Protecting the pump from dry running: methods, features, step-by-step instructions and reviews. Application and operating principle of dry running relay

Significantly reducing the service life of the pump is an emergency operating mode without water, the so-called “dry running”. Water performs both lubricating and cooling functions. Without fluid, the pump quickly overheats, parts become deformed, and the motor can burn out. Short-term dry running negatively affects equipment performance, regardless of the type of pump (drainage, submersible or surface pump).

To prevent breakdowns, automation is used:

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

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

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

1. Wrong choice of pump. Happens more often in cases with wells if:

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

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

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

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

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 from operating without water

Protection against “dry running” of the pump is provided by automation - sensors and relays that block the power supply at the moment the “waterless” mode appears or in advance. Triggering occurs differently in devices, and depends on the definition of the following quantities:

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

Let's take a closer look individual species automatic protection.

Water level switch and float

The level switch and float sensor operate to monitor the water level. The level control relay regulates the operation of the 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 it runs dry.

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

Operation scheme: control sensor is installed above the pump, working sensors are installed at different levels of the well; when the water level drops to the control sensor, a stop occurs pumping unit. When the water reaches the level of the control sensor again, the pump will automatically start working.

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

A float sensor (switch) can effectively solve the problem of “dry running” in wells and water supply from containers. It is mounted above the pumping unit. The trigger level is controlled 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 container at the moment the sensor is triggered. For submersible and surface pumps, the “critical” water level should be located above the foot valve or suction screen of the pump.

A float switch can be used to protect drainage and well pumps. To protect pumping units operated in network pipelines or wells, other automatic units must be used.

Relay and pressure sensor

To determine the pressure level at the outlet pipe, a pressure switch and a pressure sensor operate. The relay is installed minimally permissible norm pressure - usually 0.5 bar. You cannot adjust the maximum pressure level yourself. You can use a pressure switch as protection if the pump operates with a hydraulic accumulator.

When the pressure switch operates, the contacts open if the pressure drops to the set limit. It should be noted that the entire range of household 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 emergency danger, but simply detects the beginning of the “dry running” mode, turning off the pump. After the liquid supply is restored under appropriate pressure, it will be possible to turn on the pumping unit manually. Before each start, you must fill the pump with water yourself.

More wide range actions of pressure sensors. They signal that the pump stops working when the pressure drops to 1 bar or below. Pressure sensors have found their application in domestic pumping installations of network pipelines, fire extinguishing and water supply pumping stations.

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

Water flow sensor

The operating principle 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 part and a reed switch microswitch. The petal is spring loaded and has a built-in magnet on one side.

Scheme of operation of the sensor: under the influence of water pressure, the petal valve moves - the spring begins to compress, and the magnet interacts with the reed switch relay. Closing the contacts causes the pump to operate. Without any liquid entering, the valve spring expands, moving the magnet to its original position - opening the relay contacts turns off the pumping unit.

The flow sensor is built into booster pumps with low capacity. Works to determine two values ​​(pressure level and flow) of the flow switch, with additional function pressure switch, 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), the pump receives a command to start working. The pump performs its functions until the water supply stops. Due to the flow sensor built into the relay, the pump stops working. The sensor very quickly registers the appearance of a “dry running”, which allows you to avoid a long stay in the “waterless” operating mode.

Mini AKN

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

Situations when protection may not be used

You can do without installing a pump dry running sensor only in certain cases:

• constantly monitoring the water supply from a well or borehole (you will have to be nearby to respond in time to changes 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 operational experience and knows the principle of operation and design of the pump.

If the operation of the pump becomes intermittent, or it shuts down completely, it cannot be restarted without identifying and eliminating the causes of the breakdown.

Pumping equipment operates correctly only when the flow of liquid through it is constant. If the fluid supply stops, dry running occurs, and, as a result, the pump breaks down.

To prevent the pump from running dry, special devices are installed on the water supply system.

1 Dry running relay: purpose and design

There are several types of devices that will turn off equipment without water supply:

• dry running relay for pump;
• liquid flow control sensor;
• water level sensor.

Each of these devices has different area application and operating principle.

The dry running protection relay is a simple electromechanical device, which controls the presence of pressure in the water supply: if the pressure drops below the permissible level, electrical circuit will open and the pump will turn off.

The relay device contains a sensitive membrane that responds to pressure and a contact group that is open in the normal state. As soon as the pressure drops, the membrane presses on the contacts, they close, and the power supply is turned off.

A drop in pressure is possible when the water supply in the pipeline stops, the filter becomes clogged with debris, or the suction pipe is above the liquid level. In each of these cases, a “dry running” of the pump occurs, which must be stopped, which is what the protective element does.

The operating pressure of the medium to which the dry-running relay reacts is set by the manufacturer and ranges from 0.1 atmospheres to 0.6 atmospheres. Relay idle speed installed on the surface but there are also models for internal placement in a sealed housing.
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1.1 Installation

The device operates normally in any pipeline design that does not include a hydraulic accumulator. It can also be installed in conjunction with a hydraulic accumulator, but such a scheme will not provide complete protection against dry running of the pump.

The reason is the peculiarity of the structure and operating principle: the protective element is installed in front of the fluid pressure switch and the hydraulic accumulator, and is mounted between the pumping unit and the protective device check valve.

At the same time the membrane of the device is constantly under pressure, which creates a hydraulic accumulator. This standard scheme, but sometimes situations arise when a running pump does not turn off when the water flow stops and fails.

For example, a dry running situation has arisen: the pump is turned on, the container or well is almost empty, but there is a small amount of liquid in the battery. Since the lower pressure threshold is set to work at 1.4-1.6 atmospheres, it is there, but the membrane will be pressed out, and the pump will continue to idle.

It will stop working when most of the water from the accumulator is pumped out or when the engine burns out. This means that the pressure in the pipeline has dropped to a critically low level and the protective relay has tripped. Based on this, in systems with hydraulic accumulators it is advisable to install other devices to protect against dry running of the pump.

It is most effective to connect a dry-running relay paired with a surface pumping unit, when the check valve is installed after the pumping equipment.
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2 Float switch

A float switch is the simplest and most cheap way protect circulation pump from overheating and breakdown when running dry. The advantage of the device is that it can be used as a working medium level sensor and as an actuator.

They install switches in tanks, wells, tanks and use them in controlling household and industrial pumps in water supply and sewer lines. The required level of switch operation is determined by the length of the cable.

Several float switches can be placed in one container, each of which will perform a separate function. function for managing main or backup pump equipment.

Dry-running float sensors come in light and heavy sizes. The former are used for supplying and draining water, the latter - in sewers and drainage pipelines.

For correct operation of the device, a minimum well diameter of 40 cm is required. This feature does not allow float switches universal remedy protecting the pump from running dry.
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2.1 Safety pressure switch

The device is a conventional pressure switch, equipped with additional protection against idling when the pressure drops below factory settings.

This pressure switch controls the switching on and off of the surface or well pump, if the pipeline diagram includes a hydraulic accumulator or a connection to an automatic pumping station is provided. The relay operates at 0.4-0.6 atmospheres. This parameter is set at the factory and cannot be changed.

If pressure fluctuations inside the pipeline are within specified limits, then the pressure switch does not operate and the pump operates normally. When the pressure drops to the set values, which happens in the absence of water, the dry running sensor is activated, the contacts supplying the circuit are opened, and the device for pressure movement of liquid is turned off.

The process of starting the pump is carried out only manually by pressing the lever. Before this, the cause of the engine stopping is determined and eliminated. Required condition during startup – filling the pump with water.
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2.2 Which protective device should I choose?

The choice of a device to protect the pump from dry running is determined by the model of the pump itself and the tasks it needs to cope with. The optimal option is to use a dry-running sensor for the pump in the form of a float and a pressure switch. Connecting these devices to the pipeline will completely reduce the risk of breakdown of pump equipment.

The use of protective elements is not necessary if:

• the depth of the well or container is sufficiently large;
• servicing of the pumping unit is carried out by an experienced technician;
• The water level in the system does not change - there is no point in connecting with protection devices.

The operation of the pump requires increased attention: as soon as the water disappears or the thermal relay is triggered and the engine is turned off, you should immediately find out the cause and eliminate it, and only then resume the operation of the pump unit.
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Reasons for installing protection

When the pump operates properly, water flows through its cavity in a continuous flow. It performs several important functions simultaneously:

• the rubbing surfaces are lubricated, and the force to be overcome is reduced;
• During friction, heating occurs; heat is picked up by water flows and carried away from the friction area.

Excessive overheating without a pump dry-running protection relay leads to rapid wear and tear of the mating surfaces. The resulting heat during prolonged operation can deform working parts, sometimes irrevocably. The electric motor also receives excess heat, and if it is significantly overheated or there is no dry-running protection relay for the pump, it can burn out.

Not allowed for use hydraulic equipment with faulty dry-running protection sensors.

Design features

Let's take a closer look at the dry running sensor for the pump and its operating principle. The dry-running protection relay is a block with several springs. It limits the operation of the entire device.

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

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

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

Water level switch

Often pumps come with a factory setting of a minimum of 1.2 atm and a maximum of 2.9 atm, when they are completely turned off, without waiting for a drop to 1 atm.

Making adjustments

The direct mutual influence between the following quantities is derived:

• setting the pressure on the relay;
• hydraulic accumulator volume;
• water pressure.

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

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

VIDEO: Automation for protecting pumps from dry running

Carrying out setup

The dry-running relay for the pump must be adjusted under pressure while the system is running. It is worth starting the pump first to pump the level up to desired value. The system will automatically turn off the power supply, as the relay will operate.

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

• record the switching pressure;
• unplug the pump cable from the power supply;
• remove the sensor cover and slightly loosen the clamping nut of the smaller spring;
• the desired pressure parameter is adjusted by tightening/loosening the spring marked “P”;
• then open the tap, relieving pressure, and monitor the start of the electric motor;
• We record the readings on the pressure gauge, repeat the operation several times and derive the most optimal pressure values ​​empirically.

During adjustment work you will need to take into account the physical capabilities of the pump. Given the rated value with all the losses, there may be a manufacturer’s limit of 3.5 bar, so we must go to 3.0 bar so that the pump does not burn out from overload.

High-quality protection against dry running

Operating a pump without water is the most common cause breakdown of this equipment with normal power supply. Popular material For the manufacture of pumps, thermoplastic is used, which can withstand long-term operation and has an affordable cost.

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

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

• wells or wells with low water flow. The reason may also be excessive power of the device, which does not correspond to the flow rate of the liquid. During dry periods, the inflow per unit time also decreases at most sources;
• large containers serving as reserve collection tanks process water. Care must be taken to ensure that the pump does not operate in an empty cavity without liquid;
• network pipeline with an embedded pump to equalize the pressure in the system. During the dry season, there may be interruptions in water supply, leading to a drop in pressure.

External elements for protection

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

1. Float switch

The element relates to budget decisions. It is used to pump water from accessible containers. It only protects against overflow.

1. Pressure switch

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

1. Flow switch with functions

If there is no water pumping through the relay, automatic shutdown power supply A small delay does not have a significant effect on the result.

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

VIDEO: How to protect the pump from dry running

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How the modification works

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 and is applied to the winding. The screw plays the role of a retainer. The spring is compressed by a pin. When the pressure drops, the contacts open. A contactor is used to switch off the voltage.

Dry running relay for pump: connection diagram

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

Relay adjustment

To adjust the device, a screw is used, which is located in the upper part of the case. To configure the model, readings are taken from the sensor. To increase the permissible pressure level, the screw is turned clockwise. With reduced voltage, the speed of contact closure slows down. The problem may also be with the contactor with the starting system. To reduce the pressure level, the screw is turned counterclockwise. Much in this case depends on the relay parameters and the maximum power of the pumps.

Device types

There are streaming and float devices. Models can be made with one or more cameras. Modifications low pressure suitable for pumps low power. Streaming devices come in different sizes. For powerful pumps there is a high pressure switch.

Streaming devices

At hydraulic power stations, dry-running flow relays for the pump are often found. The operating principle of the modifications is based on changing the maximum pressure. This process occurs due to a change in the position of the plate. It is located at the bottom of the case. It should also be noted that relays of this type are equipped with wire 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 via an adapter.

Float models

Dry-running float relays for pumps are considered to be the largest. The device is adjusted by tightening the screw. The operating principle of the modifications is based on changing pressure. All models have one pin in the body. In this case, the pipe is located with a ring at the bottom of the structure. Most relays use a manual setting system. Devices are working of this type from a 220 V network. The frame is usually made of plastic. The contact plates may be in vertical position. Most relays operate at low frequency. Models are suitable for pumps with power from 4 kW. The operating frequency is on average 55 Hz. There is a nut at the top of the modification. In this case, the clamping screw is located on the pin.

Devices with level sensor

A dry-running relay for a pump with a level sensor 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 customize. 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 relay chamber 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 from a 220 V network. At the same time, their operating frequency is at least 45 Hz. It is immediately worth noting that the models are suitable for pumps with a power of no more than 3 kW. The contacts on the plate are in horizontal position. The pins are installed next to the plate. In total, the modifications have two nuts. A clamping screw is used to adjust the pressure. Pins of small diameter are quite often used. Models of this type are well suited for working 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. Primarily, the models are used at hydroelectric power stations. They are well suited for pumps that are used in the water supply system. They use contactors for two outputs. The working nuts are located at the top of the housing. It should also be noted that there are modifications for two cameras. Their outlet pipe is located in the center of the base. Most models are based on a dipole contactor. Modifications use several pins. The devices are well suited for submersible pumps. The pipes are available with a diameter of 2.3 cm. The relays operate at a minimum frequency of 40 Hz. The output cable must be connected to the terminal box. There is a clamping screw to adjust the plate. To equalize the pressure inside the system, the nut is turned clockwise. Sensors are very rarely found 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 produced with one or more pins. Most modifications operate at low pressure. If we consider a simple relay, then it uses a wire 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 the 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

Double-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. The devices are suitable for high power pumps. Modifications operate from a 220 V network. If we consider models with drive contacts, then they use a trigger mechanism from the module. The minimum operating frequency is 30 Hz. The frame is quite often made of steel. The pressure increases by adjusting the screw. The clamping plate in the devices is located under the contactor. The relay base has a seal. Most devices are equipped with a cap to lubricate the pin.

Three camera models

Three-chamber devices 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 with power from 4 kW. Their operating frequency is at least 4 Hz. Some relays are made on actuators. Caps are typically installed over the pin. Some devices are manufactured with two clamping plates. The output cable extends from the contactor. A relay of this type operates as a 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, they have two outputs. It is also worth noting that there are models with support posts. Cases are most often made of stainless steel. The cable at the relay comes off the contactor. The devices operate from a 220 V network. Connection to the pumps occurs through a pipe.

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Hello, dear readers of my blog nasos-pump.ru

In the “Accessories” section we will consider in more detail the operating algorithm and the design of a pressure switch with dry-running protection. I have already briefly mentioned this product in the article Methods for protecting pumps from “dry running”. This device combines a pressure switch and dry-running protection. The relay controls, based on preset pressure values, turning off and on both well or borehole and surface pumps when they work together with a hydraulic accumulator. This automation also protects pumping equipment from operation without fluid flow, which allows the user to operate it more comfortably in automatic mode without constant monitoring.

The factory setting for shutting off the product in the “dry running” mode is 0.4 – 0.6 bar. If the pressure in the water supply system changes within specified limits, this resembles the operation of a conventional pressure switch. When the pressure in the system has dropped to a level of 0.4 - 0.6 bar, the device turns off the pumping equipment in the “dry running” mode. Human intervention is required to turn on and continue to operate the pump.

Product Specifications

Specifications pressure switch with dry-running protection Let's look at the example of FFSG2G. Basic technical specifications are shown in Table 1.

Table 1

Device, design and principle of operation

A pressure switch with dry-running protection is assembled on a metal plate that serves as a housing and is covered with a plastic cover. In (Fig. 1) you can see the internal structure and main elements.

Housing 1 metal plate - where all the elements of the dry-running pressure switch are located. Connecting flange 2 with an internal thread measuring 1/4″, is used to connect the automation to the water supply system. The flange, using six screws, secures the membrane 9 and the nickel 10 to the automation body. The membrane connecting flange and the nickel together make up the working chamber. Nut 3 and a small spring that regulate the pressure difference ∆P. This is the difference between the switch-off and switch-on pressure of the automation. The more you compress the spring (tighten the nut clockwise), the greater the difference ∆P will be. The minimum difference between switch-on and switch-off pressures is 1.2 bar. Nut 4 and a large spring are designed to adjust the relay shutdown pressure. When the spring is compressed (we tighten the nut clockwise), the shutdown pressure of the automation increases, and when the nut is released, the shutdown pressure decreases. Terminals 5 and 6 for connecting the pressure switch to the power supply and to pumping equipment. Bolts 7 for connecting ground wires from the power supply and the engine. Lever 8 puts the pressure switch into operation. Cable sleeves 11 are designed for fastening electrical cables.

Installation, electrical connection and operating principle of automation

Installation of this product in a water supply system is no different from installation of a standard pressure switch RM-5. On the hydraulic part, the automation has a connecting internal thread 1/4 inch. The relay can be mounted either on the pipeline itself or on the five-piece. The only condition for installation is that a hydraulic accumulator must be installed next to the automation to prevent flotation inclusions. The capacity of the accumulator depends on the number of points of analysis and the water consumed.

The connection diagram of the pressure switch to the electrical network is shown in (Fig. 2).

Pump or pumping station must be plugged into an outlet connected through the device protective shutdown equipment (RCD). To protect pumping equipment, it is necessary to provide a motor protection circuit breaker with a current equal to rated current engine.

Operating principle next. After completing all installation work. The system and pump must be filled with water and air removed from the pump and suction pipe. We supply power to the pump, but the pump does not start because the relay contacts are open. In order for the pump to turn on, you need to press the automatic start lever and hold it pressed until the pressure in the system rises above 0.5 bar. After starting, the pump will turn off when the pressure in the system reaches the one set on the relay. You can regulate the shut-off pressure of pumping equipment using nut 4 (see Fig. 1). By tightening the nut clockwise, we increase the pump shut-off pressure. If the nut is unscrewed counterclockwise, the pump shut-off pressure decreases. The pump shut-off pressure must be monitored using a pressure gauge. When water is drawn, the pressure in the system decreases; when the lower level is reached, the automation turns on the pump and maintains the pressure in the system. The pressure difference is adjusted using nut 3 (Fig. 1). When the nut is tightened, the difference between the on and off pressure increases, and when the nut is unscrewed, it decreases. It is necessary to monitor the pump activation pressure using a pressure gauge. After water extraction stops and the set pressure is reached, the pump will turn off. In the event that water collection has begun and for some reason (lack of water, power outage, etc., etc.) the pressure in the system drops below 0.5 bar, the automation contacts will open and the pump will no longer turn on , since the relay turned off in the “dry running” mode. To put the automation into operation, human intervention is required. Before putting the relay into operation, you should find out why the pump turned off due to dry running. If the water runs out, you need to refill the suction pipe and pump with water and remove air from the pump and pipe. If the problem is in the power supply, you need to fix it and then start the automation again. We press the start lever and wait until the pressure in the system rises above 0.5 bar. After which dry running pressure switch will continue to operate automatically.

Operation, maintenance and repair

In general, this automation is very simple and reliable. If you follow the operating conditions, the relay works without problems for a long time and reliably. However, making adjustments for the quality of our water, the quality of the energy supply or high humidity, problems may arise in the work. Problems with the relay very often lead to pump failure. To avoid this, you should periodically and every time you restart the automation, check the system and automation.

If the water in the system contains hardness salts or the water contains a high iron content during operation of the automation, gradual “overgrowth” occurs working chamber and flange deposits of hardness salts or iron. There comes a time when the relay stops working completely. To eliminate such a defect, it is necessary to dismantle the relay and clean the chamber from salt deposits by performing the following steps:

1. We de-energize the automation and the pump by disconnecting the cord from the power supply.
2. Relieve the pressure from the water supply system by opening the nearest water tap.
3. Disconnect electrical cables from automation. To do this we film plastic cover from the automation and disconnect the cables from terminals 5, 6 and ground (see Fig. 1)
4. We disconnect the relay from the water supply system using a 17-mm open-end wrench.
5. Using a screwdriver, unscrew the 6 screws and remove the flange. We clean the chamber and flange from salts.
6. We assemble the automation in the reverse order. Before installation, you need to seal the threads using fum tape or sealant.

Interruptions in the operation of automation are also caused by increased humidity (oxidation of contacts), fluctuations in the supply voltage (burning of contacts). In these cases, the automation should be replaced with a new one. Like any technique, dry-running relays require attention.

Thank you for your interest.

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Specifics of operation

Pumped water in home systems involves several parallel processes:

• transportation of liquid to the consumer;
• cooling of pumping equipment;
• lubrication of elastic pump elements

The negative consequences of improper operation of vibration equipment, which is the most popular in household schemes water supply The phenomenon is also considered unacceptable for submersible, surface and drainage devices.

If there is no protection against dry running of the well pump, then the following will occur:

• moving elements heat up and increase the temperature of adjacent units;
• most parts are subject to deformation;
• in a certain situation, jamming occurs, which leads to failure of the electrical part.

In the design of the pumping station, it is necessary to install protection in a timely manner, since the consequences of “dry running” cannot be repaired under warranty; the work will have to be carried out at your own expense.

When checking the condition of failed equipment, it will not be difficult for a specialist to determine the cause of this condition. This is evidenced by characteristic deformation signs of structural elements. In the instructions for the equipment, the manufacturer clearly states that it is inadmissible to operate pumps without liquid poured into the working cavities.

One example of a burnt winding is the first obvious sign for the master

Alleged “culprits” of the breakdown

There are several most common reasons that lead to extreme pump operation:

• Unbalanced pump power. In such a situation, liquid is quickly pumped out due to insufficient flow of the well or for pumps whose intake part is located above the dynamic level.
• The connection diagram has a section intake pipe, in which there is depressurization. Air will flow in through the hole.
• The pumping pipe is clogged, which often happens with surface pump models.
• Hydraulics operate at reduced pressure.
• When pumping liquid from any container, it is necessary to prevent air entrapment.

No installed automatic systems coping with preventing “dry running” is quite problematic.

VIDEO: Disassembly, inspection and cleaning of the Aquarius deep-well pump

What kind of dry-running protection is there for a pumping station?

One of the main factors in obtaining a reliable circuit is the installation of automation. Such equipment includes the following components:

• dry running sensor for pump;
• dry running relay for stations or pumps;
• pressure switch;
• float switch.

Float switch off

One of the universal blockers is a dry-running float sensor for a submersible pump. This chain element is a relatively inexpensive aid for protecting hydraulic equipment. Thanks to the ease of installation, this dry-running sensor for a pump is used in many schemes, for example, when pumping is carried out from classic wells or some containers.

Float - protection against overheating and dry running

The dry running sensor for the submersible pump is connected to the electrical circuit for one of the power phases. A special contact inside the device will break the connection at a certain position of the float body. This way the pumping will stop in a timely manner. The actuation height is set when setting where the float is installed. The cable that connects the dry running sensor for the pump is installed at a certain level so that when the float is lowered, absolutely complete fluid withdrawal does not occur. A certain amount of liquid must remain when the contacts open.

During water withdrawal by surface or submersible units The sensor is mounted in such a way that even after the contact is broken, the liquid level is still above the intake grille or valve.

The disadvantage of the float is its zero versatility - you cannot install it in a narrow shaft.

In such a situation, it is necessary to look for other methods that will protect against dry running of the well pump.

Water pressure switch

The dry-running protection relay used is structurally electric, which makes it possible to break the contact in the circuit when the pressure and, accordingly, the water level in the source critically drop. The initial minimum value is set by the manufacturer. Usually it varies in the range of 0.5-0.7 atmospheres.

Pressure switch against dry running

The vast majority of dry-running relay models for domestic needs self-adjustment does not provide a threshold value.

IN normal conditions operation of the pumping station, the pressure in the system always exceeds one atmosphere. An underestimation of the indicator indicates only one thing - air has penetrated into the intake pipe. The automation immediately breaks the contact that powers the pump, preventing current from flowing through the cable. Start after a break is carried out exclusively in manual mode, which is additional protection.

The use of such a relay makes sense if certain conditions are met:

• the presence of a closed water supply circuit;
• mounted hydraulic tank;
• use of a pumping station with a surface or submersible pump.

The operating principle of this relay is relevant for systems with deep pumps.

Water flow sensor

The circuits use special dry-running sensors that record the speed of water flowing through the pump. The design of the sensor includes a valve (petal) located in the flow section and a reed switch microswitch. There is a magnet on one side of the spring-loaded valve.

The algorithm by which this sensor works is as follows:

• water pushes the valve;
• due to the push, the spring is compressed;
• the contacts close and the equipment begins to work.

As soon as the flow weakens or ends completely, the pressure on the valve stops, accordingly, the spring weakens, the magnet moves away from the switch and the contact breaks. The pump stops working. When water appears, the entire cycle is repeated automatically.

This sensor is built into low-power hydraulic equipment. Its work is to balance between two quantities: flow and pressure level. Positive qualities are the following characteristics:

• compact dimensions;
• ease of installation;
• speed of response to shutdown.

Thanks to high speed When triggered, it is possible to turn off the power in a timely manner, which reduces the risk of waterless operation.

VIDEO: What type of automation should I choose for the pump?

If it is necessary to install universal protection, experts recommend using a mini AKN device for emergency modes. It is based on electronic protection of self-priming equipment, which responds to specified parameters.

The advantages of the device are:

• minimal energy consumption;
• small parameters;
• comprehensive protection against extreme conditions;
• high degree reliability;
• ease of installation.

Operation without installed protection

In certain cases, you can do without installing additional protective units. This is possible in the following situations:

• liquid is taken from a source that constantly contains water;
• direct visual monitoring of the liquid level is carried out;
• high flow rate in the well.

If you hear that the unit begins to stop, or rather “choke,” you must independently disconnect it from the network. It is not recommended to restart the hydraulics without checking.

VIDEO: Electrical diagram for connecting an automatic deep-well pump

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

But the presence of protective modules makes the design more expensive. That is why it is worth considering in advance how important protection against “dry running” is for you, and whether it is worth spending money on a more expensive station - such as.

Having a device that will turn off the pump when water stops flowing into the system is highly desirable in the following cases:

• The pump is used to increase pressure by inserting a pumping station into the network water supply. This is done quite often, and in order to insure equipment in case of a water supply outage, protection is installed.
• The station is used to draw water from the reservoir. Here, the relevance of protection against “dry running” is obvious: as soon as the container is emptied, the pump will begin to “grab” air, and if it is not turned off in advance, it will quickly fail.
• As a source autonomous water supply a well or a well with low flow rate is used. Here, too, there is a risk that the hose used for sampling will be above the water level, and this will lead to breakdown.

The last case is relevant for almost all private households. IN summer time The water level is already falling, but it is further reduced due to intensive selection for irrigation. So a pumping station that pumps water out of a well or shallow well must be carefully protected.

Methods for implementing protection

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

Float switches

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

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

Pressure/flow switch

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

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

Pay attention! Restart must be carried out manually, after eliminating the cause of the relay operation and filling the system with water.

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

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

Level relay

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

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

In pumps for domestic use, the main material of the impellers is thermoplastic (plastic that is durable). It is characterized by great work potential and low cost. The material performs its functions perfectly for many years. But if it operates without water, which acts as a lubricant and a source of heat removal, then the internal components of the pump are subject to deformation. In the most extreme cases, the shaft may jam and the electric motor may fail. Usually, after this, 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 device manufacturer indicates that you cannot 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 unit failure include the following:

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

Protecting the pump from dry running is mandatory. When the container is empty, the device cannot turn off automatically. It will continue to function until it breaks or until inattentive users turn it off.

Float

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

The following types of device are distinguished:

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

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

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

Using a pressure switch with dry-running protection

The pump dry-running protection relay is a common device equipped with the additional function of opening the contacts when the pressure drops below an extreme level.

Typically this level is set by the pump manufacturer and ranges from 0.4 to 0.6 bar. This indicator is not regulated. With proper 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, the cause of the failure must be identified and eliminated. The pump is refilled with water before turning on again.

What type of design is this pump protection designed for? Only the automatic configuration (together with the hydraulic tank) will help to avoid dry running of the pressure switch. Otherwise, the operation of the device loses its meaning.

As a rule, the relay is designed for the deep pump configuration, as well as for surface system or stations. The submersible pump is also protected 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 sends a command to start the pump when the pressure in the system drops to 1.5-2.5 bar. After the water supply stops, the pump turns off, since liquid no longer passes through the relay.

The pump is protected from dry running by a sensor built into the relay. The system turns off after dry running is detected, which takes a little time and does not affect the functionality of the pump. In addition, press control provides protection against high voltage in the electrical network.

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

On average, the device operates for about 1.5 years, provided that the assembly is carried out at a high level. The device, which has been certified and has high performance, is manufactured by ACTIVE. Its cost is about $100.

Using a level switch

The level relay is based on an electronic board, to which sensors for protecting the dry running of the pump are connected. As a rule, the design of the device involves three electrodes, one of which performs a control function, and two - a working one. They are connected to the device using an ordinary single-core electrical wire. The electrodes are used to provide a signal.

How the device works

Protection against dry running of a well pump is 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 operating.

After the water rises above the control sensor, the pump automation is activated. Dry running protection has a high level of 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 boreholes. 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 taste of the user. Experts note the following.

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

It should be noted that to protect a pump intended for use in wells, they often resort to using a pressure switch. It is better to use models from the expensive segment, as well as a level relay, 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 flow rate, indicated in technical passport;
. you have adequate experience in using pumps in a well or borehole;
. you are sure that the water level in the system practically does not drop.

You should be extremely careful when operating the pump. As soon as you notice that the water has disappeared or something has happened that caused the pump to turn off, try to find out the reason for what happened, and only then operate the pumping system.

Electrical modifications

Despite the fact that protective means have been developed that operate on elementary principles and understandable criteria, it should be remembered that in addition to mechanical components (pipe, pressure switch, receiver, valve and shut-off valves), there are configurations that operate on electricity.

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

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

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

Users note the EASYPRO pressure controller from Italian manufacturer Pedrollo. It ensures the maintenance of constant automatic starts and stops of 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 device display shows all necessary information about the operation of the pumping system.

Conclusion

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

Pumping equipment serving piping systems, through which the liquid medium is transported, especially needs protection at the moment when the pressure of the liquid drops or it stops flowing altogether. To provide such protection in situations where the pump is not supplied with the liquid it pumps, it is equipped with automatic sensors - dry-running relays. Various types of such devices can be used for a pumping station.

Why pumping equipment must be protected from dry running

Whatever source the electric pump pumps water from, this equipment may find itself in a situation where liquid stops flowing into it. It is precisely such situations that lead to the fact that the pumping station begins to operate at idle (or, as they more often say, on dry) running. Negative consequence operating the pump in this mode is not even a waste of electricity, but intense heating of the equipment, which ultimately leads to deformation of its structural elements and rapid failure. Water simultaneously acts as a lubricant and coolant, so its presence inside the pump is simply necessary.

For this reason, the presence of a relay that provides protection against dry running of a well pump (or circulation pump) is almost mandatory. Majority modern models pumping equipment has built-in relays. However, such pumps are very expensive. For this reason, users often purchase dry-running protection relays separately.

Basic protection

To protect the pump from dry or idle running, various types of devices are used, the main task of which is to stop the operation of the equipment the moment water stops flowing into it. These include, in particular:

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

The differences between all of the above devices lie both in their design and operating principle, as well as in the areas of their application. To understand in what situations the use of one or another type of relay that protects pumping equipment from dry running is most appropriate, you should get to know each of them in more detail.

Characteristics of the pump dry running protection relay

A dry running sensor for a pump is an electromechanical type device that monitors whether there is pressure in the system through which water is transported. If the pressure level is below the standard threshold, such a relay automatically stops the operation of the pumping equipment, opening its circuit electrical supply.

The dry-running relay for the pump consists of:

• a membrane, which is one of the walls of the inner chamber of the sensor;
• a contact group that provides closing and opening of the circuit through which electric current flows to the pump motor;
• springs (the degree of its compression regulates the pressure at which the relay will operate).

Main elements of the dry-running relay

The principle by which such a dry-running protection relay works is as follows.

• Under the pressure of the water flow in the system, if its level corresponds to the standard value, the membrane of the device bends, acts on the contacts and closes them. Electric current in this case, it goes to the pump motor, and the latter operates normally.
• If the water pressure is insufficient or does not enter the system at all, the membrane returns to its original state, opening the electrical power supply circuit of the pumping unit and, accordingly, turning it off.

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

A pump dry running protection relay is usually installed on the surface of the earth, in a dry place, although there are models made in a moisture-proof housing that can be mounted together with pumping equipment in a well.

Relays that prevent the pump from running dry work more effectively when they are installed in systems that are not equipped with a hydraulic accumulator and are served by a surface circulation pump. It is, of course, possible to install such a relay in a system with a hydraulic accumulator, but in this case it will not be able to provide one hundred percent protection of the pumping unit from dry running. The relay connection diagram is as follows: it is placed in front of the water pressure sensor and the hydraulic accumulator, and immediately after the pumping station a check valve is installed that prevents water from moving in the opposite direction. With this connection, the dry-running relay membrane is constantly under water pressure created by the hydraulic accumulator. This can lead to the fact that the pump, which will not receive water from the source, simply will not turn off.

Effective protection of the pump from dry running in cases where it serves systems in which a hydraulic accumulator is installed is also possible, but other types of devices are used to solve this problem.

Sensors that control water flow

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

Water flow relays or sensors

There are two types of electromechanical water flow sensors:

• petal;
• turbine

The main working element of the first type of sensors is a flexible plate installed in their internal cavity, which has a cylindrical cross section. If there is a fluid flow in the system and has sufficient pressure, such a plate, equipped with a magnetic element, is as close as possible to the reed switch type, and its contacts are in a closed state. If the pressure of the fluid flow decreases or it disappears altogether, the flexible plate moves away from the switch, its contacts open, which leads to the pumping unit being turned off.

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

Sensor automatic control pump "Turbi"

Electronic water flow controllers

Electronic water flow controllers have an even more complex design, which combine the functions of a pressure switch and a device that protects pumping equipment from dry running. Such controllers, also called electronic pressure switches, although not cheap, replace several monitoring and control devices at once. Installed in water supply systems, electronic pressure switches not only protect the pumping system from dry running, but also allow you to control the pressure and fluid flow parameters. When such system operating parameters do not correspond to standard values, an electronic sensor automatically turns off the pumping equipment.

If a pump with a small head reserve is used to service water supply systems, then they can only be equipped with an electronic relay. When the system uses a pump with a large margin of the pressure it creates, a hydraulic accumulator and a separate pressure sensor are needed, since the electronic relay is not regulated by the maximum shutdown pressure of the pumping unit. Use only electronic relay in such cases, it can lead to the fact that when excess pressure is created in the system, the pumping station simply does not turn off.

Sensors that monitor the water level in the system

Water level control sensors, which are installed mainly in the water supply source - a well, well or container, can also prevent situations when the water supply system pump is idling. Thus, through such devices, the well pump is protected from dry running (or a pumping unit pumping water from the well). By design, level control sensors can be float or electronic.

Float sensors

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

The operating principle of the float relay for water level control is quite simple. As long as there is liquid in the water supply source, the float connected to the contact group is raised up. The work process will not be interrupted until the water level in the source decreases to such an extent that the float drops and thereby opens the contacts through which phase wire electric current flows from the pump motor.

It should be noted that protecting the pump from dry running using a float sensor for water level control is the most affordable and most common method.

Electronic relays

Electronic water level control sensors are capable of simultaneously solving two problems: protecting pumping equipment from dry (idle) running when the water level in the water supply source decreases and preventing cases of liquid overflow when filling containers.