How to choose a gas boiler?

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Before choosing a gas boiler we must take into account several important facts such as: the power required, the current regulations, the type of fuel used by the boiler, etc. Next, we are going to see the main data for the election of the perfect gas boiler for our home

Types of combustion chamber technologies

According to the current regulations it is only possible to use watertight condensing boilers in new installations. However, let’s look at the various types that exist:

Atmospheric boiler

The main characteristic of this boiler is that its combustion chamber is open. This means that for combustion it takes the air from the room in which it is located and it is for this very reason that there is currently a ban on new installations with this technology, due to its dangerous nature.

Watertight boiler

The watertight boilers, on the other hand, are fed with external air, which is why we gain in safety and it is currently the norm that they should be installed in homes. Within this technology there are different models.

Condensation-tight boiler: the best known and most publicized for the general public. This boiler stands out above all others for its high efficiency of 100%, because instead of wasting most of the heat generated, it is used to heat water and achieve significant savings in gas consumption. It should be borne in mind that this type of boiler will require a condensation drain. This type of boiler has low NOX emissions and a fairly high price.

Conventional boiler: the conventional watertight boiler is nothing more than the usual boiler with absorption of outside air, this type of boiler is economical and has an efficiency of approximately 90%.

Low-emission boiler: the low emission boiler is like the conventional watertight boiler but with low gas emission due to its low temperature flame. This type of boiler has an average price.

How much power do I need?

Unlike inverter air conditioners with a heat pump, the power of our boiler must be chosen according to the power required for the production of Domestic Hot Water or “DHW” because this will require a considerably higher power than heating. I leave you here an approximate table of the power required for “type” housing.

38 – 45 kW: Power for very large houses with poor thermal insulation.

31 – 35 kW: Very large houses with normal thermal insulation and very cold climates.

27 – 29 kW: Large homes and very cold or cold climates.

21 – 24 kW: Homes of about 90m2 in cold or very cold climates. This is the most common power in common houses.

20 kW: Mild climate homes. This power is the minimum recommended installation to achieve a continuous production of hot sanitary water.

To calculate in a more precise way the required gas boiler power I leave you the following table, the calculation is made in the following way:

Calculate boiler output

*Depending on the area and insulation of our house we select the W per m2 and multiply them by the meters of house to be heated and finally we add a 20% because it is always advisable to have a margin of safety and not to fall short.