How many kilowatts do you actually need? Boiler sizing with common sense

The most common mistake in buying a boiler is not choosing the wrong brand, but incorrect sizing. A machine that is too small is an obvious problem, but one that is too large is more insidious: it constantly switches on and off, runs at poor efficiency, produces soot, and unnecessarily cost more.

Rules of thumb to start with

Accurate sizing is provided by heat load calculation, but empirical values are sufficient for the order of magnitude. For an average insulated industrial hall, you can calculate with 60-100 watts per square meter depending on the ceiling height, for an uninsulated old workshop rather 100-150 watts, and for a well-insulated office or social block 40-60 watts.

As an example: the heat demand of a 500 square meter, five-meter-high, moderately insulated hall is roughly 40-50 kW. For this task, the 45-60 kW machines typically found in our warehouse are suitable, for example a Spanex 45 or a Fröling F2 class boiler. For a 2000 square meter drying plant, a capacity between 150-250 kW, a KWB TDS Powerfire or Fröling Turbomat category machine is already required.

What else to pay attention to

In addition to the nominal output, you should also look at the control range: a good industrial boiler can be modulated down to roughly one-third of its nominal output, so it does not switch on and off unnecessarily even during transitional periods. With a buffer tank, this range can be further extended, and the boiler can always run in optimal operation.

Think about expansion as well. If the site has potential to grow, it is worth choosing a machine that has power reserves, or designing a boiler room where a second machine can be installed later.

If you send us the basic data of the building, we will provide a performance estimate and a specific machine proposal from our current stock free of charge. Often, a phone call is enough.