How to choose a hot air stove?

  1. Stove power according to the size of the heated space (kW according to m3 incl. heat loss)
  2. With a heat exchanger or a stove without a heat exchanger?
  3. Stove efficiency (combustion quality)

Power of hot air stoves #

The most important element when choosing a hot air stove is determining the correct performance of the stove with regard to the size and heat loss of the heated space. If the output of the stove is higher than what is needed, you will try to reduce it and you will not use the stove economically, which will significantly reduce the efficiency of the hot air stove (in addition, there will be flue gases settling in the flue and the chimney, and the windshield of the hot air stove will be stained calculus). A stove with a correctly selected output should work at approx. 65-72% of its maximum output, with the fact that it will deliver enough heat to all heated spaces.

How to calculate the correct performance of hot air stoves?

  • We need to know the volume of the heated space in cubic meters (height x width x length)
  • We need to know the average heat loss of the heated object:
    • in older buildings, the heat loss is around the consumed 1 kW of power per approx. 20 m3 room
    • in new buildings, the heat loss is around the consumed 1 kW power per approx. 40 m3

Required power (W) = volume of heated rooms (m3) x value of heat loss (according to the specification below)

  • well-insulated or low-energy house – 23 W/hour/m3
  • moderately well-insulated house – 35 W/hour/m3
  • poorly insulated house - 50 W/hour/m3
  • cottages and cottages - 80 W/hour/m3

A precisely calculated example:
poorly insulated house, 2 rooms with a volume of 70 and 55 m3
power calculation: (70+55) x 50 = 6,250 W (6.25 kW)

In this case, we should therefore choose hot air stoves with a power of 6 - 7 kW, the maximum power of hot air stoves should not exceed 9.5 kW.

stove with a heat exchanger or a stove without a heat exchanger? #

Before choosing, it is also very important to realize whether we want to heat only one room with the hot air stove, or whether we want to connect the hot air stove to heating elements and thus heat the whole house. For this purpose, the so-called hot-water exchanger, which is implemented inside the hot-air stove, can transfer up to 79% of the total heat output to the heating elements. Therefore, if you want to connect a hot air stove to existing heating elements, choose a hot air stove with a hot water exchanger. By using hot water exchangers, you will significantly reduce heating costs, and the investment in hot air stoves can thus pay for itself in just one heating season. If you only need to heat one specific room, you can choose a hot air stove without a hot water exchanger.

Efficiency of hot air stoves #

One of the most important parameters that indicates the quality of any device is its efficiency. If we talk about the efficiency of the combustion equipment we use for heating homes, it is obvious that with increasing efficiency, fuel consumption will decrease, and thus also fuel costs. Similarly, we can state that with decreasing efficiency, we have to add more fuel to the combustion device in order to get the same heat.

The efficiency of the combustion device expresses the degree of efficiency of using the energy contained in the fuel for heating purposes. Efficiency can be determined either by direct or indirect methods.

You can read more in the professional article How to measure the efficiency of a combustion device and can the efficiency be increased somehow?