Sealing seams

System for maintaining the water level in the tank. Electrical circuits

03.09.2023

Many of us, and not only avid summer residents, have faced the problem of automation and control of filling containers with water. Most likely, this article is specifically for those who decided to make a simple scheme for monitoring the filling of a container at home. The most cost-effective way to build automation is to use a water control relay. Level control relays (water) are also used in more complex water supply systems for private houses, but in this article we will consider only budget models of conductive liquid level control relays. Controlled liquids include: water (tap, spring, rain), liquids with low alcohol content (beer, wine, etc.), milk, coffee, wastewater, liquid fertilizers. The rated current of the relay contacts is 8-10A, which allows you to switch small pumps without using an intermediate relay or contactor, but manufacturers still recommend installing intermediate relays or contactors to turn pumps on/off. The operating temperature range of the devices is from -10 to +50C, and the maximum possible wire length (from the relay to the sensor) is 100 meters, there are LED operation indicators on the front panel, weight no more than 200 grams, DIN-rail mounting, so you will need to think about it in advance placement of the control system.

The principle of operation of the relay is based on measuring the resistance of the liquid located between two immersed sensors. If the measured resistance is less than the response threshold, then the state of the relay contacts changes. To avoid electrolytic effects, alternating current flows across the sensors. The sensor supply voltage is no more than 10V. Power consumption no more than 3W. Fixed sensitivity 50 kOhm.

There are many relays of the same type on the market; let’s consider the most budget models from the manufacturers “Relay and Automation” in Moscow and new products from “TDM” (Morozov Trading House).

Level control relay. ( analogue of RKU-02 TDM)

The TDM level control relay is available in four models:

  1. (SQ1507-0002) for connector Р8Ц (SQ1503-0019) on DIN rail
  2. (SQ1507-0003) on DIN rail ( analogue of RKU-1M)
  3. (SQ1507-0004) on DIN rail
  4. (SQ1507-0005) on DIN rail

Relay housings are made of flame retardant materials. Level control sensors are made of stainless steel. (DKU-01 SQ1507-0001).

The operation of the relay is based on the conductometric method for determining the presence of liquid, which is based on the electrical conductivity of liquids and the occurrence of microcurrent between the electrodes. The relays have changeover contacts, allowing the use of fill or drain mode. Supply voltage RKU-02, RKU-03, RKU-04 – 230V or 400V.

Scheme for controlling a pump in a tank in the “filling or draining” mode.

Scheme of pumping liquid from a well/reservoir to a reservoir, level control in both media, i.e. the relay performs a protective shutdown of the pump in dry running mode (when the liquid level in the well/reservoir decreases)

Scheme of alternating or total activation of 2 pumps. The RKU-04 relay is used in places where overfilling of wells, pits, catch basins and other containers is unacceptable. The relay works with 2 pumps, and, for uniform use of their resource, the relay switches them on alternately. In the event of an emergency, both pumps are switched off simultaneously.

The relay cannot be used for the following liquids: distilled water, gasoline, kerosene, oil, ethylene glycols, paints, liquefied gas.

Comparative table of analogues by series:

TDM F&F lovato RiA
RKU-01 PZ-829 LVM20 RKU-1M
RKU-02 PZ-829 LVM20 RKU-1M
RKU-03 - LVM20 EBR-02
RKU-04 - LVM20 -

Often the reason for the breakdown of an automatic washing machine is a malfunction of the water level sensor. This is due to the fact that the pressure switch of the washing machine affects the operation of the control module. You can fix problems with the water level sensor yourself.

The pressure switch for a washing machine is made in the form of a small plastic tablet. On one side of this tablet there is a connector for connecting wiring, and on the end there is a small tube. The pressure switch in the washing machine is connected to the control module via wiring and to the tank through a special tube.

The principle of operation of the sensor is simple. The tank of the automatic washing machine is sealed: When water is added, air under pressure enters through a tube into the sealed chamber of the pressure switch with an installed membrane.

Due to the pressure in the chamber, the membrane closes the contacts that conduct electric current.

When closed, voltage is supplied to the control module. If the sensor does not work, the control module cannot detect water in the tank.


Setting up the pressure switch

To supply the correct volume of water to the washing machine tank, the sensor must be configured correctly. The setting is performed by the manufacturer, but having experience in repairing household appliances, you can adjust the pressure switch yourself.

If the washing machine is under warranty, take the device to a service center.

The water level sensor in the washing machine is adjusted using adjusting screws. The moment of closing and opening the contacts is set. It is necessary to adjust the sensor only with the device disconnected from the power supply. There should be no water in the tank of the machine during setup.

The adjustment is made by gradually turning the adjusting screw. It is recommended to turn the screw no more than half a turn at a time. After each turn, close the protective cover of the washing machine and turn on the water supply program.

Adjust until the fluid level in the tank reaches the optimum level. After adjusting the sensor, secure the screw in the socket with a sealing compound. This will prevent spontaneous rotation due to vibration during spinning.

Sensor check

To check the pressure switch of a washing machine, proceed in order:

  1. Unplug the washing machine to reduce the risk of electric shock.
  2. Remove the top cover of the machine. After unscrewing the fastening bolts, slide the cover towards the rear wall and lift it up.
  3. Find the pressure switch on top of the side or back wall of the device.
  4. Disconnect the wiring connector from the sensor. It is fixed in the socket with a special latch.
  5. Remove the hose attached to the tube.
  6. Unscrew the fastening bolt and pull it out.
  7. Connect a short length hose of suitable diameter to the tube.
  8. Blow forcefully into the device through the connected hose.

If the contacts inside the pressure switch are triggered, you can hear characteristic clicks. If there are no clicks, the sensor is not working and must be replaced.

Check the functionality of the device with a multimeter. To do this, first study the electrical circuit of the pressure switch and determine the pins to the contacts of one group.

Set the dial on the multimeter to resistance measurement mode and blow into the attached hose. When air pressure changes, the readings on the measuring device should change. If the multimeter shows no change, replace the sensor.

The machine may not operate properly due to a clogged air tube from the tank to the sensor. To solve the problem, just rinse the hose under running water.

Incorrect operation is caused by loose connections between the hose and the tube. There is an air leak and the pressure in the chamber is not enough to trigger the pressure switch.

Typical faults

The failure of the water level sensor is most often indicated by malfunctions:

  • The washing cycle starts before the washing machine has filled with water. When the washing mode is turned on, the control module turns on the heating element to heat the water. Without water in the tank, the heating element will overheat and burn out.
  • There is not enough or too much water for washing. The control module may not close the inlet valve due to a faulty pressure switch. This leads to the machine leaking and flooding the room.
  • After spinning, the laundry remains wet. The water from the tank is not completely drained after the washing cycle.
  • At the end of the session, the water does not leave the tank and the machine does not open the hatch. The pressure switch does not send a signal to the control module about the presence of water and the module does not turn on the drain pump.
  • The washing machine does not work and shows an error code on the display. This is only possible in cars with self-diagnosis. Decipher the error code to find the broken part.

Replacing the sensor yourself

If the water level sensor does not work, it must be replaced. It will not be possible to disassemble and repair it due to the solid body. The new pressure switch must be identical to the old one.

Install the sensor:

  1. Screw the new device with screws into the designated location.
  2. Connect the hose to the device tube and secure with a clamp of the appropriate size. Before connecting the hose, inspect it for damage. This is important for tightness.
  3. Connect the electrical wiring connector.
  4. Install the top cover of the washer and secure it with the provided screws.
  5. After installation, check operation by loading laundry and starting the wash.

The condition of the pressure switch is very important for the normal operation of the automatic washing machine. If a part breaks, it will have to be replaced with a new one. Do not use the machine with a non-functioning sensor, so as not to provoke serious damage.

When the need arises to control the fluid level, many do this work manually, but this is extremely ineffective, takes a lot of time and effort, and the consequences of oversight can be very expensive: for example, a flooded apartment or a burnt out pump. This can be easily avoided by using float water level sensors. These are devices that are simple in design and operating principle and are affordable.

At home, sensors of this type allow you to automate processes such as:

  • monitoring the liquid level in the supply tank;
  • pumping groundwater from the cellar;
  • turning off the pump when the level in the well falls below the permissible level, and some others.

Operating principle of a float sensor

An object is placed in the liquid and does not sink in it. This could be a piece of wood or foam, hollow sealed plastic sphere or metal and much more. When the liquid level changes, this object will rise or fall with it. If the float is connected to the actuator, it will act as a water level sensor in the tank.

Equipment classification

Float sensors can independently monitor the liquid level or send a signal to the control circuit. According to this principle, they can be divided into two large groups: mechanical and electrical.

Mechanical devices

Mechanical valves include a wide variety of float valves for the water level in the tank. The principle of their operation is that the float is connected to a lever; when the liquid level changes, the float moves up or down this lever, and it, in turn, acts on the valve, which shuts off (opens) the water supply. Such valves can be seen in toilet flush tanks. They are very convenient to use where you need to constantly add water from the central water supply system.

Mechanical sensors have a number of advantages:

  • simplicity of design;
  • compactness;
  • safety;
  • autonomy - do not require any sources of electricity;
  • reliability;
  • cheapness;
  • ease of installation and configuration.

But these sensors have one significant drawback: they can control only one (upper) level, which depends on the installation location, and regulate it, if possible, then within very small limits. Such a valve can be sold called “float valve for containers”.

Electrical sensors

An electric liquid level sensor (float) differs from a mechanical one in that it itself does not shut off the water. The float, moving when the amount of liquid changes, affects the electrical contacts that are included in the control circuit. Based on these signals, the automatic control system makes a decision on the need for certain actions. In the simplest case, such a sensor has a float. This float acts on the contact through which the pump is turned on.

Reed switches are most often used as contacts. A reed switch is a sealed glass bulb with contacts inside. Switching of these contacts occurs under the influence of a magnetic field. Reed switches are miniature in size and can be easily placed inside a thin tube made of non-magnetic material (plastic, aluminum). A float with a magnet moves freely along the tube under the influence of liquid, and when it approaches, the contacts are activated. This entire system is installed vertically in the tank. By changing the position of the reed switch inside the tube, you can adjust the moment the automation operates.

If you need to monitor the upper level in the tank, then the sensor is installed at the top. As soon as the level drops below the set level, the contact closes and the pump turns on. The water will begin to increase, and when the water level reaches the upper limit, the float will return to its original state and the pump will turn off. However, in practice such a scheme cannot be used. The fact is that the sensor is triggered by the slightest change in the level, after which the pump turns on, the level rises, and the pump turns off. If the water flow from the tank is less than the supply, a situation arises when the pump is constantly turned on and off, while it quickly overheats and fails.

Therefore, water level sensors to control the pump they work differently. There are at least two contacts in the container. One is responsible for the upper level; it turns off the pump. The second determines the position of the lower level, upon reaching which the pump turns on. Thus, the number of starts is significantly reduced, which ensures reliable operation of the entire system. If the level difference is small, then it is convenient to use a tube with two reed switches inside and one float that connects them. If the difference is more than a meter, two separate sensors are used, installed at the required heights.

Despite their more complex design and the need for a control circuit, electric float sensors allow fully automated liquid level control.

If you connect light bulbs through such sensors, then they can be used to visually monitor the amount of liquid in the tank.

Homemade float switch

If you have the time and desire, then you can make a simple float water level sensor with your own hands, and the costs for it will be minimal.

Mechanical system

In order to simplify as much as possible design, we will use a ball valve (faucet) as a locking device. The smallest valves (half-inch or smaller) work well. This type of faucet has a handle that closes it. To convert it into a sensor, you need to extend this handle with a strip of metal. The strip is attached to the handle through holes drilled in it with the appropriate screws. The cross-section of this lever should be minimal, but it should not bend under the influence of the float. Its length is about 50 cm. The float is attached to the end of this lever.

As a float you can use a two-liter plastic bottle from soda. The bottle is half filled with water.

You can check the operation of the system without installing it in the tank. To do this, install the faucet vertically and place the lever with the float in a horizontal position. If everything is done correctly, then under the influence of the mass of water in the bottles, the lever will begin to move down and take a vertical position, and the valve handle will turn with it. Now submerge the device in water. The bottle should float up and turn the valve handle.

Since valves vary in size and the amount of force required to switch them, the system may need to be adjusted. If the float cannot turn the valve, you can increase lever length or take a larger bottle.

We mount the sensor in the container at the required level in a horizontal position, while in the vertical position of the float the valve should be open, and in the horizontal position it should be closed.

Electric type sensor

For self-production of the sensor of this type, in addition to the usual tool, you will need:

The manufacturing sequence is as follows:

When the liquid level changes, the float moves along with it, which acts on an electrical contact to control the water level in the tank. A control circuit with such a sensor may look like the one shown in the figure. Points 1, 2, 3 are the connection points for the wire that comes from our sensor. Point 2 is a common point.

Let's consider the principle of operation of a homemade device. Let's say at the moment of switching on the tank empty, the float is in the low level position (LL), this contact closes and supplies power to the relay (P).

The relay operates and closes contacts P1 and P2. P1 is a self-locking contact. It is needed so that the relay does not turn off (the pump continues to work) when the water begins to rise and the contact of the low pressure unit opens. Contact P2 connects the pump (H) to the power source.

When the level rises to the upper value, the reed switch will operate and open its contact VU. The relay will be de-energized, it will open its contacts P1 and P2, and the pump will turn off.

As the amount of water in the tank decreases, the float will begin to fall, but until it takes the lower position and closes the NU contact, the pump will not turn on. When this happens, the work cycle will repeat again.

This is how a water level control float switch works.

During operation, it is necessary to periodically clean the pipe and float from dirt. Reed switches can withstand a huge number of switchings, so this sensor will last for many years.

A device that controls the presence and volume of water in the tank of a washing machine, regardless of its brand (LG, Samsung, Ariston or Indesit), is called a pressure switch, or water level sensor. The main washing algorithms are turned on or not on according to its indications. The answer to the question of where the pressure switch is in a washing machine varies depending on the model and manufacturer, but the general criterion is its location near the housing wall, under the top panel of the unit.

Description of the device and its operating principle

You can find out where the pressure switch of an LG, Samsung, Indesit or Bosch Maxx 4 washing machine is located by removing the top panel of the unit. The pressure switch looks like a flat plastic (monochrome or multi-colored) corrugated washer, to which wires with connectors fit on both planes, and a plastic tube at the end. On some machines from LG and other companies, the sensor is oval, compact, two-pin: wires fit on one plane, and a rubber tube on the other.

The water level sensor is essentially a pneumatic relay, triggered by air pressure filling a tube connected to the tank of the machine. Depending on the pressure created by the water flowing into the drum, the air pressure on the internal membrane of the relay increases. The membrane, in turn, closes and opens certain contacts, passing current through the connected wires and triggering the corresponding command in the electronic control unit.

The absence of a “response” from the relay to the started operation or the absence of continuity in the control circuit in electronically controlled units causes the washing program to stop and an error signal appears on the dashboard indicator.

Pressostat error codes depending on the manufacturer and model of the equipment:

  • LG – PE;
  • Ariston (Indesit) – F04 (F05);
  • Electrolux – E11-E12; E21-E22;
  • Bosch (Maxx 4) – F26 (F19);
  • Samsung – E7 (E2; E3).

Consequences of operating a faulty sensor

If the pressure switch of a Samsung, Ariston, Indesit, Bosch or LG washing machine does not work correctly, this will provoke one or more malfunction options:

  • overflowing water in the tank of the machine with constant addition and drainage of liquid;
  • the liquid level in the tank is too low, the quality of the wash deteriorates;
  • incomplete drainage of liquid after washing, insufficient spinning of laundry;
  • start of the program (turning on the heating element) without water, overheating of the element and its failure.

The last point threatens serious damage to the washing machine and may even cause a fire.

Sensor Test Guide

Before trying to check the pressure switch on a Bosch Maxx 4 (or Samsung) washing machine using a tester or improvised means, you should weigh the validity of this action. If the washing machine is under warranty, unauthorized interference with the operation of the unit will be grounds for refusal of warranty service by the seller or manufacturer.

Sequencing:

  1. Unplug the power cord from the outlet.
  2. Remove the top panel by removing the two small screws located on the back wall and sliding the panel back and up.
  3. Find a sensor cantilevered to one of the walls of the housing.
  4. Remove the connector, release the fastening (screw), and remove the sensor hanging from the tube from the machine.
  5. Using pliers, open the clamp on the supply tube and remove the device.

Before checking the adjustment of the device using tools, you can evaluate the overall performance of the sensor. To do this, you will need a piece of tube identical to the rubber tube of the relay. Having pulled the device out of the machine, you need to connect it to a short tube, blow strongly into it and determine whether the relay inside the device clicks in response to a change in pressure. If not, the sensor is faulty.

Hardware sensor test

To check the pressure switch of an Ariston, Samsung, LG or Bosch washing machine using a multimeter, you need to:

  • prepare a device for testing resistance;
  • place the multimeter probes on the contacts corresponding to the electrical circuit of the sensor;
  • create pressure in the air tube until a certain relay contact is activated.

If the resistance value does not change when the contact is activated, it means that the sensor must be replaced.

If all stages of the test have shown that the pressure switch of the washing machine is working, you need to additionally check how the tube is attached to it and evaluate its tightness.

Manual sensor adjustment method

If the user of household appliances is not satisfied with the water level that the LG, Ariston or other company’s washing machine draws for washing, it can be increased or decreased by adjusting the relay actuation force. Before making adjustments, you should unplug the washing machine, remove the top cover and disconnect the connector from the sensor.

The pressure switch has three adjusting screws. They are visually identified by the presence of a colored filling compound in the slots. The required screw that controls the primary force is located in the middle of the relay body. The slot of the screw is usually for a Phillips screwdriver, or “star”.

The adjustment must be made on an empty tank. The process occurs in stages with intermediate visual checks of the water level: turn the screw - assembly, connection - test and then based on the results. It is recommended to turn the screw no more than half a turn at a time: the relay contact travel is very small.

It is recommended to check, change, and adjust the water level sensor only if you have basic technical skills and theoretical knowledge; otherwise, you should seek the services of professionals.

Over time, the perfect operation of the cistern may be disrupted.

Malfunctions that arise for various reasons are eliminated in various ways.

Proper adjustment of the tank also helps.

Malfunctions make themselves known in various ways.

In all cases, adjustment of the tank drain mechanism or repair (replacement) of individual parts will be required:

  • Too much water is pouring
  • weak pressure tank human waste is poorly washed off

First you should find out the reasons for unstable operation. After determining the source of the problems, you need to do the following:

  • adjusting the lever, setting it to the required position
  • complete replacement of the defective part (shut-off valve, float)

To determine the cause and perform one of the listed actions, you must first turn off the water supply and empty it. To get to the drain mechanism of the tank, you need to remove the cover and carry out all the required work.

Before adjusting the water level in the toilet tank, you should eliminate or exclude any reasons due to which the mechanism does not work properly (accumulated debris, gasket defects, failure of fittings, etc.).

It is necessary to adjust the water level in the following cases:

  • There is not enough water drained from the tank to flush out the sewage
  • water continuously flows into the toilet, begins to flow immediately after filling the tank, the flowing water constantly gurgles, the process is accompanied by regular turning on of the water supply
  • repair or replacement of drain fittings was carried out
  • it is necessary to optimize the amount of drained water

We need to find out the reasons for the malfunction. For example, if the overflow tube is installed incorrectly (its upper edge is too low), it is necessary to adjust its height. It may be necessary to replace the tube with one that matches the tank.

Correct installation of the overflow will eliminate the problem.
The float mechanism is responsible for filling the tank with water. Its malfunction (it is skewed, a crack has formed, the membrane has stopped functioning) leads to failures in the proper operation of the drainage system.

If the shut-off valve no longer allows water to flow through or in other serious cases, a complete replacement of the fittings is required.

There are a number of reasons why the proper operation of the drainage system is disrupted, as well as ways to troubleshoot:

  • Initially incorrect adjustment or misadjustment during operation of the float valve requires setting the valve locking to the required level
  • Over time, the gasket wears out and simply needs to be replaced.
  • During operation, debris accumulates between the valve and the gasket (appears from the water supply system, fragments of broken fittings) or deposits (from hard water, if the operation of the valve is disrupted, it does not close, and the tank periodically remains empty), debris with deposits should be removed, it is necessary to ensure a tight fit of the gasket to the seat
  • the float has deviated and does not move strictly vertically, for example, if the valve is not securely fixed and has turned, return the valve to the correct position and securely fix its fastening
  • the float may jam (stick) on the guide, often it is enough to clean the parts (guide, float itself) and everything will work correctly
  • if individual parts, plastic parts of fittings break, they should be replaced;
    The seal of the float may be compromised (a crack or chip appears), then it is better to replace the float (or the entire mechanism)

Features of adjustment of various types of float valves

Two types of drain designs are common depending on placement:

  • mounted on a lever
  • moves along guides up and down

In order for the float to perform its functions correctly, it is connected to other parts of the system:

  • lever or plastic wheel (depending on the type of design)
  • piston
  • membrane valve

There are different designs of tanks, but their operating principle is similar:

  • when you press the drain, water leaves the tank and the float drops
  • going down, the part pulls a lever that acts on the piston
  • in the process, the piston opens the valve and water begins to flow into the drain tank
  • water fills the tank, and the reverse process occurs when the float floats up, acts on the lever, and the piston rises and stops the flow of water

The mechanism of the flush tank is designed so that it is possible to adjust the volume of incoming water. To do this, you should adjust the position of the lever, or rotate the plastic wheel (in different toilet designs). In this case, the float moves to the required level. If it is located higher, more water will flow into the tank, and vice versa.

There are floatless designs that use a special adjustment screw. When setting the level, loosen the locknut and move the regulator closer to the valve to reduce the amount of water. It is equally important to know how to adjust the water pressure in.

With this structure, the float is mounted on a lever. This design is located in the drain tank from above. The float is an important element in the system that must be adjusted correctly. The cistern works correctly when the required amount of water flows in and does not overflow.

Features of adjusting the float lever depend on what material the part is made of:

  • brass should be bent, establishing the required position, raising it, lowering it
  • plastic is installed with a fixing screw and secured in the required position with a ratchet

By correctly adjusting the float, you can solve the problem of water constantly flowing into the toilet and optimize its volume in the tank.

Float on vertical guides

In modern tanks, the float element has the shape of a glass. This design is resistant to water. Thanks to this structure, the service life of the entire mechanism increases. This type of float can become clogged during operation. This may cause the tank to not work properly.

The glass-shaped float moves vertically and acts on the piston through traction. This design is located inside the toilet cistern, at the bottom. It is considered the most convenient when adjusting water flow. This system is less noisy.

The float is located on an axis along which it moves up and down using a special wheel. The design provides the ability to fix it at a certain height. This is as simple as adjusting a toilet cistern with two flushes. This feature makes it possible to set the volume of water drained, for example, to save money. The position of the float determines the level to which the tank is filled.

Adjusting the toilet tank - on video: