Electric instantaneous water heater: how to choose, types

The presence of hot water is one of the indispensable attributes of a comfortable life. Citizens are so accustomed to such conditions that the temporary shutdown of hot water supply becomes a lot of inconvenience. There is also a lack of hot water outside the city, in dachas. An electric instantaneous water heater can solve this problem. This device can supply hot water not only on a temporary basis, but also on a permanent basis: you can build a hot water supply system for a private house. 

Principle, device and features of work

An electric instantaneous water heater is a small device that heats water flowing through it. The heating element is a heating element (tubular electric heater) or an open spiral. Heaters with heating elements are more common – they are safer and the heating element is easier to replace. In very compact models – faucet nozzles, etc. – there is simply nowhere to put the heating element, therefore an open spiral is used.

The device turns on when the flow appears (the tap opens), turns off when the flow disappears. The set temperature is gained in a few seconds, after which it is maintained constantly (with sufficient power of the heating element).

Externally, a conventional instantaneous electric water heater is a small plastic case connected to cold water and electricity. Has one outlet for hot water. Depending on the purpose, it can supply hot water to one (individual) or several (system) points of analysis.

The structure of a flowing water heater is simple, there are the following elements:

• Cold water inlet. It is connected to the water supply, usually with a braided flexible hose.
• Flow sensor. It monitors the appearance of water in the device (the tap is opened) and turns on the heating element. It also turns off the heating when the flow disappears (the tap is closed).
• Tank with heating element. A small container, inside of which there is a heating element, curved in the form of a spiral. This is where the water is heated.
• Hot water outlet. From the tank with water there is a tube through which heated water is discharged.

As you can see, the device is simple. There is also a control panel on the cover, where the conductors from the flow sensor and the heating element are brought out – so that you can adjust the operating mode and monitor the status of the device (on indication).

Types and connection to water supply and electricity

There are two main types of instantaneous electric water heaters: pressure and non-pressure. Pressure pumps are also called system and often have the word Sistem in their name. They are connected to a break in a water pipe, as a rule, they have more power and can provide hot water to two or more points of water intake.

Non-pressure or individual instantaneous water heaters are connected like ordinary household appliances – through a flexible hose or a water pipe outlet. They supply one point with heated water, have relatively small capacities (3-7 kW) and low cost. They exist in different forms:

• in the form of a separate device (most often a rectangular plastic box), which is fixed next to the sink or shower;
• faucet nozzles;
• faucet with electric water heating.
  

If you need to wait a few weeks when the hot water supply is turned off, you can supply an individual non-pressure electric instantaneous water heater of any kind. If a constant supply of hot water is required, it would be more rational to install a pressure unit.

Connecting a pressure water heater to the water supply

Pressure or system electric water heaters are connected to an existing water supply system through a pipe break. They crash with a tee, which installed before the first branch. Shut-off ball valves are installed at the inlet of cold and hot water. They turn off the device if there is a centralized hot water supply. These cranes are also needed so that, if necessary, the device can be removed for repair or replacement.

The quality of tap water leaves much to be desired and it is better to embed the heater after the filter. If there is no filter at the entrance to the apartment, it is advisable to install it either immediately after the branch to the apartment, or already in front of the water heater.

In a private house, such a unit will work if there is a pumping station or a self-assembled system with a hydraulic accumulator. It crashes after all the filters, from the output there is a wiring to consumers.

Non-pressure connection to water

A non-pressure (individual) electric instantaneous water heater of a standard type is connected like a regular household appliance. There must be a branch from the water supply with a tap and a thread at the end. Using a flexible braided hose, the device is connected to the water supply.

Nozzles on the tap for heating water – a small group. They are mainly screwed onto the threads at the end of the spout (gander). To do this, first unscrew the grid, which is usually installed there.

Some time ago there were quite a lot of them, but they differed in low efficiency. The nozzle itself has a solid size and you can’t attach it to a low crane – it interferes. TO In addition, faucets with electric water heating have appeared on the market, which heat water better, have the ability to adjust the temperature and are more convenient to use. They are installed in place of a conventional faucet on a sink or sink. The only difference between the installation is the need for an electrical connection.

 Electrical connection

Any electric instantaneous water heater is a powerful and requires a separate power line. As an exception, you can connect to the line that goes to the electric stove – the line is suitable for the parameters. Only in this case it is necessary to ensure that the stove and instantaneous water heater are not switched on at the same time, otherwise the machine will work on overload.

The connection of a flowing electric water heater is standard – from the shield, the phase from zero is brought to a two-contact RCD (it is imperative to break both the phase and zero), then the phase is also turned on to the machine and only after that it is supplied to the consumer.

The connection itself can be made through a three-pin plug with a socket with a mandatory ground connection. You can also install a contact plate or connect a cable directly to the appropriate heater inputs.

They pull the power line with a copper wire (mono-wire):

• up to 7 kW section 3,5 mm;
• from 7 to 12 kW – 4 mm.

The machine is selected according to the maximum current consumption (available in the technical specifications). They take the nearest higher denomination (if you take a smaller one, there will be a lot of extra operations – every time you switch to maximum power). RCDs are taken one step higher at face value, the leakage current is 10 mA.

Read more about the selection of circuit breaker ratings here.

Management type

You can adjust the operation of the electric water heater (change the degree of heating) using several regulators, which are located on the control panel. Management is hydraulic and electronic.

An electric instantaneous water heater with hydraulic control heats the water by a certain number of degrees. It always turns on with maximum power, even if it has several different heating modes. And even if one of the modes was set before turning off, it will turn on again from the maximum.

He also has one more feature – the water heats up by a certain number of degrees. It is necessary to change the degree of heating manually – switching modes after switching on. Moreover, the maximum temperature delta, most often, is 25 ° C. That is, if at the inlet you have water + 5 ° C, then at the outlet of such a device it simply cannot be warmer than + 30 ° C (with full flow). This does not mean that the unit is broken or not working properly. This means that he simply cannot make it warmer. You can slightly correct the situation by reducing the pressure, then you can achieve a slight increase in temperature, but you will not get full hot water in such conditions from such a unit.

Electronically controlled units usually have more power and a significantly higher price. This is due to the fact that they have heating elements with multi-stage power control, and they are more expensive. In addition, the “stuffing” of such an apparatus is more complicated – there are several sensors, in addition, it also contains a microprocessor that processes data and regulates the operation of the heaters. If the unit is selected correctly in terms of power, it will be able to maintain the set temperature (usually up to 40 ° C) with a deviation of one degree.

Choosing an electric instantaneous water heater by power

Whatever type of electric water heater you choose, you need to choose the right power for it. That’s right, in this case, it’s so that it lives up to your expectations. The easiest way is to focus on the number of taps that will require the simultaneous supply of hot water:

• An electric instantaneous heater with a power of up to 8 kW will consistently provide hot water to one draw-off point. If there are several of them in the system, the rest must be turned off, otherwise the temperature drops noticeably.
• With a power of 8 kW to 12 kW, a stable temperature can already be maintained in two taps.
• With a power of 13 kW, hot water can be supplied to three points of water intake.
  

Not all electrical networks can withstand such capacities. Often the total allocated power per house or apartment is much less. In this case, it is worth considering the possibility of installing less powerful individual instantaneous water heaters or storage. A great option is a gas water heater, but it is for those who have the ability to connect to a gas main.

Selection by water consumption (capacity)

You can choose an electric instantaneous water heater according to the required flow rate. There are norms for the consumption of hot water for different consumers. By adding up the required flow rate for your case, you will get the desired figure. So the average cost is:

• washbasin and sink with mixer, 2-4 l/min;
• bathtub with mixer 3,5 l/s;
• shower 5 l/min.
  

When choosing, you must match both the power value and the flow rate. In this case, water at all flow points that can work simultaneously will be supplied at a given temperature. If not, you will have to ensure that only one tap is open at a time.

What the market has to offer

The choice of electric instantaneous water heaters is at least large … You can easily get confused. What should you pay attention to besides power and performance? On the material from which the tank and the heating element are made. The tank can be copper, stainless and plastic. This information is not provided by all manufacturers, but if it is not available, most likely the filling is made of plastic. It is, of course, heat-resistant, but not as reliable as metals.

Also pay attention to the minimum and maximum cold water pressure at which the unit can operate. There are capricious models, for the connection of which it is required to install a reducer on our networks.

Separately, it is worth talking about taps with electric water heating. They are also called faucet-water heater. They appeared not so long ago, but are quickly gaining popularity, as they are easy to use, just connect.