Optimization of engineering and communication systems in the household inevitably leads to the expansion of the functionality of the equipment. This trend is gradually leading to energy savings, simplification of installation activities and improved operational ergonomics. A striking example of combining several functions is an indirect water heater. What is it in terms of purpose? These are household boiler units that can be used simultaneously for heating and hot water supply (DHW).
Equipment design
The general device is similar to typical instantaneous water heaters, but there are many differences due to the peculiarities of the principlework. As for similar features, they include plumbing infrastructure with pipes and means of regulation. What is it in an indirect water heater? Technically, the set of components of this infrastructure can be represented as follows:
- Capacity (tank containing water). This is usually an enameled steel tank.
- Heater cover.
- Electrical connection cover.
- Polyurethane insulation.
- Tubular heat exchanger.
- Pipes for directing cold and warm water.
- Hot water outlet.
- Circulation (pipeline). Mainly used in equipment with large heat exchangers.
- Thermostat with indicators and controls for operating modes.
- Safety block.
Now it is worth considering the design features of boilers with indirect heating. Mostly they are expressed in the water heating system. If gas burners and electric heat sources (heaters) are used in conventional instantaneous water heaters and storage tanks of the DHW system, then in this case a coolant flowing through the coil is used. It is he who heats the water in the tank from the inside. However, there are also indirect heating water heaters with heating elements, which can be “wet” or “dry”. That is, in one case, the electric heater is in direct contact with the aquatic environment, and in the second, it is supposed to be placed in a sealed tube that isolates the heating element, transferring thermal energy from it to the water from the outside.
Working principle
If once-through type water heaters can be considered as autonomous, then indirectly heated boilers are at least dependent on boilers. That is, a bundle is being implemented in which the boiler equipment acts as a source of thermal energy for an indirect heating water heater - what is it in operational practice? It has already been said that the main structural difference of boilers is a tubular heat exchanger in the form of a coil, through which the coolant (water or antifreeze) circulates. It is connected to the boiler through a special tubular line with a circulation pump, which ensures the movement of hot liquid. And already inside the boiler tank, water is heated as a result of heat transfer from the coil. By the way, there are different designs of heat exchangers, which largely determine the heating rate. For example, a coil-in-coil system provides fast, even heating.
But where does the energy come from for the operation of the circulation pump and the further return of water to the DHW system? Firstly, there are electric water heaters of indirect heating, some of the functions of which are supported by the local power supply at 220 V. Moreover, this does not mean at all that a heating element is necessarily present in such a unit. To ensure the operation of the circulation pump and to carry out electric heating are fundamentally different tasks that require energy costs that are incomparable in terms of volume. Secondly, the operation of pumps, thermostats and automation can be maintainedseparate power supply circuits - including those associated with boiler equipment. In this case, the boiler acts only as a structural base for containing heated water with pipeline channels for its filling and return.
Fields of application for boilers
The design complexity of an indirect water heater results in a wide range of applications. First of all, this is the household segment. In private country houses, boilers are used both for heating and for organizing hot water supply. Moreover, several points of consumption on different floors can be supplied with water at once - the possibility of delivering a resource in one volume or another will be determined by the capacity of the installation and auxiliary pumping equipment. In apartments, such devices are mainly used as a means of heating, integrating the design into a central water supply unit. In industry, for technological tasks, indirectly heated storage water heaters with heat pumps are used. In various industries, they are used both as part of heating complexes and in air conditioning systems.
Varieties of equipment
The design of the boiler with indirect heating may vary, causing certain possibilities for placement, connection and organization of the workflow. To date, the following types of this technique are actively produced:
- Wall-mounted unit. As the name implies, the design is designed to be fixed to a vertical surface, which saves space. Usually wall-mounted indirect heating water heaters are used in apartments. They are characterized by low power, modest size and small tank volume.
- Floor boiler. From the point of view of technical and operational qualities, this is the opposite of the wall model. Such units have impressive dimensions, contain large-capacity tanks and, moreover, require a special carrier platform for installation. Scope of application - private households and the industrial sector.
- Boilers with recirculation. Models with a developed internal piping system and effective support from the circulation pump. This allows you to provide almost instant hot water to the faucet.
- Models with tank-in-tank design. A special design of an indirectly heated DHW cylinder containing two tanks (one inside the other). The inner container contains directly clean water for consumption, and outside it is heated by technical hot water, the temperature of which is maintained from the associated boiler or the heating element of the boiler itself. Such a complex device is required to maintain high performance, which allows the installation to work as an instantaneous water heater with a water temperature of about 90-95 ⁰С.
Main technical and operational characteristics
Without exception, water heaters are characterized by one list of operating parameters, which primarily include:
- Tank volume. On average, the range extends from 40-60 liters to1000 l. Minimum values of the order of 30 liters will be enough to supply hot water to one low-cost consumer - for example, a kitchen appliance. For comprehensive maintenance of the house, an indirect water heater of 200 liters or more will be required.
- Power. This characteristic applies to electric boilers. The average power range varies from 1500 to 3000 watts. Power affects the rate of water heating, taking into account the capacity of the tank.
- Boiler performance. The heating time of a particular unit will be directly indicated by its performance, which is expressed in liters of hot water released into the DHW system in 1 hour. With regard to household models, we can talk about a figure of the order of 500-700 l / h. For example, an indirect water heater MEGA W-E 220.82 with a tank of 220 l provides a capacity of 630 l/h, and Ariston NHRE heats up 350 l of water in 22 minutes.
Positive feedback about boilers
Experts generally appreciate the possibilities offered by the indirect heating concept. The implementation of this principle on the example of a water heater saves the user from the mass of technical operations associated with the installation of electrical wiring. In addition, the high performance of such systems is also noted. With relatively modest operating costs, you can get full support for domestic hot water. This is especially true in cases where the tank of the indirect heating water heater is serviced by a heat exchanger from the boiler without the participation of heating elements. In this infrastructure, minimal energy costs are assumed, but with a high return.thermal energy. That is, in comparison with electrical equipment, experts note the advantage of a boiler in terms of energy efficiency, while against the background of gas units it will win in terms of safety and service life. Of course, the extent to which these positive factors of exploitation manifest themselves in a particular case depends on the characteristics of the applied model.
Negative reviews about boilers
Despite the above advantages of water heaters with indirect heating, engineers and designers of communication networks do not advise rushing to purchase this equipment without taking into account its weaknesses. Not in every case it will be possible to put up with its disadvantages:
- Powerful models take up a lot of space, which complicates the operational process and requires the installation of additional devices.
- According to price analysis, boilers are more expensive than conventional storage, and in some cases boiler equipment.
- Reviews are also ambiguous regarding the intensity of the indirect heating water heater. What is it from the point of view of an ordinary user? In essence, we are talking about the speed of heating water. It's not even that, on average, it is slow when compared with the capabilities of alternative systems. Criticism concerns the instability of heating, which may be due to external operating conditions, microclimate and season.
- Low maintainability. The technical and structural complexity of the equipment does not allow it to be repaired independently, and in somecases and perform maintenance without the participation of the service team.
Consumables for the boiler
When buying a water heater, you should also pay attention to the package. It may be incomplete or inappropriate, which in the future will force you to additionally purchase some accessories. This applies to plumbing fittings for connection - it is represented by hoses, pipes, fittings, clamps and flanges to ensure tight connections. For the installation of floor water heaters of indirect heating, it is desirable to provide a special platform with a heat-insulated coating. Factory devices are beneficial in that they make it possible to conveniently perform the lower strapping without invading the flooring structure. It would be useful to provide a set of spare parts. Experts recommend that you always have a magnesium anode on the farm to protect against corrosion and scale, a heat exchanger of a suitable format, valves and protective devices.
Indirect water heater connection
Different types of pipes can be used to perform piping (connection). If it is necessary to make a connection with a riser or a central pipeline, then metal products are used, and for less important transitional nodes between the boiler and domestic hot water, heat-resistant polypropylene can be limited. The contours are fixed with sanitary holders and clamps, but without a rigid clamp. As the instructions for indirect heating water heaters note, it should be possible tofree oscillation, since if the vibrating equipment works with a rigid grip, then damage cannot be avoided. Pipe insertion is carried out using nozzles and fittings of a suitable size. By the way, when drawing up a pipe laying scheme, it is desirable to minimize the number of transition nodes, joints and branches. If it is planned to create a multi-level DHW network with a large number of consumption points, then it makes sense to include a collector installation in the system.
Conclusion
The use of boilers can justify itself both in terms of the quality of solving the tasks of hot water supply, and in terms of economic feasibility. Both factors depend on how correctly the choice of a particular model was made. For a private house, it is quite possible to purchase a floor water heater with indirect storage type heating. The capacity can be 250-350 liters, which is enough to fully cover the needs of a two-story mansion. For a small apartment, you should give preference to a compact model with a wall-mounted installation of 60-80 liters. This solution will minimize energy costs by providing stable hot water and heating functions instead of centralized service.
