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. Their connections are quite often threaded. There are also clip-on sensors on the market, which are not very popular.

Low pressure devices

Low pressure versions are 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 in 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 popular. hallmark modifications is considered low reducibility. The limiting pressure is on average 3.3 Pa. Protection systems are used in 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 pumps centrifugal type. 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 show themselves well 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 is guaranteed high degree 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.

FLU-25 is traditional reliable control the presence of a water flow in heat and water supply systems. Produced in a factory in Germany.

The flow switch FLU25 is used to control the presence of water flow in an autonomous heating system with forced circulation, up to the minimum flow rate.
Depending on the connection scheme, the flow switch can turn on or turn off the corresponding element of the autonomous heating system when the coolant flow disappears or appears. For example, when turning off circulation pump the burner may be switched off. The flow switch can also be used to protect the circulation pump from running dry.
The FLU-25 flow switch has a metal case and can be installed in rooms with high humidity. The presence of a spring bellows (bellows seal) makes the flow switch also suitable for diesel fuel.
The package includes plates (lamellas) of various lengths for pipes from 1 to 8 inches.
Installation:
To ensure perfect operation, the flow switch must be installed on a horizontal pipeline so that the plate (lamella) is vertical. The distance between the pipe and the device must be at least 55 mm, and the distance to subsequent fittings, bends or fittings on the pipeline must be at least 5 DN. The flow switch must be oriented so that the direction of the arrow on the body corresponds to the direction of flow in the pipeline.
If there are foreign mechanical impurities in the coolant and high contamination, a mechanical filter should be installed in front of the flow switch.

Specifications:
Microswitch (relay) 6 A - 220 V
Maximum operating pressure 10 bar.
Maximum coolant temperature 110° С
Maximum temperature environment 60°C
Protection class IP 54, inner diameter of cable entry 6mm (included)
External thread G1

Mounted on pipes Du25...Du-200mm

Flow switch adjustment:
The table below gives the required lamella length according to the pipe diameter.
The operating threshold (operating point) is determined by the tension of the spring (10), the setting of the screw (8) and the length of the lamella (A).
The table shows the pipe diameters, the corresponding lamella lengths and the flow rate in m3/h at which the microswitch closes or opens, both at the minimum setting (screw tightly tightened) and at the maximum value setting (screw fully loosened).
The device is shipped with a tight calibration screw (installed minimum value). Contact 1 - 2 is open. After starting the pumps or when setting the nominal water flow, the lamella must move in the direction of the water flow, as a result of which contact 1 - 2 closes and the burner starts to work.
If the lamella does not move, this means that the water flow is too low and the device cannot respond. However, in practice, this is almost completely excluded, since the value of the water flow is usually significantly higher than the established minimum value (for example, 6.3 m3 / h at 3" pipe diameter). If the actual water flow is known, then the device can be fine-tuned (see table in the Specification section, PDF file).
Flow switch in heating systems with simple ON-OFF control do not require precise calibration. It is enough to set the minimum value so that the contact that controls the burner closes as soon as the set water flow is reached (see table).

Read more in the SPECIFICATION (PDF file below)

A flow switch is a device designed to control the flow of air, gas or liquid. It sends a control signal to another device in the system, serving, for example, to stop running mechanisms. In particular, the flow switch can control the on and off of the pumps. Some of general applications relays are designed to protect pumps, to control and signal the deviation of the flow rate from a predetermined level.

An example is the liquid and gas flow switches shown in the figure, manufactured by McDonnell & Miller. Water flow switches, for example, can be used in devices for heating water in equipment cooling water systems, in fire extinguishing systems, in water treatment systems, chlorination of swimming pools, etc.

Switches that control can be used for ventilation of rooms, filtration systems in heating mains, systems for supplying, cleaning and processing air.

The concept of flow means the physical movement (velocity) of a liquid, gas or vapor in a pipe, which actuates the flow switch. The absence of a flow means a decrease in its speed to zero, i.e. to a complete stop, allowing the switch to return to its original position.

To set a specific flow switch threshold (set point), the speed must be pre-set depending on the application. For example, a relay can stop the engine if there is no flow, start it if there is a flow, make a sound if the flow stops, or turn it off. Emergency Signal if the indicator returns to normal.

There are several various types flow switch, the most common of which is a turbine-type device.

Indispensable in general industrial applications for liquids and gases. They combine excellent performance with quality and reliability.

The fluid, entering into engagement with the rotor blades of the bladed turbine, located on the path of the flow, causes it to rotate with an angular velocity proportional to the flow velocity.

The rotor rotating inside the pipe, with the help of a special device, converts the flow rate into a pulsed electrical signal. The total pulsed electrical signal is directly related to the total flow in such a way that its frequency is directly proportional to the flow rate of the liquid (gas) flowing through the flow switch. This signal is processed electronic circuit, which eventually forms the output circuit of the flow switch in the form of a mechanical contact.

Turbine switches are used to detect fluid flow and fan rotation. They can also be used to protect the heating system with electric regulation of the intensity of the air flow coming from the fan. Turbine flow switches can also be used to give an alarm in case of inefficient operation or a complete stop of the fan.

In addition to this common duct, there are many others that differ in the mechanism and principle of operation. The choice of the manufacturer and the type of device depends on the conditions of use and the requirements for its technical characteristics in each particular case.

The device is designed to automatically turn off surface, 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). Used to manage any electric pumps operating from a single-phase network of 220 V, with a power of up to 1.5 kW. The device is installed in the line of the 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

Product specifications and photos may differ from those indicated on the site, check specifications goods at the time of purchase and payment. All product information on this website is for reference only.

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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 situations 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 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.

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 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 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 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 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 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'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	The country of manufacture	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 only turn off when it reaches 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. 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 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 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 pool water supply.

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 / container. 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.