Why a heating boiler should be chosen without a power reserve. Equipment sellers won't tell about it

When designing structures and systems, common sense prompts you to lay a margin for strength, reliability and power. There are extreme situations when this stock can save a structure or system. But not in the case of the capacity of a gas or pellet heating boiler.

In 2020, in our village, the owner of one of the plots built a house, installed a heating system with an automatic pellet boiler. And with the first autumn frosts at -10 gr. its consumption of pellets was a bag (30 kg) per day at a cost of 210 rubles per day.

This despite the fact that the area of ​​his house 140 m2 (wood concrete walls). With such an area of ​​the house, its heat loss is not higher 8-10 kWh taking into account the work of ventilation. It would be enough for him and 10-15 kW boiler, even taking into account severe frosts. But they installed a boiler with a power reserve of 25 kW.

Heat loss of a well-insulated house: 60 W / m2. Average 100 W / m2. Those. for a house of 140 m2, a boiler with a capacity of 14 kW is needed. But not 25 kW.

What difference does it make if the boiler has a power reserve or not? The difference is significant. Because the pellet boiler is powerful, then it cannot work at a minimum for which it was not designed. In the best case, the pellets will smolder, the boiler efficiency will drop, the chimney and the heat exchanger will become overgrown with soot, which will reduce the heat transfer from the fire. In the best case, it will burn more fuel than necessary and, in fact, the excess heat will fly away through the chimney. Or the boiler will constantly shut down and after a while the system will ignite the pellets with the burner again. And at the beginning of each cycle, the boiler will start operating at maximum power. Hence the excessive consumption of fuel.

The same applies to powerful gas boilers. There, work will also occur in steps (on and off): the coolant is heated - it is turned off. Gas boilers have automation and power modulation, but below the minimum values, a simple but powerful boiler will not be able to reduce its power - it will turn off.

The circulation pump will pump the system, cool the heat exchanger - the boiler will turn on. And it starts again with maximum power. And the total consumption of a powerful gas boiler will always be greater than that of a boiler of lower capacity.

Many felt all this especially well in the cold winter of early 2021. The owners of powerful boilers had an overrun 1.5-2 times higher than the owners of houses of the same area, but with less powerful boilers.

This is all confirmed by a well-known specialist, the author of this channel:

An example from video comments after this cold winter:

- House of 250 m2 and a boiler of 45 kW. Plus heats a small pool of 10 m3. Last month I paid 9500 rubles. for gas.

A good article on this topic came across here, I recommend: https://galmet.ru/publikatsii/mnogo-ne-est-horosho

What to do for those who have not yet purchased a heating boiler? Consider the heat loss at home and purchase a boiler for this value. And what if extreme frosts begin before -35-40 gr. and below? If you do not live in Siberia, then such frosts will not last for a long time. During this time, you can turn on the electric convectors.

Heat a stove or fireplace (whoever has it). Or install two gas boilers of minimum power. And connect the second one through automation in cold weather. Yes, it is more expensive in investments. But the reliability of the system also increases and there will be no excessive consumption of fuel.

If you nevertheless installed a boiler of increased power, then you can also install a large buffer capacity in the system for hundreds or even 1000 liters. If space permits. The boiler will heat it using its rated or maximum power, after heating it will shut down for a long time. And the less frequent the activation, the more you save.

There are also modern gas (condensing) boilers with power modulation up to 10 (1:10), i.e. 30 kWt the boiler without clocking can reduce its power to 3 kW. An example of such a boiler is the Baxi Luna Platinum Plus. But its cost is under 100 thous. rub. for a power of 35 kW. They write that he is worth the money. Boiler with built-in frequency pump, safety group, built-in expansion tank and three-way valve. But this is twice as expensive as a conventional turbocharged boiler.

Perhaps a double-circuit gas boiler will save the situation from overspending.

Why aren't manufacturers or sellers of boilers and equipment talking about this? It is clear that they need to sell as high as possible. More powerful boiler has more cost - more profit. Their task is not to fly with a minimum of power. And the fact that you will incur unnecessary costs during the operation of powerful boilers is of little concern to them. Or maybe many of them don't even know about it.

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