During the entire period of its operation. Installing a flow switch in the refrigeration system is mandatory, since its main function is to protect the chiller from an emergency situation: extremely small or complete absence of liquid flow through the evaporator. This is possible in the system only in one case - when the compressor of the refrigeration machine is not working.

Flow switch - a sensor (microswitch, differential pressure switch, etc.) signaling to the chiller controller that in the coolant circulation system there is a physical flow of liquid through the chiller evaporator, and the flow rate through the evaporator corresponds to the nominal calculated value for the selected operating parameters of the chiller in the refrigeration system.

In practice, flow switches are used various types: mechanical and differential relays, differential pressure sensors, etc. The purpose of the devices is one - to signal to the chiller controller about the normal flow of liquid through the evaporator. This determines the installation location flow switch- on the pipeline lines of the circulation circuit near the evaporator, as shown in Fig. 7.

It is most advisable to install a flow switch on the pipeline at the outlet of the evaporator. A straight section of pipe with a length of at least 10 gauges is selected and a flow switch is installed in the center of this section. It is not allowed to install a flow switch near pipe bends, shut-off valves or valves, control fittings.

The flow switch housing is mounted in a vertical position, and the direction of the arrow on the flow switch housing must coincide with the direction of coolant flow. When installing a flow switch, it is necessary to ensure that the contact group of the relay is protected from dirt and moisture entering the housing. It is allowed to install a mechanical flow switch on straight lines vertical sections pipes, but only if the direction of movement of the coolant is from bottom to top.

The simplest and cheapest flow relays are mechanical relays, the principle of which is to close the microswitch contacts when turning the sensitive plate (“feather”) located in the flow of moving liquid. The length of the plate is selected depending on the diameter of the line into which the flow switch is inserted.

The choice of plate length is a crucial point when installing a flow switch, since it determines its sensitivity. Yes, when short lengths plates contacts of the flow switch installed in the pipeline large diameter, will not close even at normal flow rates, as shown in Fig. 8.

At large diameters pipelines, it is recommended to place several plates of shorter length under the sensitive plate (a kind of “spring”), otherwise the relay may quickly fail due to breakage of the plate at the sealing site. Figure 9 shows typical practical errors when installing mechanical flow switches:

In the first case, when installing the flow switch, they “forgot” to install the plate; in the second case, the long plate “clings” to the pipe as it turns. In the third case, the length of the plate does not correspond to the diameter of the pipeline, so the plate was installed in some arbitrary position when installing the flow switch; in the fourth case, the arrow on the flow switch body does not correspond to the direction of flow in the line.

The closure of the flow relay contacts when the required calculated value of liquid flow in the line is reached is regulated by a screw in the relay body when adjusting the hydraulic circuit during commissioning works(see Fig. 10). If for some reason the flow rate in the main line, considered in the evaporator, becomes less (G„2

Chillers, as a rule, are equipped with two sequentially connected stages of protection for the absence or non-compliance with the calculated value of liquid flow through the evaporator. Fig. 11, as an example, shows a fragment of an electric DAIKIN with a single-screw compressor.

The first stage consists of “dry” contacts of the pump (S9L), which close when power is supplied to the pump group of the circulation circuit. The signal to turn on the pump group is sent to the controller, but this is not enough to confirm the normal flow of liquid through the chiller evaporator. For this purpose, a flow switch is used, the closure of the contacts (S8L) of which indicates that the flow through the evaporator has reached the required value. Only after this does the countdown of the chiller compressor start timer begin, and after it is reset to zero, the compressor actually starts.

If, for some reason, the liquid flow through the evaporator decreases or stops altogether, the protection chain opens and the chiller compressor stops emergency. Modern chiller controllers record an accident, so the cause can be easily identified emergency stop(flow switch).

If necessary, the chain of protection (Fig. 11) along the flow of liquid through the heat exchangers of the chiller can be expanded. So, with a water-cooled condenser, this chain includes in series the “dry” contacts of the pump group and the flow switch on the side.

When installing refrigeration station equipment, it is also necessary to take into account the electrical connection features of the chiller and pump group. It is recommended to provide power supply separately: connecting the pump group from the chiller is not allowed. When starting a refrigeration station, the pump group is always turned on first, then the chiller.

The nominal parameters of the chiller (cooling capacity, power consumption and evaporator flow) are given in the technical data at temperature environment+35°C; The coolant of the circulation circuit is water; water temperature at the evaporator outlet + 7°C; water at the inlet/outlet of the evaporator 5K.

From the conditions optimal performance heat exchanger - evaporator (heat exchange and hydraulic characteristics of the unit), an operating temperature difference is allowed in a narrow range from 3 to 8 K. In accordance with the above, the following are distinguished:

• The minimum coolant flow in the circulation system corresponding to the maximum temperature difference across the evaporator is 8K. This value is the lower threshold for flow rate in the evaporator circulation system, below which the manufacturer does not recommend operating the device - at such low flow rates the evaporator channels may freeze.
• The nominal coolant flow rate in the circulation system, corresponding to the standard temperature difference on the evaporator is 5K, the coolant is water. This value characterizes the stable operation of the chiller.
• The maximum coolant flow in the circulation system corresponding to the minimum temperature difference across the evaporator is 3K. This value is the upper limit for flow in the evaporator circulation system. A further increase in flow rate is impractical due to the deterioration of the evaporator characteristics due to an increase in its hydraulic resistance.
• The calculated coolant flow through the chiller evaporator, corresponding to the temperature difference on the evaporator selected when designing the refrigeration system, the selected chiller parameters when selecting equipment, and the selected type of coolant in the circulation circuit. For standard conditions, the calculated flow rate corresponds to the nominal value.

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This article will discuss devices used to protect against dry running. You will learn their types, design features and operating principles, as well as all the significant advantages and disadvantages.

It is with their help that it is possible to avoid the main and most well-known problems associated with breakdowns. pumping equipment or its excessively rapid wear.

1 General information about the water flow switch

As practice shows, the main reason for the failure of most water pumps is overheating, which is a consequence of idle operation of the unit, the so-called “dry” operation, when the pump is turned on but does not pump water.

This is explained by the fact that the device of any submersible requires constant cooling of the power unit by the working environment, and in the case surface devices– pumped liquid. Moreover, for a deep sample this parameter is extremely important, since it essentially consists of large quantity parts that constantly interact with each other.

For example, centrifugal deep well pump after switching on, it puts into operation several stages of impellers that rotate simultaneously. Running them without fluid is simply wearing out the device for no reason. The situation is similar with surface models.

1.1 Why use a flow switch?

Dry running submersible pump possible in the following situations:

• When the unit is incorrectly selected, its productivity exceeds the well's flow rate, and the dynamic water level of the well falls below the depth of its installation;
• If pumping is performed from a small excised source without outside supervision;
• For idle operation, it is possible due to internal clogging of the hose, or its mechanical damage, which causes loss of tightness of the hose, which occurs quite often;
• For circulation pump“dry” operation is possible when the water supply pressure is low in the pipeline to which it is connected.

Be that as it may, it is not always possible to carry out constant monitoring by constantly being present when the pump is operating, so it is necessary to take care of additional mechanisms that will monitor the presence of water flow and turn the pump on and off when necessary.

The water flow relay, also known as “”, is exactly such a device. There is no need to install a flow switch in the following cases:

• If water is taken by a low-power pump from a high-yield well;
• If you are constantly present when the pump is operating, and you can turn it off yourself when the water level drops below the permissible norm.

In all other cases, installation of a water flow switch is required, since it not only extends the life of the pump, but also significantly increases the ease of its operation. At a minimum, automating its work in terms of protection against possible problems.

2 Design features and principle of operation

There are several types of water flow switches and similar safety devices, each of which is equipped with different automation that turns the pump on and off in response to certain indicators.

Most common triggers:

• Liquid level (water level switch);
• Liquid pressure level at the outlet pipe (press control);
• Presence of water flow (flow switch);
• Temperature of the working environment (thermal relay.

Let's look at each of these devices in more detail.

2.1

Such a device consists of two main structural elements: a reed switch and a petal (valve) on which a magnet is mounted. The reed switch, which acts as a contact that responds to changes in the position of the magnet, is located outside the water flow and is reliably insulated.

On the opposite part of the structure there is a second magnet, which creates a reverse force, which is necessary to return the petal to its original position at the moment the fluid flow weakens.

When the pump is filled with water, it acts on the petal, causing it to rotate around its axis. The movement of the petal brings the magnet closer to the reed microswitch, which is activated by the resulting magnetic field.

The reed switch connects the pump contacts and electrical network, as a result of which the device turns on. As soon as the flow of liquid has stopped, the petal, which no longer receives additional pressure, returns to its original position under the influence of the force of an additional magnet and the contacts open.

Advantages paddle relay duct:

• Does not reduce water supply pressure;
• Works instantly;
• No delay between retriggers;
• Using the most accurate circulation trigger to turn on the pump;
• Simplicity and unpretentiousness of design.

There are also flow switches, the valve design of which is made without return magnets, where the second magnet is replaced by conventional springs. However, such relays in practice show less stability, since they are overly susceptible to the influence of small pressure surges in the water flow.

2.2 Press control - water flow switch combined with a pressure switch

Press control gives a command to turn on the pump only when the water pressure level in it rises to a certain level (this indicator is adjustable, most often it ranges from 1 to 2 Bar), the pump is turned off due to opening of the contacts within 5-10 seconds after completely stopping the flow of water pumped out of the well.

Such devices can be used either in conjunction with a hydraulic accumulator, performing the function of controlling the pumping station, or installed directly on the outlet pipe of the pump, protecting it from idling.

Press control, in comparison with a conventional relay that reacts to changes in the level of water flow, has one significant drawback - if it is installed on a surface-type pump, then each time before turning it on you must personally fill the unit with water. The problem can be solved by installing additional check valves, but this is far from a panacea.

2.3 Thermal water flow switch

Among all the above types of safety devices, it is the thermal relay that has the most complex design. The technology of its operation is based on the thermodynamic principle, according to which the thermal difference between the temperature of the water flow in the pump and the temperature to which the relay sensors are set is compared.

When the thermal relay is connected to the pump, which is located inside, a certain amount of electricity is constantly supplied to it, which is spent on heating the sensors to a temperature several degrees higher than the temperature of the liquid being measured.

In the presence of water flow, the sensors are cooled, which is fixed by a microswitch. The thermal change is a signal after which the connection between the pump contacts and the electrical network is made. As soon as the flow of water from the well stops, the microswitch disconnects the contacts and the pump turns off.

In addition to downhole units, a thermal flow relay is ideal option Dry running protection for the circulation pump.

The thermal relay allows you not only to increase the useful life of the circulation device, but also to save a considerable amount of electricity, since the thermal relay automatically turns off the pump when pressurizing the water flow in the heating line is not required.

When heating device is turned off and the water in the system is cold - no work is needed, and the thermal relay keeps the contacts closed. When you turn on the boiler, as the water in the pipes reaches the set temperature, the thermal relay turns on the circulator, and it begins to build up pressure to the required level.

It is worth noting that most leading manufacturers of circulation pumps independently install thermal flow switches on their devices. This is mainly typical for premium class pumps. This is due to their high cost and complexity of design.

2.4 Water level switch

The simplest and most utilitarian version of a safety device for a water pump is a water level switch, commonly known as a float switch.

The “float”, which must be mounted inside the source 20-25 centimeters above the level of the pump, monitors the amount of water in the source, and as soon as the water drops below the float sensor, the automatic shutdown pump

The relay itself is connected to the phase that is supplied to power the pump. The adjustment is made by changing the length of the adjustment cable. Better quality floats can be customized additional functions, but this already concerns expensive models equipment, which is quite rare in domestic use.

The float switch is a proven means of protection for any well and drainage devices, however, the water level switch cannot be used in deep wells, since serious difficulties arise with its precise adjustment.

Also, floats do not always work well in cramped conditions, when the difference between the diameter of the well and the pump is only a few tens of millimeters. In this case, there is simply no point in using it, since the operation of the float will become too unstable.

Use float switches as on conventional ones well pumps, and on drainage samples. Moreover, they are even more in demand there, because unlike standard wells, work environment tends to constantly decrease. Dry running of drainage models is no less harmful than borehole or well pumps.

2.5 Nuances of installing a water flow switch

Paddle switches are mounted either at the pump inlet or at the valve inlet. Their task is to record the initial entry of liquid into working chamber, and therefore contact with it must be detected first of all on the relay itself.

Pressure control units are installed only with the help of specialists, as they require adjustment. They are installed in the same way as the petals, by connecting the input to pumping device. However, unlike conventional petals, pressure switches are almost always used in conjunction with.

Thermal relays are rarely used separately, since the thing is too expensive. It will most likely be connected at the assembly stage of the pump itself. However, good master will certainly be able to cope with the installation of this device. The complexity of the installation lies in the need to mount several sensitive thermal sensors, and then bring them together.

2.6 Example of operation of a water flow switch (video)

The water supply system of a private house is impossible without a pump. But you need to somehow turn it on and off, and make sure that it does not work in the absence of water. A water pressure switch is responsible for turning the pump on and off, and the presence of water should be monitored by protection against dry running of the pump. We will consider further how to implement this protection in different situations.

What is dry running of a pump?

No matter where the pump pumps water from, at times a situation arises that the water has run out - if the flow rate of a well or borehole is small, you can simply pump out all the water. If water is pumped from a centralized water supply, its supply may simply be stopped. The operation of the pump in the absence of water is called dry running. The term “idling” is sometimes 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 and automatic on-off switching.

What's wrong with dry running, other than wasting electricity? If the pump runs in the absence of 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 the automation that will have to be purchased in addition. There are, however, models with built-in protection, but they are expensive. It is cheaper to buy additional automation.

How can you protect the pump from dry running?

There are several different devices that will turn off the pump if there is no water:

• dry running 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 when there is no water. They just work differently and have different areas of application. Next, we will look at the features of their work and when they are most effective.

Dry running protection relay

A simple electromechanical device monitors the presence of pressure in the system. As soon as the pressure drops below the threshold, the power supply circuit is broken and the pump stops working.

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

This is what protection against dry running of the pump looks like

When is it effective?

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, the filter is clogged, or 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 speed protection relay is installed on the surface, although there are models in a sealed housing. It works normally in an irrigation scheme or any system without a hydraulic accumulator. Works more efficiently with surface pumps when check valve installed after the pump.

When it does not guarantee shutdown in the absence of water

You can install it in a system with HA, but you will not get 100% protection against dry running of the pump. It's all about the particular structure and operation of such a system. Place a protective relay in front of the water pressure switch and the hydraulic 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 hydraulic accumulator. This is a common scheme. But with this method of switching on, it is possible that a working pump in the absence of water will not turn off and will burn out.

For example, a dry running situation has been created: the pump is turned on, there is no water in the well/borehole/tank, and 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. After all, 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 hydraulic accumulator. Only then will the pressure drop to critical and the relay will be able to operate. If such a situation arose during the active use of water, nothing terrible will happen in principle - several tens of liters will dry up quickly and everything will be normal. But if this happened at night, they flushed the water in the tank, washed their hands and went to bed. The pump turned on, but there was no signal to turn off. By the morning, when water collection begins, it will be inoperative. That is why in systems with hydraulic accumulators or pumping stations it is better to use other devices to protect against 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. Flow relays or sensors are electromechanical devices, controllers are electronic.

Flow relays (sensors)

There are two types of flow sensors - petal and turbine. Petal has a flexible plate that is located in the pipeline. In the absence of water flow, the plate deviates from its normal state, contacts are activated, turning 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. When there is a flow of water or gas, the turbine rotates, creating an electromagnetic field, 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: dry-running protection and a water pressure switch. In addition to these features, some models 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, ensuring the required pressure in the system, turning off the equipment when there is insufficient water flow.

Name	Functions	Dry running protection parameters	Connection dimensions	Country/manufacturer	Price
BRIO 2000M Italtecnica	Pressure switch + flow sensor	7-15 sec	1" (25 mm)	Italy	45$
AQUAROBOT TURBIPRESS	Pressure switch + flow switch	0.5 l/min	1" (25 mm)		75$
AL-KO	Pressure switch + check valve + dry-running protection	45 sec	1" (25 mm)	Germany	68$
Gilex automation unit	Pressure switch + idle protection + pressure gauge		1" (25 mm)	Russia	38$
Aquario automation unit	Pressure switch + idle protection + pressure gauge + check valve		1" (25 mm)	Italy	50$

In the case of using an automation unit, the hydraulic accumulator is an extra device. The system works perfectly when flow appears - opening the tap, triggering household appliances etc. But this is if the pressure reserve is small. If the gap is large, both a HA and a pressure switch are needed. The fact is that the pump shutdown limit in the automation unit is not adjustable. The pump will turn off only when it has created maximum pressure. If it is taken with a large margin of pressure, it can create overpressure(optimal - no more than 3-4 atm, anything higher leads to premature wear of the system). Therefore, after the automation unit there is a hydraulic accumulator. This scheme makes it possible to regulate the pressure at which the pump turns off.

Water level sensors

These sensors are installed in a well, borehole, or container. It is advisable to use them with submersible pumps, although they are compatible with surface pumps. There are two types of sensors - float and electronic.

Float

There are two types of water level sensors - for filling the container (protection against overflow) and for emptying - just protection against dry running. The second option is ours, the first is needed when filling out. There are also models that can work either way, but the principle of operation depends on the connection diagram (included in the instructions).

The principle of operation when used to protect against dry running is simple: as long as there is water, the float sensor is raised up, the pump can operate, as soon as the water level has dropped so much that the sensor has dropped, the contactor opens the pump power circuit, it cannot turn on until until the water level rises. To protect the pump from idling, the float cable is connected to the open phase wire.

Level control relay

These devices can be used not only to control the minimum water level and dry running in a well, well or storage capacity. They can also control overflow (overflow), which is often necessary when there is a storage tank in the system, from which water is then pumped into the house or when organizing a water supply for a swimming pool.

Electrodes are lowered into the water. Their number depends on the parameters they monitor. If you only need to monitor the presence of a sufficient amount of water, two sensors are enough. One - goes down to the level of the minimum possible level, the second - basic - is located slightly lower. The work uses the electrical conductivity of water: while both sensors are immersed in water, small currents flow between them. This means that there is enough water in the well/well/container. If there is no current, this means that the water has dropped below the minimum level sensor. This command opens the power supply circuit of the pump and stops working.

These are the main ways in which protection against dry running of a pump is organized in the water supply systems of a private home. There are more frequency converters, but they are expensive, so it is advisable to use them in large systems With powerful pumps. There they quickly pay for themselves due to energy savings.

Effective operation of pumping equipment is the key to uninterrupted water supply and functioning of the heating system in a private home. If you want to enjoy the benefits of civilization every day, you must make every effort to set it up correctly.

The solution to this problem includes a wide range of works, the main one being installation additional equipment, which will help to clearly monitor possible failures in the system and prevent pump failure.

The most popular and useful in everyday life are such auxiliary devices as: a temperature sensor, as well as a water flow sensor. It is the properties and operational features of the latter device that will be discussed in this article.

1 Purpose and benefits

In everyday life, emergency pump switching on without water periodically occurs, which is considered extremely dangerous, because it can cause equipment failure. Popularly called “dry running” leads to overheating of the engine and deformation of parts.

Such negative changes occur because the water in the system performs a lubricating and cooling function. Operating in “dry running” mode, even for a short time, has a negative effect on the equipment, be it circulation or. To avoid similar problems, the pumping station is equipped with automation - a water flow sensor. It will prevent negative changes in the system and avoid the cost of repairing the pump.

The water flow sensor is a device for controlling a pumping station in. In addition, this automatic device serves to increase pressure and protect the pump, which is used in heating systems.

The principle of operation of the sensor is that it monitors the power of the liquid flow and independently turns it on or off pumping station when a stream of water appears and passes through it. In this way, it is possible to prevent possible “dry running”, because the submersible or circulation pump drives the system and raises the pressure inside it only when required.

Installation of a water flow sensor entails a number of positive aspects in the operation of the pumping station:

• saving energy costs;
• reducing the risk of equipment breakdown;
• increasing pump life.

1.1 Design and operating principle

As has already become clear, the built-in water flow sensor is used in heating and water supply circulation systems of private houses. His job is to ensure that in the absence of liquid flow, machine gunners stop the pumping station and prevent “dry running”, and when water appears, put the equipment into action. The sensor obtained similar operating properties due to its design.

The device consists of a valve (“petal”), which is located in the flow part, and a reed switch. When water pressure arises, the reed valve begins to move, compressing the spring. At the same time, the magnet on the “petal” and the reed relay interact.

As a result, the contacts close, which activates the submersible or circulation pump. When there is no water and corresponding pressure in the system, the valve spring expands, moving the magnet to its original position - this causes the contacts to open and the equipment to stop.

A water flow sensor for a circulation or submersible pump is easy to install in an existing system; you just need to choose the right device, paying due attention to key parameters.

1.2 Main characteristics

The purchase of a water flow sensor should be approached carefully. We recommend focusing on the following characteristics of the device:

• material of the body and working components;
• working pressure;
• coolant temperature range;
• operating conditions and protection class;
• thread diameter.

To understand the impact each of these factors has on the operational features of the device, let’s consider them step by step. The material of the housing and operating components affect the reliability and durability of the sensor that is installed on the pump. It is desirable that the device be based on metals: stainless steel, aluminum or brass.

These materials are able to protect working elements from a powerful flow of water and hydraulic shock. Be sure to study the operating pressure level at which the sensor is capable of operating. For each circulation pump this value will be individual, so you need to calculate the appropriate parameter in advance.

There are devices that provide two levels of pump control: at the lower pressure limit of the system to turn it on and at the upper pressure limit in case of interruption or an unacceptably low level of water flow to turn off the pumping station.

A sensor with the possibility of such programming is considered optimal. When choosing equipment for controlling water flow, one cannot neglect such a parameter as the temperature range of the coolant.

Conditions for using devices may vary significantly. It’s one thing if you have to install a sensor in a heating system, where temperatures can reach 110°C, and quite another thing when the pump is used to turn on and supply cold water.

In the latter case, you can choose a device designed for a temperature range of 60-80°C. To ensure that the pump and purchased sensor remain operational for as long as possible, pay attention to the conditions under which the equipment should operate.

The instructions for the device must indicate the ambient temperature level and protection class. The last criterion determines the loads that the sensor installed in the pump can withstand.

To carry out correct and accurate installation, you will have to pay attention not only to the permissible operating temperatures of the device, but also to the diameter of the connecting thread. Only with correct and high-quality joining of the elements can the effective functioning of the sensor be achieved after its preliminary installation and switching on.

1.3 About the device and characteristics (video)

2 Adjustment and connection of the sensor

The flow sensor, which is used to monitor the water level and pressure in the system, should be adjusted immediately after purchase. The process works as follows: the device is shipped with the contacts open and the calibration screw tightened.

After turning on the pump and reaching the optimal water level, the lamella moves in the direction of the liquid flow, which leads to the closure of the contacts. If the lamella does not start to move, this means that this level of water flow is not enough. If the device does not respond, you need to set a different value and perform the operation again.

There are a number of rules that will facilitate the installation of a flow sensor, the main one is that the device must be installed on a horizontal pipeline, regardless of the temperature of the water moving inside. In this case, you need to ensure that the lamella is positioned vertically.

The distance between the pipe and the device should be carefully measured - the minimum acceptable value is 55 mm. Using a threaded coupling, the sensor is connected to the drain pipeline, regardless of the water level inside.

The device must be oriented so that the arrows on its body correspond to the direction of water flow in the system. In case high level coolant contamination is mounted in front of the sensor.

To extend the life of liquid flow devices, it is recommended that they be regularly inspected, refurbished and major renovation. But sometimes this is not enough for the pumps to work smoothly. A water flow sensor will come in handy. The protection relay prevents damage to the motor of surface and deep-well pumping equipment. Let's consider the types of equipment, conditions correct selection and do-it-yourself installation and adjustment technology.

In domestic water supply systems, there is a problem of lack of water, which leads to “dry running”. The incoming liquid cools the system elements, serves as a lubricant and ensures normal operation. If there is no water, the system runs dry, causing deformation and breakage of parts, and equipment failure. The problem occurs in pump models of any configuration.

Causes of dry running:

• incorrect choice of pumping equipment performance;
• violation of installation technology;
• deformation, pipe break;
• reduced water flow pressure;
• lack of control over the fluid level;
• debris in the pumping pipe.

An automatic or mechanical water flow sensor for the pump is needed to eliminate the risk of dry running. The device, in a given mode, takes measurements, controls and maintains a constant level of water flow. If a failure occurs in the station system, the sensor is triggered, the pump turns off in independent mode, and when the flow level resumes, it turns on.

Types of water flow switch

The most common water flow switch configuration for a pump is a petal switch. Classic scheme The device consists of the following elements:

• inlet pipe;
• valve (petal) located on the wall of the inner chamber;
• isolated switch;
• springs of a certain diameter.

The reed switch opens and closes the power supply circuits that activate the compression spring. The principle of operation of the sensor in a water flow: when the chamber is filled with liquid, the flow forcefully displaces the valve from its axis, affecting the magnet, which operates the switch. The contacts close and the pump turns on.

There are several types of sensors with their own operating characteristics and application possibilities.

Mechanical paddles

The device is a device equipped with a blade that is built into the pipeline. The principle of operation is standard: when a flow enters, the blade deflects and acts on a magnet. The contacts close, the switch sensor is activated. The simplicity of the unit explains the wide range of applications. In addition, such sensors are practically not subject to wear and do not require maintenance - there is nothing to break in them.

Mechanical piston

The device operates on the basis of a magnetic piston system. Operating principle: when a flow enters, the piston with a magnet rises, closing the contacts - the relay is triggered to start. Without flow, the piston drops to its original position, preventing dry running. The main advantage of the device is the variety of designs that allow the device to be mounted in any position. Mechanical piston relays are used in high pressure systems.

Thermal

The device is equipped with a meter for the level of thermal energy dissipation from the built-in heating element. Depending on the change in the heating rate of the liquid, the flow itself and its flow rate are recorded. The thermal sensor is used only for safe types of liquid. Due to the use of the hot-wire principle, it is prohibited to use the relay to measure flammable substances, as well as liquids that change composition when heated.

Advice! When choosing a device, you should remember that not all units operate with constant changes in flow. Thermal sensors require cleaning of the sensitive elements.

Ultrasonic

The universal pulse water flow sensor operates on the principle of the acoustic effect. The device transmits an ultrasonic pulse through the flow, determining the liquid level. The most common are products whose functionality uses the movement of vibrations of a moving fluid. The devices are suitable for any substances, including flammable ones, and are easy to install and maintain.

How to choose a water flow sensor-relay

Before purchasing the unit, you must carefully read technical characteristics, scope of application, capabilities of the device.

What to pay attention to:

• wide operating temperature range;
• amplitude of pressure level indicators;
• diameter of threads and mounting holes;
• protection class;
• application features;
• manufacturing material.

The easiest way to handle is a metal water flow switch; the price of units starts from $25-30, but it all depends on the type of device. The metal body and working elements are characterized by high strength, which means that the device will withstand long-term pressure loads from the liquid flow.

Important! The pressure indicator is selected according to the power of the pumping system - the characteristic affects the parameters of the fluid flow passing through the pipeline system.

Particularly practical are devices with two springs, one of which controls the operation of the station at the upper, and the second at the lower pressure level. Climatic operating conditions and recommended humidity levels are taken into account. The maximum permissible load limit is indicated in the protection class characteristics.

Thread diameter and mounting holes checked for subsequent installation of the device. If it perfectly matches the pipeline elements, joining will not cause any difficulties, and there will be no leaks during equipment operation.

Review of famous manufacturers and prices

Several models in the $30-40 price category are considered the most famous and reliable:

1. Genyo Lowara Genyo 8A. Manufacturer – Poland. The main direction of the company is the production of electronic equipment for control systems. The relay is designed to work in water pipes household use and is characterized high quality, long service life. By monitoring the flow pressure in the pipes, the sensor starts the pumping system at a water flow rate of 1.6 l/minute. The unit requires an electrical connection and consumes 2.4 kW/hour. Worker temperature regime+5..+60 C.
2. Grundfos UPA 120. Manufacturer's plants are located in Romania and China. The device has small dimensions, is convenient to install and is indicated for individual water supply systems. That is, it can be used both in private buildings and apartments. The device starts up at a liquid flow rate of 1.5 l/minute, completely preventing the system from functioning at idle. Extreme indicator operating temperature+60 C.

The models have been tested and adapted to domestic operating conditions. Numerous reviews characterize metering sensors as durable and practical units at an affordable price.

Installation of a relay on a pump or station

If installation of the device is required, the work can be done independently, especially if you have to be away and there is no way to constantly monitor the operation of the pumping equipment.

When you do not need to install a relay:

• if water is pumped from a well with a large volume, that is, liquid reserves are not limited, and the pump power is minimal;
• It is possible to turn off the installation when the water level drops.

Equipment installation rules:

1. It is important to monitor the membrane - the part must take a vertical position.
2. Installation is carried out to the drain pipeline section using threaded couplings. There is a special slot for this.
3. Before starting work, the threads are sealed with linen or other plumbing thread. Winding the thread towards the end clockwise will increase the reliability of fastening and fixation.
4. Factory sensors are equipped with an arrow drawn on the body - this is the direction of flow, which must match during installation.
5. When installing relays in water supply pipelines with dirt particles, cleaning filters are first installed. Mount them better nearby with sensor to extend the life of the device.

Testing of the installed device is carried out with connection to the power supply:

• the free ends of the contacts are connected to the wire core;
• grounding is mounted to the screw;
• the device is connected by connecting the device with a wire (watch the color of the corresponding wires);
• system functionality is checked.

Worth knowing! If the device is connected correctly, the pressure mark on the pressure gauge will begin to increase, and then the pump will turn off at automatic mode, as soon as the pressure gauge needle goes beyond the limit value.

Self-adjustment of the water movement sensor

The factory device is equipped with bolts, by tightening or loosening which you can increase/decrease the spring compression. Bolts will be required if you need to install the sensor at a certain pressure level at which the mechanism is triggered.

Algorithm of actions:

• drain the liquid from the system;
• wait until the pressure mark reaches zero;
• start the pumping unit;
• run the water back in the slowest mode;
• remember the flow pressure indicator when the pump relay is turned off;
• drain the liquid again, recording the indicators when the system starts operating.

Now you need to open the relay, use the bolt to adjust the compression level of the larger spring - this will trigger the device when the pump starts. The adjustment is made taking into account that strong compression will increase the degree of pressure, and weak compression will decrease it. Then the compression force of the smaller spring is adjusted - here the limit of the maximum pressure level is set, upon reaching which the relay will automatically turn off the pump.

As soon as the adjustment is completed, start the system, evaluate the results of the work when filling the pipeline and draining the flow. If adjustment changes are necessary, repeat the procedure. Checking functionality and adjusting operating parameters is an annual procedure that extends the life of the device.