Daxom Three-Level Heating Capacity Control: More Control Without Losing Modulation

One of the useful features of a Daxom electric boiler is the ability to limit its maximum heating output without turning off its modulation capability.

This gives installers and homeowners greater control over how much electrical power the boiler can draw for central heating, while still allowing the boiler to automatically adjust its output to match the actual heating demand.

Three maximum heating levels

Daxom boilers with the three-level capacity setting can be configured to operate at P1, P2 or P3:

Setting	Maximum output of a 12 kW boiler
P1 – 1/3 capacity	4 kW
P2 – 2/3 capacity	8 kW
P3 – Full capacity	12 kW

The Daxom operating manual specifically describes P1 as one-third capacity, P2 as two-thirds capacity and P3 as full capacity. For a 12 kW boiler, this corresponds to 4, 8 and 12 kW respectively

Importantly, this is a maximum limit — not a fixed output

The capacity setting should not be confused with selecting a fixed heating output.

For example, if a 12 kW Daxom boiler is set to P2 (8 kW), the boiler does not simply operate at 8 kW whenever the heating is switched on. Instead, 8 kW becomes the maximum available heating output, while the boiler continues to modulate its power according to the heating demand.

The 12 kW Daxom models are designed for full modulation and can modulate down to approximately 2 kW.

This means that, in simplified terms, an 8 kW setting allows the boiler to operate anywhere within its available modulation range up to an 8 kW maximum, rather than repeatedly switching between full power and zero.

A simple example

Imagine a property that requires only 3 kW of heat on a mild winter day.

With a 12 kW Daxom set to P3, the boiler has up to 12 kW available, but its modulation system can reduce the actual output to match the lower demand.

If the same boiler is set to P2, its maximum output is reduced to 8 kW. The boiler can still modulate below that level, but it cannot increase its heating output beyond 8 kW.

If it is set to P1, the maximum heating output is reduced to 4 kW.

This provides a useful way of matching the boiler’s available heating capacity more closely to the requirements of the property.

Why is this useful?

Modern properties can have relatively low heat losses compared with the maximum output of an electric boiler. A boiler that has considerably more available capacity than the building normally requires does not necessarily need to be replaced with a smaller boiler.

The Daxom three-level capacity control provides another option: retain the higher-capacity boiler while limiting the maximum heating output.

This can be particularly useful where:

• the calculated heat loss of the property is below the boiler’s maximum rating;
• the electrical supply has limitations;
• the installer wants to restrict the maximum heating load;
• a boiler is being installed in different sizes of property;
• the heating requirement varies considerably throughout the year.

Capacity limitation and modulation work together

The real advantage is that capacity limitation and modulation are complementary features.

The capacity setting establishes the maximum ceiling, while modulation determines how much power the boiler actually needs at any given moment.

For a 12 kW model:

P1 → maximum 4 kW → boiler modulates below this as required

P2 → maximum 8 kW → boiler modulates below this as required

P3 → maximum 12 kW → boiler modulates below this as required

This is different from a conventional simple on/off electric heating system, where the electrical elements may operate at their available fixed stages and then switch off when the target temperature is reached.

With modulation, the Daxom can reduce its output as the heating water approaches its target temperature. Daxom describes its electric boilers as operating with full modulation and states that modulation is intended to provide comfort and energy savings.

A practical example for a 12 kW Daxom

Consider a 12 kW boiler installed in a property where the maximum space-heating requirement is estimated to be around 7 kW.

Rather than allowing the boiler to use the full 12 kW available for heating, the installer could select P2, limiting the heating capacity to 8 kW.

The boiler still retains its ability to modulate its output as the heating demand changes. On a mild day, it may only require a few kilowatts. During colder weather, it can increase its output, up to the 8 kW limit.

This gives the installer a useful balance between available heating capacity and controlled maximum electrical demand.

The key benefit

The three-level capacity function is therefore best understood as a maximum-output limiter, rather than a three-stage heating system.

For a 12 kW Daxom:

P1 limits maximum heating output to 4 kW, P2 to 8 kW and P3 to 12 kW — while the boiler continues to modulate its actual output within the selected limit.

That combination of adjustable maximum capacity and full modulation gives Daxom electric boilers considerable flexibility when sizing and commissioning a heating system.

Note: The exact capacity-setting procedure and the suitability of a particular setting should be checked against the installation and operating manual for the specific Daxom model. The capacity setting relates to the boiler’s heating operation and should not be assumed to mean that domestic hot-water performance is reduced in the same way on every model.