Water flow sensor petal. Water flow sensors for gas boilers and pumps

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

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

All these devices are designed for one thing - turn off the pump in the absence of water. They just work differently different area 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. it conventional scheme. 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 it is used up from the accumulator most water supply. 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 impulses 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 quality protection, serving several parameters at once, providing the required pressure in the system, turning off the equipment in case of insufficient water flow.

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 / 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.

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, fire extinguishing systems, 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, the relay can stop the engine if there is no flow, start it if there is flow, sound if the flow stops, or turn off the alarm 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 medium, engaging 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 by adjusting the intensity of the electric air flow coming from the fan. Turbine flow switches can also be used to give an alarm in case of inefficient operation or 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 manufacturer and type of device depends on the conditions of use and requirements for its technical specifications in each specific case.

Good day, dear readers of the blog site

In the heading "Accessories" we will consider another type of flow switch FLUSSTRONIC series 2 and series 3. This equipment is manufactured by the Italian company Nercos. The FLUSSTRONIC flow switch, as well as, is used to protect pumping equipment from operation without fluid flow "dry running". The flow switch disconnects the pumping equipment from the power supply if the water in the water supply system, tank or well runs out, and also after all taps are closed. When turned on, the relay starts the pumping equipment and maintains this state as long as there is water consumption. When water consumption stops completely, the pumping equipment is turned off due to the lack of fluid flow. The FLUSSTRONIC relay will constantly keep the pumping equipment running if the water flow exceeds 1 liter per minute.

If the water runs out, then the equipment is switched off according to the “dry run” mode. At the same time, the red LED lights up, indicating that there is no flow of liquid inside the pump and, therefore, the pump is stopped. The "Restart" button allows you to restart the equipment in case it was stopped in the "dry run" mode. The flow switch can be used for water supply systems with a water temperature of not more than 60°C. This relay has a function to prevent blocking (jamming) of the pump If the pump has never been turned on during the day, then every day it automatic switch on for 5 seconds.

Specifications and job description FLUSSTRONIC

Technical characteristics of the flow switch are given in table 1

Control panel FLUSSTRONIC series 2

The FLUSSTRONIC series 2 control and display panel is shown in fig. one.

Series 2 and 3 will keep the pump running as long as the water flow exceeds 1 liter per minute. The minimum pressure for switching on the pump in the series 2 flow switch is 1.5 bar. This pressure is set at the factory and cannot be changed. If the water runs out during pump operation, the series 2 and series 3 flow switch will immediately turn off the pump from the power supply and the red LED on the housing will light up, indicating the “dry run” mode. You can restart the relay manually by pressing the “Restart” button. Every 20 minutes of time, FLUSSTRONIC series 2 and 3 will run the pump for 10 seconds (to avoid damage to the pump). If during the operation of the pump for 10 seconds a pressure appears on the discharge pipe of the pump above the minimum value, the relay will automatically exit the “dry run” state and return to the normal operating mode. The number of dry-running starts is unlimited, and these starts will continue until water appears. At any time in the "dry run" mode, you can press the "Restart" button and start the pump manually for a period of 10 seconds.

The control and indication panel of FLUSSTRONIC series 3 is shown in Fig.2.

Control panel FLUSSTRONIC series 3

The main difference between the series 3 flow switch and series 2 is that in series 3 you can adjust the lower pressure for turning on the pump in the range from 1.5 to 3.5 bar in 0.5 bar increments using the “SET” button (2) . And the second difference is the presence of an indicator indicating the current pressure in the water supply system.

Table 2 shows the relationship between the lower turn-on pressure of the pump, maximum height water column H max and the maximum pressure created by the pump for the flow switch series 2 and 3.

In the FLUSSTRONIC relayseries 3 have function automatic determination of the maximum pressure for switching on the pump. When the dry-running switch is activated, it detects the maximum pressure the pump is producing and automatically adjusts the maximum setpoint for the pump cut-in pressure. This pressure is equal to the maximum pressure generated by the pump in bar minus 1 bar (for example, the pump generates a maximum operating pressure of 4 bar, for FLUSSTRONIC series 3, the lower cut-in pressure of the pump will be 3 bar). This function allows you to protect the pump connected to the flow switch and prevents you from mistakenly setting the switch-on pressure higher than the maximum pressure generated by the pump.The series 3 flow switch has a function to protect the water supply system from a sharp decrease in pressure This function is activated if the water flow is 24 liters per minute or more. At this flow rate, the pump will be switched on before the pressure in the system reaches the set lower value of the pump switch-on pressure.

If you keep the "Set" button pressed for more than 30 seconds, then all 5 green LEDs will flash, indicating the switch-on pressure, and the set lower switch-on value of the pump will be reset to the factory settings (1.5 bar).

When the relay fails or turns off FLUSSTRONICseries 3 from the mains, all previous set parameters and values.

Mounting relayFLUSSTRONIC

The installation diagram of the flow switch is shown in fig. 3.

The main features that you need to pay attention to when installing flow switch FLUSSTRONIC the following:

1. For correct operation, the dry-running relay must be mounted in a vertical position. You can determine the correct orientation of the relay by the inscriptions on the front panel (position 6 in Fig. 3).
2. The flow switch can be mounted immediately after the pump (1) on the supply pipe (4).
3. A filter (2) must be installed on the suction pipe (3) directly before the pump.
4. There can be no water flow between the pump outlet and the flow switch (5). All tapping points must be downstream of the FLUSSTRONIC dry-running relay.
5. The pressure generated by the pump must exceed by at least 0.5 bar the value of the lower start pressure of the pump, programmed in the "dry running" relay (table 2).
6. The highest point of water parsing “H max” (7) must not exceed the value indicated in table 2. In case “H max” exceeds the pump switch-on pressure value of 1.5 bar, the FLUSSTRONIC series 2 “dry running” relay will work incorrectly.
7. For ease of installation, it is recommended to connect the relay output to the water supply system using flexible hose(eight). The delivery set of the flow switch includes two plastic nipples with an elongated thread. All flow switches at the inlet and outlet are equipped with union nuts with rubber gaskets. That's why IT IS STRICTLY FORBIDDEN TO WIND a fum nipple connected to a union nut with tape or tow. The nipple is screwed directly into the union nut without a seal.
8. Before switching on the “dry running” relay, it is necessary to make sure that the pump and the suction pipe are filled with water and during the first start-up there will be no problems with the normal operation of the pump.

Electrical connection flow switch

All electrical connections must be made by a qualified electrician. It is necessary to make sure that the voltage indicated on the front panel of the flow switch corresponds to the voltage in the electrical network. The pump to which the relay will be connected is installed in a dry and moisture-proof location. In addition, the rated current drawn by the pump motor does not exceed the current value indicated on the front panel of the flow switch. It is very important that the flow switchFLUSSTRONICwas connected to an outlet powered by an RCD (equipment) with a leakage current of 30 mA. The FLUSSTRONIC dry-running relay is available in two versions:

1 "TYPE A": without connecting cables. Wiring diagram pic 4.

2. "TYPE B" power cable 150 cm long with a Schuko plug (Euro plug), for connecting to a socket and a cable 100 cm long with petals on the cores for connecting to the pump motor. Wiring diagram fig 5.dry run relay, flow switchFLUSSTRONIC

After connecting the plug to the socket, the FLUSSTRONIC relay is ready for operation. Subject to all rules and regulations of installation, as well as electrical connection the flow switch does not require special maintenance and repair. For normal operation of the flow switch, it is necessary to use only clean water that does not contain sand and dirt. It is also prohibited during operation to use water containing detergents, corrosive and abrasive materials. In case of equipment failure, repair flow switch needed in service centers. Sometimes a flow switch repair can be quite expensive and can be commensurate with the cost of new equipment.

Thank you.

The water flow switch is a multifunctional device, the main task of which remains the automation of the pump, the regulation of the water supply. The sensor switches water on and off depending on its presence in the system. We supply sensors made only from high quality environmentally friendly materials. clean materials, thanks to which the water flow switch can interact even with drinking water without distorting its composition. At the same time, our price for water flow sensors is lower than in city stores.

Sensors are mainly connected to pumps with high power, as they effectively protect the pump from overheating and other possible malfunctions. Thanks to this, the water flow switch for the pump extends its life and ensures the convenience of using the pump. The advantages of the flow switch for the pump are: small size, high sensitivity, versatility, affordable price, long term operation. If you do not have time to constantly monitor the operation of the pump, then the sensor will do it for you.

When installing a pressure control sensor, it is worth resorting to the help of specialists, since initially the flow switch for the pump needs to be configured. Installation is carried out as follows: the inlet water flow switch is connected to pumping device. With a sufficient volume of water flow, the device is activated due to pressure on the sensor blade. When the water flow decreases, the sensor blade returns to its original position and the water supply stops. You can buy a water flow sensor for a pump in Moscow at optimal price payment method convenient for you.