What are the functions of the water flow switch for pumps? Water flow switch - purpose, principle of operation and independent connection Scheme for switching on a pump with a flow switch.

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, sometimes a situation arises 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 the dry running of the pump is one of the components of automation that will have to be purchased. There are, however, models with built-in protection, but they are expensive. Cheaper to buy automation.

How can the pump be protected from running dry?

There are several different devices that 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 contact group which 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.

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 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 sealed case. 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 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 the usual pattern. But with this method of switching on, a situation is possible when a running pump, in the absence of water, does not turn off and burns out.

For example, a dry run 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 on the order of 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 accumulator. Only then will the pressure drop to critical and the relay will be able to work. If such a situation arose during active use water, nothing terrible will happen in principle - a few tens of liters will run out quickly and everything will be fine. But if it happened at night, they let the water out of the tank, washed their hands and went to bed. The pump has turned on, there is no signal to turn off. By the morning, when the analysis of water begins, it will be inoperative. That's why in systems with hydraulic accumulators or pumping stations it is better to use other water pump dry running protection devices.

Water flow control devices

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

Relay (sensors) of the flow

There are two types of flow sensors - 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.

Name	Functions	Parameters of operation of protection against dry running	Connecting dimensions	Producing country	Price
BRIO 2000M Italtecnica	Pressure switch + flow sensor	7-15 sec	1" (25mm)	Italy	45$
AQUAROBOT TURBIPRESS	Pressure switch + flow switch	0.5 l/min	1" (25mm)		75$
AL-KO	Pressure switch + check valve + dry running protection	45 sec	1" (25mm)	Germany	68$
Dzhileks automation unit	Pressure switch + idle protection + pressure gauge		1" (25mm)	Russia	38$
Aquario automation unit	Pressure switch + idle protection + pressure gauge + check valve		1" (25mm)	Italy	50$

In the case of using an automation unit, a hydraulic accumulator is an extra device. The system works perfectly on the appearance of a flow - opening a tap, triggering household appliances etc. But this is if the headroom is small. If the gap is large, both a GA 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 creates maximum pressure. If it is taken with a large margin of pressure, it can create overpressure(optimum - no more than 3-4 atm, everything above leads to premature wear of the system). Therefore, after the automation unit and the accumulator. This scheme makes it possible to regulate the pressure at which the pump is turned off.

Water level sensors

These sensors are installed in a well, borehole, tank. Suitable for use with pumps submersible type, although they are compatible with surface ones. There are two types of sensors - float and electronic.

float

There are two types of water level sensors - for filling the tank (protection against overflows) 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 this way and that, and the principle of operation depends on the connection scheme (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 pulled up, the pump can work 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 a break in the 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 tank. 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 water supply to the pool.

Electrodes are lowered into the water. Their number depends on the parameters they track. If you only need to monitor the presence of a sufficient amount of water, two sensors are enough. One - falls to the level of the minimum possible level, the second - the base - is located a little 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 / tank. If there is no current, it means that the water has dropped below the minimum level sensor. This command opens the power supply circuit of the pump and it stops working.

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

The device is intended for automatic shutdown superficial, borehole pumps, automatic water supply stations in the absence of water in the water intake systems. Switching off pumps and stations ensures their protection against damage as a result of operation without water (dry running mode). Serves to control any electric pumps operating from a single-phase 220 V network, with a power of up to 1.5 kW. The device is installed in line pressure pipeline. In this case, the pump power is connected to the device, and the power cable is connected to electrical network 220V. The place of installation of the device must be protected from the risk of water flooding, in a well-ventilated area.
OPERATING LIMITATIONS:

Temperature working environment: 0°C - 110°C
Maximum allowable pressure-6 Bar
Connection 1" (external and internal)
The maximum allowable water flow is 100 l/min

DESIGN FEATURES:

Switching voltage - 220 -240V ~ 50Hz
Maximum working current: 10A
Degree of protection - IP65
Restart - automatic
Shutdown condition - flow less than 2 l/min

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The water flow sensor is a device that regulates the pressure inside the water supply system. It is connected to the pumps through pipes. The main parameters of devices should include not only the limiting pressure, but also the output voltage. Manufacturers also indicate without fail throughput. Today there are many types of modifications. To understand the issue in more detail, it is worth first of all to study the device of the water flow sensor.

Model device

The standard water flow sensor circuit includes a relay and a set of plates. Inside the modification there is a wide chamber. The flask is always in a stationary state. Inside it is a small float. There is a feeding channel at the output. Many modifications are made with an adjusting tap, which is installed at the outlet. Models with valves are equipped with movable fittings. They use magnetic force to work.

Sensor: DIY

Making a water flow sensor with your own hands is quite simple. First of all, it is recommended to install the camera. A small plastic container is suitable for this. Then you will have to cut three plates that are installed in a horizontal position. The flask as a result should not come into contact with them. If we consider simple model, then one float is enough. It is more expedient to install the fitting on two adapters. The valve must withstand a pressure of at least 5 Pa.

Types of modifications

By design, only relay and fitting devices are distinguished. Additionally, modifications are separated according to the pressure level. Devices for circulation pumps are allocated in a separate subcategory.

Relay models

Relay water flow sensor for gas boiler suitable for small pumps. As a rule, models are produced with one chamber. Many experts say that they have low conductivity. However, it is worth noting that there are devices with a vertical arrangement of plates. Their limiting pressure is at least 5 Pa. Protection systems are quite often used by the P48 series. All this suggests that water leaks are rarely observed. Modifications are characterized by excellent stability. Their suction power is at least 3 N. Very rarely, models have faucets.

Union devices

The most common devices for pumps are choke modifications, which are produced with one chamber. Their plates are usually located in a horizontal position. Some modifications are equipped with two valves. And their limiting pressure parameter is approximately 5 Pa. Protection systems are quite often used class P58. In this case, the conductivity depends on the size of the fitting. Some modifications can boast high speed pumping. Connections are fairly common. threaded type. There are also clip-on sensors on the market, which are not very popular.

Low pressure devices

Modifications low pressure well suited for centrifugal pumps up to 4 kW. Their conductivity depends on the size of the chamber. The most common on the market is a water flow sensor for a two-float pump. In this case, the pumping force is on average 5 N. Protection systems are used different classes. Many sensors are installed through pads. Output contacts are designed for wire adapters. It is also worth noting that there are many inexpensive models on the market.

High pressure modifications

Models high pressure, as a rule, are made with one oblong fitting. The plates on the water flow sensor for the pump are most often installed in a horizontal position. If you believe the reviews of experts, then the models are great for centrifugal pumps. When choosing a modification, it is important to pay attention to the throughput of devices. The dimensions of the devices are also taken into account. Many models are made with two cameras. However, they only use one valve. If we consider standard model, then the limiting pressure averages no more than 6 Pa. The protection system in the devices is applied class P70. It is very rare to find models with a crane. Basically, ordinary switches are installed.

Devices for circulation pumps

Sensors for circulation pumps are very much in demand. hallmark modifications is considered low reducibility. The limiting pressure is on average 3.3 Pa. Protection systems are used by the most various classes. It is very rare to find devices with two cameras. When choosing a model, it is important to pay attention to the shape of the fitting. It should have a wide head and a narrow channel. Otherwise, leaks will often occur. In addition, it is worth noting that devices on floats are on the market. Their contacts are designed for adapters.

Features of models for two cameras

Sensors for two chambers, as a rule, are distinguished by large dimensions and a high pressure parameter. There are many models on the market for two valves. They have a suction force of 4 N. Protection systems are used in the P88 series. The plates of the sensors are always installed in a horizontal position. If we talk about the shortcomings of the devices, it is important to note that they use very large output channels. For pumps with a power of up to 8 kW, models are not uniquely suitable. There are devices on the market with and without taps. Additionally, there are modifications based on contactor switches.

Devices with three cameras

Sensors for three chambers are connected for centrifugal pumps. Their compressive strength is very high. It is also worth noting that the models are produced with short channels. Valves they use rotary type. They are protected by a special membrane. According to experts, the conductivity depends on the size of the chamber. If we talk about designs, it is worth noting that there are models on the market with oblong fittings. They have extremely low suction power. However, they can last a long time. In stores, devices with switches are very rare. As a rule, three-chamber models are made with small cranes.

Models for small pumps

The water flow sensor for pumps of low power should be selected only among fitting modifications. The limiting pressure indicator should be about 5 Pa. The protection system is welcome class P48. Many experts praise devices based on two cameras. Their suction force is approximately 4 N. Relay modifications for low-power pumps are not suitable in the best way.

Modifications with a vertical arrangement of plates

Devices of this type perform well on centrifugal pumps. They have good conductivity and no problems with high blood pressure. However, do not forget about the disadvantages of modifications. First of all, they often clog the channel. If we consider an inexpensive water flow sensor, then it may have problems with the valve. For the normal operation of the system, it is more expedient to select devices with output contacts for 12 V. The protection system must be installed class P55. Experts also say that the water flow sensor should be with a contactor switch.

Devices with a horizontal arrangement of plates

The water flow sensor for this type of boiler is suitable for a wide variety of pumps. The conductivity of the models depends on the dimensions of the chamber itself, as well as the channel. Additionally, the diameter of the fitting is taken into account. Many experts recommend installing two-chamber modifications. Their pumping force, as a rule, does not fall below 5 N. The protection system is quite often used by the P50 series. All this suggests that the manufacturer guarantees a high degree of sealing and overall reliability.

When choosing a device, it is important to evaluate the parameters of the valve. If it is made of ordinary plastic, then it is not able to last for a long time. Copper counterparts perform well, but are expensive. The main flask of the sensors is made of plastic. Very rarely there are modifications with transitional contacts. Relay modifications boast high conductivity. They are not afraid of overload. And they use high-quality protection systems.

The main task of any water supply system is not only to provide water to the consumer, but also to implement its uninterrupted operation in automatic mode without breakdowns. For this purpose, the commonly used pressure switches and dry running, float devices for monitoring the liquid level are intended. These devices, in addition to automating the operation of the system, protect the pump from dry running and, as a result, from overheating and failure. Water flow switches for a pump are less known and common, but are also designed to automate work. plumbing system and protect its key equipment from failure.

The flow switch is designed to monitor the flow of liquid in systems of cold and hot water supply, heating, cleaning and cooling installations.

Its main purpose is to protect electric pumps, motors and other devices from operation in the absence or small amount of water in the system, leading to overheating and equipment failure.

Fig.1 Appearance of the flow switch

The relays are designed for installation in a pipeline and allows you to automate the process of controlling the supply of liquids in domestic and industrial systems.

The water flow sensor for the pump is used in the following cases.

If there is no hydraulic accumulator in the system. This does not allow the installation of a pressure sensor designed to be paired with expansion tank, it is better to use a flow sensor to protect the electric pump.
In low pressure systems. The minimum response threshold for typical models of pressure sensors is 1 bar, that is, at a lower pressure in the system, the pump will always be turned off. Flow devices have a wider range of action, which can be expanded with adjustments. This allows the use of equipment protection devices in underpressure systems.

To adjust to work with a wide range of pressures, some petal models are equipped with petals different area providing different resistance to water flow. Sometimes notches are applied to the blade indicating the length. When installed, it is cut to obtain required pressure tripping according to the table with different combination petal length and inner diameter pipeline.

Figure 2. Flow switch with adjustable blade length

The vast majority of flow relays are designed to operate in heating systems, so the temperature of their working fluid can be 100 C or more.

Device and principle of operation

The principle of operation of the flow switch is based on the mechanical action of the water flow in the pipeline on the sensor that controls the electronic circuit for turning on and off the electric pump. Relays have a different principle of operation and, depending on design sensors are divided into several types.

Petal relays

One of the most common types, the main elements are a petal sensor with a magnet, located in the water flow and a reed switch, placed in the device body and reliably isolated.

Fig.3 Petal mechanical relay

When the water flow passes through the pipeline, the vertically located petal sensor rotates along its axis and deviates from the vertical position, bringing the built-in magnet closer to the reed switch. Its contacts inside the cylinder are closed and through the triac (double symmetrical thyristor) the pump is connected to the power source.

In the absence of water in the pipeline, the petal returns to its original position, moving the magnet away from the reed switch and thereby opening its contacts.

This leads to the termination of the supply voltage to the pump through the sevenstor, as a result of which it turns off.

Fig. 4 External view of the relay with a reed switch and a sevenistor

Rotary relays and flow type sensors

Rotary sensors are mainly used to measure and control fluid flow. Structurally, they are made in the form of a paddle wheel rotating in a fluid flow, its rotation speed is recorded by sensor sensors. The electronic circuit allows analog, frequency or discrete control of equipment operation.

Fig.5 Rotary sensors

Piston devices

The piston is placed in the valve seat and, under the influence of water pressure, moves in a vertical direction to a height proportional to the flow force. Permanent magnet, mounted on the piston, approaches the reed switch and the contacts close in it. Piston units can be installed in horizontal and vertical pipelines due to the built-in return spring that returns the piston to its original position in the absence of flow.

Rice. 6 Working principle and appearance piston relays

Water flow switch, unlike pressure switch and dry run, float switches, are not so widely used for automatic control of electric water pumps in domestic water supply systems. This is due to the fact that they cannot work independently in the water intake system - to turn them on, it is necessary to create a flow of water and turn on the pump by other devices. Relays are designed to turn off electric pumps and are often built into electronic water supply control units in conjunction with other automation.

The water flow sensor for the pump is an integral part of the equipment designed to protect the device from running dry. The sensor has small size and has simple design, which allows you to install it even for a beginner.

Features and Benefits of the Water Flow Sensor

Often there are situations in which the pump starts at the moment of complete absence of liquid in the pipeline. This provokes heating of the motor of the unit and its further breakdown. To avoid such situations, a fluid flow sensor should be used. This device works automatically and controls the flow of water inside the pipeline. If the amount of liquid passing through the sensor is less than the norm, the device automatically turns off the pump. Thus, the water flow switch not only prevents the pump from running dry, but also maintains normal operating conditions for the unit.

The benefits of using a sensor include:

Reducing the electricity consumed by the pump and saving money;
Protection of equipment from breakdowns;
Extending the life of the pump.

Among other things, the water flow switch for the pump is distinguished by its modest dimensions, low cost and ease of installation.

Water flow switch - principle of operation and design

The main function of the sensor is to disable pumping equipment in the event of a drop in water level or an increase in pressure in the pipeline. If the amount of water increases or the pressure drops, the liquid flow indicator restarts the equipment. Its structural elements are responsible for the stable performance of the tasks assigned to the relay.

The device device consists of the following parts:

A pipe through which liquid enters the device;
A membrane that plays the role of one of the walls of the inner chamber of the device;
Reed switch, which is responsible for opening and closing the circuit in wiring diagram pump;
Two springs of different diameters - by compressing them, the water pressure is controlled, at which the fluid flow sensor will be triggered.

The principle of operation of the relay is as follows:

When it enters the internal chamber of the device, water exerts pressure on the membrane, thereby shifting it to the side;
The magnet located on the back of the membrane gets closer to the reed switch, due to which its contacts close and the pump turns on;
If the water level drops, then the membrane with the magnet moves away from the switch, which leads to the opening of its contacts and turning off the pump.

Installing a liquid flow detector in a pipeline is quite simple. To do this, you need to study the features of connecting the device and its correct configuration.

Device connection diagram

The performance of a relay is highly dependent on its correct installation. It must be remembered that the device can only be installed on those sections of the pipeline that are located horizontally. In this case, it will be necessary to ensure that the sensor membrane is in a vertical position. Correct scheme The relay connection looks like this:

During installation, the sensor must be connected to the drain part of the pipe by means of threaded connection. The distance at which the relay must be located from the pipe must be more than 5.5 cm.

On the body of the device there is an arrow indicating the direction of circulation of the liquid. When installing the device, make sure that this arrow coincides with the direction of the water flow in the system. If used for domestic purposes dirty water, then a cleaning filter should be installed in front of the sensor.

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