How to choose an air conditioner for electrical cabinets: the correct sizing method

Heat in electrical panels: an underestimated problem

In the world of industrial automation, cooling is a critical aspect for ensuring operational continuity, reliability, and equipment longevity.
And yet, how often do we choose a device based on experience, the catalogue, or, at worst, the “one size fits all’ model? This practice can prove to be costly.

• An undersized unit fails to maintain the operating temperature within design limits, resulting in premature component degradation, machine downtime, and unforeseen maintenance costs.
• An oversized unit: it burdens the purchase budget, consumes more energy than necessary, and still doesn't guarantee stable thermal conditions.

It's not enough to find “something that cools”; you need to choose the right solution for your application. And to do that, you need a method.

Air conditioner, heat exchanger, or fan?

The technologies available for cooling electrical cabinets are:

• The air conditioner actively cools the electrical enclosure even when the outside temperature is higher than the internal temperature, making it the almost inevitable choice for hot environments. In indoor applications equipped with chilled-water systems, an air-to-water heat exchanger is a valid alternative.
• The air-to-air heat exchanger transfers heat from inside the enclosure to the outside without using mechanical refrigeration. More energy-efficient than an air conditioner, an air-to-air heat exchanger can operate only when the outside temperature always remains lower than the inside temperature, with a sufficient temperature difference to dissipate the entire heat load.
• The filter fan is a simple and cost-effective solution for low heat loads and clean, cool environments where allowing outside air to enter the enclosure is acceptable.

The choice depends on the specific context and, in many cases, is not immediate. This is where a valuable selection tool becomes useful.

How the sizing process works: a practical example

To understand how WebSelect simplifies selection, let's look at a practical case.

Situation
A panel builder is creating a control panel for a packaging line, to be installed within a manufacturing plant. The panel houses a PLC, three 5 kW drives, a 500 W power supply, and some I/O cards. The ambient temperature of the installation site reaches peaks of 45°C in summer. The maximum permissible temperature inside the panel is 35°C.

STEP 1 – Type of Application
The type of application – inside or outside buildings – influences the type of device proposed and the calculation of the thermal power to be dissipated. For example, for outdoor applications, the contribution of solar radiation and wind to the total thermal load can be significant. For our example, we select “Indoor”: this excludes outdoor solutions, which have features unnecessary for the application.

STEP 2 – Environment
The desired temperature inside the enclosure (35°C) and the maximum temperature outside it (45°C) are selected. The fact that the outside temperature is higher than the inside temperature automatically excludes air-to-air heat exchangers and filter fans, which require the opposite differential to operate. The thermal power transmitted through the enclosure walls also depends on this difference.

STEP 3 – Enclosure
The characteristics of the electrical switchboard are selected: its dimensions, the covered sides not exposed to the air, and the material of the panels all affect the thermal power transmitted through the walls. Furthermore, the dimensions of the switchboard may rule out certain cooling devices because they are too bulky. For the purposes of our example, and for the sake of brevity, let us assume that the thermal power transmitted is negligible.

STEP 5 – Product Selection
With a thermal load of approximately 515 W, the indicated technologies are the industrial air conditioner and the air-to-water heat exchanger.

If the packaging line is not equipped with a chilled water system, which would make a heat exchanger more convenient, then an industrial air conditioner becomes the only option. WebSelect offers Protherm CVE models suitable for this cooling capacity, which fall within the set tolerance range: in our case, the CVE11 model.

The system also suggests variants based on the available space in the unit, with their respective technical data sheets and downloadable documentation. For wall installation, the proposed options are the Compact Protherm CNE10 and the SlimIn CDE10. For roof installation, the Top ETE09 model.

Why does this approach make a difference?

Relying on a structured sizing tool isn't just a matter of convenience: it's a professional choice that has concrete impacts on quality, costs, and the final client's satisfaction.

• Technical safety
  Correct sizing ensures the cooling system is always adequate for the actual load, even in the most critical environmental conditions
• Reducing waste and returns
  Choosing the right product first time means fewer corrections during testing, fewer post-installation replacements and fewer hidden costs.
• Supporting documentation for the offer
  The results obtained with WebSelect can be used as a technical basis for the final client's offer, demonstrating that the choice is motivated by precise calculations and not by empirical evaluations.
• Design autonomy
  The panel builder does not have to wait for external technical support for an initial selection: they can work autonomously, at any time, and involve the Cosmotec team only for the most complex cases or for final validation.

Tools such as Cosmotec WebSelect provide panel builders with a rigorous and accessible method for making this choice with the same level of attention dedicated to the rest of the project. Just a few minutes of configuration can make the difference between a system that operates reliably for years and one that starts experiencing problems after its first summer. `