Modulating boilers: How do they work?


The modulating boiler is one of the best recent inventions. Modulating boilers, by their very nature, provide a significant energy saving and are, in fact, one of the most energy-efficient boilers on the market today. Read on further if you would like to find out more about what a modulating boiler is, how it works, and some other interesting points.

What is a modulating boiler and how does it work?

Modulating boilers are known to be the most energy-efficient boilers on the market today. This is especially important now that our planet is in a critical situation and we need to reduce our emissions of polluting gases into the atmosphere. The fact that a boiler can meet these high standards is good news.

A modulating boiler, as its name suggests, is a boiler that is able to modulate its power in real-time in order to provide the exact level of heat needed. This means that they are incredibly energy-efficient when it comes to fuel usage. Modulating boilers are the perfect boiler type as they only consume the fuel that is actually needed, which is something that no other boiler can do.

Every other boiler type always consumes more fuel than it needs to maintain a set temperature. This doesn’t change over time and is not affected by external conditions, the number of people in the household, etc.

So, what does modulating mean? What does this term mean from a specific point of view? Let’s take a look at this in detail. A modulating boiler means that the unit doesn’t continuously work at 100% of its power. When it operates, it only uses a percentage of its power and only how much it needs to maintain the set temperature. The amount it uses depends on the ambient temperature, the external temperature, the number of people currently in the household, and other similar parameters.


These boilers do not start, switch off or remain at full power unnecessarily. By avoiding unnecessary start-ups (which typically results in a fuel spike), energy efficiency can be maximized. Modulating boilers can operate with more or fewer modulation stages. The greater the number of stages, the greater the energy efficiency.

Modulating boilers have various parts, including modulating burners, modulating exchangers, modulating thermostats, modulating coils and electronic cards, modulating controllers, and modulating pumps.


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What is a modulating heating thermostat?

In order to explain what a modulating heating thermostat is, we need to briefly explain what the term modulating means, what a boiler thermostat is, how it works, what a heating thermostat is, and how it works. In this way, we will be able to give a clear definition of what a modulating heating thermostat is and how it works.

Modulating means “to modulate”, and increasing or reducing its power depending on real-time needs.

Generally speaking, a heating thermostat is an electrical part that can open or close a circuit in order to maintain a pre-set temperature. A heating thermostat greatly expands on how a traditional thermostat operates as it allows the user to program various setpoint temperature profiles according to the time, day, season, weather, etc.

Everything can be programmed and the heating thermostat can operate independently. (You can find more details about this in our article entitled “How a heating thermostat works”).

Now that we have explained these definitions, we can ask: What is a modulating heating thermostat? A modulating heating thermostat is a thermostat that includes all the capabilities of other thermostats we have described so far. However, it is also a kind of real-time temperature probe that can make precise changes according to what has already been programmed into it.

Modulating heating thermostats achieve complete fuel efficiency and domestic comfort as they manage the boiler’s operation so that it generates the exact heat level that you have programmed into it without having to restart.


Although modulating boilers have a modulating design, this is not enough for the boiler to achieve its operational goals. In order to achieve maximum fuel efficiency, a modulating boiler must work with a modulating heating thermostat, in addition to an external probe to help the boiler detect the precise external temperature conditions in real-time. In doing so, the boiler has a synergistic modulation way of working that allows it to achieve optimal performance.


Modulating boilers and the new regulations: Let’s look at the numbers

If we want to fully appreciate the way in which modulating boilers work, we need to look at them in the context of the new regulations, which are remarkably demanding in terms of the energy efficiency of machinery working with fuel. As you know, the European Union is currently governed by the ERP and ELD regulations, which stipulate that technology must be of an eco-design and have high energy efficiency. A modulating boiler is a condensing or low NOx boiler that can perform the great feat of achieving 110% energy efficiency.

Another interesting related topic that is quite important in terms of ecological design is the poly fuel boiler which has automatic ignition and modulating power. This is a boiler that has a singular burner that can generate both a flame and heat (both heating and sanitary heat), using various types of biomass-type fuels, be they pellets from various organic sources or firewood, coal, wood chips, sawdust, etc. In addition, it has a modulating design that can adjust its energy expenditure according to the household’s actual needs in real-time.

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