The principle of operation of the pressure switch idle speed sensor. Dry running protection for a pumping station. Device, design and principle of operation

For continuous and trouble-free operation of the pump ( pumping station) a prerequisite for operation is the presence of a sufficient amount of water. Regardless of where the fence comes from (well, well, open water, centralized or drainage systems), pumping equipment must be equipped with protection against idling. This is due to the fact that water, when passing through the pump, provides its lubrication and cooling. In the absence of water or its insufficient quantity, the operating pump overheats and fails.

In order to exclude damage that is not covered by the manufacturer's warranty obligations, a pump dry-running protection relay should be installed.

1 Causes of dry running

Connect a dry-running relay for protection pumping equipment necessary in the following cases:

when performance (power) well pump significantly exceeds the resource capabilities of self-recovery of a sufficient volume of water in the well;
the natural water level in the source is significantly lower than the installation level of the pump;
there is constant clogging with sand, silt, foreign objects of the intake pipe or filter mesh;
the tightness of pipes and their connections is violated from the physical influences of the soil or due to improper installation;
the circulation pump operates at low water pressure or insufficient water in heating (cooling) systems;
water is taken from a source being filled - a well (well) slowly restoring the water level, a storage tank, an unstable water supply system.

Connecting the idle relay to the pumping station - required condition because she works in automatic mode without outside control.

2 Dry running protection devices

The main devices that exclude the possibility of pumping equipment without water in automatic mode include:

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

Under certain conditions, sensors and relays interrupt the power supply to the pump motor, causing it to stop. The protection operation is determined by the following parameters:

water level;
outlet pressure;
by the strength of the water flow.

The combined control on several parameters at the same time is possible.

2.1 Float switch

Float-type dry-running sensors work effectively when installed in wells, drainage systems, and storage tanks. The actuation process (power off) occurs when the water level in the source drops to a minimum value. When, together with the decreasing water, the float drops to the lower operating level, the contacts open in the power supply phase of the pump, which leads to its stop.

The float switch can be connected to submersible or surface pumps. In this case, its location should be above the bottom valve or the protective grille of the suction pipe with fixation of operation by insufficient water level.

Installation of such a sensor is not possible when taking water from wells and centralized water supply systems.

2.2 Level switch

With the help of this device, the water level in the source (tank) is monitored. When the level drops to a critical value, the control relay is activated to adjust the operation of the flow valves or turn off the pump.

The main advantage of this protection is that the power supply to the pump is switched off before it starts running in idle mode.

The level switch consists of an electronic board and three electrodes (sensors) that are mounted on different height in close proximity to each other. The electrodes, being immersed, exchange low-frequency currents, since water is a good conductor of electricity. When the water level drops to the lowest control sensor, the electrical connection between the electrodes is interrupted, which leads to the operation of the relay to stop the pumping device. When the working water level is restored, the pump is switched on again.

2.3 Pressure switch

The principle of operation of the pressure switch is based on determining sufficient pressure (from 1 bar) at the outlet pipe of the device pumping water. In the event of a pressure drop below 0.5 bar, the contacts are opened by the pressure switch.

When the pressure is restored, with sufficient for safe work pressure pump, you must manually fill the dry pump with water and turn it on yourself.

Pressure switches are used during installation household pumps connected to centralized networks water supply, water supply and fire extinguishing stations. Installation is recommended at pumping stations that work with a hydraulic accumulator (storage tank).

2.4 Flow sensor

The device is reed valve, which is installed in the flow part of the pump. The principle of its operation is to respond to the force of the flow (the passage of a certain volume of water in the pipe per unit of time).

The spring-loaded petal of the sensor, under the action of passing water, compresses the spring and interacts with the reed relay through the magnet fixed to it. In this case, the contacts included in the power supply circuit of the pump are connected. In the presence of a strong flow, the petal sensor is constantly deflected and the pump motor is running.

Without liquid in the pipeline or its weak movement, the spring deflects the petal with the magnet to its original position, which leads to the opening of the contacts and the stop of the pumping device.

The flow sensor has compact dimensions and low weight, which allows it to be used not only in industrial, but also in household devices.

3 Is it possible to do without protection against dry running?

In some cases, this is acceptable provided that:

the pump does not work often and for a short time (seasonal water supply in the country);
constant control (observation) of the operation of the pumping device is carried out;
water is taken from a guaranteed inexhaustible source;
the user has sufficient operating experience, is familiar with the design and technical characteristics of the water supply device.

3.1 How to connect a dry-running relay to the pump? (video)

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

To prevent breakage, automation is used:

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

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

Consider the main situations of insufficient water supply:

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

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

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

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

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

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

Ways to protect pumps from running without water

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

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

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

Water level switch and float

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

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

Operation scheme: the control sensor is installed above the pump, the working sensors are 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 turn on.

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

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

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

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

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

Relay and pressure sensor

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

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

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

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

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

Water flow sensor

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

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

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

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

Mini AKN

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

Situations when you can not use protection

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

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

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

Reading 6 min.

Most private houses have autonomous water supply, which is provided by a pump. With various layouts of systems that supply water, there is always a need for constant monitoring and control of work.

Automatic switching on and off takes place with the help of a relay, which is triggered by changes in water pressure. If the water source dries up (does not have time to recover due to intensive intake), the pump protection against idling is automatically activated and the pump turns off.

What is dry (idle) running?

Each natural water source has its own specific resource, which depends on such parameters as depth of occurrence, soil composition, intensity of movement ground water. With intensive use, the water supply is quickly exhausted, and in case of connection to centralized systems, there are accidents and planned outages.

In the absence of water, the pump runs dry. This is dry or idle.

If the pump is not turned off in time, it will overheat, which will lead to breakdown and costly. The absence of water in the house for a considerable time will be added to the trouble that has occurred, if there is no spare (backup) device.

In order to eliminate this situation, manufacturers produce models with protection against the dry running of the pump. But they are more expensive than usual, so, in some cases, it makes sense to buy and install automatic protection separately.

Protection methods

In order for a running pump to automatically turn off when there is not enough water in the source, use the following devices:

automatic relay;
water flow control device;
water level sensor.

Each of these devices is able to stop the water supply (if it is not enough), to protect the pump unit from overheating and breakdown.

Protection relay

A simple electromechanical element that responds to pressure changes in the water supply system. When the pressure drops below a certain value, the power circuit is automatically broken. Power is not supplied to the pump and it stops working.

Structurally, the relay has a bending membrane, which, when the pressure drops, changes its position and closes the circuit on the contact group, which leads to a power outage.

Depending on the manufacturer's settings, the relay is activated when the pressure drops from 0.6 to 0.1 atmospheres, in the absence of water, its insufficient level or clogging of the filter on the suction pipe.

In systems in which a hydraulic accumulator is present, the operation of the relay will not be effective. This is due to the fact that usually, between the protection and the pump, check valve, which holds pressure due to the presence of water in the accumulator. And since minimum value pressure for such a system is 1.4-1.6 atmospheres, the protection will not work even if there is no water in the source, due to the fact that it is in the drive.

How to connect a dry running relay to the pump (video)

Water flow control

The use of a pump with protection against dry running provides for the inclusion in the system of devices that control the flow of water:

relay (sensor);
controller.

The former belong to the group of electromechanical devices, the latter are electronic.

Relays (sensors)

They are produced in two versions:

The first ones are made in the form of a flexible plate, which, being in the pipe, deviates under the pressure of moving water. In the event of a cessation (absence) of water movement, the plate is leveled and closes the contacts for turning off the power supply of the electric motor.

The second work on the principle of creating electromagnetic field turbine rotating in the flow of water. With a decrease in the number of electromagnetic pulses, in the event of a weakening of the flow or its absence, the pump power is turned off, and when it increases, it resumes.

Some inconvenience in the use of these devices is that they must be inside the pipeline. If solid particles (sand) get inside the system, interruptions in operation or their complete stop are possible, which requires partial dismantling water supply systems.

Controllers

Devices that provide reliable protection pump motor against overheating, which, in some models, have an additional built-in check valve and pressure gauge. In fact, such devices are electronic relays that respond to changes in pressure in the plumbing system.

The main functions are protection against dry running and control of fluid pressure. The use of several parameters in the work leads to the timely shutdown of the equipment in case of a lack of water and the maintenance of a stable working pressure in the system.

The plumbing system, in which this device is included, works stably at any flow rate. water resources– when taps are opened or automatic household appliances are activated.

Level sensors

Water level sensors are installed directly in wells, wells, tanks. They are used with both submersible (submerged) and surface (above water) pumps.

According to the principle of work, they are divided into two types:

float;
electronic.

float

Designed to control the filling (to avoid overfilling of containers) or drainage (protection against dry operation) of water sources.

Models of float switches are produced that operate in two modes, i.e. turn off the pump and when the water level drops and when it is excessive in a confined space.

The principle of operation is as follows: the sensor is placed so that the float is on the surface of the water for set height. When the level drops, the float lowers, which is pivotally connected through a lever with the contact group. During a critical lowering, the contacts of the phase wire open, and the pump motor stops.

In the case of monitoring the filling of the container, everything happens the other way around. With rising water, it rises and, whose work is set not to lower, but to raise the level.

Electronic

Such devices perform the same functions as float devices, but their principle of operation is different.

Two electrodes are lowered into the water of a source or storage tank. One to the depth to the minimum acceptable level, the other to the level of working filling (basic). Since water is a good conductor electricity, the electrodes are interconnected by currents of small strength. The control device receives the signal and keeps the pump running. As soon as the currents disappear (when the water level drops below the critical level), the power supply is turned off, since there is no conductive material (water) between the electrodes.

The devices described above and methods of their use are suitable for protecting pumping equipment, monitoring the level and pressure of water in small systems for personal use. For a private house or cottage.

On large farms or apartment buildings, at the device autonomous water supply, should be used for protection and control purposes. Their cost is much higher, but when working with powerful pumping devices, you cannot do without them.

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

Why is the pumping system running dry?

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

Dry running float switch for pump

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

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

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

Types of dry running sensors for pumps

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

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

Disassembly of the dry running sensor for water

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

Dry running sensor diagram

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

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

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

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

Attention! The installation of a flow motion switch for pumping substations in an autonomous source of water supply occurs strictly according to circuit diagram. There should not be any deviations from the indicated values, since the probability increases incorrect operation devices and failure of protection.

How to choose a device and install it at home?

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

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

How to connect a dry running sensor to a pump

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

Typical mistakes of masters

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

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

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

Choosing a dry running sensor for a borehole pump

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

Dry running sensor

To prevent breakage, automation is used:

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

Possible causes of "dry running"

Consider the main situations of insufficient water supply:

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

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

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

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

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

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

Ways to protect pumps from running without water

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

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

Water level switch and float

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

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

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.

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

Relay and pressure sensor

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

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

Water flow sensor

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

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

Situations when you can not use protection

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

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

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

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

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

How to protect the pump from running dry

The water supply system of a private house is impossible without a pump. But it must somehow be turned on and off, to ensure that it does not work in the absence of water. The water pressure switch is responsible for turning the pump on and off, and protection against dry running of the pump should monitor the presence of water. How to implement this protection in different situation and consider further.

What is a dry running pump

Wherever the pump pumps water, at times a situation is created that the water is over - with a small flow rate of a well or well, you can simply pump out all the water. If water is pumped from a centralized water supply, its supply can simply be stopped. The operation of the pump in the absence of water is called dry running. Sometimes the term "idling" is used, although this is not entirely correct.

In order for the water supply at home to work normally, you need not only a pump, but also a dry water protection system, automatic on-off

What's wrong with dry running, besides wasting electricity? If the pump runs without water, it will overheat and burn out - the pumped water is used to cool it. No water - no cooling. The engine will overheat and burn out. Therefore, protection against dry running of the pump is one of the components of automation, which will have to be bought in addition. There are, however, models with built-in protection, but they are expensive. Cheaper to buy automation.

How can the pump be protected from running dry?

There are a few different devices which will turn off the pump in the absence of water:

dry run protection relay;
water flow control devices;
water level sensors (float switch and level control relay).

All these devices are designed for one thing - turn off the pump in the absence of water. They just work differently and have different applications. Next, we will understand the features of their work and when they are most effective.

Dry run protection relay

A simple electromechanical device controls the presence of pressure in the system. As soon as the pressure drops below the threshold, the power circuit breaks, the pump stops working.

The relay consists of a membrane that reacts to pressure and a contact group that is normally open. When the pressure drops, the membrane presses on the contacts, they close, turning off the power.

This is what dry running protection looks like.

The pressure to which the device responds is from 0.1 atm to 0.6 atm (depending on factory settings). This situation is possible when there is little or no water at all, the filter is clogged, the self-priming part is too high. In any case, this is a dry running condition and the pump must be turned off, which is what happens.

An idle protection relay is installed on the surface, although there are models in a sealed housing. It works normally in an irrigation scheme or any system without a hydraulic accumulator. Works more effectively with surface pumps when a check valve is installed downstream of the pump.

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

You can put it in a system with GA, but you will not get 100% protection against dry running of the pump. It's all about the features of the structure and operation of such a system. They put a protective relay in front of the water pressure switch and the accumulator. In this case, there is usually a check valve between the pump and the protection, that is, the membrane is under pressure created by the accumulator. This is a common scheme, but with this method of switching on, a situation is possible when a running pump does not turn off in the absence of water and burns out.

For example, a dry running situation has been created: the pump has turned on, there is no water in the well / well / tank, there is some water in the accumulator. Since the lower pressure threshold is usually set to about 1.4-1.6 atm, the protective relay membrane will not work - there is pressure in the system. In this position, the membrane is pressed out, the pump will run dry. It will stop either when it burns out or when most of the water supply is used up from the accumulator. Only then will the pressure drop to critical and the relay will be able to work. If such a situation arose during the active use of water, nothing terrible will happen in principle - a few tens of liters will run out quickly and everything will be fine. But if it happened at night, they let the water out of the tank, washed their hands and went to bed. The pump has turned on, there is no signal to turn off. By the morning, when the analysis of water begins, it will be inoperative. That is why in systems with hydroaccumulators or pumping stations it is better to use other devices to protect against the dry running of the water pump.

Water flow control devices

In any situation that causes the pump to run dry, there is insufficient or no water flow. There are devices that monitor this situation - relays and water flow controllers. Relays or flow sensors are electromechanical devices, controllers are electronic.

Relay (sensors) of the flow

The flow switch is of two types - petal and turbine. Flap has a flexible plate that is in the pipeline. In the absence of water flow, the plate deviates from the normal state, contacts are activated that turn off the power to the pump.

Turbine flow sensors are somewhat more complicated. The basis of the device is a small turbine with an electromagnet in the rotor. In the presence of a flow of water or gas, the turbine rotates, an electromagnetic field is created, which is converted into electromagnetic pulses read by the sensor. This sensor, depending on the number of pulses, turns on / off the power to the pump.

flow controllers

Basically, these are devices that combine two functions: protection against dry running and a water pressure switch. Some models, in addition to these features, may have a built-in pressure gauge and check valve. These devices are also called electronic pressure switches. These devices cannot be called cheap, but they provide high-quality protection, serving several parameters at once, providing the pressure required in the system, turning off the equipment when there is insufficient water flow.

Protection against dry running of the pump: types, installation

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

Dry running sensor for pump

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

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

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

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

1. Presence of pressure. Mainly defined with inexpensive device(dry run relay)

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

Dry run relay setting:

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

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

There is another way float sensor

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

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

Capacitive level sensor

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

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

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

Disadvantages by indirect signs:

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

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

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

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

Download with good resolution

Encyclopedia of plumbing 100% Pump protection against dry running

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

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

In pumps for domestic needs, thermoplastic (high-strength wear-resistant plastic) is most often used as the main material for impellers and diffusers, which, being distinguished by high manufacturability and low price, has been doing its job well for many years. But when working without water, which under normal conditions works both as a lubricant and as a source of heat removal, internal details pump start to touch, heat up and deform. In extreme cases, the pump shaft may jam and the motor may burn out. As a rule, after such a test, the pump either completely stops supplying water, or supplies it without giving out its passport characteristics.

"Dry running" is quite simply identified by a specialist when disassembling the pump and does not apply to warranty cases!

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

Typically, this is the following:

Pumping water from wells or wells with a low flow rate. The reason for this may be an incorrectly selected pump (with very high performance) or natural phenomena(in a dry summer, the water level in many wells or wells drops and the flow rate of the well / well, or, more simply, the amount of water that feeds the well / well from underground sources per unit time, is lower than the performance of the pump itself).
Pumping water from tanks. It is imperative to ensure that the pump does not pump out all the water from the tank and turn it off in advance.
Pumping water from network pipelines. In this case, the pump cuts directly into the network pipeline and serves to increase the pressure in the system. Since the pressure in the network pipeline, especially in summer, is often insufficient, this is a fairly common scheme for using pumping stations. Keep track of when network will disappear water, very often not possible.

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

The main types of protection against "dry running":

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

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

Pressure switch with dry run protection. This device is a conventional pressure switch with the additional function of opening contacts when the pressure falls below a threshold level. Usually this level is set by the manufacturer at the level of 0.4-0.6 bar and cannot be adjusted. Under normal operating conditions, the pressure in the system cannot fall below these values, since all pumps used for private needs operate at significantly higher pressures (from 1 bar and above). The pressure can drop to 0.4-0.6 bar in almost only one case - if there is no water in the pump. No water - no pressure, and the relay, registering a "dry run", opens the contacts supplying the pump. It will be possible to start the pump again only manually, having previously established and eliminated the cause of the "dry run". The pump, before a new start, will again have to be filled with water.

It should be noted that the use of a pressure switch with "dry run" protection is possible only if automatic operation pump (together with a hydraulic tank), otherwise the use of this relay loses its meaning. It is mainly used together with a downhole submersible (deep) pump, but can also be used with surface pumps (or pumping stations).

Flow switch with pressure switch functions(press control). Many manufacturers suggest using a compact device instead of a hydraulic tank and a pressure switch - the so-called "flow switch" (or press control). This relay gives a command to turn on the pump when the pressure in the system drops to 1.5-2.5 bar, depending on the setting. The pump is turned off after the withdrawal of water is stopped, due to the lack of fluid flow through the relay. Protection is “dry running” and is carried out thanks to the flow sensor built into the relay, which registers the actual fluid flow through the relay. The pump is switched off with a short time delay after a dry run is detected, which does not affect the pump's performance. In addition, the press control performs other protective functions, such as current and voltage protection. The main advantage of press control is its very small dimensions and weight. Unfortunately, there are now a large number of press controls produced in an unknown place. Average term the service life of such devices does not exceed 1-1.5 years, and then, if you're lucky. A certified and high-quality press control (as with ACTIVE pumping units) costs about 100 USD.

It is an electronic board to which several sensors (electrodes) are connected. Usually there are three of them, one control and two working. Sensors are connected to the relay with ordinary single-core electric wire, and serve only to signal. The principle is as follows: the sensors are lowered into the well at different levels and when the water level drops below the control sensor, which should be located slightly above the installation level of the pump itself, a signal from it is transmitted to the level switch and a command is given to stop the pump. After the water rises above the control sensor, the pump will automatically start. This method of protection is very reliable, however, a little more expensive than the others. It can also be used in the case of pumping water from containers. The level switch itself is located in a house or other place protected from moisture.

Which method of protection to choose depends on the specific task and preferences. From experience, we can say the following: when pumping water from tanks / tanks / wells by a pumping station, almost 100% guarantee of protection will be the use of both a pressure switch with “dry run” protection and a float installed in the tank. They will just duplicate each other. At a price, this option will come out no more than installing one flow switch. When protecting a borehole pump, a pressure switch with dry-running protection is most often used. But it is better to use a slightly more expensive, but also more reliable way protection, using a level switch.

Note that if you have drilled a deep well with a good flow rate (confirmed well certificate) or if you have significant experience in operating pumps in your well / well and know that the water level practically does not decrease during continuous operation of the pump, you can protect against "dry running" ' and don't use it. The most important thing is to be careful - as soon as you see that the water has disappeared in the pressure pipe or the thermal relay has tripped and the pump has turned off, you do not need to immediately try to start it again, first try to establish the cause of the malfunction, and only then start the pump again.

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