To provide the house with the necessary amount of hot water, an additional device is used - an indirect heating boiler (BKN). Its use can be considered one of the most rational and economically viable.
We will try to find out which circuit of the indirect heating boiler strapping is the most effective and how to connect the equipment in order to avoid common mistakes.
Choice of indirect heating boiler
Before buying and connecting a buffer battery tank (also called BKN), you should understand the design features of the most popular types. The fact is that there are many types of equipment, including combined models that work from heating systems and alternative energy sources at the same time.
We will look at traditional boilers with a coil that use hot water as a heater.
Design features and principle of operation
What does indirect heating mean? Direct-heated devices operate by connecting to electricity or a gas burner; the BKN has a different heat source. Water is heated by connecting to a hot water supply, that is, it turns out that the source is the coolant - hot water (or its substitute).
Outwardly, the BKN resembles a standard water heater - that is, it has a barrel-shaped form, although modern models are more ergonomic. For ease of use and installation, they are given a rectangular configuration
If we consider new models of well-known brands, we can see that gas boilers and KN boilers often have the same design. They are mounted next to or one below the other - so you can save on the area of accommodation.
The main element that performs the heating function is a steel or brass heat exchanger (coil) with a large surface area, which is located inside a metal tank covered with a protective layer of enamel. To prevent water cooling from happening too quickly, on the outside the case is surrounded by a layer of thermal insulation, and some models by a casing.
If you want the water in the boiler to heat up quickly, choose a model with several heat exchangers, and to cool slowly - with high-quality thermal insulation
An important part, which is now equipped with most of the heating devices, is the magnesium anode. A rod mounted in the upper part of the device protects metal parts from corrosion, as a result, the water heater lasts much longer.
High pressure barriers include a safety valve and an integrated thermostat. If the tank is not equipped with a safety group, it is installed separately, when arranging the strapping.
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Connecting the boiler to communications
Operation of a water heater paired with a boiler
Application in a strapping of a broad tank
Indirect boiler automation
Often the water circulating in the heating system does not exceed 65-70 ° C. Many doubt its effectiveness when it acts as a heat source for heating in BKN. In fact, the indicated temperature is enough, because the speed and magnitude of the heat transfer largely depends on the area (rather large) of the coil contacting with water.
How is the heating process? Cold water intended for heating enters through a separate hole and fills the entire tank. Water, but already heated, also enters the heat exchanger from the boiler. The hot walls of the coil transfer heat to cold water, which at the outlet already has a temperature suitable for taking a shower or washing dishes.
Advantages of Controlled Equipment
Possibility of control - a characteristic that affects the assembly of the entire water heating system. There are two types of BKN: simple (cheaper) and with a built-in control function.
The control of the heating process is necessary if the main heating device - for example, a gas or solid fuel boiler - does not have a control unit
A distinctive feature of the controlled models is the additional equipment with a temperature sensor and the possibility of feeding / stopping water supply to the heat exchanger. Such equipment operates in automatic mode.
To start, you must connect:
- hot water inlet / outlet;
- cold water supply to the tank;
- collector for the distribution of heated fluid at the outlet.
After that, you can start the boiler - the water will begin to heat up.
If the boiler operates in automatic mode, there is no need to control the boiler. But it’s still better to equip it with a temperature sensor, for this there is a place in the case
The process of connecting and tying an indirect heating boiler occurs in one of the ways (description below).
How can control affect water temperature? Almost nothing. The maximum value that the outlet temperature can reach does not exceed the parameters of the coolant in the DHW system. Most likely, it will be 1-2 ° C lower.
If more intensive heating is needed (this can happen if the boiler usually operates in low temperature mode), then it is better to choose a model with a built-in heating element.
It is advisable to buy such equipment together with solid fuel boilers (water remains hot even after the boiler cools down).
Varieties of devices with additional features
Tanks with a simple design are only part of the assortment on the market for water heating equipment. There are many boiler models, the functions of which are very useful for integration into the domestic hot water system.
For example, one of the purposes of more expensive models is heat storage. If there may be a power outage or daily consumption rates are too high, the accumulation mode will be very useful. The structural features of such models are enhanced thermal insulation and an increased volume of the tank (300 l or more).
Another option that implements the fastest supply of hot water to the taps is a recirculating boiler. Unlike the conventional design, this one is equipped with three communication pipes with a hot water supply system. Hot water is supplied in two, cold in one. The water supply is carried out using a pump.
When using a model with recirculation, you can arrange an additional useful circuit, for example, for mounting a heated towel rail.
Less common than devices with coils are tank-in-tank models. The water tank to be heated is inside, the heating circuit is outside
Water in such a tank heats up faster than in units with a heat exchanger, but its cost is higher.
Tank size and value
Cylindrical and cubic tanks differ in their size. Their volume is indicated in liters: there are small models for 80-100 liters, but there are also bulky ones that can hold up to 1400-1500 liters. The size is selected based on the family's need for hot water.
Dimensions are important during installation. For wall mounting, only light models are suitable - up to 200 liters, all the rest are floor-mounted. Both horizontal and vertical wall mounted units have special mounts; floor-mounted units are equipped with legs or a small stand.
The nozzles necessary for connecting water and coolant are usually discharged from the back and top, so that it is more convenient to connect the tank to the pipes. The front panel of a number of models is equipped with a temperature sensor (relay) and a technical hole
Rectangular units occupy a little less space than cylindrical ones, due to the tight fit to the pipes.
The nuances of the strapping device
It is easier to make wiring and piping if the KN boiler is installed together with the boiler, pumps and other equipment involved in the assembly of the DHW system. Embedding an additional device into an existing network is much more difficult.
In any case, for the normal operation of the devices you will have to follow a number of rules:
- choose the right installation location - as close to the boiler as possible;
- provide a flat surface for mounting the boiler;
- to protect against thermal expansion, install a membrane accumulator (at the outlet of heated water), the volume of which is at least 1/10 of the volume of the BKN;
- equip each circuit with a ball valve - for convenient and safe maintenance of devices (for example, a three-way valve, pump or the boiler itself);
- to prevent backflow on the water supply pipes, install check valves;
- improve water quality by tapping filters;
- correctly position the pump (or several pumps) - the motor axis should be in a horizontal position.
For safety reasons, do not attempt to attach heavy devices to plasterboard or thin wooden partitions. Suitable are concrete and brick walls. Brackets or other types of holders are fixed with brackets, anchors, dowels.
Regardless of the type of device - floor or wall - if possible, it is mounted above the level at which the boiler is installed, or at the same level. For the floor, you can make a pedestal or a solid stand up to 1 m high
When installing, the nozzles are directed towards the boiler (even if they are masked in the back or behind the false wall). Unreliable equipment, such as corrugated hoses that do not withstand the pressure and pressure of the water, must not be used.
For the normal operation of the indirect storage water heater, the following functional devices must be included in the piping:
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A sophisticated technical system should be equipped with pumps that supply hot sanitary water to the taps and stimulate the movement of the coolant along the heating branch, as well as along the water heating circuit in the boiler
Cold water coming from a common or autonomous water supply must be cleaned through a sump or filter system that destroys lime salts before being fed to the boiler. Filtration will prevent the formation of mineral sediment
A pressure reducer should be installed after the sump or water filtration system. However, it is needed only if the pressure in the branch exceeds 6 bar
Before the cold water enters the boiler, a check valve is required, which will prevent the reverse flow
In order for the heating water to have a reserve for expansion during the period when it is not used, an expansion tank and a pressure relief valve to relieve pressure are included in the piping
In order to prevent excessively hot water from entering the faucets that threatens burns, a three-way mixing valve must be installed in the circuit. It will mix cold portions with hot water, as a result, the water will be at the water temperature necessary for the user
In order for the heat transfer agent from the heating to enter the “shirt” heating sanitary water only when it is needed, a two-way thermostat is installed. Its server is connected to the temperature sensor of the water heater
If the consumption of hot water in the house is large enough, it is advisable to purchase a boiler with a built-in additional instantaneous water heater or buy a separate device and include it in the branch of hot water supply. In case of lack of it, a miniature flow-machine will turn on and save the situation
Circulation and pressure pumps
Sump for cleaning cold water
Water pressure reducer in water supply
Check valve before entering the boiler
Safety valve and diaphragm tank
Three way mixing device
Two-way thermostat heating circuit
Optional flow-through heat exchanger
Priority Connectivity
Before installing an indirect heating boiler in the DHW system, it is necessary to choose the principle of its connection: with or without priority. In the first case, when it becomes necessary to quickly obtain a large amount of hot water, the entire volume of the coolant is pumped through the BKN coil, as a result of which the water heats up much faster.
After the water temperature has reached the required level (measured with a thermostat), there is a way to redirect the flow to the radiators.
Connection without priority does not allow the passage of the entire volume of the coolant, and the boiler serves only part of the total flow. With the equipment of such a scheme, the water heats up longer.
BKN connection scheme without priority: a separate circuit is connected to the boiler, therefore, there is no possibility to cut off radiators (or other heating devices)
The priority scheme is more effective, since it makes it possible to quickly heat the required amount of water without compromising heating. If you turn off the heaters for 30-50 minutes, the temperature in the rooms in such a short period of time is unlikely to drop, but there will be enough heated water.
The only condition for priority circuit equipment is a powerful boiler.
Schemes and rules for connecting BKN
The wiring diagram and installation features of the indirect heating boiler depend on the class of the device and the heating system in the house. It is necessary to choose the installation site correctly, focusing on the location of the boiler, the inset of the pumps and the existing wiring. Let's try to figure out what needs to be considered when installing heating equipment.
Option # 1 - piping with a three-way valve
This is one of the most popular schemes, since when it is used, the heating system and the BKN are connected in parallel, equipped with shutoff valves. The boiler must be installed near the boiler, feed the circulation pump, then a three-way valve.
This scheme is successfully applied if several heating devices are used, for example, two different boilers.
The three-way valve is a kind of switch that is controlled by a thermal relay. When the temperature drops, the automatics are triggered, and the coolant flow from the heating circuit is redirected to the BKN
In fact, this is a priority system that provides quick heating of water in the boiler with the radiators completely turned off for a while. As soon as the temperature rises to a predetermined value, the three-way valve is activated again and returns the coolant to its former channel - to the heating system. This binding method is useful for those who use the boiler in constant mode.
Option # 2 - circuit with two circulation pumps
If the boiler is rarely used (for example, seasonally or on weekends) or there is a need for water, the temperature of which is lower than in the heating system, a circuit with two water heating systems with forced circulation is used: circuits, implementation options, technical details of circulation pumps. The first is installed on the supply pipe, directly in front of the BKN, the second - on the heating circuit.
The circulation pump is powered via a thermal relay, therefore it only starts to operate when the temperature drops below the required value. Acceleration of heating occurs along with the inclusion of forced circulation
There is no three-way valve in this circuit; the harness is equipped with simple connecting tees.
Option # 3 - harness with hydraulic arrow
This connection is used for volumetric boilers (200 l and more) and branched heating systems with many additional circuits.An example is the heating system in a two-story house, where in addition to a multi-circuit radiator network, heated floors are used.
A hydraulic distributor (hydraulic arrow) is needed to simplify the heating system layout and to avoid installing recirculation pumps on each heating branch
The equipment of the hydro-arrow allows avoiding thermal shock, since the water pressure in each circuit will be the same. It is quite difficult to make a strapping on this scheme yourself, so it is better to contact professional installers.
Option # 4 - Use of coolant recirculation
Recycling is useful when there is a circuit that needs a constant supply of hot water - for example, a heated towel rail. If it is connected to the heating system, the coolant will constantly circulate, and the dryer will function and at the same time serve as a heating device.
The use of recirculation has one big advantage - no need to wait until the water heats up to the desired temperature, it will always be hot
But this scheme also has drawbacks. The main one is an increase in fuel costs, because constant heating of the water cooled in the circuit is required. The second minus is the mixing of water in the boiler. Typically, hot water is in the upper part, and from there it flows to the points of drawdown, here it mixes with cold, as a result of which the temperature at the outlet is slightly lower.
There are models of boilers with built-in recirculation, that is, with ready-made pipes for connecting a heated towel rail. But it’s cheaper to buy a regular tank, using tees to connect.
Option # 5 - non-volatile boiler system
A distinctive feature of this scheme is the installation of a boiler at a higher level than the boiler and heating devices. Preference is given to wall-mounted models that can be hung at a height of 1 m above the floor.
Floor models, specifically within the framework of this scheme, are inferior to wall speed and heating quality. The water temperature is much lower (approximately as in the return pipe), therefore, the supply of hot water is less
The non-volatile type of heating is based on the application of the laws of gravity, therefore, the coolant will circulate when the power is turned off. In normal operation, the circulation pumps can be connected.
Indirect heating boiler connection progress
After choosing a circuit, it becomes clear what equipment is required. In addition to the main devices, valves, ball valves, distribution combs, valves (three-way or reverse) may be needed.
Procedure:
- prepare the installation site (on the floor or on the wall);
- make a wiring by marking the outlets of hot / cold water in red / blue;
- integrate the tee and pressure relief valve, securing the joints with sealant;
- fasten the taps of hot (top) and cold (bottom) water;
- connection to a source of electricity, install a thermostat and automation;
- select a heating mode;
- test the connection.
These are general guidelines needed to present the scope of work. When connecting a specific model, you must follow the instructions that come with the kit.
The following videos will tell you how to determine the connection diagram and install the equipment correctly.
General information about wiring diagrams:
Practical tips for connecting equipment:
How to make the binding of an indirect heating boiler can be found in the following video:
Professional overview of a 80 liter boiler:
In addition to installing and connecting the BKN, regular maintenance is required. It consists in washing the inner cavity of the tank, removing deposits and scale, replacing the magnesium anode. Maintenance of the equipment does not require much effort. If the wiring is done correctly, an urgent repair is not required, but if you encounter problems with the equipment, we recommend that you contact a specialist.
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