How to choose a small instantaneous water heater

Such a story happened to my friend. On the eve of March 8 I decided to give my wife a gift. And I bought an instantaneous water heater so that my beloved would not suffer with basins and ladles during the hot water shutdown. I called an electrician, he ran a separate cord from the shield. Because the device is powerful enough – 5 kW. In general, he showed an enviable activity. The hour “X” came, the wife proudly retired to the bath, and he, pleased, to the TV – watch “Deadly Force”. And suddenly … from the bathroom – a terrible scream. The essence of the “message”, omitting some words and phrases, was as follows: “The water is cold, if I turn off the tap so that the water becomes hot, a trickle is so weak that I’m covered in soap and freeze. You are a man, do something “…

The “man” ran to the service center. And what do you think they told him there? It turns out that if the power of an instantaneous water heater is 3.5 kW, then you will not get hot water more than 3 liters per minute in any case. And to take a full hot shower, you need a power of 8 kW and above.

Here’s a story. What to do? After all, instantaneous water heaters are successfully sold today by many companies, they extol their advantages, and they certainly are. Firstly, with an installed instantaneous water heater, no matter how much you keep the tap open, hot water will never run out. Unlike storage water heaters, in which hot water in the tank may run out and after a while, it is quite possible (depending on the volume of the tank), cold water will flow. But this will never happen with an instantaneous water heater..

Secondly, in comparison with storage, instantaneous water heaters are made small. Since they don’t need a hot water storage tank.

The main advantage of small instantaneous water heaters is their small size

Now about the disadvantages of the “flutes”. As the experts told me, their disadvantages include a large one-time power consumption. And one more thing: if several points of water intake are connected to a flow heater at once, in other words, several taps, the temperature of the hot water will depend on how many points are operating simultaneously. Let me explain. Let’s say your instantaneous water heater is “divorced” to the kitchen tap and the bathroom. So, if you decide to take a shower, and your wife – to wash the dishes, then you will have to bathe in cold water.

Having visited several companies that sell water heaters, I realized: you can get a lot of hot water using an instantaneous water heater only if its capacity is from 8 kW and above. This means that this pleasure is available only in those houses where there is a three-phase electrical network. Alas, in old buildings with 16-ampere plugs, a water heater with a capacity of more than 3.5 kW simply cannot be installed. And in houses with electric stoves and new houses where there are 40- or 32-ampere meters, it is permissible to install 6 kW “flutes”.

What to do? It turns out that there is a way out. In order to have hot water in that only summer month, when preventive maintenance of the central water supply is underway, shops offer a large selection of so-called small instantaneous water heaters operating from a 220 V network with a power consumption spread from 1.5 to 8 kW.

So, small flow-through electric heaters can be divided into two groups:

Pressure – instantaneous water heaters without any nozzles, they only provide an inlet and outlet for water. They are installed in a riser and “bred” for the whole apartment. This is very convenient, since during the period when hot water is turned off, you can not only take a shower, but also use hot water from any tap in the apartment. Such a water heater turns on and off automatically, responding to the flow of water.

Free-flow – instantaneous water heaters equipped with their own shower head (included with the device) and working only as a shower. It is undoubtedly convenient, say, in the country. But in the apartment, in my opinion, it is a little strange when two shower heads hang side by side in the bathroom – one shower from an ordinary mixer, and a “shower” of a water heater sticks out next to it.

A small pressure flow water heater is installed in a riser (photo on the left)
Non-pressure instantaneous water heaters are equipped with a shower head (photo on the right)

In addition, here, for example, what I was told in one service center.

Cases are different…

As we have already said, small instantaneous water heaters with a capacity of 3 to 6 kW can be used only in summer. And that’s why. Recently, in winter, a man came to the service center. With a complaint that the water heater worked fine in the summer, and now, during an accident in the heating network, it refuses to heat the water. Like, fix it…

It is popularly explained to him: in summer the temperature of the “cold” water “entering” from the tap was + 15 ° С. Its small instantaneous water heater with a capacity of 3.5 kW (with Dt – 25 °, giving 3 l / min) in the summer easily “warmed up” it by another 25 °. That is, 15 ° + 25 ° = 40 ° C is a perfectly suitable temperature for washing. And in winter the water in the tap is colder, about 5 degrees. So: 5 ° + 25 ° = 30 ° C – under such water you will freeze, of course. And the device itself has nothing to do with it, it works as usual, nothing broke in it, it’s just the climate we have.

This is how several firms commented on this situation to me. It turns out that small instantaneous water heaters were developed for the warm countries of Asia and Africa. And there are no such differences between winter and summer temperatures, and the water temperature in the tap is always around + 15 °. It only needs to be slightly “warmed up”.

This photo clearly shows how a small instantaneous water heater from Stibel Eltron works

Or one more case. The client sometimes comes across independent. Without consulting with specialists, he buys a gravity water heater. Moreover, it connects it in a completely unacceptable way. Let me explain. According to the instructions, before turning it on, you first need to open the cold water tap. But for “simplicity”, some craftsmen do this: they unscrew the shower head on the water heater, which is sold complete with a non-pressure water heater, and put an ordinary tap instead. And, without thinking twice, they connect the device to the water supply system. Simply put, now the role of the mixer is actually performed by the water heater.

But the fact is that the tank of this water heater is not designed for such water pressure. As a result, the water heater fails. As I was figuratively described this picture in the service center, “it swells and bursts.” Imagine! Meanwhile, in all the instructions it is written in detail how the device should be connected, so that later there will be no problems.

Or here’s a completely exotic example. It is known that water heater shower heads need to be cleaned from time to time. In a certain bathhouse, small instantaneous water heaters were used as showers. Over time, the holes of the shower head became clogged with pieces of lime scale and dirt (our water, as you know, is not the best). As a result, the water heater literally “squeezed” hot water out of itself … And in the end it overheated and … completely melted.

The thing is that shower heads for small flow heaters have very narrow openings (compared to conventional showers). And that’s why. A small instantaneous water heater is able to heat a not very large amount of water to the required temperature. Therefore, in order for the jet to be stronger, very small holes are provided in the shower head. Naturally, such micro-holes become clogged with scale or debris much faster..

The Ariston Eureka model is a cross between an instantaneous and a DHW cylinder (left)
It is better to entrust the installation of a small instantaneous water heater to a specialist (right)

What do the service center specialists advise??

The first. If you notice that the water jet from the shower head of the instantaneous water heater has become weaker, it (the nozzle) must be cleaned. And we advise you to do it regularly. Unscrew, rinse or soak for a while in a descaling solution.

Second. Buy water heaters only from specialty stores or firms. For example, when I told these “incidents from the life of water heaters” in the representative office of Stibel Eltron, they were very surprised. The fact is that their branded devices have a fuse that, at a water temperature of more than 65 ° C, turns off the device simply automatically. Therefore, it not only melts, but cannot even overheat..

What to choose?

So, we briefly talked about what you need to know before you go to the store to choose an instantaneous water heater. Let’s sum up.

1. Find out the details, a three-phase network or additional wiring is required for an instantaneous water heater that you liked. And check with the housing office what electrical equipment you have in your apartment.
2. Specify the capacity of the selected instantaneous water heater. In other words, “for what” it is enough: only for washing hands and dishes, only for taking a shower or hot water is enough for all these manipulations at the same time.
3. Ask: who will install the device? Do I need to call a specialist from the company (and, of course, how much it will cost) or is it easy to do it yourself?
4. And, of course, be sure to find out the warranty period and addresses and phone numbers of service centers.

In addition, it is harmless to ask if we have spare parts in our country for the device you have chosen. And if there is, do not be lazy to clarify how much it will cost. It happens that some small but very important detail will cost a rather large amount.