Filling and draining a wall-mounted storage water heater. Water heaters for a summer residence - how to make the right choice Gravity instantaneous water heater

Our topic today is the organization of water supply in country house. We will analyze several solutions for different water sources (wells, wells and country water supply) and compare several types of water heaters for hot water supply needs. So, let's go.

Country water supply

Given:

A summer water supply runs through the site or along its border;
Water for irrigation is supplied through it two to three times a week;
We need to ensure a continuous and round-the-clock supply of water to the country house.

You can learn more about how to install a water supply at your dacha in the video in this article.

Scheme with gravity water supply

The obvious solution to the problem is storage capacity. If you install it under the ceiling of a residential floor or in the attic, the water will flow to the water collection points by gravity.

Plus: complete energy independence of such a water supply scheme.

Minuses:

Pressure limited by the height of the tank above the point of water collection;

Help: for work household appliances connected to the water supply, excess pressure is required. For example, an instantaneous water heater will simply refuse to turn on the heating elements if the water supply is less than 0.3 kgf/cm2 (which corresponds to a pressure of 3 meters).

The need to insulate the attic or dump the tank during the cold season;
Large load on the floor with a significant volume of capacity. If you need a water supply of 3-4 cubic meters, place a tank of the appropriate size on wooden floor- a very dubious idea.

Implementation:

The water supply inlet from the country water supply is inserted into the storage tank as close as possible to its lid and is equipped with a filler float valve (the same as those installed in toilet tanks);
The water pipe cuts into the bottom of the tank or into the side wall as close to the bottom as possible. The insert should be equipped with a tap or valve: then to repair the faucet in the house you will not have to dump all the water from the container;
When water is supplied to the country water supply system, the tank is filled, after which the inlet is closed with a float valve. Water flows into the water supply system by gravity when any tap is opened.

Scheme with tank and pumping station

The lower insert, as a rule, has already been made by the manufacturer - a brass pipe under the drain valve is always installed above the bottom of the tank. The hole for the fill valve is drilled with any drill and expanded to the desired size with a sharp knife. Then a brass insert with a nut and rubber gaskets is screwed into it.

Water supply from a well or well

What does the organization of water supply to a private house from a well or well look like?

Scheme with a submersible pump and hydraulic accumulator

The water supply scheme includes:

Image	Description
	A borehole pump that supplies water from depth. The pressure at the pump outlet is calculated as the sum of the water intake depth, the height of the upper water intake point above the ground, the reserve for excess pressure (at least 5 meters) and for compensation of hydraulic losses in the pipeline (very roughly - 1 meter per 10 meters of water pipeline length).
	Check valve. It is placed at the inlet immediately after the pump and does not allow water to drain back into the ground when it is turned off.
	Automatic pump control with pressure sensor. It turns the device on and off at its threshold values.
	Hydraulic accumulator. We have already mentioned its tasks: smoothing out pressure surges and saving pump life.

It’s not hard to guess how this scheme works:

When the pump is turned on, the pressure in the hydraulic accumulator and water supply increases until the pump is turned off automatically;
As soon as the number of atmospheres in the water supply circuit reaches a predetermined value, the automation turns off the power to the pump, after which the check valve blocks the water from returning to the well;
When drawing water, the pressure slowly drops until a lower threshold value is reached, at which the automation turns on the power to the well pump.

Scheme with a pumping station

The design of the pumping station is already familiar to us: a pump with a hydraulic accumulator and automation on a common frame. The check valve is moved to the suction pipe, and the outlet pipe of the station is connected directly to the water supply.

Everything is simple and clear.

It would seem that such a scheme is much more practical than water supply with submersible pump. But that was not the case: the pumping station can lift water from a depth of no more than 8-9 meters.

Yes, because a pressure difference of one atmosphere (that is, the difference in pressure between the air at the surface of the planet and absolute vacuum) corresponds to a height of a water column of 10.3 meters. The water will not rise higher. Physics, you know. And the pressure in the suction pipe surface pump far from vacuum.

The captain is obvious: circuits with pumps, hydraulic accumulators and storage tanks can be combined. For example, water can be supplied to a storage tank with gravity water supply from a well pumping station. This organization of water supply to a dacha is perfectly adapted to long-term power outages.

Water heating

Geyser

In the country, as a rule, non-volatile gas water heaters with a pilot burner and piezo ignition are used.

Principle of operation: a bimetallic temperature sensor increases the gas supply when cooled with running water. As a result, the main burner lights up from the pilot burner. The degree of heating is controlled by the temperature of the water in the heat exchanger.
Advantage: minimum cost thermal energy (0.5-0.8 rubles per kilowatt-hour).
Flaw: instability of water temperature. The mechanical thermostat is very late when changing the water pressure in the mixer. As a result, instead of taking a comfortable shower, you constantly fight with the faucet taps and leave the bathroom either frozen or scalded.

In addition: politely speaking, not all dacha cooperatives have mains gas. Bottled gas makes this solution much less economical, with operating costs approaching geyser to electric heaters.

Flow-through electric heater

An inexpensive water jet will allow you to wash dishes or take a shower in relative comfort during the warm season.

Operating principle: Heating elements turn on when water flows through the device and turn off when closed taps. Heating is controlled by a flow sensor and manual step-by-step power adjustment using switches on the device body. Fine adjustment of the temperature is carried out by changing the water pressure of the taps.

Advantage: extremely easy to connect the device yourself. You can screw a mixer shower hose to its inlet pipe and use its taps to adjust the pressure.

In addition: the flower is more economical storage water heater, since it does not store a supply of hot water and does not dissipate heat through the walls of the case.

Flaws:

Large power consumption (for younger models - 3.5 - 5 kW). Not everywhere country wiring is capable of providing this;

Linear relationship between inlet and outlet water temperatures. With a power of 3.5 kW, you can wash with relative comfort in the summer, but in winter, when the inlet water is colder, taking a shower is not so pleasant;
Power-limited performance. Accordingly, special watering cans and spouts with small nozzles are used with flow jets, which also does not contribute to the comfort of the owner.

Boilers

The boiler is quite suitable for year-round hot water supply in any region (see).

Operating principle: water is heated by a relatively low-power (1-2 kW) heating element and stored in a thermally insulated tank. The operation of the heating element is controlled by a thermostat; in this case, the heating temperature can be set manually.

Advantages:

Low power consumption, which makes the device compatible with weak country wiring;
Stable outlet water temperature up to the consumption of most of the tank volume;
No restrictions on water consumption per unit of time. Simply put, mixer taps can be opened to full pressure.

Disadvantage: less economical compared to a flow machine. Heat is continuously lost through the thermal insulation, and the heating element of the device has to compensate for the losses.

Conclusion

We hope that our material will help the reader in building his own country water supply system. Good luck!

A person needs hot water not only in a city apartment, but also in the country. How to solve the problem of providing your family with warm water during the summer season? The solution is simple - use storage water heaters for your dacha.
Types of water heaters

Gas and electric
Storage (boilers) and flow-through
Vertical and horizontal

Water heaters have their disadvantages and advantages.

The advantage of an electric storage water heater is that it heats a large amount of water and maintains a certain temperature for a long time. In addition, it can be used in homes where there is no main water supply network. The disadvantage is the heating time.
A gas water heater heats water in a matter of seconds, while saving energy. Its disadvantage is the need for a water supply network with high water pressure, as well as a gas pipeline to the house.

Introductory video instructions

Construction of a storage electric water heater for a summer residence

The basis of the boiler is a body made of metal or white plastic. There is a tank inside. Between the body and the tank there is a layer of thermal insulation to ensure temperature regime. On the inside, the tank has a glass porcelain coating. In more expensive models, titanium coating is applied over glass ceramics.
There are two tubes inside the tank. Cold water flows through a tube located at the bottom of the tank. In this case, the heated water rises to the upper part, where it is taken and supplied through the second tube, as necessary, to the consumer.

On the body, in its lower part, a support flange is secured with bolts, on which the following are mounted:

A heating element made in the form of a nichrome spiral, protected by a copper casing.
Thermostat equipped with double protection.
Magnesium anode for collecting scale.

Maximum heating temperature – (+85) C. If this indicator is exceeded, the thermostat is activated and the heating element is turned off. Automatic switching occurs when the temperature reaches +3 C. You can adjust automatic switching, for example, when the water in the tank cools to (+30?). More detailed instructions you can read about it in one of our previous lessons

What you need to pay attention to when choosing a storage water heater for your dacha

The range of heaters is quite wide. And sometimes it’s difficult to figure out which one is better? What should you pay attention to when buying a storage electric water heater for your summer cottage?

Heater capacity. For kitchen needs, a heater with a capacity of no more than 30 liters is sufficient. For use in a bathroom for a family of two people, a boiler with a capacity of 50 liters is suitable. A family of 4 people will need a heater with a capacity of 100 liters.
Overall dimensions and location (horizontal or vertical). The choice depends on the size of the kitchen or bathroom.
Durability. This indicator depends on the spray inside the tank. The longest service life of a heater with a stainless steel tank is up to 10 years. A little less - up to 8 years, a titanium-coated tank will last. The cheapest ones (with a tank coated with glass ceramics) last no more than five years.
Type of heating element. They can be “wet”, located directly in the water, or “dry”, inserted into a special tank for heating. The latter last longer.
Power. The higher it is, the faster the water heats up.
Control system. Electronic is preferable, but storage water heaters for dachas with a mechanical control system are cheaper.

Heater installation technology

Despite the fact that in one of our previous lessons we already talked in detail about this, let’s once again briefly look at the connection diagram and installation technology

It is necessary to choose a suitable location for installing the boiler. It must be located in a location with easy access for maintenance work. It is not recommended to fix it too close to the ceiling, cover it with cabinets, etc.
To hang the unit on the wall, use plugs and screws (they are included in the kit).
Install water supply pipes: cold and hot, connecting them with the corresponding risers, heater and consumers.
Install the safety valve. It needs to be drained into a sewer (to drain excess water in critical situations). Install shut-off valves. For installation, use pipes made of metal-plastic or polypropylene. Flexible hoses are not suitable for this purpose.
At the inlet supply tube cold water install a filter.
Check the connections for tightness.
To connect to the electrical network, a separate PVS type cable with a cross-section of 3x1.5 mm is used, as well as an individual switch or socket. Grounding is mandatory.

If the water supply is in country house missing, solve the problem with water supply to the storage tank electric water heater for a summer residence, you can use a pump connected to the boiler pipeline.

It will supply the boiler with cold water directly from artesian wells or wells. Another option is to install a container of water above the heater, connect it to the inlet pipe, and the water will fill the water heater tank by gravity.
This concludes our lesson, successful repairs

Storage heat exchangers are hydraulic accumulators in which a limited volume of water is heated over a certain period of time. Structurally, they are arranged as follows: a thermally insulated container with a heating element - a heating element inside () or a gas burner () and a lining on the outside, on which there are heating temperature and power control elements.

The desired temperature can be set on the thermostat. The water is heated to a predetermined temperature, which, when cooled or consumed, is maintained automatically using a thermostat. Effective thermal insulation prevents heat loss and keeps water hot for a long time. Water heaters usually have frost protection, which prevents the water temperature from falling below 5-7 °C.

According to their design, storage water heaters are divided into those operating under pressure (pressure) and without pressure (gravity). The word “non-pressure” does not mean that pressure is not required to supply water to the tank and water can flow from the tap by gravity. The point is that when water is heated, excess pressure does not arise inside the tank, since the “extra” water formed as a result of heating flows freely through the spout of a specially designed faucet. In this regard, non-pressure water heaters can only be used in conjunction with a special mixer that shuts off the water at the inlet to the water heater when water supply stops, and, accordingly, work only at one water supply point. Due to the low operating pressure, it becomes possible to manufacture the internal capacity of the tank from polypropylene, which significantly reduces the cost of such water heaters. In addition, polypropylene is not subject to corrosion, which guarantees long lasting performance devices of this type. Since non-pressure water heaters operate on only one tap, their volume is usually small (5-10 liters).

Drives closed type, operating under pressure, can be built into a hot water supply system and work at several water points. The water in them is under the pressure of the water supply system, which is usually in the range of 2-6 bar, and the “extra” water flows through a special valve. The tank of such water heaters usually withstands pressure up to 10 bar. Their internal container is made of steel. To protect against corrosion, the internal surface of the water heater is coated using a special technology at high temperatures with high-quality anti-corrosion enamel. All closed-type storage water heaters require the mandatory use of a safety group consisting of an overpressure valve, a check valve and a reducer (at a pressure of plumbing system more than 6 bar).

Storage water heaters are widely used in country houses and cottages. When choosing a water heater, you need to proceed from the fact that devices with a volume of 5-15 liters can only cope with a sink and washbasin. Water heaters with a capacity of 30-50 liters can be used for showers. If you plan to use the bathroom, you need a tank with a volume of 80-150 liters. If the need for hot water is even greater, then it is advisable to use a floor-mounted water heater with a capacity of 200-400 liters. An important role when choosing an electric water heater is played by the boiler capacity, on which the speed of water heating depends. Small volume storage water heaters (up to 50 l) usually have a power of 2 kW and are powered by a 220 V network (necessarily with grounding, which is necessary both for safety and for the proper functioning of the anti-corrosion anode).

Some models of tanks with a volume of 5-30 liters, produced by Vaillant (Germany), recognized as a leader in the production of heating and water heating equipment, are equipped with a power plug and can be plugged into a European socket. For large-volume water heaters, using such a small power is impractical, since the water in them will take too long to heat up. Approximate heating time can be calculated using a simplified formula: with a power of 1 kW, you can heat 860 liters of water per 10 °C in 1 hour. For example, 2 kW standard power storage devices heat water with a volume of 100 liters to 65 °C in approximately 3 hours. In order not to wait too long for hot water, Vaillant offers water heaters of the VEH exclusiv series with a volume of 50-150 liters and floor-mounted 200-400-liter water heaters, which, in addition to the usual, have an accelerated heating mode at a power of up to 6 kW. The fast heating button allows you to quickly restore the supply of used hot water, and the presence of a mode for heating water at night (at a lower tariff) allows you to reduce energy costs.

A hot water column with a shower using solid fuel, type KVE and KVTs, belongs to the capacitive type heaters. It is quite widespread. In all houses and cottages with stove heating, that is, where there is no gas, this is usually installed. The reason for its great popularity lies in its reliability and efficiency. You don't need much fuel to heat water.

The column is a galvanized (letter C in the abbreviation) or enameled (letter E) container, inside of which there is a flue that heats the water. The column is operated without automatic control of the water supply, since the supply is constantly under pressure from the water supply network to which it is connected. The presence of a network water supply in the house is a prerequisite for installing a column.

The lower part of the column is a cast iron or steel firebox with a blower. It is installed in the bathroom directly in front of the bathtub or shower tray. External heating of the firebox allows you to additionally warm up the room. When installing the column, you need to take into account all the fire safety measures that are provided when installing stoves. Recently, combined hot water heaters have begun to be produced, operating both on solid fuel and using electricity.

When operating a water heater, it is periodically necessary to drain water from it for maintenance and repair. Not knowing the operating principle of a storage water heater, many users believe that this procedure is nothing complicated and that it is enough to open the hot water tap. As soon as water stops flowing from it, the water heater is drained for them.

In reality, draining water from a storage water heater is a rather labor-intensive procedure. Based on my experience, a storage water heater is always more difficult to dismantle than to connect.

But in order to explain to you all the difficulties of draining a water heater, you need to understand the principle of its operation.

Most wall-mounted water heaters have two pipes: the first for supplying cold water to the water heater, the second for supplying hot water from the water heater; some models of water heaters (usually horizontal) have a drain pipe.

A wall-mounted storage water heater operates as follows (see figure on the left). Cold water is supplied through the cold water pipe to the bottom of the inner tank. There it is heated using a heating element (heating element) installed in the internal tank. The heating element heats the water. The heated water rises to the top of the internal tank. Its place at the heating element is taken by a colder one, which, in turn, having heated up, rises to the top, etc. Thus, the entire volume of water in the water heater is gradually warmed up. In heat engineering, this heating process is called natural convection. The essence of natural convection is that hot water is lighter than cold water, it has increased buoyancy, and it always “floats” when surrounded by cold water.

It is important to understand that the heating element is always installed at the bottom of the water heater, because this is the only way it can start the convection process. It is also important to understand that it is more advisable to take hot water from the top of the storage water heater. There are several reasons for this: at the top of the tank it is hottest; if the water heater is turned on, you can consume hot water from the upper layers without waiting for the entire volume to warm up. Therefore, the hot water pipe always goes through the entire inner tank to the very top (image below left).

The image below right shows the cold water inlet. It is plugged at the top and supplies water through the side holes so that cold water does not rise to the top due to the pressure of the jet and does not mix with cold water, disrupting the convection process.

Filling the storage water heater

Attention! Do not connect the water heater to the electrical network until it is filled with water!

In order to fill the storage water heater, cold water begins to be supplied to it. Water enters the water heater through the cold water pipe and gradually fills the volume of the water heater. Its level is rising. She begins to squeeze the air out of the tank. This should not be prevented and therefore you should open the hot water tap in the nearest mixer to which the water heater is connected.

The water level in the inner tank will rise until water begins to flow into the hot water pipe (level B in the figure). Here is another reason that the hot water intake pipe goes almost to the very top of the internal tank. This will ensure that the water heater is filled with water.

During the process of filling the storage water heater with water, air will come out of the open mixer, hissing and spitting. Don't be alarmed, wait until water flows out of the faucet in a steady stream. After that, wait another half a minute and close it.

The water heater is full!

An important element when installing a water heater is the correct use of the non-return safety valve.

This valve prevents:

emptying the water heater by draining the water back into the cold water pipeline when, for example, the cold water is turned off;
penetration of heated water into cold pipelines.

Emptying the water heater during operation leads to damage to the heating element, since it is not designed to operate dry.

Draining the storage water heater

From the design and operating principle of a storage water heater described above, it is clear that it is impossible to drain water from the water heater simply by opening the hot water tap.

Before draining the water heater, disconnect it from the electrical network and, if there is hot water in it at the time of draining, let it through by opening the hot water tap in the nearest mixer until cold water flows out of it.

To properly drain the water you must:

Close the shut-off valves on the cold and hot water pipelines;
Disconnect the hot water pipe from the hot water connection. Thus, we will add a little water to the cut of the hot water pipe (from level D to level B in the figure). This way, air can flow inside the water heater through the hot water pipe;
After this, you need to unscrew the return safety valve from the cold water pipe, having previously armed yourself with a pair of buckets or a drain hose. The water will drain from the hot water pipe end to the cold water pipe end (from level B to level B). It is important that during draining the hot water pipe is disconnected from the water heater so that there is no vacuum in the internal tank, otherwise water will not flow through the cold water pipe;
If you want to drain the water heater completely (to level A), for example, to clean the internal tank, you need to unscrew the heating element.

Using a certain set of fittings, you can avoid dismantling the pipelines when periodically draining the water heater. The figure below shows how to properly make the hydraulic connections for this.

The red tap to the left of the hot water pipe is used to drain water to the level of the cutoff of the hot water pipe and then allow air to enter the internal tank. The drain valve to the right of the cold water connection is used to drain the remaining water from the water heater. It is important to install it between the water heater and the return safety pipe.

Please remember that it is strictly prohibited:

install shut-off valves directly on the cold water pipe between the water heater and the non-return safety valve;
replace the non-return safety valve with a simple non-return valve.

By the way, it is unacceptable to drain water through the non-return safety valve.

The drainage hole of the non-return safety valve is not intended for draining the water heater. It may become clogged with sediment and scale particles from the internal tank and stop working properly.

Conclusion

Storage water heaters are quite difficult to drain, so it is advisable to connect them to the water supply according to a scheme that eliminates the disassembly of hydraulic connections for subsequent maintenance.

Follow basic safety rules when filling and draining the boiler. Disconnect it from the power supply and run water if it is hot at the time of draining.

Do not violate the rules for using and installing the non-return safety valve.

Installing and connecting an electric boiler by plumbers is one of the simplest tasks. But those not initiated into the “mysteries of pipes” may have questions. Further details about a common phenomenon - connecting a water heating tank - what, why, why... and how to do it correctly.

An electric boiler is beneficial for desperate situations

Electric boilers are mainly installed in apartments, but in private houses they prefer to heat water using cheaper energy sources - gas, wood, coal... i.e. indirect heating boilers.

But in an apartment with firewood you can’t walk around. It’s also difficult with gas; additional equipment requires a project; it’s cheaper to heat with electricity. In addition, there are no difficulties with an electric boiler - all you need to do is purchase a storage heater, it is easy to install and connect.

At the dacha, it is also often easier to get hot water without worries with an electric tank. In general, the item is in demand and is often installed...

What volume of water heater is needed?

There are no special calculations here - the volume of the boiler is selected according to water consumption, which is very individual. They are also guided by monetary costs - the larger the tank itself, the more expensive it is, but it is even more expensive to heat a large volume, which is often not consumed and gradually cools down in vain...

Typically, a 60 – 80 liter water heater is suitable for a small family with moderate water use. The remaining cooling water is not large...
For those who do not consider costs and love baths, you need 120 - 150 liters.
About 100 liters is not entirely economical, but there will be no shortage of hot water if you have a moderate appetite.
Small, 20 - 40 liters - suitable for one person, anywhere in the country... But it heats up quickly and is more economical!

How to position the tank correctly

The correct location of the storage water heater is the minimum distance to the taps. In apartments they manage to arrange it – from the boiler there is one step to the shower, and through the wall there is a kitchen tap, for example. And it's a great location.

A long hot pipeline (more than 2.5 meters) from the boiler is simply not acceptable due to the economic waste of cooling and excessive water consumption.

The device needs to be hung higher so that water can be drained from it by gravity without problems, and if necessary, empty it, and this happens all the time. It is also possible to organize a gravity supply of water to the taps when cold water does not flow - the tank will be filled with air.

But you need to leave a gap of at least 5 cm to the ceiling in order to freely remove and put on the tank on the hook mounts.

Fasten securely

In older apartments, the bathrooms are enclosed in plaster cubicles. You should not anchor a heavy tank on a plaster wall - it is dangerous. The exception is fastening with through bolts, which are connected on the other side by a strip - the metal reinforced frame of the cabin is involved in fastening.

Classic fastening - installation on anchor hooks with a diameter of 8 - 10 mm in concrete wall.
You need to drill the anchor (plastic cartridge 14 - 16 mm) with a hammer drill. Naturally, having previously made markings on the wall. The tank must be positioned vertically - the mount is strictly horizontal, it is advisable to draw the center line of the device, the location of pipe supply points, drilling points...

Connection to water supply

The mounted tank must be connected to hydraulics.
The simplest connection, but workable for small-volume tanks - a safety valve with an outlet (supplied in the kit) is installed on the cold tank. And that's all the necessary harness. If necessary, all water from the tank is discharged through this outlet.

This valve also works as a return valve - it lets water into the tank, but not back. Thanks to it, water does not go back into the pipe when the cold supply stops.

An additional mandatory element is taps on the supply pipes, cold and hot. They are necessary for maintenance, shutting off in case of drainage....

The simplest strapping scheme

The scheme is slightly complicated by the presence of a tee on the cold side, and a separate tap for discharging water. All this can be easily distinguished in the photo, from top to bottom, cold:

tee with tap and hose for draining water;
safety check valve with opening lever and tap;
shut-off valve;
American - switching to polypropylene.

For hot water:

shutoff valve;
American - transition to polypropylene pipes.

How to get water when there is no cold water

Our supply of cold water is often not constant. And when there is no cold water, not a drop will come out of a normal ordinary boiler. What to do, how to increase comfort?

Manufacturers help with this; some models make it possible to draw hot water by gravity without pressure or supply. Those. This device turns into a regular heated storage tank.

The trick is to install an automatic air vent at the top of the body of the device and a different configuration of tubes inside. When the pressure drops, the air vent valve opens and allows air into the tank, allowing water to escape.

Moreover, all this happens automatically, and the user has nothing to worry about, almost...
Disadvantages - the air vent leaks, and the tank itself can produce cold and hot temperatures during intensive intake (bathroom), since the hot tube inside is too low.

Boiler connection diagram for constant water drainage

But even from a conventional boiler for heating water, it is possible to disassemble the water by gravity when there is no cold pressure. The scheme is as follows.

Draining is only possible back into the cold pipeline, bypassing the check valve.

On the cold diagram:

tee with tap and bypass hose made of polypropylene;
safety valve;
tap and American;
a tee where water flows from the tank through a hose, bypassing the valve.

Hot:

tee with stopcock;
shut-off valve.

When there is no cold supply, in order to get water from the boiler into the cold pipeline, you need to:

close the main cold valve at the entrance to the network (into the apartment...) so that the water from the tank does not go back into the common pipes;
open the tap on the cold tee to the bypass hose;
slightly open the plug valve on the hot tee to supply air to the boiler.

When it gets cold, all this needs to be done in reverse order...

Correct circuit for switching on the heating tank

All the diagrams shown implied a small boiler. In it, the thermal expansion of water when heated is compensated by the elastic deformation of the body, or even by the operation of a safety valve.

But if the volume of water is large, then you will have to compensate decently. But constant operation of the valve (emergency situation) is unacceptable and leads to its rapid failure.

Therefore, it is connected to the circuit on the hot pipeline or on the cold one above the valve expansion tank. Volume up to 1/10 of the amount of water.
And it is inflated with air up to 2.0 atm.

Now the connection of the heating boiler is correct - there is normal protection against overpressure.

Connecting electricity to the boiler

A powerful electrical consumer (1.5 kW - 2.0 kW) requires particularly good network contacts. The fact is that a water storage heater works for hours a day, not 5 minutes like an electric kettle. And if there are bad contacts in the socket or on the supply mains, then this will manifest itself... by heating, melting, fire...

It is best not to install a socket, but to use a differential circuit breaker to turn it on and off, i.e. it has an RCD - protection against leakage to earth. And this is not a waste of money at all. The fact is that the heaters inside the boiler often burn out; their body is destroyed by electrochemical corrosion (after the magnesium anode is used up), resulting in a 220V leak to the pipes and the ground. Even a stream of water can give you an electric shock.
Be careful with electricity; to connect the storage boiler, use an RCD configured for a phase difference of 10 mA.

Craftsmen make this connection themselves, but if you haven’t messed with the wires before, it’s better to call an electrician, he will connect the boiler correctly in 5 minutes.