How to replace the thermostat on a water heater. Thermostat for a water heater: operation of the device, troubleshooting, tips for efficient operation

On this moment One of the current purchases for the home is the purchase of a water heater (boiler), which is explained by the enormous popularity autonomous heating and hot water supply.

The prerequisites for this process were an increase in costs by centralized hot water supply and the ability of people not to depend on the hot water supply schedule, which is especially important in summer period in our country.

Purchasing a water heater is not as simple a process as it might seem at first glance. Buying a boiler requires care and attention in order for the device to serve effectively and for as long as possible, without causing the owners much trouble.

Types of thermostats

The boiler itself is quite simple. You can even install and connect the device yourself. But when choosing a unit, you need to pay attention to what kind of thermal relay is installed in it. For example, if it has temperature control or lacks it. Exists several types of thermostats, on the basis of which water heaters are divided into several types:

• Programmable or simple. This affects temperature management.
• Electromechanical or electronic. The control of the device depends on this.
• Mortise or overhead. The installation of the unit depends on this.

Most common rod, electronic and capillary thermal switches. Rod models are obsolete and consist of a tube 35 cm long and 1 mm wide. Their operating principle is as follows. When exposed high temperature the tube expands in size, causing pressure on the switch. The disadvantage of this model is its inaccuracy. Because the tube cools too quickly, the boiler runs longer than necessary.

The operating principle of the capillary thermostat is more modernized. A capillary thermostat is a tube containing cylinders filled with a liquid that differs in density from water.

As the temperature rises, the liquid filling the cylinders of the capillary thermostat increases in volume and begins to put pressure on the membrane and the switch. The error in the discrepancy is 3 degrees.

Electronic thermostats are the most common models and the most accurate. The advantage of this model is in direct interaction with the protection relay. Thanks to its presence, an emergency automatic power shutdown is carried out in the event of a lack of liquid in the tank.

Thermostat for water heater

The thermostat provides safe work water heater. This process is explained in the following way: When the water temperature rises, the pressure inside the tank, which is sealed, increases.

When the increase in pressure is not controlled, then all the structure will explode, which is dangerous not only for equipment and surrounding objects, but also for human health, if a person is nearby during the explosion.

The thermostat allows you to keep the temperature at required level. Bottom Line: Temperature Controller protects against explosion, overheating, damage to equipment and property, ensures the safety of people.

Most manufacturers try to equip the boiler with a thermostat, because this is what controls water heating at the moment when the device is connected, and for timely blocking of the heating element.

Available on the market a wide range of models, but the principle of operation is the same for all of them. At the moment when you need to connect the device to the network, you need to immediately adjust the water heating level, which is done using the control panel, which is located on the body.

Next you need to adjust the water heating. The relay that is installed on the thermostat will be responsible for opening the contacts of the heating element. When the tank has completely cooled down, the temperature will drop and become lower than normal. In this moment the contacts will close The heating element of the relay, due to which the system will start again and the liquid in the tank will begin to heat up again.

Replacing and connecting a thermostat for a boiler

If the water heater does not work, it should not be restarted. If it does not start, it means the unit is not working! And you shouldn’t expect it to suddenly turn on; you need to check for problems. If it is determined that the problem lies in the thermostat, it must be replaced. The main thing is the ability to choose the right device and install it correctly. Both online resources and consultants in a store or market will help you figure this out.

To replace the thermostat, you must perform the following manipulations:

• disconnect the boiler from the power supply;
• shut off the water supply to the tank with a special valve;
• drain all the water that is there from the tank;
• remove the bottom panel of the device, this will allow you to get to the heating element;
• remove the pressure ring located on the heating element;
• remove the sensor in the thermostat and the control unit;
• install a new regulator;
• return the pressure ring to the heating element;
• Replace the bottom panel of the device.

To purchase the necessary new thermostat for your boiler, you must adhere to the recommendations of specialists. When going to a retail outlet to buy a regulator, you need to take with you the technical passport of the device. With it, it will be much easier for the sales consultant to figure out which model and with what characteristics you should choose.

When purchasing a thermostat yourself, you must remember that it must be the same model, as it was before. Even the smallest difference can lead to failure of the entire water heater. You need to buy a thermostat taking into account the type of product, parameters, installation methods, what operating current and functionality it has.

Common thermostat problems

Any device, even the most reliable and expensive, fails over time, which is facilitated by many different factors, both internal and external. Breakdowns that require close attention:

If you do not have knowledge and skills in working with thermostats and connecting them, then it is better entrust this issue to specialists. This will allow, on the one hand, to relieve you of unnecessary doubts and worries, and on the other hand, to ensure correct work unit and the safety of others.

The thermostat for the water heater plays the same important role, like a fuse in any electrical network. The user sets the required water temperature in the water heater, and the thermostat maintains it. That is, it allows the heating element to work until the water temperature reaches a set value.

Then the heating element stops working. The water temperature decreases (forced or naturally) and the thermostat again gives a signal to the heating element to begin its direct duties.

Separate, specially designed types of thermostats have additional function– turn off the power supply to the heating element if the latter breaks down. This avoids the possibility of electrical shock, which often happens with ungrounded boilers.

Types of thermostats

Today, many types of thermostats have been developed, but if we talk about devices specifically for boilers, the three most successful are:

1. Rod. Such a thermostat is represented by a tube of small diameter (usually up to 10 mm) and short length (no more than 35 cm). The operating principle is based on the elementary laws of physics: when heated, the tube expands linearly, which allows you to press the switch. Such thermostats have long been the most common in boilers. However, their accuracy left much to be desired - when hot water left the water heater, the incoming cold water instantly cooled the thermostat due to the latter’s close location to the inlet cold water. Thus, the boiler could work beyond the allotted time, and this significantly affected financial costs.
2. Capillary. A more progressive type of thermostat, also working according to the laws of physics. The tube in which the temperature-sensitive cylinder with liquid is located is usually made of a material that cannot be oxidized over a long period of time. Inside the cylinder there is a liquid that has a different density from water. When heated, the density of the liquid changes, the volume changes accordingly, and the liquid presses on a special membrane, which turns off the power. Such thermostats are more accurate when compared with rod thermostats. The temperature deviation is approximately 3°C.
3. Electronic. More modern type and, accordingly, more accurate. It usually works in tandem with a protective relay - if the boiler is empty when voltage is supplied to the heating element, then the protection will work and turn off the power.

According to another classification, all thermostats can be divided into:

1. Electromechanical and electronic. The first type works due to bimetallic elements, the second - thanks to electronic special sensors.
2. Simple and programmable. In the first type, the temperature is set manually mechanically. The second type is more precise in its work.
3. Overhead and mortise. For boilers, the overhead type is most often used if the control is electronic, and the mortise type if the control is mechanical.

Another interesting option– thermostats designed for indirect heating boilers. Such boilers allow you to heat water using only power for heating device, which means there are significant savings. But circulating in heating system the liquid cannot heat above a given level, while for a boiler the consumer may need a different temperature (and most often this happens). In this case, you should buy a thermostat specially designed for this purpose.

Having carefully studied the articles on self-production, you can try to make a thermostat yourself.

Malfunctions and their solutions

The thermostat for your water heater may fail. Unfortunately, such phenomena are not uncommon, but there is nothing fatal here. Firstly, as a rule, there is no repair - a thermostat that has worked faithfully is thrown away and a new one is bought. Buy the same or with a different resistance - the choice is up to the consumer. Secondly, with proper operation of the water heater, thermostat breakdown can be avoided or, in extreme cases, its life can be significantly extended.

How does a consumer notice a broken thermostat? As a rule, this is the most common method - the water is not heated in the boiler. In this case, there may be either a malfunction heating element, either a malfunction of the thermostat itself, or (less commonly) a malfunction of both elements. To check the latter, its resistance should be measured.

If during testing the picture on the display of the test device does not change, you need to buy a new thermostat. It's not that much money, so there's no need to grieve. Another option for testing the thermostat is possible: measuring the resistance when the thermostat itself heats up. If even then the test device does not show any changes, that’s it, now it’s time to go to the store.

How to choose

Typically, a faulty thermostat can be replaced with a similar one in shape and operating principle. However, if it is possible to buy and install another thermostat and there is an urgent need for it, then why not. The main thing is to be able to choose correctly the required device and install it. Although here, too, the consumer can be helped by the Internet or a consultant at the point of sale.

But we should not forget: any independent actions without certain knowledge and strict adherence to safety rules can lead to a very unpleasant outcome.

It would seem that the heating element or volume should be important in a boiler, but, as it turned out, the thermostat and its role cannot be neglected. By setting the desired temperature and protecting the boiler from overheating, the thermostat is extremely important in the operation of the heating device.

In household storage boilers A capillary thermostat is used as a temperature sensor - the device is quite unpretentious, however, in my case, after three years of use, it died out for a long time. The search for a similar one in our area was not successful, so the question arose about an electronic regulator - as simple as possible and, if possible, reliable. I started surfing the Internet, and one of the first I came across was a well-known scheme:

In preparation for her practical implementation, I found an article on the Internet: “A simple thermostat based on an adjustable zener diode TL431,” which was accepted for implementation.

My modified version:

Differences from the original scheme:

• Thermistor – rated 22 kOhm.
• Variable resistor – 33 kOhm. Since I don't need a wide range of the regulator, I deliberately moved it towards a higher temperature, in return for a smoother adjustment.
• Instead of the 7805 stabilizer, its Russian analogue KR142EN5A was used.
• The manual mode toggle switch has been replaced with the KM1-1 button.
• The complete starting block is used as a load switch
• IEK KMI-22560, in the housing of which the circuit was mounted.
• Power supply 220/12V - converted from a power supply unit from Sega. I stabilized the 12-volt voltage, so to speak, with a reserve; theoretically, you can do without it. If you decide to leave it, then instead of a transistor and a zener diode you can use KR142EN8B. Alas, I didn’t have it on hand.

In place of the “stop” button there is a neon indicator connected in parallel to the contacts of the intermediate relay, signaling the Standby mode. On the front side, through the hole, the KL102 LED is visible - an indicator of power supply to the control board. The SG-5 connector is used to connect 12-volt voltage and a temperature sensor.

Inside view:

A variable resistor installed on the side of the printed conductors simultaneously plays the role of a printed circuit board holder.

Now – about the temperature sensor itself. The fact is that in storage boilers there is a special sealed tube on the bottom side, approximately half the height of the tank (the actual length of the tube depends on the capacity of the boiler). It is into this that the capillary rod of the standard regulator is inserted. I did the following: I took a piece of PUNP 2x1.5 wire, 60 cm long. Having removed the outer insulation at a distance of 45 cm, I wrapped one of the wires with a thin strip of FUM, which is used in plumbing. Next, having soldered the thermistor leads to the conductors and insulated the soldering points, I wrapped the entire structure with FUM - from the thermistor to the rest of the insulation. One edge was treated with tsapon-varnish, and a terminal block was attached to the second:

Having inserted the resulting temperature sensor into the tube, I fixed it at the outlet with electrical tape:

The temperature sensor was connected to the circuit with a shielded wire to eliminate possible interference. Do not forget to also close the contacts that were connected to the old sensor, otherwise the heater circuit will remain open

Assembled view:

Perhaps not entirely aesthetically pleasing, but quite functional. Two months of operation showed that the scheme works in normal mode, no trigger effect is observed, the accuracy of operation is noticeably higher than that of its mechanical counterpart.

When implementing the scheme, I was guided by the principle of “minimal intervention” - i.e. if necessary, everything can be quickly returned to normal. But I don't think I will need it.

Maxim Taranets, Kartaly 2016

The thermostat for a water heater is one of the components of the boiler protection system (the second is safety valve). It is needed for convenient operation - thanks to it you can always find out how much stock is currently in the container.

The thermostat also controls the heating process and prevents overheating. If it fails, it needs to be replaced. We can say that this is an element that stops the action of the heating element (heating element) when the temperature has approached the established limits. In the event of a breakdown, the temperature will begin to rise and enormous pressure will form in it. After some time this may lead to an explosion.

That's why correct operation in general, and also individual parts, will save your money and ensure safe use. It is for this purpose that this article will reveal the principle of operation, types, technical problems, diagnostic methods and tips for effective operation.

Principle of operation

Externally, they may be very different, but basically their operating principle does not change much. The main part is the heat-conducting rod. It expands when heated and sets in motion a system of contacts, which in turn disconnect the heating element from the network. As the rod cools, its length gradually decreases. Then the thermostat transmits a signal to the heating element, which will soon put the heating element into action again. The temperature that the regulator must maintain is set by the user himself in accordance with his needs.

In short it can be described as follows:

• Setting the desired temperature level using a lever, button or switch
• Measuring temperature and turning on the heating element if necessary
• When the desired division value is reached, the heating element turns off
• after cooling, the thermostat starts working again and heating starts again

Today, there are devices that have an additional function - turning off the electricity supply to the heating element in the event of a breakdown. Thanks to this, the safety of use is increased and the risk of electric shock is prevented.

Main types

There are heating elements different power. The more powerful it is, the more intensely the liquid inside is heated. Moreover, the thermostat is exactly the part that is the basis. If you have chosen everything correctly specifications and conscientiously follow all the rules for its operation, the water heater will serve for a long time without unscheduled cleaning. So what are they like?

Rod

It consists of a steel tube of small diameter (up to approximately 10 mm) and length (about 25 to 45 cm), which depends on the volume and power of the heater. This thermostat is placed in the heating element tube and it works according to the elementary laws of physics. As the tube heats up, it expands linearly, allowing the switch to be pressed. However, their main drawback– inaccuracy and high cost of use. When hot water leaves the tank, the incoming cold one cools the thermostat very quickly. For this reason, the boiler heats up more than it actually needs, and this increases electricity costs and shortens the service life of its parts.

Rod apparatus

Capillary

This type is considered more progressive. It consists of a polyester body that does not oxidize for a fairly long time. It has a built-in switching device (thermal regulator). Its operation occurs on the principle of the volume of expansion liquid in a capillary tube (the same physical law as in the previous one). The expansion liquid inside the cylinder, which differs in density, changes its density when heated, after which it acts on the installed membrane and turns off the power supply. Compared to rod devices, such devices are more accurate in their readings and, as a result, more economical.

Electronic

Electronic is the most modern type, which means the most accurate and safe.

In turn, they come in two types: safety thermostat and control thermostat. If it is empty at the moment when voltage is supplied to the heating element, then the protection will turn on and turn off the power.

Other types

1. Electronic and electromechanical. The first works thanks to special electronic sensors. The second is due to bimetallic elements.
2. Simple (the required degrees are set manually) and programmable (higher accuracy).
3. Invoices (if electronic control are used most often) and mortise (more intended for mechanical control).
4. Designed for boilers with indirect (indirect) heating. They will significantly save your money because they heat water using only power for the heating device. But the liquid that circulates in the heating system cannot heat up above the level that was initially set.

The most common breakdowns

How to detect and eliminate:

• The water is too hot (this may occur due to the failure of the structure that performs the regulating function)
• Failure in copper capillary tube. This part itself is very sensitive to various kinds mechanical damage. Unfortunately, it cannot be repaired, only a new one can be installed.
• The adhesion of the heating element and electrical connectors is insufficient.
• The thermostat turns on and off very often (the reason is excessive scale formation, which exceeds the permissible limit).
• The water is not heated enough, although the power of the heating element is very high (this occurs when the adjustment is incorrect)
• Malfunction of electrical components (most often this is due to voltage fluctuations in the electrical network; you need to install a means that will provide uninterrupted power supply or a voltage stabilizer)

Diagnosis of failure and selection of a new device

It is quite simple to detect damage in a timely manner in order to avoid unnecessary expenses and maintain your health. What can be detected even with the naked eye is that the water has stopped heating. To check its functionality and serviceability, remove it from the heat exchanger itself, and then put it to measure resistance (Ohm). A special tester is used for this. If the tester does not show any reaction (no changes occurred on the device screen during testing), then we can conclude that the device is faulty and needs to be replaced with a new one. Thermostats cannot be repaired.

A water heater thermostat is a special regulator that automates the operation of the boiler. Only this unit “knows” what temperature the water should be heated to and when to turn off the boiler from the network. Therefore, the thermostat not only controls, but also automates the operation of the water heater.

In addition, this block is a kind of “fuse” that saves not only the owner’s wallet, but also the integrity of the water heater itself and the structure being serviced. After all, extra “degrees” are not only extra “kilowatts” that increase the electricity bill. Overheating can “burn out” not only the water heater, but also the building itself where it was installed.

In short, a thermostat for a water heater is a mandatory component that must be present in every boiler. After all, without such a device, any boiler is just a huge “boiler” built into a storage tank. But such a combination does not guarantee either effective work device, nor the safety of the owner.

Therefore, in this article we will look at the operating principle, typical range and methods of replacing thermostats for boilers.

How does a thermostat work?

Tubular electric heater – heating element – ​​with thermostat for water heater accumulative type reduces the energy consumption of such a device, ensures the safe operation of the pressure tank and automates the entire process of operating the boiler.

Such results are explained by the operation of only one component of the boiler design - the thermostat.

After all, this element functions as follows:

• When the water is heated to the “required degree,” the temperature relay of the regulator opens the contacts of the tubular electric heater.
• After the temperature in the storage tank decreases, the relay “turns on” the contacts and the heating element begins to heat the water.

As a result, the boiler stores a “reserve” of water heated to the desired temperature. Moreover, in an empty boiler tank, the relay should turn off the power to the heating element, triggered by the temperature of the heating element. Therefore, this element is mounted on the same console with the electric heater.

In addition, the thermostat prevents the water from boiling for a very long time, increasing the pressure in the tank. That is, this regulator also works as a fuse, preserving the integrity of the water heater and the life of the boiler owner. After all, the steam formed after the liquid boils can rupture the boiler body, turning a peaceful water heater into an almost military explosive device.

Typical types of thermostats?

IN modern boilers three are used typical varieties regulators, namely:

This is the cheapest and, until recently, the most common type of regulator. This thermostat operates on the basis thermal expansion A 40-centimeter rod, the dimensions of which increased as the water temperature increased and decreased as the liquid cooled. Moreover, the “increased” rod turned off the power to the heating element, and the “reduced” rod turned on the heating of the water. The first regulator of this type was a thermostat for a Termex water heater. However, such a device did not serve as the standard for thermostats for very long. It quickly became clear that when cold water is supplied to the boiler tank, the rheostat rod decreases in size, activating the heating element to boil already decently heated water.

Therefore, rod rheostats are gradually going out of use, remaining on the market only as a spare part for older boiler models.

The cost of such a thermostat is 400-1500 rubles.

for a storage type water heater, this is a more advanced type of rod detector. This regulator operates based on the same thermal expansion. Only in this case, it is not the rod that changes in volume, but the liquid sealed in the tube, “pressing” the on/off switch of the heating element.

With the help of such a design solution, it is possible to eliminate the problem of “zeroing” the signal from the thermostat sensor in the case of cold water being supplied to the tank. Therefore, everyone is still equipped with such devices. budget models boilers.

The cost of a capillary regulator is up to 3,000 rubles.

This is the most advanced model of the regulator, equipped with two sensors that monitor the water temperature and monitor the fact that the heating element is overheating. The electronic regulator works based on changes in sensor resistance under the influence of increasing temperature.

Moreover, by controlling the dielectric properties of the active element of the sensor, you can control the operation of the boiler, “programming” heating and cooling with an accuracy of a couple of degrees. As a result, electronic versions of the thermostat ensure maximum energy efficiency of the boiler.

Having purchased a water heater with electronic thermostat, you will save on your energy bills. However, the side regulator is not cheap.

For example, for electronic thermostats for Ariston you will have to pay up to 9,000 rubles.

Replacing the water heater thermostat

If the water heater is under warranty or your manufacturer has offered a sufficiently long period free service, then it is better to leave it to professionals to replace the thermostat.

If the warranty and free service period have already expired, then you can try replacing the thermostat yourself.

To do this you need to do the following:

• Disconnect the boiler from the network.
• Shut off the “cold” pipeline, stopping the water supply to the heater tank.
• Drain the water from the boiler by opening the “hot” valve of the nearest tap.
• Remove the bottom cover of the housing, exposing the mounting pipe of the heating element.
• Dismantle the pressure ring of the heating element.
• Remove the thermostat sensors and remove the control unit.
• A “fresh” thermostat is installed in place, selected according to the boiler’s data sheet or the manufacturer’s recommendations.
• Reinstall the pressure ring and cover.

Finally, close the tap, turn on the cold water supply, check the tightness of the joints and plug in the boiler.