Fan filter units and filters are an economical solution to cooling down an electrical panel, especially if the room temperature is lower than the required temperature inside the cabinet. Obviously, there is not a single solution for all the cooling cases, but pros and cons of the different possibilities offered must be evaluated.
So when it comes to choosing a cooling method you can consider the following alternatives:
Cooling with natural convection
If the thermal load inside the electrical cabinet is limited to low values, the use of a couple of exhaust filters can be an effective solution. However, this solution offers a limited cooling effect compared to the current components requirement.
In this case, the installation of two filters, one at the bottom and one at the top, allow the electrical cabinet to be cooled by natural convection, since the hot air tends to rise upwards.
The same effect is achieved by positioning a filter in the lower part of the cabinet and a roof exhaust unit without a fanat the top of the cabinet.
Cooling with forced convection
When internal thermal loads are more important, it’s necessary to use a forced ventilation system, choosing between different possible configurations:
Fan filter unit at the bottom+ exhaust filter at the top of the enclosure:
This configuration takes in the air from the outside, generating a slight overpressure compared to the external environment. The light pressurization will prevent the entry of dust from other openings and also the life of the fan improves, because the air that crosses is at the external temperature, therefore lower than the internal one.
Fan filter unit in reverse configuration + exhaust filter, both at the top of the elnclosure
This configuration, unlike the previous one, extracts air from the cabinet and generates a slight internal depression and the possible infiltration of dust and pollutants through the holes of the cabinet. in addition, the fan works in hot air conditions, reducing its avarage life.
Fan filter unit at the bottom of the cabinet + fan filter unit in reverse configuration atthe top of the enclosure
This configuration greatly improves the air flow rate compared to the previous two, in fact the total air flow rate is comparable to that declared in open air. The higher cost of this solution could be a point of disadvantage, but in some cases it remains the only possible solution.
Roof exhaust unit with fan at the top + exhaust filter at the bottom of the enclosure
In this case the depression generated by the roof unit takes in air from the outside through the filter, allowing a change of air and heat dissipation. In this solution there are the disadvantages of the second solution (internal depression), but it can be useful when some side walls of the cabinet are covered by obstacles, walls or other panels.
Internal orientable fan
A solution that goes a little way from the previous ones, but that can still be useful in some cases, is the internal forced ventilation. In this case, the air is not exchanged with the outside, but circulates internally with the use of swivelling fans. The intent is to distribute heat and lower the temperature, to cool localized hot spots or to spread the cold air released by a cooling unit. This adjustable fan can be used also with the other configurations listed above, improving the cabinet cooling work.
It’s certainly important to filter the air entering the electrical cabinet to prevent internal components from being damaged by dust or other polluting agents. Not infrequently, it happens that in unfiltered enclosure the dust can combine with the humid air causing short circuits, with consequent downtime and collateral damage of a certain entity, i.e. corrosion.
It’s also very important to correctly calculate the required airflow in relation to the thermal load present inside the electrical cabinet, because a too high internal temperature drastically reduces the life of the components. As the saying goes “prevention is better than cure”, so during the planning also take into account these tips.