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ENCLOSURES, RACKS & CABINETS FEATURE    


Four myths about electrical enclosures


There are a number of misconceptions about enclosures. Simon Brammer, product sales engineer – thermal management at Axair Fans busts the four most common myths


1. INTERNAL COMPONENTS CAN BE PLACED ANYWHERE INSIDE THE ENCLOSURE It is often tempting to position electrical equipment where it is most convenient and comfortable for the installer. Sometimes this means clustering equipment at mid-height. However, it is imperative to carefully choose the position of the components to ensure a distance that allows the correct circulation of air and proper distribution of power loads. By doing so, not only will this


save energy in ventilation, but unwanted hot spots and loss of thermal inefficiency can be avoided.


2. ELECTRICAL ENCLOSURES ARE ALWAYS DRY BECAUSE THEY ARE SEALED It is true that with the correct enclosure ventilation accessories rated for ingress protection, electrical cabinets can achieve a water-tight seal. However, this does not take into account that condensation may form inside the panel, due to rapid temperature drop below the dew point. This is due to changes in temperature outside of the enclosure, for example, at night when temperatures drop or equipment is shut down. To avoid this, we need to heat


the cabinet with one or more anti-condensation heaters, especially during machine shutdown or in cold rooms. Additionally, a pressure


compensation device (or vent plug) is recommended to prevent condensation forming inside the enclosure, as a result of humid air entering through door seals due to a negative internal pressure (caused by forced ventilation). It does this by preventing the


ingress of dust and water (rated IP55), whilst allowing the humid air to escape through a membrane. Thus, achieving


pressure equalisation within the enclosure. Condensation reduces the reliability and lifetime of electrical and electronic equipment, causing serious malfunctions.


3. ELECTRICAL ENCLOSURES RESIST DUST Whilst cabinets reduce the amount of dirt and dust that the equipment is exposed to, they are not completely dust-free. Steps can be taken to increase the degree of protection against dust, for example, ensuring that the ventilation exhaust and fans have a high IP rating. The panel and its components


must have an appropriate degree of protection suitable for the conditions of use. Furthermore, a regular cleaning and maintenance routine should be put in place. This should include the washing of or replacement of soiled filter media for filter fans and washing surfaces for sanitation, particularly in the food and beverage industry. Allowing dust and dirt to settle


on electrical components may compromise their functioning, especially if there are oils or condensates that cause moisture and prevent effective cooling.


4. FILTER FANS ALWAYS REDUCE THE INTERNAL TEMPERATURE OF THE ENCLOSURE In some circumstances, a filter fan is not enough to cool the cabinet. When the outside temperature is higher than 40°C, ventilation is not enough and heat penetrates through the filter grid, increasing the panel’s internal temperature. It is, therefore, advisable to


choose an active cooling solution such a thermoelectric unit under these conditions.


Axair Fans axair-fans.co.uk  ELECTRICAL ENGINEERING | JULY/AUGUST 2019 15


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