Boiler indirect heating: an apparatus and principle of operation

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In private homes, cottages, sports complexes and hotels often use indirect heating boiler - water heater operates without connection to the public water supply. This equipment handles large volumes of water by heating, easily maintains the desired temperature and ensures an uninterrupted supply of hot flow.

In short, if you were looking for a budget heater supplied to the single-loop boiler - consider the option to install in the house BKN. And in order to simplify the task of choosing, we suggest to familiarize with the boiler purchase criteria, the principle of its operation and connection diagrams.

The content of the article:

  • Design features and principle of operation BKN
    • How does the boiler indirect heating
    • Pros and cons of BKN
  • Types of equipment and model variations
  • What to look for when choosing BKN
  • Nuances and the boiler wiring diagram
    • General principles of installation of the device
    • Wiring diagrams BKN to the source
    • return circulation system
  • Conclusions and useful videos on the topic

Design features and principle of operation BKN

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Indirect heating boiler can operate only on resources external source, but to maintain the system in the warm season, you can connect the heater.

To ensure an uninterrupted supply, the system provide recirculation loop - water will constantly moving through the pipes, and when you open the tap in the circuit connected to the water taps will flow hot flow.

boiler-boiler system

Indirect heating boiler is usually installed next to the boiler, and the "duet" covers quite a large area, especially if both units Floor Type

Thus, the device allows you to save a lot of energy, but at the same time receive no less comfortable than using a centralized hot water system.

How does the boiler indirect heating

Device, heating water by indirect principle. - a storage capacitance with insulation, which is installed inside the heating element, from the external coolant.

Tank itself can be made in the shape of a rectangle or a cylinder, and its walls are provided tubes - for the circulation of hot water from the heating system and the input / output water pipes.

The basis of design is a metal or plastic container with a capacity of ten to several thousand liters. Inside the tank can be treated with a coating of enamel, ceramic or glass porcelain, which helps to maintain proper water quality and avoiding corrosion.

Heat loss from the housing protects the insulation layer of polyurethane foam or mineral wool.

Driving device MKB

Spiral coolant can uniformly arranged across the container, or firmly stacked bottom to heat the incoming cold water to faster (+)

To prevent scaling in the top of the container set magnesium or titanium anode, which softens the water, it protects the metal from corrosion and galvanic prolongs the "life" of the device.

Also, the device is provided with a temperature controller controlling the heating to a certain temperature, and safety valvesWithin a protected group.

Pros and cons of BKN

The main advantage of indirect heating boiler - saving on energy. For his work do not need to connect a gas burner or use electricity, it requires a direct heating device.

Heating provides all the necessary resources, so hot water - practically free "bonus", which will help to save the family budget in the cold season.

Heater for boiler

Most water heaters of indirect heating additionally equipped with heating elements with temperature control, to be able to use the device and in the warm season, when the heating is switched off

Other advantages of PEM:

  • High performance - a tank with a volume of 100 liters is able to "give" for hour about 400 liters of hot water (assuming a sufficiently powerful boiler).
  • Long service life - the coolant is not in contact with running water, in similar devices of direct heating.
  • Do not overload the power grid - it operates from an external power source.
  • Instantaneous hot water - no need to wait until the leak cold stream as using gas columns, or heat up the spent tank like electric boiler.
  • affordable - If desired, the system can be assembled and with their own hands.
  • Connectivity to several energy sourcesFor example, the solar collector to the vacuum, the boiler, geothermal heat pump.

Of course, without the drawbacks too, was not here. With all the advantages, the speed of heating the water in the device leaves much to be desired - for processing 100 liters even modern equipment will spend at least 15-20 minutes, and the home-made system can not cope and hour.

Also indirect heating boilers rather cumbersome, therefore occupy an impressive amount of free space. For larger tanks may need a separate room.

Indirect heating boiler own hands

Indirect heating boiler can be made from readily available materials, using a bent copper tube coil, ample barrel with a lid or a gas cylinder to the tank

In addition, the cost really is the device will be only during the heating season, and will either have to start the boiler, or provide alternative sources of heat in the warmer months - solar panels, TEN. And the price-quality "kosvennika" exceed counterparts with direct heating.

Types of equipment and model variations

The most common type of device is a storage tank, inside which are placed steel or brass tube (coil) with circulating coolant.

From the number of turns of the helix at its speed depends on the water heating. The operating principle of such design indirect heating boiler is extremely simple: in cold water enters the tank and heat transfer fluid moving through the coil, it heats up to the desired temperature.

But there are also devices designed on a "tank in tank", where instead of coiled tubing two containers of different diameters are used.

The system works as follows: in a smaller reservoir of the incoming cold water which is heated by hot coolant circulating between the walls of the tanks.

In such devices water becomes warm in a few minutes - a large heating area allows the equipment to operate efficiently in a continuous mode, ensuring an uninterrupted supply of hot flow.

boiler scheme

Boilers operating according to the "tank in the tank", not only was rapidly heated to 90⁰S water, and have a self-cleaning function (+)

Combined PEM for heating the water can use the energy from several sources or be equipped with embedded TAN.

Varieties KN boiler


  • Wall - typically, a device with a small engine capacity of up to 200 liters. Mounted on special brackets on any vertical surface, sufficiently strong, to support the weight of a fully filled tank (plasterboard definitely not fit). It can be positioned high enough not to occupy valuable area of ​​the room.
  • Floor - capacious boiler, designed for a large number of consumers. However, for the device with a capacity exceeding 1000 liters, it is recommended to allocate a separate room - equip boiler. But such a system is usually installed to service the large houses, businesses, hotels, and other institutions, for family use, you can do on the device 250-300 liters.

The shape of the tank:

  • Horizontal - it takes up much space, but it is easier to maintain your own desired level of water, without having to connect.
  • Vertical - saves space, but very limited in spaciousness.

Depending on the use of nuances, the characteristics of the layout and the space available, you can choose optimal model of BKN, which is organically fit into the design space and provide an uninterrupted supply of your home hot water.

What to look for when choosing BKN

One of the main parameters, which should be the decisive factor when buying a boiler - its capacity. To learn the necessary capacity of the tank, it is advisable to focus on the number of people in your family.

Recommendations on engine capacity:

  • 80-100 l - 2 consumer;
  • 100-120 l - 3 persons;
  • 120-150 l - 4 user;
  • 150-200 l - 5 consumers.

It is important to separate the concept of "total capacity of the tank" and "working capacity", because the spiral pipe located inside the boiler, occupies a large area. Therefore, be sure to ask when buying, how much water actually placed into the instrument. The technical characteristics of this nuance must be specified.

Also, in addition to "indiscriminate" conversion of potential customers, it is necessary to take into account both the frequency and the volume of water use. For example, if your family like to soak in a warm bath, not a quick take a shower, a working tank capacity must be appropriately - not less than 120 liters.

Outdoor boiler with a boiler

BKN is advantageous to use complete with a single-circuit or solid-gas boiler, but if the water flow is less than 1 l / min, would be cheaper double-pressure boiler, which will be replaced by much less than the system with indirect heating

Other important parameters are:

  1. Power - the more water consumption, the higher should be the life of the device. But it is important to power "kosvennika" does not exceed the capabilities of the heating system (or other external power source). For example, if the volume of the storage tank varies from 120-150 liters, boiler capacity should be at least 23 kW, and for the need to have 160-200 liters 31-39 kW.
  2. heating time - parameter dependent on the tank volume and the number of turns on the coil (large or combined capacity may be provided with multiple helices).
  3. tank material - for long-term use is best suited stainless steel or medical steel boilers.
  4. thermal insulation - in the cheaper models applied foam, which quickly wears out and skips the heat, so it is best to buy a more expensive device, which has been used polyurethane.
  5. Control - The device can operate in an automatic mode, and if necessary cutting off the flow of water running, controlling heating by the temperature sensor.

When selecting the shape and size of the tank is also necessary to bear in mind that although it is theoretically possible to boiler to install in any room where there is access to the heating main, its optimal location - close with the boiler. Since heat transfer is most efficient.

Indirect heating boiler can be done personally. Instructions for the production of the unit is described in this article.

Nuances and the boiler wiring diagram

As mentioned, for water heating BKN uses energy external source. Therefore, before connecting to the coolant is important to select a suitable circuit for device mounting. Consider the most common options.

General principles of installation of the device

Mount the boiler must be prepared on a flat surface in the immediate vicinity of the boiler. Suspended models are mounted on a concrete or brick wall at the same level or slightly above the boiler.

For outdoor device - should be leveled on a level plot allocated for placement of the tank (if critical uneven floor, the stand can be in the form of a podium).

Itself tying BKN It is intended to connect the device to two systems - water and heating. For this purpose, special connections available housing.

Boiler Safety Group

The boiler security group includes indirect heating return and relief valves, which protect the system against leakage of high pressure hot water and

joining principles:

  1. Cold water from the drainage system must come to the bottom of the tank and hot - leaving from the top.
  2. At the inlet of cold water must be set check valveWhich warns the leakage flow of hot boiler by decreasing the pressure in the system.
  3. In the middle of the device may be arranged for supplying the recirculation point.
  4. When the heating circuit is activated, movement of the coolant should be from top to bottom. That is, a hot water pipe is put into the upper nozzle and the tube cooled with - out below.
  5. All the connections you need to provide valves with cap nuts to secure the opportunity to turn off the boiler, for example, in case of device replacement or repair work.

With this scheme, the maximum efficiency of the device is achieved, as the coolant circulating in the coil heats the water in the tank top, the residue gives low temperature layers and heat is supplied for the new heating within the caldron.

Wiring diagrams BKN to the source

To choose the right connection of the boiler circuit to the heating system, must take into account the possibility of the existing layout and position of the heater. There are several solutions.

Option 1. The most common scheme for permanent use hot water - connection via a three-way valve. It presupposes the existence of two heating circuits - core and single for BKN.

For this purpose, hot water supply cuts circulation pumpAnd after it is installed three-way valve, which is controlled by the boiler thermostat.

The circuit works as follows: when the water temperature in the boiler falls below a predetermined mark, on a signal switches the thermostat valve system for heating storage tank, and after reaching the desired parameter - sends the stream to circulate obschedomovyh circuit.

three-way system

For correct operation of the three-way circuit is important to adjust the thermostat data to programmed for the boiler temperature was set lower than that in the boiler thermostat (+)

option 2. Installing double-pump system - the scheme should be used if there is no need for a permanent and large quantities of hot water. For example, the boiler is set in a country house and is only used on weekends.

In this case, BKN and the boiler are connected in parallel, and the coolant flows will move along two highways. To force the movement of the water pump is set two: in the heating circuit feed pipe and a boiler.

Heating is provided by a thermostat, which temporarily disconnects heating radiator, directing all resources of the system to the boiler.

dual pumping scheme

By dvuhnanosnoy circuit heating circuit is switched off for the duration of the boiler, but those for 30-60 minutes, which is needed for heating the tank "from scratch", radiators will not have time to cool critical (+)

option 3. For areas where multiple loop heating system used, e.g., in addition to the radiators installed warm floor, Used hydraulic distributor.

Gidrostrelki redistribute the pressure on the individual circuit sections and provide smooth movement without the aid of coolant circulating pumps.

Scheme gidrokollektorom

Without engineering experience such a complex scheme are unlikely to be able to do most - to provide mass nuances and establish smooth operation of the system, it is better to turn to professional designers (+)

Without gidrokollektora in multi-loop system can be damaged pumps and even heat stroke happen to damage the radiator.

return circulation system

If in the boiler, a third input thereto possible to connect the recirculation system. To this point in the recirculation on the device is put looped path.

recycling scheme

The water flow is in constant motion due to the circulation pump, so instantaneously delivers warm water to the point of consumption (+)

To implement the additional circuitry needed to mount the circuit and set the following items:

  1. check valve at the inlet to the heater.
  2. automatic air ventThat protects the pump against air infiltration before starting.
  3. Safety valveThat will prevent the pressure differentials.
  4. Diaphragm expansion tank, Which will leave a surplus of water at the pressure in the system. Please note that the capacity of the reserve capacity should be not less than 1/10 of the volume of the BKN.

If in the indirect heating device is not provided for the boiler inlet for the recirculation loop can make a frame return line to the cold water pipe and install a pump. Then the connection is made with the following scheme.

recirculation loop

Selection strapping circuits, with or without recycling it should be based on the design MKB and heating system and power equipment (+)

Connection through the return circuit provides an uninterrupted supply of hot water - i.e., will not have to wait until the coolant warms the water in the tank.

Conclusions and useful videos on the topic

Before deciding on the purchase and installation of a new water heater in the house, we offer to study videos that demonstrate the benefits of "kosvennika» and the nuances of his connections.

In this video you can learn how to operate boilers of indirect heating with coolant, located inside the coil:

All the nuances of the internal structure and operation of various types of boilers of indirect heating in a detailed video of the lecture in master practitioner:

Browse and connect the device to 300 liters, which is powered by two coolants - boiler and solar panels:

Detailed analysis of PEM devices and circuits connected. Practical tips from the master:

As for maintenance, the boiler Indirect heating - quite unpretentious equipment. When properly installed and adjusted the system may need only a replacement of the magnesium anode every 6-12 months and preventive flushing tank.

The frequency of maintenance depends on the quality of tap water and use intensity. But if you have a device that works on the "tank in tank" technology, which has self-cleaning function, Consumable not need to change.

However, the regular maintenance of the equipment can always negotiate with the masters, specialize in the installation and repair of water supply systems.

Questions? Or have a desire to share their personal experiences on the selection, connection and use of indirect heating boiler? Please leave comments on this article.

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