Principle of operation of a wall-mounted gas boiler

The heating system we choose is very important when it comes to keeping our homes warm and comfortable. A wall-mounted gas boiler is one choice that is well-liked by many homes. This small but mighty appliance heats homes effectively and dependably by using the principle of gas conversion into heat.

A wall-mounted gas boiler functions fundamentally by heating water through the use of natural gas or propane. The heated water is subsequently distributed via a system of pipes to radiators or underfloor heating systems located all over the house. The combustion chamber in the boiler, where gas is ignited and heat is subsequently transferred to the water, is essential to this process.

The heat exchanger is a crucial part of a wall-mounted gas boiler. Heat is transferred from the combustion gases to the water that circulates inside the system by this crucial component. The heat exchanger, which is usually constructed of premium materials like copper or stainless steel, guarantees effective heat transfer while withstanding the demands of continuous operation.

One big benefit of wall-mounted gas boilers is their efficiency. Modern boilers are made to be as efficient as possible by condensing the water vapor that is produced during combustion, in contrast to older heating systems that may experience energy losses during heat distribution. Gas boilers are an affordable heating option because of the condensing process, which increases the amount of heat extracted from the flue gases while simultaneously lowering energy consumption.

Component	Function
Gas burner	Ignites and burns gas to produce heat
Heat exchanger	Transfers heat from the burner to the water circulating in the system
Pump	Circulates hot water through the pipes to radiators or underfloor heating
Thermostat	Monitors and regulates the temperature of the water
Flue	Removes exhaust gases safely from the boiler to outside

The principle of operation of a two-circuit gas boiler, complete set and types

A device that serves as the heat carrier for both the heating circuit and the hot water supply is known as a two-circuit gas boiler (Fig. 2). 1. Anyone who owns a two-circuit gas boiler in their home should be familiar with its operating principle. It’s important to remember this device’s primary functions:

• Providing the heating system with coolant and further maintaining the temperature in the system;
• Hot water supply, i.e. providing the house with hot water for domestic needs.

Fig. 1: Two-circuit system operation

In understanding how a wall-mounted gas boiler works, it"s like having a miniature power plant tucked away in your home. This compact unit efficiently heats water, which then circulates through your house to provide warmth and hot water whenever you need it. Here"s the gist: the boiler burns natural gas to produce heat, which is then transferred to water within a closed system. This hot water flows through pipes to radiators or underfloor heating systems, releasing its warmth into your home. Additionally, the boiler ensures you have hot water on demand for showers, baths, and taps. It operates intelligently, adjusting its output to meet your heating needs while conserving energy. In essence, it"s the heart of your home"s heating system, quietly keeping you cozy and comfortable.

Principle of operation

The coolant in a heat exchanger is heated by a two-circuit boiler. The thermostat, which activates the two-circuit boiler when the coolant temperature falls below a predetermined threshold, is responsible for the entire heating process. The circulation pump receives a command from the thermostat when it turns on. Consequently, the pump initiates operation and transfers the coolant within the return pipe. Coolant, which has been heated in the heat exchanger, begins to flow through the system as a result.

The gas appliance operates at low power when it is first started, but it increases to its maximum power while it heats up. However, the boiler reaches the necessary temperature when the operation mode is selected. Automation regulates this process; if it heats up too quickly, it turns off the boiler, or the burner’s gas supply.

Fig. 2: Two-circuit wall-mounted boiler

The heat energy released during the combustion of gas heats the heat exchanger. Consequently, the heat exchanger is positioned above the combustion chamber, which has the burner at its bottom.

The burner in the heating system gradually goes out until the coolant reaches the desired temperature, at which point the gas stops flowing altogether. After that, the two-circuit gas boiler is in standby mode until the thermostat issues a new command.

A three-way valve is used to accomplish the hot water supply function, which is the second purpose of the two-circuit unit. As water enters the secondary heat exchanger—which is intended for district heating and cooling—it blocks the heat carrier’s path to the heating system. Above the main heat exchanger is where you’ll find this one. When the water tap is opened, the two-circuit boiler heats the coolant for the radiators while the three-way valve remains activated.

There are two ways that gas boilers can be ignited:

• Electric – this type of ignition is in appliances that operate from electricity. Thanks to the control unit such ignition occurs in automatic mode;
• Piezo ignition – inexpensive boilers are equipped with this type of ignition, it is an energy-independent system. The ignition is triggered by pressing a button on the housing. At the same time, the igniter is constantly lit.

3 Floor-mounted dual-circuit boiler for rice

DHW circuit operation

A two-circuit boiler has the feature of being able to be used as a gas column in the summer. In summer, how does a two-circuit gas boiler operate? Open the water tap to bring the boiler out of standby mode. The pressure switch closing is to blame for this.

This uses no more than 2.5 liters of water per minute. The automation command causes the ignition to occur and the gas supply to progressively increase. In addition, the three-way valve closes the heating circuit when the tap is opened. Water is then fed into the secondary heat exchanger, which heats it up, from the primary heat exchanger.

The device operates at a reduced power and only modifies even heating once the water in the heat exchanger reaches the necessary temperature. If the temperature drops by one degree, the gas burner ignites.

Condensing and convection devices

There are two ways that dual circuit gas boilers can function:

The gas convection unit works on the basic principle of producing steam through gas combustion and releasing it through the combustion product exhaust system. Conversely, condensing models operate in a different way. The exhaust vapors from the burning of fuel are collected in an extra combustion chamber that they possess. The secondary heat exchanger is then heated by further heating them to a specific temperature. The hot water circuit is intended for use with the secondary heat exchanger.

Regarding boiler operation, the convection principle is more straightforward and manageable. Since condensate does not form inside the chimney where the steam exits, the likelihood of corrosion is reduced. Because condensing boilers include an extra combustion chamber, their efficiency index is higher.

Design of the two-circuit appliance

Three primary components make up the apparatus of a two-circuit gas boiler (Fig. 4), which is present in all kinds of appliances:

The body of the gas heating unit, which has a layer of thermal insulation on it, is another essential component.

Fig. 4: Two-circuit gas boiler design

The entire body of the gas burner is perforated, and nozzles are located inside. To create an even flame, the gas is supplied and distributed by the nozzles. The burner comes in various varieties:

• Single-stage – this burner is arranged so that it can not be regulated, it works in one mode;
• Two-stage – this device has 2 power adjustment positions;
• Modulated – the power of such a burner can be regulated, due to this boilers use fuel more economically.

Exchanger of heat. Gas appliances with two circuits have two heat exchangers:

• Primary – this is where the heat transfer fluid for the heating circuit is heated up. It is made of steel or cast iron;
• Secondary is a heat exchanger in which the water for the hot water supply circuit is heated. It is usually affected by temperature somewhat less than the primary, so it can be made of materials such as copper, stainless steel, etc.д.

Figure 5: Main heat exchanger for a gas appliance with two circuits

An automation unit manages how the gas appliance operates. It consists of a sensor network and an electronic circuit. The electronic circuit that controls the mode of operation or disconnects the device receives readings from sensors related to the two-circuit boiler operation.

An apparatus required for a forced-circulation heating system is the circulation pump. This is a constituent element of a system that depends on energy. This kind of pump delivers the required pressure.

The following options for the combustion product removal system:

• natural draught. In this case, the products of combustion are removed to the chimney pipe, which should rise above the roof at least 1 meter;
• forced draft. Boilers with this system have a fan in the design for the output of combustion products in the coaxial chimney (pipe in a pipe). Such boilers are called turbine boilers.

Tank expansion. The coolant expands when heated to a high temperature, and any excess briefly seeps into the expansion tank. Depending on the boiler’s capacity and the amount of coolant in the system, the tank’s volume may vary.

The combustion chamber resembles a thermally insulated metal tank. The burner is situated at its bottom, and the primary heat exchanger is situated above it. A gas appliance’s combustion chamber can be:

An open chamber gas two-circuit appliance draws its combustion air directly from the space where it is installed, making it a potentially energy-independent device. It is advised that these units be installed in boiler rooms, which are designated spaces apart. They should be set up in accordance with all the guidelines, which include having a window and adequate ventilation. Carbon dioxide will be released by the two-circuit boiler with an open combustion chamber if there is not enough air.

An appliance that draws combustion air from the street via a coaxial chimney is a gas two-circuit appliance with a closed chamber. The unique "pipe in pipe" design of the coaxial gas exhaust system forms the basis of its operation (Fig. 6). In other words, a larger diameter pipe contains a smaller diameter pipe. The combustion products exit through a small pipe, while air is drawn into the gas boiler through a larger one. A coaxial chimney has the benefit of being able to be installed both vertically and horizontally.

Figure 6: Coaxial chimney pipe (pipe within a pipe)

Energy-dependent and energy-independent boilers

The basic working principle of an energy-dependent two-circuit gas boiler is essentially the same as that of an energy-independent boiler. Electricity-powered components enable them to operate. This includes a fan to remove combustion products, automation (complete control of the unit), and a circulation pump. Energy-dependent two-circuit units have the following drawbacks when operating:

• Such equipment is sensitive to voltage fluctuations in the network, so it is necessary to additionally purchase a voltage stabilizer;
• If there are any failures on the power line and there is no light, the boiler will not function. In this case it is necessary to get a generator or an uninterruptible power supply unit.

The coolant naturally circulates in boilers that operate on the convection principle. The pipes in the heating system need to have a bigger diameter in order for such a unit to function normally. Furthermore, the expansion tank needs to be open in this situation. Additionally, the piping in the heating system is angled for optimal circulation. The removal of combustion products system operates using the natural draught principle. A chimney pipe that is installed for this purpose needs to be at least 4 meters high.

Because non-independent appliances have an open combustion chamber, they require a continuous air supply. This implies that frequent ventilation of the space is necessary. The fact that this two-circuit boiler is completely unaffected by an absence of electricity is, of course, its greatest benefit.

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Principle of operation of a two-circuit boiler

• Features and types of boilers produced
• The principle of operation of the boiler and its device
• Types of gas burners

Features and types of boilers produced

An apparatus that can prepare hot water for hygienic purposes and heat the heating medium in the heating system to predetermined temperatures is a two-circuit gas boiler. When you use a boiler like this, you can prepare hot water without the need for extra appliances like gas columns, storage heaters, and flow electric heaters. The methods and procedures used to transfer the thermal energy of gas combustion to the heating and hot water circuits form the foundation of a two-circuit gas boiler’s operation.

Piping system connection to a two-circuit gas boiler.

Boilers of the two-circuit wall type come in a wide variety of technological configurations. The primary kinds of two-circuit boilers manufactured are:

• with an open gas burner;
• with a closed gas burner, turbo;
• having two separate heating circuits for the heating system and hot water;
• combined type;
• condensing.

Go back to the contents table.

The principle of operation of the boiler and its device

Image 1 shows a two-circuit boiler’s hydraulic diagram in heating mode.

The working principle of gas appliances with two heating circuits is as follows. The heat exchanger, which is situated above the gas burner, receives heat from the natural gas that has been burned. The heated water in this heat exchanger will circulate throughout the heating system because it is a part of the mains of the heating system. A pump that is integrated into the boiler helps to circulate water. The two-circuit device has a secondary heat exchanger for hot water preparation.

The equipment design and operational procedures are depicted in PICTURE 1’s scheme:

1. Gas burner.
2. Circulation pump.
3. Three-way valve.
4. DHW circuit, plate heat exchanger.
5. Heating circuit heat exchanger.

• D – input (return) of the heating system for heating;
• A – supply of ready coolant for heating appliances;
• C – cold water inlet from the mains;
• B – output of ready hot water for sanitary needs and domestic use.

The following is the DHW water preparation principle: After entering the second plate heat exchanger (4), heated water from the first heat exchanger (5)—which is situated above the gas burner (1) and serves to heat the heating circuit—transfers its heat to the DHW circuit.

Two-circuit boilers typically include an expansion tank built in to adjust for variations in coolant volume.

The two-circuit boiler’s design only permits the production of hot water in separate modes for heating purposes.

Design of a gas boiler with two circuits.

It is not feasible to utilize the boiler for heating and DHW at the same time. For instance, when the device is heating the heating system to a predetermined temperature, the boiler automation controls the process of maintaining the temperature, and a pump circulates coolant throughout the heating network.

When the domestic hot water tap is turned on at a specific time, a unique flow sensor built into the boiler is triggered as soon as water begins to circulate through the DHW circuit. The boiler’s three-way valve (3) is used to readjust the water flow circuits. In other words, the water heated in the heat exchanger (5) is fed to the plate heat exchanger (4), which transfers the heat to the domestic hot water heater (DHW) system. In other words, the cold water entering the apartment or house through pipeline (C) is heated and then supplied to the consumers through pipeline (B).

At this point, the heating system is not heated for the duration of DHW use, and the circulation moves in a small circle. The flow sensor is activated and the three-way valve reopens the heating circuit to allow for additional heating of the heating system as soon as the tap on the DHW water intake is closed.

The layout of a two-circuit gas boiler’s device typically indicates the inclusion of a plate heat exchanger. Its function is to transfer heat from the water supply circuit to the heating circuit, as was previously mentioned. The idea behind such a heat exchanger is that heat is transferred by assembling sets of plates with hot and cold water in a package.

Because the connection is made hermetically, liquids from different circuits cannot mix. The metal used to make the heat exchanger undergoes processes of thermal expansion as a result of the continuous temperature change, which helps with the mechanical removal of the accumulating scale. Devices for plate heat exchange are composed of brass or copper.

Schematic of a boiler with two circuits.

A two-circuit boiler scheme with a combined heat exchanger is available.

It has two tubes and is situated above the gas burner. In other words, a hot water supply tube is housed inside the heating circuit tube.

With this design, you can prepare hot water more efficiently by eliminating the need for a plate heat exchanger.

The drawback of boilers with a combined heat exchanger is that limescale deposits between the thin tube walls, which deteriorates the boiler’s operating conditions.

Returning to the contents table

Types of gas burners

Boilers of the two-circuit wall type are made with both closed and open types of gas burners. The room where the gas boiler is installed must have the appropriate quantity of air supply for the open gas burner in the boiler to burn gas. Consider the well-known design of a standard gas water heater.

The closed-burner device has a separate area where gas from the room can burn. Outside of the building is where the air intake for the combustion process takes place. These devices are typically connected via a coaxial chimney that exits on the building’s exterior wall. It is made up of two pipes nested inside one another. Air is drawn through the outer tube for burning, and combustion products are expelled through the inner tube.

Air intake with lateral pipe supply and combustion product emission into the building’s designated chimney can both be connected. Because they have an integrated air blower akin to an electric turbine, closed burner boilers are referred to as turbocharged boilers. These gas appliances have the benefit of being safe to use. They don’t need continuous air supply control, room ventilation, or combustion product intrusion into the apartment or house in order to operate. The high draught causes the water to heat up more quickly and with greater efficiency.

Wall-mounted gas boiler apparatus.

In boiler mode, two-circuit gas appliances can be connected. In this mode of operation, water is heated and then builds up in the boiler, where it is then supplied to the water intake points.

The ability of condensing gas heating devices to allow condensation of water vapor found in the combustion products of gas is one of their distinguishing features. Extra heat is produced by the condensation process and is either used for the heating circuit or the DHW circuit. Condensate formation on an extra device placed above the primary heat exchanger or on a primary heat exchanger with a unique shape could be part of the plan.

For correct and secure operation, every two-circuit gas boiler must have a block of automatics and control sensors. Automation can be used in conjunction with remote sensors to monitor the room’s air temperature because it keeps an eye on the parameters that are set for water heating in the circuits. The safest possible operation of the boiler is made possible by traction sensors and control over the emergency gas supply shutdown.

The installation of a gas appliance should be done competently for long-term use. This includes capacity calculation, installation in compliance with safety regulations, and well-executed commissioning procedures.

Only specialized gas services with a certificate of performance should handle gas equipment installation work.

Device and principle of operation of a two-circuit gas boiler

Here you will learn:

Boilers with dual circuit heating have gained a lot of popularity because of how convenient and small they are. In addition to providing heat for the house, they also supply hot water. In other words, there is no longer any need to purchase a separate water heater or heating appliance. What components make up a two-circuit gas boiler and what is its basic operating principle? We’ll discuss it in our review.

Device of a two-circuit gas boiler

Understanding the gas two-circuit boiler’s device is essential to comprehending its working principle. It is made up of numerous separate modules that switch to the DHW circuit and heat the coolant in the heating circuit. You can rely on the equipment to operate trouble-free thanks to the coordinated operation of all its parts. Understanding the two-circuit boiler’s device will help you comprehend how it works.

Since we now know enough about the primary nodes’ functions, we won’t be taking the two-circuit boiler device down to the screw. Within the boiler are the following:

Models with a heating and DHW circuit are designed.

• Burner, located in an open or closed combustion chamber – it is the heart of any heating boiler. It heats the coolant and generates heat for the operation of the DHW circuit. To ensure accurate support of the set temperature, it is endowed with a system of electronic flame modulation;
• Combustion chamber – this is where the above mentioned burner is located. It can be open or closed. In the closed combustion chamber (or rather, above it) we will find a fan responsible for air injection and for the removal of combustion products. It is the source of quiet noise when the boiler is switched on;
• Circulation pump – provides forced circulation of the coolant through the heating system and during operation of the DHW circuit. Unlike the combustion chamber fan, the pump is not a source of noise and operates as quietly as possible;
• Three-way valve – it is this thing that is responsible for switching the system in the mode of hot water generation;
• The main heat exchanger – in the device of a two-circuit wall-mounted gas boiler it is located above the burner, in the combustion chamber. This is where the heating medium used in the heating circuit or in the DHW circuit for heating water is heated;
• Secondary heat exchanger – it is where the hot water is prepared ;
• Automation – it controls the parameters of operation of the equipment, checks the temperature of the coolant and hot water, controls modulation, switches on and off various components, monitors the presence of flame, fixes errors and performs other useful functions.

Spigots for connecting gas, hot and cold water pipes, and the heating system are located in the lower portion of the bodies.

Dual heat exchangers are used in some gas double-circuit boiler models. However, the fundamental working principle is essentially unchanged.

It is evident that the gas column device is identical except for the lack of a heating circuit.

We discovered that the device is a wall-mounted, two-circuit gas boiler. Although it appears a little complicated at first, the complexity vanishes when you realize why each node is there. This is where the similarities to the gas flow water heater, which still had a burner and heat exchanger, can be seen. Everything else comes from boilers with single circuit wall mounting. The inclusion of built-in piping, which includes an expansion tank, circulation pump, and safety group, is unquestionably advantageous.

It is important to keep in mind that the coolant and water from the DHW circuit are never combined when analyzing the gas two-circuit boiler’s working principle and mechanism. Coolant is poured into the heating system via a different pipe that is attached to the heating system. A secondary heat exchanger circulates a portion of the heat transfer fluid to prepare hot water. But that is a topic for a bit later on.

Comprehending the fundamental workings of a wall-mounted gas boiler illuminates its indispensable function in home insulation and heating systems. These small units put forth a lot of effort to effectively provide warmth and comfort. They use propane or natural gas to create heat through combustion, which is then transferred to the water that is circulating in the system.

Warmth is distributed throughout the house via a network of pumps and valves that transfer the heated water to underfloor heating systems or radiators. By removing cold spots and ensuring uniform heat distribution, this technique maximizes energy efficiency. Furthermore, sophisticated controls are a common feature of contemporary boilers, enabling homeowners to modify settings for maximum comfort and savings.

Any heating system must be efficient, and wall-mounted gas boilers perform exceptionally well in this area. They reduce waste by converting a large portion of the energy from burning gas into useful heat. Because of their efficiency, they are a sustainable option for heating needs because they lower energy costs and have a smaller environmental impact.

Moreover, wall-mounted gas boilers are the perfect choice for homes with limited space due to their compact size. Their installation flexibility enables them to be placed in utility rooms, kitchens, or even inside cabinets. With this flexibility, homeowners can make the most of their available space and still benefit from energy-efficient heating.

In summary, effective combustion, heat transfer, and distribution are at the core of a wall-mounted gas boiler’s operation. These systems are essential for insulation and heating because they reduce energy use while maintaining warmth and comfort. Because of their small size and great efficiency, they are a sensible option for contemporary homes looking for dependable and environmentally friendly heating solutions.

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