Flow sensor- a device that generates an output signal in the presence of a flow of liquid or gas. They are installed in pipelines and air ducts where the presence of working fluid flow is a critical parameter.

This sensor is also called flow switch, because its principle of operation is similar, with the only difference that its operation is caused not by the appearance of a control voltage on the coil, but by the presence of a flow of liquid or gas. But the result of triggering a flow sensor, as well as a conventional relay, is a change in the state of the output contacts to the opposite.

As a rule, the sensor has a normally closed (NC) and a normally open contact (NO). When a flow of working medium appears, the NC contact opens and the NO contact closes.

There are several types of flow sensors:

Petal flow switch

The figure shows a diagram of a petal-type flow sensor.

As the name suggests, the main working element of this type of flow sensor is a flexible petal that is in contact with working environment and deviates from the vertical position in the presence of flow. The petal is mechanically connected to the output contacts and changes their state when it bends itself.

Caleffi (left) and Danfoss (right) petal flow switches

Turbine type flow sensor

The figure shows a diagram of a turbine-type flow sensor.

Such sensors are a small turbine whose rotor is equipped with a magnet. When a flow of working substance passes through the device, the turbine begins to rotate, resulting in a magnetic field that is converted into electrical impulses, arriving at electronic circuit sensor The electronics cause the output contacts to change state when flow is present, just as in a paddle switch.

Thus, such flow sensors have two types of outputs: output contacts (NO and NC) and pulse output. The latter is used to determine the flow speed: the higher the pulse repetition rate, the higher the flow speed.

Flow sensor (turbine) for Ariston boiler

An example of this type of sensor is a flow switch gas boiler Ariston. When a flow appears (when the user opens a hot water tap), the sensor generates an output signal and switches the boiler to DHW heating.

Using Flow Sensors

Flow sensors most often perform protective, informational or control functions.

The protective function is associated with detecting the presence of flow in systems where its absence can lead to emergency situations or equipment breakdowns. For example, they protect pumps, because When operating in the absence of water flow, they overheat and fail. You can also determine the lack of air flow in ventilation systems when the filter is clogged, the damper is closed, or the fan breaks down. Using a flow switch, you can detect leaks in water supply systems, determine the lack of water in storage tank etc.

The information function of a flow relay is spoken of when the presence or absence of a flow is not related to emergency, but is a significant event in the system that the user needs to know about. In such cases, the sensor is used to trigger a light or sound indication, or generate a message on the operator panel.

The flow switch performs the control function when other equipment is turned on or off based on its signal. For example, in DHW systems when the user opens the tap with hot water, the gas boiler must turn on the pump and switch to DHW heating mode. This happens just when the flow sensor is triggered after opening the tap.

Flow switch connection diagram

The following figure shows typical diagram turning on the flow sensor for the pump.

If there is no flow, NO contact 1-2 is open, and NC contact 1-3 is closed, the power circuit is open, and the pump is stopped. When a flow of water appears through the relay, its contacts change their state, the power supply circuit of the pump is closed and it turns on.

Now we will figure out why a water flow sensor is needed (also called a “flow switch”) and look at the principle of its operation. You will also learn what types of these sensors there are and how to install it yourself.

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In everyday life, sometimes an emergency switching on of a pump without water occurs, which can lead to equipment breakdown. Due to the so-called “dry running,” the engine overheats and parts are deformed. In order for the pump to function at maximum efficiency, it is important to ensure an uninterrupted water supply. To do this, you need to equip the heating and hot water supply system with a device such as a water flow sensor.

Water flow sensor

Design and principle of operation

A water flow sensor is a device that monitors the pressure inside the water supply system; it is connected to the pump via pipes.

Standard circuit of a water flow sensor:

• relay;
• set of plates;
• There is a wide chamber inside the device;
• a small float, which is placed inside a stationary flask;
• outlet feed channel;
• Most models are equipped with an adjustment valve installed at the outlet.

Operating principle of the sensor: when there is no liquid flow, it automatically pauses pumping station and does not allow dry running, and when water appears, it starts the device.

Application area

Water flow sensors are usually found in devices where it is necessary to constantly monitor the life support system and observe a certain operating mode.

Most often, water flow sensors are used in boilers operating on gas. Modern gas boilers equipped with such sensors are used for both heating and water heating.

Device located on the supply line tap water when water enters, it sends a signal to the boiler control board and operation circulation pump stops. Then the board turns on the nozzles responsible for heating running water, and the water in the heat exchanger begins to heat up. When the tap closes, the sensor notifies that the water supply has been stopped.

Most households are equipped with systems autonomous water supply, thanks to which you can have the most comfortable conditions.

The function of the water flow sensor is that when you turn on any of the devices connected to the water supply system, the sensor turns on the pump and water begins to flow.

When choosing a water flow sensor, be sure to consider the throughput of the devices and their size.

Types of water flow sensors

According to the type of design, relay and fitting devices are distinguished. In addition, there are varieties based on pressure levels.

Relay type water flow sensor used for pumps with low power. Typically these models are single-chamber. Experts note their low conductivity. Models with vertical plates are available, their maximum pressure is at least 5 Pa.

Protection systems are often used in the P48 series. Thanks to all these indicators, there are practically no water leaks, and such devices are also characterized by good operating stability.

The most widely used water flow sensors for pumps are fitting models. Their plates are usually placed horizontally, and some samples are equipped with two valves. Their maximum pressure is approximately 5 Pa. Protection systems are most often class P58. Conductivity is directly dependent on the size of the fitting.

Sensors low pressure applicable for pumps with a power of no more than 4 kW. The size of the chamber affects the conductivity. Most often on the market you can find a water flow sensor for a pump with two floats. Their price is low and you can easily choose the right model.

Models high pressure usually available with one extended fitting, the plates are mounted horizontally. Experts advise installing such samples in centrifugal pumps. Maximum pressure - does not exceed 6 Pa, protection system class P70.

Also, according to the mechanism of action, it is divided into:

• a water sensor based on the operating principle of a Hall sensor: it signals not only the flow of water, but also the speed of its flow;
• a reed switch sensor operating on the principle of a magnet: inside it there is a magnetic float, which, as the water pressure increases, moves around the chamber and affects the reed switch.

Design and principle of operation of a reed switch water flow sensor

DIY installation and manufacturing

Most water flow sensors are included in the design of the devices, so they need to be installed only in the event of a breakdown and the need to replace them. However, there are cases when the water flow sensor must be mounted separately, for example, if it is necessary to increase the water supply pressure. This is due to the fact that in the central water supply system, the pressure is low and does not reach the norm. And in order to turn on a gas boiler in hot water supply mode, you need good pressure.

In such situations, an auxiliary circulation pump , which is equipped with a water flow sensor. First the pump is installed, and then the sensor. It follows that as soon as water starts flowing, the sensor will turn on the pump and the pressure will begin to increase.

System booster pump Grundfos water supply UPA 15-90 with built-in water flow sensor

Making a water flow sensor with your own hands is not difficult. First you need to install the camera, then you need to cut out three plates, they should be mounted horizontally, there should be no contact between them and the bulb. For a simple design, one float will be enough.

It is rational to install the fitting on two adapters; the valve must withstand a pressure of at least 5 Pa.

Manufacturers

Thus, the water flow sensor is designed to protect the operation of boilers and pumping equipment.

The operation of modern household and industrial appliances largely depends on the correct and uninterrupted operation of electronic devices. In many ways, this state of affairs suits us, however, as soon as a failure occurs, the normal rhythm of life turns into a complete hassle. But in principle, nothing bad happens, just one of the components fails.

It is to such components of modern household appliances and includes a water flow sensor. A simple device that is equipped with gas hot water boilers, autonomous water supply systems, irrigation systems, well pumps.

Like all electronic components, the water flow sensor also has principles by which it works. In principle, everything is simple here, the whole point of its work is to signal whether there is water movement or not. The sensor is installed, for example, in a pipe. When the tap is closed, there is no water movement, but as soon as the tap opens, water begins to move and the sensor is triggered, the contacts close and the signal goes to the control board.

True, it is necessary to immediately point out that the sensor is pre-set to a certain sensitivity threshold - this is when the water movement must reach a certain point, for example, 1.7 liters per minute. Then the sensor will turn on, and will continue to work until the water supply speed decreases below the mark, and then the contacts will open and the control board will no longer receive the signal.

Areas of use

IN living conditions Water flow sensors have found their application mainly in devices that require constant monitoring of the life support systems of the house and compliance with a certain mode of their operation. By controlling the water supply, motion sensors can significantly reduce the cost of maintaining a home and make life much more comfortable and safer.

For gas boiler

The main place of application of the water flow sensor is in modern houses steel gas boilers. Modern gas boilers equipped with such sensors combine the functions of a water heater and a heating boiler.

The water flow sensor installed on the tap water supply pipeline reacts to the start of water movement when the hot water tap is opened.

The sensor sends a signal to the boiler control board, and the electronics turns off the heating circulation pump, extinguishes the gas heating nozzles, and closes the water circulation valve in the heating system. And then the board turns on the nozzles for heating running water and the process of heating water begins in the heat exchanger. When the tap is closed, the sensor detects that the water movement has stopped, which is signaled to the control board.

For pump

Many modern households are equipped with autonomous water supply systems. Such systems allow you to have a level of comfort in a private house comparable to apartments, but at the same time not depend on a centralized water supply.

A system consisting of a pump, water tank and control system allows you to service everything necessary for comfortable stay systems – automatic washing machines, dishwashers, use hot water and toilet.

The role of the water flow sensor is that when any of the devices connected to the water supply system is turned on or water selection begins, the sensor turns on the pump and the water supply automatically starts.

It doesn’t matter whether the laundry starts, the kitchen faucet opens, or the toilet cistern flushes. Another option for using water flow sensors are systems automatic watering

Kinds

. Here, in addition to the opening function, the flow sensor controls the amount of water used for irrigation. This function is necessary to control dosed watering and avoid waterlogging of the soil. A sensor installed on the central pipeline supplies information to the system control panel.

Today, two types of water flow sensors are most widely used: a Hall sensor and a reed switch relay.

The reed water flow sensor is a sensor based on the principles of a magnet. Fundamentally, this sensor looks like this - inside a chamber made of composite material there is a magnetic float; when water pressure increases, the float moves around the chamber and affects the reed switch.

The reed switch, which is nothing more than two magnetic plates in a chamber without air, opens under the influence of the magnetic field of the float, and the control board switches the boiler to hot water supply mode.

Installation

Considering that most water flow sensors are structurally included in the devices, their installation is required only in case of replacement due to failure. However, there are situations when the water flow sensor must be installed separately, for example, when there is a need to increase the water supply pressure.

After all, situations often occur when there is insufficient pressure in the central water supply system, and in order to turn on the gas boiler in hot water supply mode, it is necessary to create good pressure. In this case, an additional circulation pump is installed, equipped with a water flow sensor.

IN in this case the sensor is installed after the pump, so when the water starts moving, the sensor turns on the pump and the water pressure increases.

Review of models and prices

Water flow sensor for Grundfos UPA 120 pump

Main Application – automatic control water supply pump. The sensor is designed to provide water supply to an individual house or apartment equipped with an individual water supply system. The automatic sensor switches on when there is a steady flow of liquid in the range of 90-120 liters per hour.

The main purpose is to protect the pump from idling. The sensor is used with pressure booster pumps GRUNDFOS series UPA. These units have small linear dimensions, which allows installation directly into the water supply line.

Using a sensor allows the pump to operate in several operating modes, allowing both automatic switching on and switching on when necessary. The automatic sensor turns off the pump if the pressure in the water supply rises to normal.

Characteristics:

• power consumption – up to 2.2 kW;
• degree of protection – IP 65;
• manufacturer – GRUNDFOS;
• country of origin – Romania, China;

Price: $30.

Water flow sensor GENYO series – LOWARA GENYO 8A

Products of a company specializing in the production of various electronic devices for control systems. The model is designed to control the pump of a domestic water supply system based on actual water consumption. The main feature of the sensor is to control the pressure in the water supply system during operation. The LOWARA GENYO 8A sensor is designed to start the pump when the water flow rate reaches 1.5-1.6 liters per minute.

Characteristics:

• the pump starts at a water flow rate of 1.5 liters per minute;
• sensor operating voltage – 220-240 V;
• frequency of current consumption – 50-60 Hz;
• maximum current consumption – 8A;
• power consumption – up to 2.4 kW;
• operating temperature range – 5-60 degrees Celsius;
• degree of protection – IP 65;
• manufacturer – LOWARA ;
• country of origin – Poland;

Price – 32 dollars.

Designed for installation in gas double-circuit boilers of the Immergas brand. Compatible with models: Mini 24 3 E, Victrix 26, Major Eolo 24 4E | 28 4E. The flow sensor for hot water supply is designed for installation in gas boilers of the Immergas brand, chimney and turbocharged versions. The flow sensor is made in a plastic housing with a threaded connection. Hall sensor 1.028570 allows you to receive water at the outlet of the hot water supply circuit at a stable temperature,

Price $41.

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

Features and Benefits of Water Flow Sensor

Situations often arise in which the pump starts when there is no liquid in the pipeline. This provokes heating of the unit’s motor and its further breakdown. To eliminate 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 normal, 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 advantages of using the sensor include:

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

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

Water flow switch - operating principle and design

The main function of the sensor is to turn off the pumping equipment if the water level decreases or the pressure in the pipeline increases. If the amount of water increases or the pressure drops, the liquid flow indicator starts the equipment again. Its structural elements are responsible for the stable performance of the tasks assigned to the relay.

The 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 internal chamber of the device;
• Reed switch, which is responsible for opening and closing the circuit in electrical diagram pump;
• Two springs of different diameters - by compressing them, the water pressure is controlled, at which the liquid flow sensor will be triggered.

The principle of operation of the relay is as follows:

1. When water enters the internal chamber of the device, it puts pressure on the membrane, thereby moving it to the side;
2. Located with reverse side membrane, the magnet becomes closer to the reed switch, which causes its contacts to close and the pump to turn on;
3. If the water level drops, the membrane with the magnet moves away from the switch, which opens its contacts and turns off the pump.

Installing a liquid flow detector into 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 operating efficiency of a relay greatly depends 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, you will need to ensure that the sensor membrane is in a vertical position. The correct relay connection diagram looks like this:

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

There is an arrow on the body of the device indicating the direction of liquid circulation. When installing the device, you need to make sure that this arrow coincides with the direction of water flow in the system. If used for domestic purposes dirty water, then cleaning filters should be installed in front of the sensor.

Hydraulic water flow sensor - also simply records the presence of a flow, regardless of the amount of passing liquid, ranging from 1.7 to 30 l/min. The sensor is triggered by pressing the switch button under the influence of the pressure of passing water. The water flow acts on the boiler membrane, moving the rod with the plate pressing the button of the DHW flow sensor. After the water movement stops, the pressure on both sides of the membrane is equalized and the rod moves back, releasing the flow sensor button to its original position - the contact opens. The use of this principle of flow determination faded into the background with the beginning of the use of reed flow switches, which have proven themselves to be more reliable, simple and durable.

Water flow switch- allows you to instantly determine the emerging water flow. Structurally includes a float original design with built-in magnet and reed switch. Under the influence of water flow, the float moves to the upper position, it approaches the sensor. The built-in magnet acts with its magnetic field on the micro reed switch, which causes the contacts to close. The design feature is that the float does not float up, but moves relative to its axis under the pressure of water. The minimum flow is 1.7 l/min, which can be fixed by a flow switch; a flow limiter of up to 15 l/min is installed at the outlet. bandwidth. It helps to avoid a situation where the flow through the heat exchanger exceeds the boiler’s DHW capacity. Due to too high flow rate Insufficient heating may occur in the hot water circuit. Often, in our conditions, we are faced with the opposite situation, when the pressure and water flow are very low, as a result the boiler does not start or severely overheats the water when operating in column mode, the way out of the situation is to dismantle the flow limiter.

Hall Sensor- when the magnet located in the turbine rotates, a rotating magnetic field arises. The rotation speed of this field completely coincides with the amount of water passing through the water flow sensor. The Hall sensor, under the influence of this field, generates electrical impulses that are read by the boiler board. Based on the frequency of these pulses, the speed of water flow through the boiler is calculated. Thanks to the Hall sensor, we get water at the outlet with a stable temperature, which does not depend on the amount of flow. The use of such a sensor is due to the constant desire of manufacturers gas equipment achieve maximum comfort when operating boilers and dispensers. The error in water temperature when working with such a flow sensor is reduced to a minimum of 1-2 degrees.