that the entire range of domestic pumping units can pump water at a pressure of 1 bar. Therefore, in practice, the pressure switch is activated when the water supply is completely stopped.

The relay does not warn of an emergency, but simply states the beginning of the "dry run" mode, turning off the pump. After the resumption of the fluid supply under the appropriate pressure, it will be possible to turn on the pumping unit manually. Before each start, you must fill the pump with water yourself.

Wider range of action for pressure sensors. They signal the cessation of the pump when the pressure drops to 1 bar and below. Pressure sensors have found their application in household pumping installations of network pipelines, fire fighting and water supply pumping stations.

When the pressure of the water flow at the inlet to the pump decreases, sensors are triggered that send a signal to the control panel of the pumping unit.

Water flow sensor

On measuring the flow of water passing through the pump, the principle of operation of the flow sensor is built. The sensor consists of a valve ("petal") located in the flow part and a reed microswitch. The "petal" is spring-loaded and has a built-in magnet on one side.

Sensor operation scheme: under the influence of water pressure, the petal valve moves - the spring begins to compress, and the magnet interacts with the reed relay. Closing the contacts causes the pump to work. Without the flow of liquid, the valve spring is unclenched, moving the magnet to its original position - opening the relay contacts leads to the shutdown of the pumping unit.

The flow sensor is built into booster pumps with little performance. Works to determine two values (pressure level and flow) of the flow switch, with additional function pressure switch, the so-called "press control". The device is distinguished by its compact dimensions (light weight and volume).

At a pressure level in the range of 1.5-2.5 bar (depending on the automation model), a command is sent to the pump to start working. The pump performs its functions until the withdrawal of water is stopped. Due to the flow sensor built into the relay, the pump stops working. The sensor very quickly registers the appearance of a "dry run", which avoids a long stay in the working "waterless" mode.

The universal device from emergency modes is Mini AKN. It is based on the electronic protection of single-phase pumping units. The mini ACV responds to the power factor and current of the pump motor. The main advantages of the device: comprehensive protection from emergencies, small dimensions and power consumption, ease of installation, reliability.

Situations when you can not use protection

It is possible to do without installing a pump dry running sensor only in some cases:

constantly monitoring the water supply from a well or well (you will have to be nearby in order to respond in time to a change in water flow);
pumping is carried out from an inexhaustible source;
the drilled well has a high flow rate;
the person controlling the operation of the pump has experience in operation, knows the principle of operation and design of the pump.

If the operation of the pump has become intermittent, or it has turned off altogether, it must not be restarted without identifying and eliminating the causes of the breakdown.

Dry running sensor for a well pump: types and how it works

What measures can be taken to protect the pump from “dry running”. Consider the types and types of sensors.

How to protect the pump from running dry

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 situation and consider further.

What is a dry running pump

Wherever the pump pumps water, at times a situation is created 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 dry running of the pump is one of the components of automation, which will have to be bought in addition. 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 which 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 different area 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.

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 efficiently with surface pumps when check valve installed after the pump.

The electrical circuit for switching on the pump protection relay against dry running

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 a common scheme, but with this method of switching on, a situation is possible when a running pump does not turn off in the absence of water 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 to about 1.4-1.6 atm, the protective relay membrane will not work - 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's why in systems with hydraulic accumulators or pumping stations it is better to use other water pump dry running protection devices.

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

The flow switch is of two types - 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 relays pressure. 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.

Protection against dry running of the pump: types, installation

Why do we need protection against dry running of the pump, in what ways it is possible to protect against idling, in which cases it is better to use which devices.

Dry running sensor for pump

There are 3 or 4 types of dry run protection: By pressure, by current consumption, by water sensor, by flow sensor. If only two methods are used, then 100% protection of the pump against dry running can be achieved. Let's consider this below. But you can also use only one method that will protect the pump from dry running with a 100% guarantee.

To protect the pump from running dry, you need the pump to run on water or pump water, not air. And he worked without closed taps on the pump line.

One way or another, all methods of protection individually carry the definition of water only by indirect signs.

To determine if there is water in the system where the pump is located, use indirect signs that the pump works in water:

1. Presence of pressure. Mainly determined by an inexpensive device (dry-running relay)

The pressure of the system is constantly maintained above atmospheric from about 1 Bar. And if this pressure drops, then the dry-running relay turns off the pump. And the dry-running relay, in turn, registers a lower pressure of 0.5 Bar and above. How the dry run relay works is described here: How to do automatic water supply in a private house

Dry run relay setting:

This method uses: Float water sensor, electrode sensors, capacitive and others.

The float sensor works according to the principle of mechanics (the float is lighter than water and changes its position, changing the switching contact after it).

There is another way float sensor

In this method, a magnet is used in the float. With the help of magnets on the float and the contact mechanism, force is transferred to the contact. A switching contact with a magnet is hidden inside the tube. The float moves along the stem of the tube. Depending on the position of the float, the position of the magnet on the contacts changes. By these means, the closing and opening of contacts is carried out.

The electrode principle is based on the conductive effect of water (That is, if two electrodes are lowered into water, then a current can be passed between the electrodes that will pass through the water. If there is no water, then the current will not pass. And a special device will determine the passage current and execute the necessary commands for closing and opening contacts).

Capacitive level sensor

A capacitive sensor works on the principle of water touching a special surface, and again a special device detects this touch. When water comes into contact, the capacitance changes, and a special device executes commands to close and open contacts.

3. Current consumption. In this case, a special device monitors the current consumption of the pump, and if the current goes beyond the set thresholds, the pump turns off for a while. Unfortunately, such a device is either expensive or difficult to handle. Therefore, the demand for such a device is not great. Also, there is no clear explanation of such a device.

4. Flow sensor. Moving water presses on a special paddle and the paddle changes the positions of the contacts with an angular force. Or in another way. The principle is based on the determination of the flow in the pipeline. If there is no flow, then the pump will be powered off.

Disadvantages by indirect signs:

1. When water is determined by the presence of pressure. In the water supply system, a situation may arise when there is pressure in the system, but there is no flow, and as an evil: The water is over. At this point, the pump continues to work and will not stop until the pressure reaches the set threshold. It was discussed in more detail on the forum: http://santeh-baza.ru/viewtopic.php?f=4&t=69 it also tells how to effectively set up a dry-running relay.

2. Direct contact with water. This method only detects the presence of water where the pump is located. But the trouble arises when, for some reason, the tap on the pump line is closed and the pump is idling with water. In such a situation, you need to protect yourself from the fool and not put taps on the pump line. But here sometimes technical requirements require the installation of valves for repair and replacement of the pump. There is a way out - to install a flow switch, but without a time delay, such a "gadget" is useless. Below is a diagram.

4. Flow sensor. There is one very simple circuit where a flow sensor is used. But just the flow sensor is a dummy in protecting the pump from dry running if the pressure in the system is created by the same pump. If we consider such a scheme, then it is used only to increase the flow where pressure and flow already exist. For example, to increase pressure.

Electrical diagram operation of the flow switch with a time delay to protect the pump from idling.

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Encyclopedia of plumbing 100% Pump protection against dry running

Dry running sensor for the pump There are 3 or 4 types of dry running protection: By pressure, by current consumption, by water sensor, by flow sensor. If only two methods are used, then

Any electric pump, pumping water from a well or well, functions normally only in the presence of a working environment. Water for this mechanism is both lubrication and cooling. If the pumping unit runs idle, then after a few minutes it may become unusable. To monitor the presence of water flowing through the pump, a dry running sensor for the pump is called. At his command, the power supplied to the pump must be turned off in the absence of water.

So, dry running is the most common cause pump breakdown. Moreover, in this case it will not even be possible to perform a warranty repair if the examination proves this cause of the breakdown. Such a nuisance can happen in the following situations:

Incorrect choice of pump suspension height in a well or in a well. This can happen if the depth of the water tank has not been measured in advance. When the pump pumps out water to the level of its location, it will begin to entrain air, resulting in overheating of the electric motor.
The amount of water in the spring naturally decreased. For example, a well (well) silted up or water simply did not have time to get into the well after the last pumping. After the complete pumping of water from the well, it is necessary to wait a certain time to fill the well.
If a surface pump is used, which is located on the water surface, then the reason for its failure may be different. There are frequent cases when the suction pipe of the pump loses its tightness. Water is sucked in together with air, as a result of which the pump motor does not receive sufficient cooling.

So, if there is no protection of the downhole pump from dry running, then the pump overheats and burns out. This applies not only to the electric motor. Modern pumps have a large number of plastic parts. Plastic, in the absence of cooling and lubrication, can also be deformed. This will first lead to a decrease in the performance of the device, and then cause it to overheat, jam the shaft and engine failure. Masters are familiar with this type of failure resulting from overheating. Having disassembled the unit, you can easily find those parts that have undergone overheating.

Types of dry running sensors and features of their work

Expensive pump models already have built-in dry-running protection sensors. In particular, all pumps from the manufacturer Grundfos are already equipped with such sensors from the start. When operating cheaper units, a dry-running sensor for a submersible pump must be installed additionally. Let's try to understand the intricacies of the device and the operation of various types of dry running sensors.

Water level sensors

1. Float switch. The connection diagram of the dry running sensor for the pump must be built so that its contacts are included in the power supply circuit of the pump motor. The float is afloat. When the water level drops, the float changes its location, its contacts automatically open, as a result of which the power to the pump is turned off. This is the simplest type of protection, characterized by reliability and ease of operation.

Tip: In order for the float to work on time, it is necessary to adjust it correctly. It is important that the pump body is still immersed in water when the sensor is triggered.

2. Water level control sensor. Let us consider in more detail such a dry running sensor for a pump and its principle of operation. This is a relay consisting of two separate sensors lowered to different depths. One of them is immersed to the lowest possible level of pump operation. The second sensor is placed a little lower. When both sensors are underwater, a small current flows between them. If the water level drops below the minimum value, the current stops flowing, the sensor trips and opens the power circuit.

Sensors that monitor the water level are good because they allow you to turn off the pump even before the unit body is above the water surface. Therefore, the equipment is reliably protected from damage.

Protection relay

This is an electromechanical device that controls the pressure of the water flowing through the pump. When the pressure drops, the pump power supply circuit opens. The pump dry running protection relay consists of a membrane, a contact group and several wires.

The membrane controls the water pressure. In the working position, it is open. When the pressure drops, the membrane compresses the relay contacts. When the contacts are closed, the pump is switched off. The membrane operates at a pressure of 0.1-0.6 atmospheres. The exact value depends on the settings. A drop in pressure to this level indicates the presence of such problems:

water pressure has dropped to a minimum. This can happen for several reasons. Including, the loss of performance by the pump itself due to the exhaustion of the resource;
the pump filter is clogged;
the pump was above the water level, causing the pressure to drop to zero.

The protection relay can be built into the pump casing or surface mounted as separate element. If the water pumping system includes a hydraulic accumulator, then a protective relay is installed together with a pressure switch, in front of the accumulator.

Water flow and pressure sensors

There are 2 types of sensors that control the passage of the working medium through the pump unit and provide protection against dry running of the pump. These are flow switches and flow controllers, which will be discussed below.

1. The flow switch is an electromechanical type device. They are turbine and petal. The principle of their work is also different:

The rotor of turbine relays has an electromagnet that generates an electromagnetic field when water passes through the turbine. Special sensors read the electrical impulses generated by the turbine. When the pulses disappear, the sensor disconnects the pump from power;
The spade relays have a flexible plate. If water does not enter the pump, the plate deviates from its original position, as a result of which the mechanical contacts of the relay open. The power supply to the pump is then interrupted. This version of the relay is distinguished by its simple design and affordable cost.

Flow sensor example

Such blocks turn off pumping equipment if there is no water flow and turn it on if the pressure in the system has dropped below a predetermined level.

2. Flow controllers (automation unit, press control). This electronic devices tracking multiple important parameters water flow. They control the water pressure, signal the termination of its supply, automatically turn the pump on and off. Many devices are equipped with . The high reliability also led to the high cost of these devices.

What protection to choose?

It is not easy to choose the right version of the protective device. It is necessary to take into account several factors at the same time:

depth of the water tank;
well diameter;
features of the pumping equipment used. For example, a submersible or surface pump is used;
their financial possibilities.

For example, the simplest and cheapest means of protecting a pump from dry running is a float switch. However, it should be borne in mind that its use in a well of small diameter is impossible. But for the well, it fits perfectly.

If the water in the working tank is obviously clean, then the most the best option will use a water level sensor. If you are not sure about the quality of the water supplied to the pump, it is better to use a flow switch or a water pressure sensor.

Note: If there is a possibility of clogging the pump filter with debris or dirt, then it is not advisable to use a level sensor. It will show a normal water level, although no water will be supplied to the pump unit. The result will be a burnout of the pump motor.

We can make a small conclusion. It is possible to use a pump without protection against dry running only if it is possible to constantly control the flow of water from a well or well. In this case, you can quickly turn off the power to the pump if the water stops flowing from the source. In all other cases, it is better to play it safe by installing a protective sensor. Its price fully pays for itself, given the cost of buying a new pump to replace burned-out equipment.

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, protection of the borehole pump from dry running is needed.

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

Drop in water level below critical as a result of wrong choice 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 recovers 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, for all Grundfos models there is protection not only against dry running, but also against overload, overheating, power surges and reverse axial displacement. The cost of quality equipment from 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 a cheap pump to the price additional equipment and its installation - 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 quality equipment, originally 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 dacha, 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 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. V general case the sensor is set to a value of 0.5 bar, a lower pressure with the pump engine 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 structure

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 monitoring 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 parameter measurements.

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 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

Most 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 related to the target equipment. For effective work such devices, even the introduction of automation is not necessary. Most often, mechanical protection is used for a 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, the optimal height of the water column for borehole pumps is on average 150-200 cm, and lowering to 100 cm will be a 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 operating mode of the control system records the temperature and pressure indicators. 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. Such devices are 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 electronic board and some 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 control fittings performed at the stage of assembly of the pump structure. First of all, a non-return valve with a filter is mounted on the suction line, after which it is possible to proceed with the integration of the 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 power from 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 the optimum level. For this technological period, the dry running sensor for the pump must be activated. The principle of its operation at this stage is adjusted to the service mode, in which idling is allowed, but without 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, you should also set the threshold pressure value at which the 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 a maximum pressure of 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 by a 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

It is also not worth underestimating the consequences of idling for pumping equipment. For some models, long-term operation in this mode will make itself felt in the form of breakdowns of individual consumables, which can be replaced with 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.

If the pressure in the pump drops, the device needs protection. For this purpose, special relays are used. The standard model consists of a pin, a set of contacts and a special cable for closing. There is an adjustment screw on the top of the device. There is a small spring on the pin. The contactor in the device is installed with a trigger mechanism. Cases are most often made of aluminum alloy. In the lower part of the modifications, branch pipes of different diameters are installed.

The principle of operation of the modification

How does a dry running relay for a pump work? When the pressure inside the system decreases, the contactor is activated. Voltage passes through the contacts, which is applied to the winding. The screw acts as a retainer. The spring is compressed by a pin. When the pressure drops, the contacts open. A contactor is used to turn off the voltage.

Dry running relay for pump: wiring diagram

The device must be connected via an adapter. In this case, the outlet pipe is connected to the tube. The cable is terminated at the terminal. The cover is directly fixed on the pump housing. To tighten the outlet, you need a nut. The nozzle is often fixed with a clamp. Some types of relays are connected through a pass-through adapter to two outputs. If we consider a circuit with several pumps, then a contactor expander is used.

Relay adjustment

In order to adjust the device, a screw is used, which is located in the upper part of the case. To set up the model, readings are taken from the sensor. To raise the level of allowable pressure, the screw is turned clockwise. At undervoltage the speed of contact closure slows down. Also, the problem may lie in the contactor with the starting system. To lower the pressure level, the screw is turned counterclockwise. Much in this case depends on the parameters of the relay and the maximum power of the pumps.

Device types

There are flow and float devices. Models can be made with one or more cameras. Low pressure modifications are suitable for low power pumps. Streaming devices are released different sizes. For powerful pumps there is a relay high pressure.

Streaming Devices

In hydropower plants, dry-running flow relays for the pump are often found. The principle of operation of the modifications is based on changing the limiting pressure. Is happening this process by changing the position of the plate. It is located at the bottom of the case. It should also be noted that the relays of this type are equipped with wired contactors. There is only one start button. Many models use power contacts. The circuit is closed by pressing the plates. The dry running relay for the pump is connected through an adapter.

float models

The most dimensional is considered to be dry-running float switches for the pump. The device is adjusted by tightening the screw. The principle of operation of modifications is based on a change in pressure. All models have one pin in the body. In this case, the branch pipe is located with a ring in the lower part of the structure. Most relays use a manual setting system. Devices of this type work from the network. The frame, as a rule, is made of plastic. The contact plates can be in a vertical position. Most relays operate at low frequency. Models are suitable for pumps from 4 kW. The operating frequency averages 55 Hz. At the top of the modification is a nut. In this case, the clamping screw is located on the pin.

Devices with level sensor

A dry-running relay for a pump with is considered quite common. However, it is important to note that the models have a number of disadvantages. First of all, experts say that the models are difficult to configure. If he talks about relays on contactors, then they use one input. Thus, failures often occur. It is also important to note that the models are not capable of working with submersible pumps. Devices are connected via cable. The camera at the relay is made with a solid base.

Low pressure models

Dry running relays for low pressure pumps are produced with only one chamber. Contactors for modifications may differ in design. Most devices operate on a 220 V network. At the same time, their operating frequency is at least 45 Hz. It should be noted right away that the models are suitable for pumps with a power of not more than 3 kW. The contacts on the plate are in a horizontal position. The pins are installed next to the plate. In total, modifications have two nuts. A clamping screw is used to adjust the pressure. Pins are quite often used with small diameters. Models of this type are well suited to work with submersible pumps. Frames in devices are used with varying degrees of security, and in this case, much depends on the manufacturer.

High pressure devices

Dry running relays for high pressure pumps are very popular. First of all, the models are used in hydroelectric power plants. They are well suited for pumps that are used in the plumbing system. Their contactors are used for two outputs. The working nuts are located in the upper part of the housing. It should also be noted that there are modifications for two cameras. Their outlet is located in the center of the base. Most models are formed on the basis of a dipole contactor. Modifications use several pins. The devices are well suited for submersible pumps. Branch pipes are available with a diameter of 2.3 cm. Relays operate at least at a frequency of 40 Hz. The output cable must be connected to There is a clamping screw to adjust the plate. To equalize the pressure inside the system, the nut is turned clockwise. Sensors are very rare in modifications of this type. The start buttons are located directly on the contactors. The models are very easy to maintain.

Single chamber models

Single chamber dry running relays for pumps are available with one or more pins. Most modifications work at low pressure. If we consider a simple relay, then it uses a wired contactor from a 220 V network. The minimum operating frequency is at 45 Hz. The first nut is located on the pin. To increase the pressure in the system, the screw is turned clockwise. If we consider a dry-running relay for the Grundfos pump (with a double contactor), then it uses two cable outlets. The minimum frequency for a modification of this type is 55 Hz.

Dual chamber devices

Two-chamber devices are manufactured with low conductivity contactors. Most models are equipped with multiple pins. The nuts are usually located at the top of the housing. The outlet pipe is used with a diameter of 4.4 cm or more. The devices are suitable for pumps high power. Modifications work from a 220 V network. If we consider models with drive contacts, then they use a start-up mechanism from the module. The minimum operating frequency is 30 Hz. The frame is often made of steel. The increase in pressure is due to the adjustment of the screw. The clamping plate in the devices is located under the contactor. The base of the relay has a seal. Most devices are equipped with a cap for lubricating the pin.

Models for three cameras

Devices for three chambers allow you to very accurately regulate the pressure inside the system. Most modifications are launched from the module. To connect the device, adapters with a ring are used. Models are suitable for pumps from 4 kW. Their operating frequency is at least 4 Hz. Some relays are made on drives. Covers are usually installed over the pin. Some devices are manufactured with two clamping plates. The output cable comes off the contactor. This type of relay operates as standard from a 220 V network.

Devices for 2 kW pumps

Relays for pumps are usually made with one pin. Most modifications are equipped with overlays. If we consider devices with wired contactors, then they have two outputs. It is also worth noting that there are models with support racks. Cases are most often made of stainless steel. The cable at the relay departs from the contactor. The devices operate from a 220 V network. Connection to the pumps occurs through a branch pipe.