In detail: DIY repair of a water heater thermostat from a real master for the site my.housecope.com.
The water heater thermostat is an automatic boiler heating controller that controls the heating limit and the minimum temperature at which the water must be heated again. Formally, this is a conditional fuse that is triggered to turn off when the water has reached the maximum permissible heating temperature, and to turn on when it has cooled down. If there is no such fuse, the water heater is a sealed container with a boiler that will heat the water until it explodes or fails.
The presence of a thermostat allows not only to always keep the boiler ready for operation, but also reduces electricity costs.
The energy intensity and safety of any storage boiler depend on a thermostat that automates the process of its operation.
The basis of its work is to open the contacts of the heating element when the water reaches a given temperature, and when the latter cools, the tubular electric heater is turned on. The relay also responds to the lack of water.
The main task of the thermostat is to control the heating / cooling. On the one hand, it prevents the water from boiling for too long, increasing the internal pressure in the tank proportionally to the time. On the other hand, it keeps the boiler in constant readiness, so there is no need to wait until the water heats up and you can start bathing procedures.
Advanced thermostats can provide additional signals. For example, if a heating element or other element breaks down, the device is forcibly disconnected from the power supply. The same happens if the heating element does not cope with its functions due to scale. In the latest models, the error code is indicated on the display, and therefore it is easy to determine the cause of the breakdown.
Video (click to play).
Currently, there are several types of thermostats, among which 3 main ones can be distinguished:
The most popular and most obsolete on the market today. This is a tube of minimum diameter, which works according to the laws of physics - when heated, it expands linearly and presses on the switch, when cooled, accordingly, it contracts, and the heating element turns on.
The disadvantage of this design is the inaccuracy of the work associated with the location close to the water supply.
The storage boiler is designed in such a way that when hot water comes out, cold water immediately begins to flow into the tank so that the water level is the same all the time. Considering that the rod thermostat was located near the cold water supply, it did not even have time to expand to the required size. Cold water instantly cooled it down, and the boiler worked almost non-stop during its use.
A more modern and therefore thoughtful way of thermoregulation. At the base is the same small-diameter tube in which the capsule with contrast liquid was located. When the water was heated to a certain temperature, the structure of the liquid and its volume changed, as a result of which the relay was triggered on shutdown. When the water was cooled below a predetermined level, everything happened the other way around - the liquid decreased in volume, and the relay was already activated. The permissible deviation in water temperature is + - 3-4 degrees.
The most convenient and accurate type of thermostats that respond to a specific water temperature. Moreover, a protective relay is provided here, which opens the power supply circuit when there is no water in the tank.
According to their technical characteristics, thermostats are divided into:
electronic and mechanical - in the first version, bimetallic elements are triggered, in the other - an electronic temperature control sensor
programmable and mechanical - in the first version, a specific temperature is set, in the second it is triggered either for boiling, or the maximum bar is set manually;
overhead and built-in - with electronic control, the first option is used, with mechanical control - the second.
It is noteworthy that thermostats are designed not only for individual storage water heaters, but also for indirect heating. It is not very convenient, although very economical. Water in this case is heated from a certain heating element, without interfering with its main functions. Of the minuses - the coolant also heats up to a certain level, respectively, there will never be hot water with indirect heating. If you like to take a cool shower and want to save money, this will be the best option.
Unfortunately, any structure tends to break, and the thermostat is no exception. As a rule, such devices are not repaired, preferring to buy a new one, similar or with increased resistance. But if you use it correctly and follow the elementary rules, its service life will be much longer than the warranty.
The main malfunction is that the water stops heating. In this case, there are 2 options - the heating element is out of order (you will learn how to clean the heating element and replace the magnesium anode in the article "Why and what is a magnesium anode in a water heater for"). The second option is a thermostat breakdown. In order to check this, measure its resistance. If there are no changes on the test device, it's time to go to the store for a new thermostat.
There is no sense in repairing a thermostat; moreover, this requires special knowledge. It is much easier, faster and cheaper to buy a new one and deliver.
when purchasing a new one, be sure to show the seller the data sheet for the water heater - you will be selected the model that is right for it;
do not throw out the relay first, and then buy it. Each unit has a special marking that will allow you to choose, if not identical, then exactly suitable for a specific model;
when choosing a device on your own, take into account the dimensions, current and resistance, functional characteristics.
Ideally, if the manufacturer offered more favorable terms of cooperation, for example, increased the warranty period, and then the replacement process should be entrusted to professionals.
According to the well-known law, breakdowns of household appliances and electronics in 99.99% of cases occur at the moment when the warranty expires.
If you have run out of warranty and free service, you can do the following:
Disconnect the water heater from the power supply by pulling out the plug from the socket.
Shut off the cold water pipe (a supply tap is provided for this).
Drain all the water, for which first open the hot tap, then unscrew the bottom and unscrew and remove the protective cover and let the remainder drain.
Unscrew the nuts, remove the flange and the heating element clamping ring. We remind you about the need for a bowl for collecting water, it will continue to flow.
Pull out the thermostat sensor and disconnect the control relay.
Install a new thermostat on the boiler, return the retaining ring and screw on the cover with a Phillips screwdriver. It is advisable to photograph the whole process in order to avoid mistakes.
Turn on the water supply and control the boiler for 2-3 hours for the tightness of the lid and the tank as a whole, and then operate it as usual.
How to replace the thermostat - on video
An electric boiler is an effective solution to the problem of hot water supply for a private house. Such equipment, however, like any other, breaks down periodically.
If serious breakdowns have to be eliminated in a service center, then any more or less experienced craftsman can perform a small repair of the water heater with his own hands.
To minimize problems with the device, you should study its design and principles of operation. Usually, in private households, not flow-through, but storage models are used, which make it possible to use electricity more efficiently. Such a device consists of a heat exchanger tank, inside which a heating element is installed - a heating element, connected to the power supply.
An important part of the device is the thermostat. This element allows you to maintain a constant water temperature inside the storage tank. The water is piped to the heat exchanger. If its temperature is too low (and this is usually the case), then the thermostat gives a signal and turns on the heating element.
The water is heated until it reaches the required temperature. After that, the thermostat works again and turns off the heating element. Hot water is taken from the tank and replaced with cold water, the heating process is repeated over and over. This is a general diagram of the device and operation of a conventional storage water heater.
Flow models are arranged somewhat differently. They do not heat a static volume of water, but a stream. They use more powerful heating elements that start working when the water is turned on and stop when it is turned off. To study in more detail the operation and structure of a particular model, you need to carefully familiarize yourself with the accompanying technical documentation.
The heater tank is a sturdy stainless steel container, one or two millimeters thick. No matter how resistant this material is to corrosion, nevertheless, these processes periodically arise and develop, which leads to the flow of water from the device. One of the most common causes of such breakdowns is electrical corrosion.
To prevent it, you need to regularly, i.e. Replace the internally mounted magnesium anode annually. This element is designed specifically to prevent electrical corrosion. Over time, it wears out, and the owners of storage tanks lose sight of replacing this important part.
As a result, the tank, which has served well for some time, suddenly starts to leak. The incorrect state of the magnesium anode can also affect the state of the heating element. The outside of the storage tank is usually enclosed in a metal or plastic housing, and it also has a heat-insulating shell that prevents heat loss.
Damage to the outer shell and insulation is rare, usually due to careless handling of the device. Cracks and chips on the body of the water heater may not disrupt its operation, but this will lead to a deterioration in the properties of the heat insulator, and will negatively affect the functioning of the device as a whole.
Cold water inlet and outlet pipes - for hot water usually do not cause any problems if the installation of the heater is done correctly. Usually, a water heater is equipped with two thermostats, one of which is designed to control the water temperature, and the second monitors the state of the first device.
Sometimes a third thermostat is also used, which determines the good condition of the heating element. In any case, the broken thermostat will have to be completely replaced. There are capillary, rod and electronic types of thermostats. Their design is different, but the principle of their work is the same.
The insulating gasket not only serves to seal the connection between the elements of the water heater, it is also necessary as an electrical insulator. It is recommended to replace this element regularly at every maintenance of the water heater.
The thermostat shows exactly what temperature the water inside the device is heated to. If this element breaks down, the water heater will still perform its functions, although data on the degree of heating will not be received.
Breakdown of heating elements is a typical problem for both flowing and storage water heaters. This element works under high stress and therefore wears out quickly. If the power supply is connected, but the water in the tank does not heat up, most likely the problem has arisen with the heating element.
First, you should check if electricity is supplied to the heating element and the thermostat. In the places where the cable is connected, the presence of voltage is checked with a tester. If there is no voltage, you may need to replace the cable itself or check for a power outage throughout the house.
If there is electricity and the cable is working properly, then problems have arisen with the heating element, which will have to be replaced, or with the thermostat. To figure out what exactly broke, you need to remove the thermostat and check it with a tester. Testing the health of the heating element is carried out as follows. First, the measuring scale of the device is set to the interval of 220-250 V. Then the resistance is measured at the terminals connecting the heating element to the mains.
If there is voltage, disconnect the heating element from the network and check the potential at the terminals of the heating element. Lack of response from the tester will indicate that the device is defective. If there is a reaction, you need to continue the diagnosis. First, disconnect the water heater from the power supply. Then the heating element is disconnected from the thermostat so that the contacts of the heating element remain not isolated.
Tester contacts are applied to them and the reaction is monitored. If it is, the heating element is working, if not, it needs to be replaced. In this case, it does not matter what kind of numbers the tester produces, only the presence or absence of a reaction is important. These troubleshooting methods are suitable for both storage electric water heaters and flow-through models.
To check the serviceability of the thermostat removed from the water heater, you need to set the adjustment knob to maximum and measure at the inlet and outlet of the device. If the needle of the tester remains calm, i.e. its position does not change, which means that the thermostat is faulty and needs to be replaced.
If the arrow deviates, then you need to continue testing. Now you should set the minimum position on the thermostat and attach the test leads of the tester to the contacts. It will not be easy to continue the diagnosis alone, the probes will have to be fixed or asked someone to hold them in the correct position for a while.
After that, you need to take a lighter and heat the tip of the temperature sensor. If the thermal relay is triggered, the circuit will open, and the resistance on the tester's scale will sharply go down, then the thermal relay can also be considered serviceable. If the system does not respond to heating, then this element is damaged and needs to be completely replaced.
Occasionally, the water heater can stop working due to a blown thermal fuse as a result of dangerous overheating of the device. It is enough to correctly adjust the operation of the device for it to start working as usual.
If the check showed that both the heating element and the thermostat are in good order, most likely problems have arisen with the control board. It is almost impossible to repair such an element at home. It will have to be replaced with a new one, and you will have to use the help of a specialist who will help you set up the electronic equipment. Most often, you just need to contact the service center, where the required element will be selected and installed correctly.
A tank leak is a serious problem that cannot always be corrected on your own. In some models, either the tank or the entire heater will need to be replaced. Sometimes the leak can be sealed, but care must be taken to restore the integrity of the outer casing and the thermal insulation layer. Usually such measures are insufficient and short-lived, and soon the leak will reoccur.
The water heater tank most often leaks if:
damage to the internal tank has occurred;
the heating element has deteriorated;
leaky gasket.
If water flows at the place where the heating element is attached, it may not be necessary to repair the tank itself. A special gasket is installed in this place, the leak can be caused by its damage. The gasket is replaced and thus the problem is solved.
A water heater tank leak usually occurs due to neglect or untimely maintenance, which also includes the replacement of the magnesium anode. Another common problem is lack of grounding. This can also lead to the development of corrosive processes and the occurrence of leaks.
If you need to replace the gasket or heating element, it is best to first dismantle the faulty element in order to take it with you and find an exact analogue. Obtaining parts by eye can result in unnecessary costs. This replacement is relatively straightforward. But if problems arise with the tank, you will at least have to contact the service center. Immediately it is necessary to find documents for the water heater and clarify the warranty periods and service conditions.
Regardless of the nature of the breakdown, before starting repair work, you first need to turn off the power supply, remove the protective cover, disconnect the wires, pipes and drain the water. Wall-mounted models are usually removed from the brackets. The protective cover that hides the place for connecting the electrical wires and the fastening of the heating elements may have a different position depending on the model.
On horizontal devices, such an element is usually located on the left, on vertical heaters - at the bottom, and on small models - in front. On some devices, you first need to unscrew the main mounting bolt located in the center. Sometimes this element is hidden under a decorative sticker.
After that, you need to carefully remove the thermostat, and then remove the tubes of the temperature sensor. They must be handled with great care. If the integrity of the thermosensor tube is broken, liquid filler will leak out. As a result, the water heater will simply have to be thrown away and a new device bought.
If there are stickers on the body with the serial number indicated, they must be kept, even if it interferes with the maintenance and repair of the product. This can affect the manufacturer's fulfillment of the warranty obligations, as well as facilitate the work of the service center employees.
The fact that there are problems in the operation of the device may indicate some changes in the mode of its operation. For instance:
increasing the time for heating water to a predetermined temperature;
the appearance of unusual sounds accompanying the operation of the device;
the appearance of impurities in tap water, a change in its color, smell or taste.
If at least one of these signs is observed, the water heater should be cleaned immediately. To do this, you will have to perform the following operations:
Disconnect the device from the power supply.
Remove the protective cover.
Disconnect the contacts of the electric wires.
Shut off cold water supply.
Remove residual water from the tank using a hose.
Unscrew the screws that hold the heating element.
Remove the heating element and descale it.
Clean the inside of the drive from dirt and scale particles.
Rinse the device thoroughly.
Check the health of the magnesium anode.
If necessary, replace this element immediately.
Wait until the cleaned tank is completely dry.
Install the heating element in place.
Reassemble the device.
Check the tightness of all fasteners.
Connect the water heater to the power supply.
Check for grounding.
The heating element should be removed from the tank carefully, the bolts may be too stubborn, sometimes the heating element is difficult to remove due to too much scale layer. The heating element is cleaned by mechanical or chemical means, as is the removal of contaminants from the tank.If a large amount of scale is found inside the device, you should consider revising the operating mode of the water heater.
This phenomenon is often observed when the device has been operating at maximum power for a long time. It is recommended to set the maximum heating temperature not higher than 60 degrees in order to increase the life of the device and reduce the number of breakdowns. If the body of the heating device shocks, it is possible that the heating element is deformed and ruptured, or there is a breakdown in the control system.
A detailed video on diagnostics of the condition, maintenance and self-repair of domestic water heaters can be viewed here:
