What happens when the ventilation opening of an electrical panel is on the same side where an HMI or display is installed? The operator could be hit by the outgoing hot air flow, making the procedures difficult, but also causing possible damage to his health.
The optimal location of the ventilation openings in an enclosure
In this blog, we have dealt several times with the positioning criteria of forced ventilation openings in cabinets to ensure effective heat dissipation, generated by internal components.
In fact, to obtain an effective cooling, the most widespread configuration involves the use of a filter fan unit positioned in the lower part of the cabinet, which draws the air from the surrounding environment into the enclosure itself. The overpressure that is created compared to the external environment helps the flow of cooler air upwards and, once “heated” by the working components, it’s discharged towards the outside, through a filter without a fan.
The position of the ventilation openings in an electrical cabinet with HMI or display, according to the standard
Here, however, we are examining a case study in which it’s quite easy to make mistakes, as we have seen in years of experience.
If the exhaust air filter is located on a cabinet wall where an HMI or any other control equipment is provided, the operator’s position is affected by the hot air from the filter.
This issue is also covered by UL508A (2-22.1- Rev. July 2022), but attention must be paid to its interpretation. The standard is concerned with preventing harmful substances emitted by the components in the event of a fault, which can directly hit the operator, especially in extreme cases of fire in some parts inside the cabinet.
First, the standard defines the area occupied by the operator in the space of 30″ horizontally from the center of the control panel, display or disconnect handle and up to 6.5″ from the floor. If the forced ventilation system acts in this area, a barrier or duct must be provided to redirect the airflow in a direction of 90° or higher.
It might be tempting to solve the problem by mounting the filter rotated 90° or 180°. Although UL508A does not prevent you from doing so, you must remember that, in this way, the degree of protection against water according to EN 60529 is no longer guaranteed. The shape of the flaps on the cover is in fact specially designed to protect the filter element from splashes of water for IP X4 models or from jets for IP X5 models.
The most correct solution, in these cases, is the adoption of a protection hood, such as the one present in the Fandis SSC range, compatible with all Fandis filters.