How to make a do-it-yourself indirect heating boiler: instructions and manufacturing tips

The presence of a water supply with hot water is part of the usual comfort for a modern home. However, it is not always possible to solve the problem of supplying centralized communications to suburban real estate.

Therefore, owners of private households arrange an autonomous supply of hot water, using a heating circuit as a source of heating. To solve the problem, you just need to build an indirect heating boiler with your own hands.

We will tell you how to make a device useful in everyday life. The article describes in detail the rules for installing and connecting equipment that supplies sanitary water to water points. You will learn how to prepare the boiler for launch and how to put it into operation.

Indirect heating boiler device

In fact, the apparatus is a conventional heat exchanger.

True, heat exchangers are traditionally built on the principle of “pipe in pipe”, and in this case, the elements of heat exchange are a vessel and a tubular coil. The storage vessel plays the role of an external “pipe”, inside of which is placed an “pipe” internal or a coil.

Passes through a tubular coil heating medium, and the inner region of the vessel is filled with cold water. The heat carrier heats the walls of the tubular coil, and those, in turn, warm the cold water in the vessel.

The traditional scheme of connecting an indirect heating boiler looks something like this. In this case, the device is paired with a heating boiler

Scheme indirect heating boiler usually done using counterflow technology of two media, different in temperature level. In other words, if the outlet for heated water is provided in the lower part of the tank, and the cold water feed pipe is higher, in this case the coolant is supplied to the coil at the upper level.

Reverse configuration is performed if the cold water inlet and outlet are reversed. In practice, schemes with an upper outlet of heated water are more common.

In order to reduce heat loss, a do-it-yourself indirect heating boiler should be insulated. Good heat insulator - mineral wool

Considering that the indirect heating boiler belongs to the thermal plumbing equipment, the apparatus and the piping adjacent to it are subject to thermal insulation.

It is wise to mount the system in close proximity to boiler heating system. This approach will provide less installation costs, and heat losses on the way from the heating system to the indirect heating boiler will be significantly reduced.

The following photo selection will familiarize with an example of manufacturing the simplest indirect heating boiler:

DIY design and installation

The main task at the design stage with your own hands is the selection of the storage tank, which would cover the demand for hot water with its volume.

Storage capacity selection

For most cases of operation of the system, the calculation of the need is done for 3-4 people (average family). According to the regulations, one person consumes about 70 l / day.That is, for an average family, it is enough to install an indirect heating boiler with a volume of 200 liters. With such a capacity, the need is fully satisfied.

Particular attention should be paid to the selection of a vessel for remaking it into an indirect heating boiler. It should be a tank strong, durable, not susceptible to corrosion

A tank for heating cold water is usually chosen for vertical installation, but the option of mounting in a horizontal position is also possible. It is permissible to use a container made of durable heat-resistant materials as a boiler tank.

Of course, the container material should be selected taking into account its high anticorrosion properties, permissible thermal expansion, and other operational characteristics.

Suitable materials include:

• aluminum;
• stainless steel
• special polymers.

It should be remembered: boilers of any type belong to vessels operating under pressure. In addition, the coolant of the heating system can be heated to a high temperature (90 ° C and above). Based on these properties of boiler systems, you should design and build a system with your own hands.

In practice, quite absurd constructions are often found, also made by one's own hands, for example, on the basis of an ordinary milk flask or a dining pan. Such decisions should be avoided.

This is a parody of an indirect heating boiler. Done with your own hands, but a completely different approach is required to compare with a really reliable and efficient device

The design of an indirect-heating boiler, executed by one's own hands, also includes the calculation of a tubular coil. Here it is necessary to calculate the required thermal power of this device in order to determine the length of the coil pipe and its diameter from the calculation results.

Calculation of coil length

The traditional material for the manufacture of boiler coils is copper or brass. It is recommended to choose exactly one of these materials, since both materials have a high heat transfer coefficient.

The efficiency of the coil (heating time and set the required temperature) largely depends on the correct calculation. It is also important to correctly install the spiral inside the vessel

To calculate the required values ​​for the manufacture of a boiler coil, the formula is suitable:

L = Q / D * (Tg - Tx) * 3.14

The letter designations are here:

• L - tube length
• Q - thermal power of the coil,
• D - tube diameter,
• Tg - hot water temperature,
• Tx - temperature of cold water.

Let's look at an example of how to calculate the length of a copper pipe under a 20 kW spiral for an indirect heating boiler.

There is a copper pipe with a diameter of 10 mm, purchased on the market in the bay. A vessel with a capacity of 200 l was taken under the boiler. The calculated temperatures of cold and hot water are 15ºС and 80ºС, respectively.

It is necessary to determine the size of the length of the copper pipe, sufficient for the production of a heat-exchange tubular spiral with a capacity of 20 kW. According to the formula, the following calculation is carried out: 20 / 0.01 * (80-15) * 3.14. Calculation result: the required length of the copper pipe is 10 meters.

The manufacture and processing of the coil

For the manufacture of an indirect heating boiler coil with a capacity of 150-200 liters, as a rule, a copper or brass tube with a diameter of 10 - 20 mm is taken. The tube is twisted in a spiral, taking into account a residual gap of 5-7 mm between turns.

The gap must be done necessarily (it is allowed to push the turns after winding), since compensation for the expansion of the metal is necessary. In addition, with this design of the spiral, full contact of water with the surface of the copper (brass) tube is achieved.

An example of self-winding a coil for an indirect heating boiler. A thick-walled polyethylene pipe is used as a drum. After winding, the coils move apart by 1-2 mm

In principle, copper or brass coils can be found ready for use.For example, take a coil from some technological equipment. But then you have to take into account the size of the available capacity and the correspondence of the spiral in terms of heat transfer power.

Often, selection in exact accordance with the parameters fails. Therefore, in order not to lose precious time in this sense, it is more profitable to make a tubular spiral heater yourself.

It is difficult to make a coil with your own hands without experience, but such a task is feasible. The main thing here is to perform high-quality winding of the spiral. It is recommended to use a drum of suitable material for winding a copper (brass) tube.

The diameter of the drum is less than the internal diameter of the boiler capacity by about 10-15%. As a result, if the inner diameter of the tank is 500 mm, then the diameter of the coil will be: (500 - 500/10) = 450 mm.

One of the options for installing a threaded fitting on the end of the coil pipe. The free end of the threaded fitting will fit into the hole on the vessel wall.

On the ends of the tube, twisted into a spiral, you will need to mount contact threaded fittings. To solve this problem it is necessary:

1. Get an even cut at the ends of the pipe by treating them with a pipe cutter.
2. Slip on the end of the pipe with crimping nuts.
3. To process edges of a pipe development.
4. Install fittings and tighten them firmly to the pipe with nuts.

It is not necessary to use exclusively threaded double-sided fittings. If you have the skills of soldering copper pipes and the corresponding tool, you can install one-way threaded fittings by soldering.

Also, depending on the material of the vessel body, the option of soldering directly to the walls of the vessel is not excluded. However, with the independent manufacture of an indirect heating boiler, this step is not recommended because of the complex technological operation.

When assembled on fittings or soldered, the heat exchange element (boiler coil) can already be considered ready for installation and subsequent operation. It remains to prepare the place for installation directly on the boiler tank and introduce a water heater into the vessel.

Boiler capacity preparation

How to put a finished copper (brass) spiral inside the boiler tank, if the tank is solid? In this case, it is necessary to carefully cut off the upper part and make a cover that will be bolted to the vessel body.

The seats of the lid and tank are leveled, ground, equipped with a rubber gasket. Meanwhile, the internal installation (and maintenance) seems more convenient if you make two caps on the tank - top and bottom.

An example of a device for a lid on a vessel that is used under an indirect heating boiler. Sealing is achieved by gasket and bolt fasteners around the entire circumference

After installing the cover on the boiler tank, the problem with installing the coil inside the tank disappears by itself. Now it’s enough to drill two holes on the vessel body, focusing on the location of the end parts of the spiral pipe. The diameter of the holes should correspond to the diameter of the threaded part of the fittings with a margin of 1-2 mm.

The threaded parts of the fittings are passed into the holes, after installing the gaskets. Then, on the outside of the tank wall, counter fittings are wound and the connection is tightly tightened.

With such a fastening, the heating coil is quite stable, but additional supports must be made. The flow of the coolant under pressure inside the pipe is often accompanied by the appearance of vibrations. Additional supports will compensate for the defect.

Variant of transition from the tubes of the coil of the boiler to the main lines with the heating medium coolant. Direct fittings simultaneously serve as fasteners

On the body of the indirect heating boiler, it is also necessary to make holes for collecting and draining water, press in short pipes in them, and install shut-off valves on the pipes.If desired, you can supplement the device with a pointer thermometer.

Having completed the installation of all components, the vessel body is closed from the outside with insulation material. Mineral wool with a top foil coating is suitable here.

Instructions for connecting and starting the system

First of all, a home-made indirect indirect home boiler needs to be connected to the heating main. Where an autonomous heating system is used, boiler include into the network of a home boiler.

Mechanical connection is made with the lid open on the boiler tank. After connecting, you need to open the shut-off valve, which connects with the return line of the coolant, and make sure that there are no leaks both on the outside of the device and inside.

Before you turn on a home-made indirect heating boiler fully in operation, it is recommended to test the system for leaks. In the photo - a factory copy

If no leaks are detected, open the coolant supply line. It is necessary to wait some time for the coil to warm up to the temperature of the heating system. In full heating mode, carefully check the coil and all connection points for possible leaks again.

If the check shows the integrity of the system, close the lid of the vessel and connect parsing lines heated water. Test the system in real heat transfer mode.

Conclusions and useful video on the topic

A used gas cylinder is often used to make home-made devices. Presenting a video on how to make BKN from a cylinder body.

Here is described only one option out of all possible that exist and are successfully applied. It should be noted that there are many options for independent designs of indirect heating boilers.

For example, instead of a cylindrical storage tank, rectangular vessels are used. The coil of the coil is made not single-layer, but multi-layer. Supplement the water heater with an electric heating element. Design ideas have no boundaries.

Do you want to share your own experience in the manufacture of an indirect heating boiler or useful information on the topic? Please write comments in the block below. Here, ask questions, express an opinion and post a photo.