The principle of operation of the indirect heating boiler

The key to keeping our homes warm and comfortable is being aware of how our heating systems operate. The indirect heating boiler is a vital part of many heating systems. This essential appliance is essential to the effective distribution of heat in our houses, particularly in places where direct heating techniques might not be feasible or practical.

An indirect heating boiler functions somewhat differently from direct heating systems, which run hot water or steam directly through baseboards or radiators. It functions by indirectly heating water via a different closed-loop system. This implies that the water used for cooking, bathing, and other household tasks is separate from the water used for heating. Our heating systems are safe and effective thanks to this separation.

An indirect heating boiler operates on a fairly straightforward but very efficient principle. A heat exchanger is a component found inside boilers that transfers heat without direct fluid contact between two fluids, typically water or a mixture of water and glycol. The fluid inside the heat exchanger is heated by a burner or heating element when the boiler is turned on, increasing the fluid’s temperature.

The heat exchanger’s fluid transfers its heat to the water in the closed-loop system as it heats up. Warmth is then released into each room of the house via the circulation of this heated water through pipes to radiators, baseboards, or radiant floor systems. In the meantime, the heat exchanger’s fluid stays contained inside of its own system, guaranteeing a secure and effective heating process.

An indirect heating boiler’s adaptability is one of its benefits. It works with a variety of heat sources, such as heat pumps and solar thermal systems, as well as conventional gas or oil-fired boilers and renewable energy sources. This flexibility lowers energy use and lessens the impact on the environment by enabling homeowners to select the most sustainable and appropriate heating options for their needs.

What is an indirect heating boiler and what they are

A heat exchanger (coil or water jacket type, cylinder in cylinder) is housed in a water tank that serves as a water heater or indirect exchange boiler. The heating boiler or any other system that circulates hot water or another heat carrier is connected to the heat exchanger.

The heat exchanger’s walls are heated by the hot water from the boiler, which then transfers the heat to the water in the tank. This is how heating works. Such a water heater is referred to as "indirect heating" because heating does not happen directly. As needed, the heated water is used for domestic purposes.

An indirect heating boiler device

The magnesium anode is a key component of this design. The tank lasts longer because the intensity of the corrosion processes is reduced.

Types

Boilers for indirect heating come in two varieties: those with integrated controls and those without. Boilers without control powering a heating system are connected to indirect heating boilers with built-in controls. They have an inbuilt temperature sensor and a control on them that allows you to switch the hot water supply to and from the coil. All that’s required to connect this kind of equipment is to connect the cold water supply, the hot water distribution comb to the upper output, and the heating supply and return to the proper inputs. You can now fill the tank and begin heating it.

The primary boilers used by conventional indirect heating boilers are automated boilers. A temperature sensor must be installed during installation in a specific location (there is a hole in the body) and connected to a specific boiler input. Next, construct the indirect heating boiler’s plumbing in line with one of the schemes. They can be connected to non-volatile boilers, but special schemes are needed for this (see below).

What it should be remembered that the water in the indirect boiler can be heated slightly below the temperature of the coolant circulating in the coil. So if you have a boiler in a low-temperature mode and gives, say +40 ° C, the maximum temperature of water in the tank will be exactly that. You will not be able to heat it any more. To bypass this limitation, there are combined water heaters. They have a coil and a built-in heating element. The main heating in this case goes at the expense of the coil (indirect heating), and the heating element only brings the temperature to the set temperature. Also such systems are good when paired with solid fuel boilers – the water will be warm even when the fuel has burned out.

About the design elements, is there anything more to say? Multiple heat exchangers are installed in large volume indirect heaters, which shortens the time it takes for the water to heat up. Selecting models with thermal insulation is preferable because it will shorten the time that the water must warm up and allow the tank to cool more slowly.

Which boilers can be connected to

Boilers that use indirect heating can operate with any hot water source. Fits any solid fuel hot-water boiler that runs on wood, coal, briquettes, or pellets. Any kind of gas, electric, or liquid fuel boiler can be connected to it.

Diagram showing how to connect a gas boiler with an additional outlet for indirect boiler heating

As was already mentioned, there are models that have their own control, and then there are those that require less work for installation and piping. If the model is simple, the temperature control system and the boiler’s conversion from heating radiators to heating hot water must be considered.

Forms of tanks and methods of installation

Indirect heating from a boiler can be mounted on the wall or placed on the floor. The maximum capacity of wall-mounted models is 200 liters, while floor-standing models can accommodate up to 1500 liters. There are models that are vertical and horizontal in both scenarios. When installing a wall-mounted version, brackets are typically mounted on the appropriate kind of dowels.

When it comes to shape, these devices are typically fashioned like cylinders. Nearly every model has all of its functional outputs (connection pipes) located at the rear. It looks better and is simpler to connect with. A temperature sensor or thermorelay can be installed on the front of the panel, and in certain models, a TEN can be installed to heat the water further in the event that the heating power is low.

They come in wall-mounted and floor-mounted configurations, with capacities ranging from 50 to 1500 liters, depending on the installation type.

It’s important to keep in mind that the system won’t function properly during installation unless the boiler has enough capacity.

Nuances of the strapping device

Installing the boiler along with the pumps and other equipment needed to assemble the DHW system makes wiring and plumbing easier. It is much harder to cut a new device into an already-existing network.

In any case, a number of requirements must be met for devices to function normally:

• choose the right place of installation – as close to the boiler as possible;
• Ensure a level surface for mounting the boiler;
• to protect against thermal expansion install a diaphragm accumulator (at the outlet of the heated water), the volume of which is not less than 1/10 of the volume of the BCN;
• equip each circuit with a ball valve – for convenient and safe maintenance of devices (eg, three-way valve, pump or the boiler itself);
• To protect against counterflow on the water supply pipes install check valves;
• improve water quality by installing filters;
• Properly position the pump (or several pumps) – the motor axis should be in a horizontal position.

It is not advisable to try attaching heavy appliances to thin wooden partitions or plasterboard for safety reasons. Walls made of brick and concrete work well. Dowels, anchors, and staples are used to fasten brackets and other holders.

Whichever kind of device—floor or wall—it is mounted either at the same level as the boiler or above it, if at all possible. You can construct a strong stand up to one meter high or a pedestal for a floor-standing one.

When installing, make sure the spigots face the boiler (even if it’s hidden behind a fake wall or in the back). It is not advisable to use shoddy equipment, such as corrugated hoses that break under the pressure of water or head pressure.

The following functional components need to be incorporated into the piping system for the indirect storage water heater to operate properly:

In the world of home heating, understanding how an indirect heating boiler works is key. Unlike direct boilers, which heat water directly for domestic use, indirect boilers use a heat exchanger to transfer heat from another source, typically a furnace or a solar panel, to the water. This setup offers a few advantages: it keeps the water in a separate closed system, reducing the risk of contamination and scaling; it allows for the use of multiple heat sources, giving flexibility and efficiency; and it ensures a steady supply of hot water, even if the main heating system is turned off. Essentially, the principle is simple: heat from one source is transferred indirectly to the water in the boiler, providing warmth and comfort to the home.

How to choose the right boiler

The following are crucial traits of the indirect heating boiler:

• volume;
• coil material;
• tank material;
• insulation material;
• Availability of additional heating elements and alternative heating sources.

Boiler volume

Because your heating system is carrying the weight of the water heating, the boiler volume you choose should be determined by its capacity. Your heating system might not be able to handle a unit that you purchase if its volume is too high. This is problematic because the water in the heating devices won’t be hot enough to heat the space. Knowing the boiler’s heating medium volume is essential to avoiding mistakes; it should not exceed 30–40% of the water volume in the heating system, or the system’s performance will be significantly reduced.

Finding out how big of a boiler your family needs is very simple. A person needs between 60 and 80 liters on average to take a shower. It takes roughly six hours to heat 200 liters. These numbers should be used to calculate the boiler’s volume, which should be sufficient to meet the family’s needs while also accounting for the amount of time until the next heating cycle.

Materials

The coil is one of the most crucial components of the boiler, so you should find out in advance what kind of material it is made of. A steel coil on less expensive models is just welded to the tank. It is detachable and composed of brass in more costly models, which is superior in many ways. The removable version’s ability to be disassembled and cleaned from scale makes it even more appealing.

The material of the tank is also crucial because leaks are a common issue with all water heaters. The enamel inside of less expensive models is easily cracked by changes in temperature. This consequently increases the risk of the metal corroding quickly.

Purchasing the models with the stainless steel tank is recommended. If the magnesium anode is replaced on time, it will last longer even though it might cost more.

And this in turn is dangerous because metal corrodes quickly. Purchasing options with a stainless steel tank is the best choice. As long as the magnesium anode is changed on schedule, it might be more costly but last longer.

The effectiveness of such a system is also significantly influenced by the quality of the insulation. Ordinary foam rubber is occasionally used, but it falls short in many ways. For thermal insulation, polyurethane and related materials work best.

Other parameters

In addition to having two indirect water heating sources, the boiler has the option of having a heating element installed so that it can provide heat even when the heating season is over. Although these designs are far more costly than traditional ones, they are incredibly useful.

Boilers come in two varieties: wall-mounted and floor-mounted. It must correspond with the kind of heating system. Therefore, the boiler should also be of this type if the system is wall-mounted. Only models with a capacity of less than 200 liters can be wall-mounted.

Although they may not be the most attractive feature of your house, indirect heating boilers are essential to keeping you warm and comfortable. These boilers make sure that the water used for heating doesn’t mix with the water in your home system by using a heat exchanger. This design not only keeps your home clean but also makes heating it more effectively.

The ability of indirect heating boilers to work with different energy sources, such as gas, oil, or electricity, is one of their main benefits. Because of this flexibility, you can select the option that most closely matches your requirements and situation. There’s probably a solution that meets your needs, regardless of whether availability, affordability, or environmental friendliness are your top priorities.

The capacity of indirect heating boilers to deliver dependable, constant warmth throughout your house is another advantage. They can maintain a constant temperature without the fluctuations frequently seen with other heating methods because they rely on a closed-loop system. This improves comfort levels and lowers energy waste, which will ultimately result in lower utility costs for you.

The maintenance and longevity of indirect heating boilers are also highly advantageous. Compared to some other heating systems, they usually require less servicing and have a longer lifespan because they have fewer moving parts and a simple yet sturdy design. For homeowners, this translates to fewer headaches and possibly lower long-term costs for replacements and repairs.

In summary, even though indirect heating boilers aren’t the most glamorous part of home heating, they are unquestionably necessary. They are a dependable option for keeping your house comfortable all year round because of their effective and adaptable design, consistent warmth, and low maintenance needs. Homeowners can ensure efficiency and comfort in their living spaces by making educated decisions regarding their heating systems by knowing the fundamentals of how they work.

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