Combi Boilers and Types

A combi boiler is a device installed in homes for both heating and hot water supply. The word "combi" is derived from the English word "combined". This device, which takes up little space, is quiet, lightweight, and easily portable, can operate in summer and winter modes. In summer mode, the combi boiler only heats water. In winter mode, in addition to heating water, it transfers the heated water to the radiator, performing the function of providing heating. A combi boiler consists of an electronic board, a pump, a three-way valve, a burner (nozzle), a heat exchanger, a fan, an expansion tank, control parts, temperature sensors, a flue sensor, and other mandatory system and safety details.

To meet the heating and hot water needs in apartments, it is sufficient to assemble all parts of the combi boiler system according to requirements, lay the water pipes covering all rooms, and connect them to the device. After the natural gas and water lines are connected, the combi boiler heats the water to the required temperature via its electronic control system and pumps it into the system. For the installation of the combi boiler, you can use a HILL FAN combi set, HILL FAN composite pipes for the hot water line, and the appropriate HILL FAN simple water pipes for connecting the cold water line.

Attention! The use of PPR pipes is not allowed.

Four water pipe lines and one gas line are connected to the combi boiler: lines to radiators and the heating system, flow and return (20mm metal outlets), as well as hot water outlet and cold water inlet (15mm metal) lines. The diameter of the outlet pipes from the device varies according to the area of the house. Normally, these lines are 32mm or 25mm HILL FAN composite pipes. However, pipe diameters are gradually being replaced by smaller diameters. 20mm pipes are laid for each radiator and the last radiator line.

When choosing a combi boiler, the area of the house, the power of the device, and its type should be considered, and attention should be paid to the warranty period and whether it has a certificate. The warranty period is usually determined by the manufacturer. However, if there is no such period, according to the legislation, it is considered to have a warranty of at least 2 years. Combi boilers with capacities of 16, 18, 22, 24, 28, 32, 35, 36, 40, 50, 55, and 60 kW are widespread. A 24 kW combi boiler has the power to heat approximately 120 m², a 28 kW one up to 160 m², and a 35 kW one up to 220 m².

COMBI BOILER TYPES

There are different types of combi boilers based on flue, combustion, or heating technology.

*According to the flue type (based on how the burned gas is discharged into the atmosphere), combi boilers are divided into two types: open-flue and sealed (hermetic). Open-flue combi boilers take the oxygen needed for combustion and discharge unnecessary gases through a suitable flue at the end of combustion. In this case, the conformity of the flues to standards is very important. Sealed combi boilers draw the air used for combustion from the external environment via a fan and discharge the waste gas generated after combustion through the same system to the outside. In this case, there is no need to change the air in the room, because the room's air is not used during combustion.

*There are also two types of combi boilers based on combustion or heating technology.

• Traditional (conventional) combi boiler
• Compressor-condensing combi boiler

Traditional (conventional) combi boilers are themselves divided into two types: single heat exchanger and double heat exchanger.

As the name suggests, a single heat exchanger combi boiler has one heat exchanger. The heat exchanger is combined into a single structure for central heating (radiator) and domestic hot water line heating. Another feature of such combi boilers is that the circulation pump does not operate in domestic water mode. Since domestic water passes directly through the heated heat exchanger, it does not require a pump for heating. This leads to a reduction in electricity consumption during the use of heating water (radiator) and an increase in the lifespan of the circulation pump. Compared to double heat exchanger combi boilers, the initial heating rate of domestic water is higher.

In double heat exchanger combi boilers, the central heating (radiator) and domestic hot water system are separate. These combi boilers have a primary and a secondary heat exchanger. The primary heat exchanger is made of copper to prevent limescale buildup and ensure efficient heat transfer. Flame heating takes place here. The secondary heat exchanger is made of stainless steel. This heat exchanger is located at the bottom, behind the boiler. Domestic water is heated here. There is no contact with the flame. The water heated in the primary heat exchanger passes through this heat exchanger in the direction of the three-way motorized valve. When the plates in the exchanger are heated by this water, the domestic water passing through the domestic water line also heats up. In double heat exchanger combi boilers, the central heating (radiator) and domestic hot water lines pass through separate channels and do not mix.

Compressor-condensing combi boilers produce a large amount of water vapor when burning natural gas. These types of combi boilers utilize the energy of the generated steam, and after gaining energy, the condenser discharges the steam. While the heat utilization in conventional combi boilers is 80-90 percent, in compressor-condensing combi boilers, it is 105-109 percent.