Significantly reduces the pump service life, emergency operation without water, the so-called "dry running". Water performs both lubricating and cooling functions. Without liquid, the pump quickly overheats, deformation of parts occurs, and the engine may burn out. Short-term dry running has a negative effect on the performance of the equipment, regardless of the type of pump (drainage, submersible or surface).

Automation is used to prevent breakage:

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

Protection must be provided in a timely manner, since the costs of repairs after dry running are not included in the list of warranty claims. Having disassembled the pump, the specialist will quickly determine the cause of the breakdown. The operating instructions state that the pump must not be operated without water.

Let's consider the main situations of insufficient water supply:

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

• the pump performance exceeds the 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 the water enters.

4. At low water pressure (or lack thereof) in the water supply system to which the pump is connected. Without automatic devices the pump will not turn off by itself and will continue to "idle" until it is turned off or it breaks down.

5. When supplying water from an excised source (container), it is necessary to constantly monitor the level of the incoming liquid.

Methods for protecting pumps against dry operation

Protection against "dry running" of the pump is provided by automatic equipment - sensors and relays that block the power supply at the moment of the appearance of the "waterless" mode or in advance. Triggering occurs in devices in different ways, and depends on the definition of the following values:

• water level;
• pressure in the outlet pipe;
• water flow;
• combined indicators.

Let's consider in more detail certain types automatic protection.

Water level switch and float

By monitoring the water level, the level switch and the float sensor work. The level control relay regulates the operation of water control valves and pump starters. It is one of the most reliable, but also expensive, methods of protection. The main advantage is that it turns off the pump before dry running occurs.

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

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

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

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

The switch cable is connected to the phase supplying power to the pump. When the water level falls below the float sensor, the electrical circuit is opened - the pump stops.

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

A float switch can be used to protect drainage and well pumps. For protection pumping units operating in a network pipeline or wells, other automatic installations must be used.

Relay and pressure sensor

By determining the pressure level at the outlet, a pressure switch and a pressure sensor function. The relay is set to the minimum permissible pressure rate - usually 0.5 bar. You cannot independently adjust the pressure limit level. 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 cut off.

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

More wide range actions at pressure sensors. They signal the stopping 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, pumping stations for fire extinguishing and water supply.

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

Water flow sensor

The principle of operation of the flow sensor is based on measuring the flow of water passing through the pump. The sensor consists of a valve (“petal”) located in the flow path and a reed switch 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 switch. Closing the contacts puts the pump into operation. Without liquid inflow, the valve spring expands, moving the magnet to its original position - opening the relay contacts leads to shutdown of the pumping unit.

The flow sensor is built into booster pumps with low capacity. It works to determine two values ​​(pressure level and flow) of the flow switch, s additional function pressure switch, the so-called - "press control". The device is distinguished by its compact dimensions (low weight and volume).

At a pressure level in the range of 1.5-2.5 bar (depending on the automation model), the pump receives a command to start operation. The pump performs its functions until the termination of the drawdown. 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 "waterless" operating mode.

Mini AKN

The Mini AKN is a universal device against emergency modes. It is based on the electronic protection of single-phase pumping units. Mini AKN reacts to the power factor and current of the pump motor. The main advantages of the device: comprehensive protection against emergency situations, small size and power consumption, ease of installation, reliability.

Situations when you can not use protection

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

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

If the operation of the pump becomes intermittent, or it turns off altogether, it cannot be restarted without identifying and eliminating the causes of the breakdown.

Plumbing repair after independent intervention can be more expensive, no friend or neighbor will offer you a guarantee for their services, as we do. You cannot be sure of your adjustment of the idle relay on the accumulator, you make it correctly and the pump will not fail. Our masters with extensive experience in connecting and adjusting any kind of pressure switch.

The P3 pressure switch is used in automatic water supply systems, irrigation installations, fire extinguishing installations, air conditioning systems, etc. The working environment of the systems in which the relay is used must be water.

The device is a two-contact relay for switching electrical circuits, triggered by water pressure. The principle of its operation is as follows: initially, the group of relay contacts is open and in order for it to close, it is necessary at the first start to press and hold the button located on the relay cover for a while. The relay contacts are closed. When the pressure drops to 0.4 - 0.05 bar (depending on the preliminary adjustment), the relay contacts open. Thus, the relay can be used as a dry-running protection device for a device, such as a pump.

Accumulator repair
Specifications:
Working environment temperature: 0-40 ºС
Cut-off pressure operating range: 0.1 - 0.5 bar
Maximum operating current: 10A
Supply voltage: 220-250 V
Pipe connection: 1/4 "
Class electrical protection: IP 44

Relay design

Structurally, the "dry running" relay is assembled in a plastic case and closed with a lid
All operating elements are located on the base of the relay. A flange is attached to the base. We examined the flange design in detail in the article devoted to the three-phase pressure switch. The flange has a nut with internal thread 1/4 ″ for connection to the water supply system. By means of a nut and a spring, the cut-off pressure of the relay is regulated. When the spring is compressed (tighten the nut), the shutdown pressure will increase. When we unclench the spring (unscrew the nut), the shutdown pressure will decrease. The button is used to forcibly turn on the dry-running relay into operation. Terminals are used to connect electrical wires. At the same time, it does not matter which terminals are input (~ 220 V power is supplied), and which are output (the motor is connected). The terminals for connecting the "grounding" wires from the power supply network and the motor are separated separately. For firmly fixing and securing the mains supply cable and electrical cable motor connections, cable clamping sleeves are used. All working elements of the pressure switch are closed with a cover.
The diagram of the installation of an automatic pumping station using the LP relay is shown. check valve with mesh. A pressure switch, a hydraulic accumulator and a dry-running relay are mounted on the pressure pipeline. A non-return valve is mounted behind the dry-running relay. Sequence of electrical connections: mains plug - pressure switch - dry-running relay and pump motor. But this sequence can be as follows: mains plug - "dry running" relay - pressure switch and pump motor. The basic principle for connecting these two relays is that they must be connected in series.

The principle of operation and adjustment of the dry-running relay

The device is a two-contact switching relay. Initially, its contacts are in an open state. To start the device into operation, press and hold the red button pressed until the pressure in the system rises higher than specified. When the pressure in the system drops below that set on the relay, the contacts open and the device turns off the pump in the "dry running" mode. The relays are sold with factory-set switch-on pressure (see Table 1). To change the factory settings of the switch-on pressure, use the adjusting nut and spring (Fig. 1). The more we squeeze the spring, the higher the switch-on pressure is set by the relay, and when the spring is weakened, the switch-on pressure decreases. It is necessary to control the value of the switch-on pressure using a pressure gauge.

Operation, maintenance and repair of relays

The dry-running relay, like the pressure switch, is very simple and reliable device used to protect autonomous system water supply. If the operating conditions are observed, it works without interruptions. However, given the quality of our water, voltage fluctuations or high humidity, there are failures in its work. Voltage fluctuations also lead to unstable operation of the pressure switch. electrical network entering the air supply system. The reasons for the failure of the "dry running" relay, how it can be disassembled, repaired or repaired, we considered in more detail in the article devoted to the three-phase pressure switch.

Possible causes of dry running

Let's consider the main situations of insufficient water supply:

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

• the pump performance exceeds the 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 the water enters.

4. At low water pressure (or lack thereof) in the water supply system to which the pump is connected. Without automatic devices, the pump will not turn off by itself and will continue "idle" operation until it is turned off, or it breaks down.

5. When supplying water from an excised source (container), it is necessary to constantly monitor the level of the incoming liquid.

Methods for protecting pumps against dry operation

Protection against "dry running" of the pump is provided by automatic equipment - sensors and relays that block the power supply at the moment of the appearance of the "waterless" mode or in advance. Triggering occurs in devices in different ways, and depends on the definition of the following values:

• water level;
• pressure in the outlet pipe;
• water flow;
• combined indicators.

Let's consider in more detail certain types of automatic protection.

Water level switch and float

By monitoring the water level, the level switch and the float sensor work. The level control relay regulates the operation of water control valves and pump starters. It is one of the most reliable, but also expensive, methods of protection. The main advantage is that it turns off the pump before dry running occurs.

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

Scheme of work: a control sensor is installed above the pump, working sensors - at different levels of the well; 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 start working.

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

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

The switch cable is connected to the phase supplying power to the pump. When the water level falls below the float sensor, the electrical circuit is opened - the pump stops.

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

A float switch can be used to protect drainage and well pumps. Other automatic installations must be used to protect pumping units operating in a network pipeline or wells.

We will solve your problem today - and not in three days! All the craftsmen are Slavs, with over 7 years of experience - people "from the street" do not work for us!

We give a guarantee for all types of work!We will fix the cost of services before starting work - the price will not change!We will deliver all the materials - help on your choice!

Discount 10% regular customers!

Call now and we will give you a 15% discount on the second service in your order (when calculating the discount, works with the lowest cost are taken into account).

In our company you can call the plumber around the clock , on weekends and holidays.

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

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

What is dry running

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

Most manufacturers explicitly indicate in the operating manuals about the inadmissibility of dry running.

Let's figure out what are the reasons for this phenomenon and why it should not be allowed.

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

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

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

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

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

When contacting the service, the masters easily diagnose dry running as the cause of the breakdown - because of this, the mechanism arises whole line characteristic distortions of details.

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

How to protect a pumping station from running dry

Today, several solutions have been developed that protect the pump from dry running by turning it off when the water supply is interrupted. Each of these solutions has its own strengths and weak sides, therefore, the optimal effect is given by several protection systems combined together.

But to determine how to create effective dry-running protection for your pump, you must first figure out which features are specific to the individual components.

Protection relay

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

Depending on the model and the settings set by the manufacturer, the relay is capable of triggering from a pressure drop from 0.6 (highest sensitivity) to 0.1 (lowest sensitivity) atmosphere. Usually this sensitivity is sufficient to detect the occurrence of an idle situation and turn off the pump.

The most common such mechanism is for surface-mounted pumps. But some models have a case that is protected from water ingress and can be mounted on deep pumps.

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

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

Water flow control

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

• Lobe relays are the simplest in design. In them, the flow of water bends the plate, which, in the absence of pressure, will bend and short-circuit the relay contacts. Then the circuit that supplies the pump with electricity will be disconnected.
• The turbine relay is more perfect, but more complex in design. His main element- a small impeller mounted on a shaft. The current makes it lie, and the sensor reads the pulses generated by an electromagnet attached to the axis of the turbine. If the number of pulses falls below the reference value, the circuit is disconnected.

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

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

Water level sensors

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

By design, there are two types:

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

Required tools and materials

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

• The relays themselves.
• Tool for working with electric wires: a knife for stripping contacts, screwdrivers.
• Wires to create an electrical circuit.
• Keys for mounting relays on highways.
• Means for sealing connections: sealants, rubber gaskets (usually included with the relay).

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

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

You can see the wiring diagram of the pressure switch and dry-running fall protection in the figure:

The installation procedure is as follows:

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

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

• Before buying, carefully study the passport of the selected relay and make sure that its sensitivity and other characteristics are at the proper level for your well and pump. You can study the passport directly in the store or find it on the manufacturer's page of the protective device and download it in pdf format.
• Make sure all wiring and circuitry to be created is adequate for the power being used. V otherwise there is a risk that a conductor or relay will burn out.
• The most advanced protection system can be powerless if used ineptly. If any of the components has worked, do not restart the pump until you have found out the cause of the problem and made sure that it has been completely eliminated.
• Remember that every relay requires periodic verification and replacement. Replace expired protective system components promptly.

In addition, we offer several videos so that you can see the order of connecting the relay with your own manholes:

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

Although the purchase and installation required devices and requires some investment of time and money, but these costs are much lower than the losses that would have to be borne if the pump burns out.

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

In pumps household use The main material of the impellers is thermoplastic (durable plastic). It is characterized by great potential for work and low cost. The material has been performing well for many years. But if it works without water, which acts as a lubricant and a source of heat dissipation, then the internal components of the pump are subject to deformation. In the most extreme cases, shaft seizure and failure of the electric motor can occur. Usually, after that, the pump cannot supply water, or it supplies it of very poor quality.

Who can diagnose a breakdown?

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

Rules to follow

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

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

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

Dry-running protection of the pump is mandatory. When emptying the container, the device is not able to turn off automatically. It will continue to function until it breaks or until it is turned off by inattentive users.

Float

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

There are the following types of devices:

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

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

Unfortunately, the float is not very versatile. It simply won't fit in a well or a network pipeline. Other types are used here.

Using a pressure switch with dry running protection

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

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

A drop to the limit threshold can only be observed if there is no water in the pump. Without water, there is no pressure, and the relay, reacting to dry running, opens the contacts that power the device. The pump can only be started manually. Before doing this, you must determine and eliminate the cause of the failure. The pump is filled with water again before being switched on again.

What type of construction is this pump protection for? Dry running of the pressure switch will help to avoid only automatic configuration (in conjunction with the hydraulic tank). Otherwise, the operation of the device becomes meaningless.

Typically, the relay is designed for a deep pump configuration as well as a surface system or station. Protection is also carried out submersible pump from dry running.

Flow switch equipped with pressure function

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

Dry-running protection of the pump is provided by a sensor built into the relay. The system is turned off after fixing dry running, which takes a little time and does not affect the functionality of the pump. In addition, the press control provides protection against overvoltage in the power supply.

The main advantage of the unit is its small size and weight. Unfortunately, the market is overwhelmed with devices that are produced by some unknown country. It is sometimes very difficult to understand the quality of a particular model.

On average, the device works for about 1.5 years, provided that the assembly is performed at a high level. A device that has passed certification and has high rates, produced by ACTIVE. Its cost is about $ 100.

Using a level switch

The level switch is based on an electronic board to which the dry-running protection sensors of the pump are connected. As a rule, the design of the device assumes three electrodes, one of which performs a control function, and two - a working one. They are connected to the device by means of an ordinary single-core electrical wire... The electrodes are used to supply a signal.

How the device works

Dry run protection borehole pump carried out when the sensors are immersed in a container at different levels. When the water drops below the control sensor, which is installed slightly above the installation of the pump itself, the electrode transmits a signal to the level switch, and the pump stops working.

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

Which device should you choose?

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

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

It should be noted that pressure switches are often used to protect a pump designed for operation in wells. It is better to use models of an expensive segment, as well as a level switch, which is distinguished by a high degree of reliability.

Note that the application protective equipment optional if:

The well is deep and has a good production rate as specified in technical passport;
... you have proper experience in using pumps in a well or borehole;
... you are sure that the water level in the system is practically not dropping.

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

Electrical modifications

Despite the fact that protective equipment has been developed that function on elementary principles and understandable criteria, it should be remembered that in addition to mechanical components (pipes, pressure switches, receiver, valve, etc. shut-off valves), there are configurations that operate on electricity.

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

But nowadays there is a wide range of electronic devices on the market, and this makes the task much easier. There are even special automatic units that combine the function of a protection relay and a pressure switch. Some models provide a soft restart of the pump.

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

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

Conclusion

Applying your knowledge and skills when implementing a pumping system protection scheme is not so difficult. Any mechanical configuration is simple.
Having not only a theoretical base, but also knowledge of several options for solving this problem, you can ensure the smooth operation of your pumping system.

The workflow of water pumps is fraught with numerous structural threats. These include contamination, engine overheating, breakdowns due to faulty connections, etc. But even the correct organization of the operational process in accordance with the instructions does not guarantee the elimination of indirect threats. Lowering the level of pumped water below minimum value can lead to equally serious damage. To prevent this from happening, manufacturers recommend using a dry-running sensor for the pump, which detects the critical level of the working environment and decides to turn off the equipment.

General principle of operation of the device

Most of the protective devices of this type are associated with control automation. The controller fixes the operating parameters for the subsequent correction of the supply volumes, switching on or off the unit. In this regard, dry or idle sensors act as only one of the signaling devices about the state of the working environment. Determination of water scarcity 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 to work as a pressure gauge. And when a sufficient pressure level is restored, it also resumes the pump function through the control controller. Again, the symptoms of water scarcity can vary.

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

Dry running sensor classifications

The simplest systems of this kind provide protection based on the indications of mechanical alarms. These are models of float and flow-through type, which can be directly structurally related to the target equipment. For effective work even the introduction of automation is not necessary for such devices. Often mechanical protection used for borehole pump. In this case, the dry-running sensor should not even determine the critical level of lack of the pumped medium, but its approach to the place of intake. For example, optimal height the water column for borehole pumps averages 150-200 cm, and a decrease to 100 cm will be a critical point. Automatic systems, as noted above, assumes control by means of automation. The control relay stops supplying power and the equipment stops. But in both cases, the principles for determining the parameters of water supply may be different.

Float sensors

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 cuts 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. In the case of submersible systems, the pump dry-running protection sensor is located above the protective grille of the nozzle or the bottom valve. The device can be integrated as an option, or in the basic design it can 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 fixes temperature regime 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 normative indicator 1.5-2 atm. This is the threshold level at which the system turns on or off depending on the up or down dynamics. Of course, the user can adjust the dry running sensor for the pump to different peaks, 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 the most common in the industry. Such devices are used to accurately control the level of technical environments in production tanks, and recently they have begun to be used in plumbing.

How does a dry running sensor work for this type of pump? The monitoring relay includes an electronic board and several electrodes. Sensitive elements are installed at different points of the tank, in which water is pumped out, and during operation they exchange signals with each other. Liquid acts as a conductor for currents of low frequency, therefore, the termination of communication will mean that there is no water at a sufficient level. When the signal is interrupted, the circuit is opened and the power supply is cut off.

What to consider when choosing a sensor?

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

Dry-running relay connection

Installation of control valves is performed at the stage of assembling the pumping structure. First of all, a check valve with a filter is mounted on the suction line, after which you can start integrating 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 supply from 200 V: socket - relay - pressure gauge - motor. Wiring loops usually operate with a current strength of the order of 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-pole relay. In this state, the pump cannot be started, since it will start operating at the same idle speed. Initially, the accumulator should be filled with water until the pressure reaches the optimal level. During this technological period, the dry-running sensor for the pump should be activated. The principle of its operation at this stage is adjusted to the service mode, in which idle operation 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 transferred 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 are offered by direct pump manufacturers. For example, Grundfos is working on combining centralized control panels, which include water supply fittings and a multifunctional package. protective automatics... Domestic developers of controllers have 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 a high protection class - IP65. Decent in price and quality offers are also produced by the companies "Belamos", "Dzhileks" and "Zubr".

When should you not use dry run protection?

The additional load in the form of sensors is far from always justifying itself. Obviously, pumping water from a lake, reservoir or pond does not involve dry running risks. Another thing is that a change in the position of the equipment itself can lead to a shift in the water intake level, 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 least for wells and wells, a seasonal schedule can be set when the risks of sudden changes in water levels rise and fall. Accordingly, for these periods it is necessary to adjust the operating mode of the control equipment.

Finally

Underestimate the impact of idling on pumping equipment also not worth it. Some models long work in this mode, it 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 directly depend on water supply. In versions with rotary units, the pumped liquid can be used as a technical lubricant or as a cooling medium. Therefore, a dry running sensor for the pump can prevent very significant damage to the motor. For the same reason, manufacturers themselves in basic configurations increasingly provide for the presence of monitoring equipment. Moreover, refusal to use protective devices is a condition for the loss of warranty, since the instructions for operating the equipment are violated. These nuances should be taken into account even when developing a water intake scheme, assessing the connection possibilities of the most effective means control.