{"id":9152,"date":"2026-09-07T10:00:00","date_gmt":"2026-09-07T07:00:00","guid":{"rendered":"https:\/\/thermohouse.uz\/dvuhkonturnyy-kotel-kak-vybrat\/"},"modified":"2026-09-07T10:00:00","modified_gmt":"2026-09-07T07:00:00","slug":"dvuhkonturnyy-kotel-kak-vybrat","status":"publish","type":"post","link":"https:\/\/thermohouse.uz\/en\/dvuhkonturnyy-kotel-kak-vybrat\/","title":{"rendered":"Combi boiler: how to choose one for a house or apartment"},"content":{"rendered":"

What is a combi boiler<\/h2>\n\n\n\n

A combi boiler does two jobs: it heats the house and prepares hot water. The first circuit serves the radiators and underfloor heating. The second heats water the moment you open the tap.<\/p>\n\n\n\n

A system boiler only provides heating. Hot water for it is prepared by a separate indirect water heater.<\/p>\n\n\n\n

Parameter<\/th>Combi boiler<\/th>System boiler + water heater<\/th><\/tr><\/thead>
Space<\/td>Compact, everything in one casing<\/td>Requires space for the water heater<\/td><\/tr>
Hot water<\/td>Instantaneous, no reserve<\/td>Stored in a tank, stable temperature<\/td><\/tr>
Several outlets at once<\/td>Pressure is shared between taps<\/td>Enough for 2-3 outlets at once<\/td><\/tr>
Suitable for<\/td>Apartment, house with 1-2 bathrooms<\/td>House with 2 or more bathrooms<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

How to calculate heating output<\/h2>\n\n\n\n

For a preliminary estimate, use the rule of thumb: about 1 kW per 10 m\u00b2 with ceilings up to 2.7 m and average insulation. A 150 m\u00b2 house needs a boiler of roughly 15 kW. Add a 10-15% margin for cold days.<\/p>\n\n\n\n

If the house is poorly insulated, the windows are old or the ceilings are higher than 3 m, the load increases. An accurate figure comes from a room-by-room heat loss calculation.<\/p>\n\n\n\n

How to estimate hot water output<\/h2>\n\n\n\n

Domestic hot water output is given in litres per minute. You can work out a guideline yourself:<\/p>\n\n\n\n

Litres per minute = boiler output (kW) \u00d7 14.3 \/ water temperature rise (\u00b0C).<\/strong><\/p>\n\n\n\n

A 24 kW boiler heating water by 25 \u00b0C delivers about 13-14 l\/min. That is enough for one shower and a kitchen tap. If the house has two bathrooms used at the same time, instantaneous hot water will not be enough. In that case it is better to choose a system boiler and an indirect water heater<\/a>.<\/p>\n\n\n\n

Gas, condensing or electric<\/h2>\n\n\n\n

A gas boiler with a sealed combustion chamber<\/strong> is the most common choice for a private house in Tashkent. It draws air from outside through a coaxial flue, so it is safe for living spaces.<\/p>\n\n\n\n

A condensing boiler<\/strong> recovers additional heat from the flue gases. The gain is noticeable when the return water is colder than 55 \u00b0C: with underfloor heating and radiators sized for low temperatures. It saves gas over the entire service life.<\/p>\n\n\n\n

An electric boiler<\/strong> needs neither gas nor a flue. It suits homes without gas or works as a backup heat source. Before buying, check the allocated capacity of your power supply: a 12 kW boiler needs a three-phase connection.<\/p>\n\n\n\n

A solid fuel boiler<\/strong> is used where there is no gas and little electricity. It needs space for fuel storage and regular maintenance.<\/p>\n\n\n\n

What else to look at<\/h2>\n\n\n\n