They are often called the most economical units. It is believed that for the operation of the water heater indirect heating no fuel is required and thus no running costs. However, this statement is incorrect.

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On the picture:

If you look inside his tank, you can see a tube twisted in a spiral. It runs from the lid to the bottom of the tank and is connected to the supply pipe of the heating system.

Fuel It would seem that we can conclude that an indirect water heater does not need fuel at all. However, this is by no means the case. It receives heat from the liquid circulating in the heating system of the house. And it is heated with the help of a water heating device - a boiler, a fireplace with a water circuit, etc. That is, the unit, albeit not directly, but still uses the energy that was released earlier during the combustion of fuel.

In the photo: an indirect heating water heater running on fuel oil

Operating principle

The internal arrangement of an indirect water heater is extremely simple. Passing through the tube, the coolant gives off part of the accumulated heat to the water in the tank. The heat exchange surface is the walls of the tube. Simply put, a kind of radiator for a water heating system is installed inside the tank, which heats not the air in the room, but the water in the tank.

Power

It is quite difficult to talk about the power of the unit with indirect heating. It depends on many parameters that are not directly related to it. For example, on the power and performance of a heating boiler or fireplace.

If you initially set hot water device, strictly corresponding to the area of ​​\u200b\u200bthe house and the degree of its insulation, and then add a water heater of the type in question to the system, then neither heating nor hot water supply will be able to function normally. The water will not be hot enough, and the temperature in the house will be set below a comfortable level. Thus, if you plan to use indirect water heaters in the future, then when choosing a boiler, you should consider the possibility of increasing the load.

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On the picture:

Indirect water heater powered by solar panels.

Nuances

As you can see, storage water heater indirect heating depends entirely on the operation of the heating system. There is no problem in this winter period, however, the heating is switched off during the summer. What, in the warm season will have to be left without hot water? In no case. There are several ways to solve this problem.

Of these, the most obvious and at the same time the most difficult is the organization of a separate heating circuit used exclusively for the needs of hot water supply. By the way, in the vast majority of cases, this is exactly what is done. That is, apart from the indirect heating water heater, there is nothing else in this part of the heating system. For the summer, all circuits are blocked, except for the one mentioned, and the boiler is switched to low fuel consumption mode.

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On the picture:

Scheme internal device storage water heater.

You can organize something similar in another way, while overpaying a little for the equipment itself, but significantly saving both money and time on its installation and connection. We are talking about indirectly heated water heaters, originally installed inside the boiler body, that is, built-in, as well as combined devices that can heat water in two or more ways. However, these are topics for separate articles.

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And the plus of such water heaters is large volumes and good thermal insulation, which allows you to keep water hot for a long time (the temperature can drop by only 5 degrees per day!).

An indirect heating boiler, unlike heating elements and double-circuit boilers, is designed for real long term operation (50-60 years). That is, it is a very reliable and durable device. In addition, it does not require much attention in terms of maintenance (it is enough to bring the water temperature in it to a maximum (90 degrees) once a year to kill the possible “microflora” in it).

Indirect water heater device

The device of an indirect heating water heater is not much different from the device of a storage water heater. There is also an inner case in thermal insulation and an outer case (click on the picture to enlarge):

Indirect heating boilers are produced in large volumes: from 50 liters and above. Therefore, an inspection hole is provided in the housing through which the tank can be cleaned.

The tank is connected to the heating system: there is an inlet and outlet for the circulating coolant. The hot coolant passes through a coil immersed in water intended for a hot water supply system. Water, colder at the bottom of the tank, heating up, rises to the upper part, from where it is taken to consumers (shower, bath, sinks). Of course, the tank is also connected to the water supply system, from which cold water flows as it is consumed.

Magnesium anode for protection inner surface the tank itself, located at the top.

How to connect the water heater to the water supply system?

The scheme for connecting the water heater to the water supply is the same for all types of water heaters:

Any water heater has an “inlet” for cold and an “outlet” for hot water. We connect the input to the water supply system from a well or from central system. Outlet - to the pipeline through which hot water to consumers.

A safety valve must be installed on the inlet pipe, which must come with the boiler. Safety valve protect the boiler from water hammer and overpressure that occurs when water is heated. The safety valve included in the kit is already set to the pressure that is permissible for the boiler (as a rule, this is 0.6 MPa).

Before and after the water heater must be Ball Valves to quickly disconnect the device from the system.

Before connecting the water heater, you need to read the instructions for the purchased model, as there may be different “ambushes” in the form of connecting threads, but located on the back of the case. That is, you will not be able to connect the pipes after fixing the boiler to the wall (if it is suspended) without removing it again. On the boiler body itself there may be diagrams showing the order of circulation of the coolant, we also carefully familiarize ourselves with these diagrams.

Connecting an indirect heating boiler

If the length of the pipeline is large, then the following situation is observed: we open the tap, for example, in the bathroom and wait until the cold water drains and hot water flows. It seems that we do not use cold water at the same time, but we will pay for the water meter as for used water.

Therefore, an indirect heating boiler is connected with recirculation, the meaning of which is to “loop” the movement of hot water in the water supply system, to make this movement continuous. And then, whenever we open the tap, hot water will flow from it.

However, if the length of pipelines is small (within 2-3 m from the source of hot water to consumers), then recycling can be omitted. At a greater distance - it is desirable (the reason is described above).

So, consider connecting an indirect heating boiler with recirculation:

The main rules here are as follows: the main riser coming from the hot water outlet, if it is a PPR pipe, then its diameter is 32 mm, the wiring can be made 20 mm and it can also be returned to the outlet for connecting the recirculation.

If there are a lot of consumers, then it is better not 20 mm, but 25 pipe for wiring. So, for a house of 600 m2, the 20th pipe is enough. The second prerequisite is the insulation of the entire pipeline, since we spend energy resources (= finances) to get hot water, and with a long pipeline there will be large heat losses. Especially if the pipe is hidden in concrete. You can insulate with polyethylene foam.

The pump must be with a brass body. Pump power starts from 15 W and above. The choice of pump power depends on the number of consumers and the length of the pipeline. Towel warmers are especially important.

There are pumps with a timer, which has a scale of 24 hours; this timer can be programmed to make hot water at the required time (when there is a need for it, for example, in the morning for washing or in the evening for a shower, bath ...). At other times, the pump does not work, hot water does not “run” through the pipes, which means it does not cool down and therefore resources are not wasted on heating.

The heated towel rail must be connected without breaking the main line, but parallel to it, like radiators in single pipe system. This is necessary so that the pipeline is not interrupted if the heated towel rail is removed.

If consumers are connected through a collector, then recirculation can be diverted directly from the collector and to the boiler. And it is possible and from the last consumer.

Another scheme for connecting an indirect heating boiler with recirculation:

I think it's not worth explaining what the numbers mean, all the devices in the diagram are easily recognizable. Why are they put in the water supply system here? expansion tank? For the same purpose for which it is installed with heating systems: heating water is accompanied by its expansion, excess water needs to be displaced somewhere, it is better to go into an expansion tank than through connections in pipes.

Not all indirect heating boilers are designed for recirculation. Those that are intended have three inputs: 1 - for cold water inlet, 2 - for heated water outlet, 3 - for recirculation connection (this input is somewhere in the middle of the case, which was discussed in the diagrams above).

Is it possible to recirculate if there are two inputs on the boiler? It is possible: from the outlet on the boiler we lead the pipe to the consumers and, returning it, we cut it into the cold water supply pipe somewhere not far from the place where it is connected to the boiler. This place must be installed check valve which will not give cold water to act to consumers on this branch.

Well, since we have already touched on the topic of recycling, we will analyze a couple more questions.

Why not connect the recirculation to a wall-mounted boiler, without a boiler?

Can. But with any opening of the tap (in the bathroom or in the kitchen), the gas burner will light up, while the pump for the heating system will turn off. With frequent use of water taps, the heating system will turn off every now and then, which is not good either for it or for the boiler.

In order to mitigate this disadvantage, it is desirable to have storage capacity(not necessarily an indirect heating boiler), well insulated, in which hot water will accumulate.

So you can recirculate in the presence of a heated towel rail:

That is, the recirculation pipe is connected to a heated towel rail (or vice versa?), which is why the heated towel rail is warm at any time of the year.

Results for choosing a water heater

Let's sum up the choice - not only indirect water heater, but in general, because this article is the final one in a series on how to choose a water heater.

Before buying, you need to decide which energy carrier will heat the water: gas or electricity.

If there is no gas, then, most likely, to choose between electricity and ... electricity (or firewood? - but I don’t want to talk about something completely sad :)). And then the question arises: instantaneous or storage water heater is better?

To be honest, the question is not correct. A well-formulated question already has part of the answer...

The Right Questions here:

What are my (family's) water needs?

For what purposes do I (we) need water?

Is it important for me (us) to save energy (=money)?

If you're thinking about an instantaneous electric heater, will the wiring hold up? If you stopped at the accumulative one, then you should look for a place for it - due to the considerable volume of the unit.

If you already have a double-circuit wall-mounted gas boiler, then there are no questions at all (if such a boiler provides enough hot water).

If the gas boiler is floor-standing, single-circuit, or there is not enough hot water from a double-circuit boiler, then you should pay attention to and simply connect it to the boiler, as referenced in the same article above.

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Country houses and cottages are rarely connected to centralized system hot water supply. In most cases, their owners set their own DHW system. Depending on the individual needs of residents, different types standalone equipment:

• with instantaneous water heaters;
• with a double-circuit boiler and built-in boiler;
• with a single-circuit boiler and an indirect or combined heating boiler.

Buying a single-circuit boiler with an indirect or combined heating boiler is suitable for a large family. The installation of such equipment involves several points of consumption and a large consumption of hot water.

Types and principle of operation of equipment

Indirect heating boilers are wall-mounted or floor-mounted, but the principle of operation is similar. They use the energy of the heat carrier for space heating and for parallel heating of domestic water.

The design of the boiler is a tank with a coil connected to the heating circuit of the boiler. A coolant circulates through the coil, which heats the water. The larger the area of ​​contact with water, the more intense the heating process.

Capacitive units have a slightly different design. A container of a smaller volume with sanitary water is placed in a larger container, and the space between them is filled with a coolant. Due to this, the water in the internal tank is heated.

The disadvantage of the above systems is the dependence of water heating on the boiler and on the functioning heating system. This is extremely inconvenient in summer period when space heating is not required, and hot water is needed even in larger volumes than in winter.

Combined heating water heaters are used to solve this problem.

Combined heating boiler design

Combined type devices - indirect heating units (through the heating system) with switching to direct heating. To change modes, the equipment is equipped additional elements — gas burner or TEN. With all the convenience optional equipment requires security and individual systems control, which affects the price of the boiler.

Manufacturers of combined heating water heaters

Leading manufacturers heating equipment produce various modifications of boilers - wall, floor and combined. Many indirect heating devices of the brands ACV, Alphatherm, Drazice are presented in wall and floor versions with a built-in heating element. Other brands produce indirect heating equipment with the ability to connect a heating element as an additional option.