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.
The protection relay is installed idle move on the surface, although there are models in a 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 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 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 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 relays pressure. 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 | Manufacturer 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 and so on. 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 for protection 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 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 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 / 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 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. The water flow switch for the pump is less known and common, but is also designed to automate the operation of the plumbing system and protect its main 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 switchThe 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 threshold for triggering 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 the required set pressure according to the table with various combinations of the length of the petal and the internal diameter of the 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 switching on and off the electric pump. Relays have a different principle of operation and, depending on the design of the sensor, 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 close 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 hemistor, 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 turn off the 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;
- located with reverse side membrane magnet becomes 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.
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, however, as soon as a failure occurs, the normal rhythm of life turns into a continuous hassle. But in principle, nothing terrible happens, just one of the components fails.
It is to such components of modern household appliances that the water flow sensor belongs. A simple device that is equipped with gas boilers, systems autonomous water supply, irrigation systems, well pumps.
Like all electronic components, the water flow sensor also has the principles by which it works. In principle, everything is simple here, the whole point of his work is to signal whether there is a movement of water or not. The sensor is installed, for example, in a pipe. When the faucet is closed, there is no water movement, and as soon as the faucet opens, the 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 indicate that the sensor is preliminarily adjusted to a certain sensitivity threshold - this is when the movement of water must reach a certain level, for example, 1.7 liters per minute. That's when the sensor will turn on, while it will continue to work until the water supply rate drops below the mark, and then the contacts open and the control board stops receiving a signal.
Areas of use
IN living conditions water flow sensors have found their application mainly in devices that require constant monitoring of home life support systems 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, make life much more comfortable and safer.
For gas boiler
The main place of application of the water flow sensor in modern houses steel gas boilers. Equipped with such sensors, modern gas boilers combine the functions of a hot water heater and a heating boiler.
Water flow sensor installed on the supply pipeline tap water reacts to the beginning of the movement of water 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, turns off the gas heating nozzles, and closes the water circulation valve in the heating system. And then the board turns on the heating nozzles running water and the water heating process starts in the heat exchanger. When the tap is closed, the sensor detects the stoppage of water movement, 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 comparable to apartments in a private house, but at the same time not depend on a centralized water supply.
A system consisting of a pump, a water tank and a control system allows you to service all the systems necessary for a comfortable stay - automatic washing machines, dishwashers, enjoy 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 is taken, the sensor turns on the pump and the water supply automatically starts. It doesn't matter if the laundry starts, the tap in the kitchen opens or the toilet bowl goes down.
Another option for using water flow sensors are systems automatic watering. Here, in addition to the opening function, the flow sensor controls the amount of water used for irrigation. This function is necessary to control metered watering and avoid waterlogging of the soil. The sensor installed on the central pipeline provides information to the system control panel.
Kinds
Today, two types of water flow sensors have found the greatest application - a Hall sensor and a reed relay.
The flow water sensor, based on the principle of operation of the Hall sensor (it is also called a flow meter), is a small turbine on which a magnet is mounted. When the turbine rotates, the magnet creates a magnetic field and, like a turbine in a hydroelectric power plant, it generates small electrical impulses that go to the boiler control board. The speed of rotation of the turbine depends on the speed of the water supply, the greater the flow, the clearer the pulses. Thus, thanks to the Hall sensor, it is possible not only to signal the flow of water, but also the speed of the water supply.
The reed water flow sensor is a sensor based on the principles of a magnet. Basically, this sensor looks like this - inside the chamber made of composite material there is a magnetic float, with an increase in water pressure, the float moves around the chamber and acts on the reed switch.
Reed switch, and this is nothing more than two magnetic plates in a chamber without air, under the action of magnetic field the float opens, and the control board switches the boiler to hot water mode.
Installation
Considering that most water flow sensors are structurally part of the devices, their installation is required only in case of replacement in case of failure. However, there are situations when the water flow sensor must be installed separately, for example, when it becomes necessary to increase the pressure of the water supply.
After all, situations often occur when the system central water supply insufficient pressure, and to turn on the gas boiler in hot water mode, it is necessary to create a good pressure. In this case, an additional circulation pump is installed, equipped with a water flow sensor.
In this case, the sensor is installed after the pump, so when the water begins to move, the sensor turns on the pump and the water pressure rises.
Overview of models and prices
Water flow sensor for pump Grundfos UPA 120
Main application - automatic control water system pump. The sensor is designed to provide water supply individual home, apartments equipped with an individual water supply system. Switching on the automatic sensor occurs with 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 GRUNDFOS booster pumps of the UPA series. These units have small linear dimensions, which allows installation directly into the water supply line.
The use of a sensor allows the pump to operate in several operating modes, allowing both automatic switch on, and inclusion if necessary. The sensor automation turns off the pump in the event of an increase in pressure in the water supply to a normal value.
Characteristics:
- power consumption - up to 2.2 kW;
- degree of protection - IP 65;
- manufacturer - GRUNDFOS;
- country of origin - Romania, China;
The price is 30 dollars.
Water flow sensor of the 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 household system water supply based on actual water consumption. The main feature of the sensor is to control the pressure in the water supply during operation. The LOWARA GENYO 8A sensor is designed to start the pump when the water flow reaches 1.5-1.6 liters per minute.
Characteristics:
- the pump is started at a water flow rate of 1.5 liters per minute;
- operating voltage of the sensor - 220-240 V;
- current consumption frequency - 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;
The price is 32 dollars.
Designed for installation in gas double-circuit boilers trademark Immergas. Compatible with models: Mini 24 3 E, Victrix 26, Major Eolo 24 4E | 284E. The flow sensor for hot water supply is designed for installation in gas boilers of the Immergas brand of chimney and turbocharged versions. The flow sensor is made in a plastic housing with a threaded connection. Hall sensor 1.028570 allows you to get water at the outlet of the hot water circuit with a stable temperature,
Price $41.
FLU-25 is traditionally reliable water flow control in heating systems. Produced in a factory in Germany.
The FLU25 flow switch is used to control the presence of water flow in an autonomous heating system with forced circulation, down to the minimum flow rates.
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 housing 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 working 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 (minimum setting). 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, the device can be fine-tuned (see the table in the Specification section, PDF file).
Flow switches 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)
