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 ENCLOSURES FEATURE


A MATERIAL MATTER Of the numerous materials available for electrical enclosure construction, each offers its own protective benefits. While painted carbon steel is the most cost effective metallic choice, it has limited resistance to solvents, alkalis and acids and is thus best suited to indoor applications. Stainless steel provides a much


higher resistance and variants such as grade 316 are specified in industries that require resistance to chemical attack, such as pharmaceutical manufacturing, which must avoid excessive metallic contamination. As the material has better resistance against sulphates, seawater and high temperatures, Cressall recommends this type of steel as the preferred choice for both indoor and outdoor applications. Away from metals, fiberglass is a


lighter weight choice, making it suitable for wall or pole mounted installations. As fiberglass is not conductive, any open circuits would stay safely inside the enclosure and wouldn’t be transmitted through the material. The conductivity offered by a metallic enclosure enables it to be ground connected to reduce the risk of electrical shock, should an exposed conductor come into contact with the enclosure.


FOLLOW THE RULES Many manufacturers design and build enclosures at a central location, such as Cressall’s facility in Leicester, before shipping the equipment to the end user. For an enclosure to comply with local


guidelines, manufacturers must consider its end destination. Standards typically referenced are the International Electrotechnical Commission (IEC) 60529 Specification for ingress protection (IP) for countries using IEC standards, while the applicable EN standard should be followed for the European market. Understanding these regulations


can be daunting, which is why manufacturers should work alongside their customers to advise on the most effective solution. If the IP rating is too high, for example, it will place tighter restrictions on the openings in the enclosure panel work and restrict ventilation. Enclosures should only be


opened using a key or tool and when all live parts are disconnected. Installing a viewing window reduces the need to access inside the enclosure. Other safety features include interlocking the enclosure door with a disconnecting device to prevent direct human contact with equipment, should the door need to be opened. The considerations for enclosures


extend beyond straw, sticks and bricks. However, if designers are to learn anything from the pigs, it is that we should never underestimate the value of a home’s materials. Enclosures may seem like just a box, but they play a vital part in equipment protection and their design needs to be carefully considered.


Cressall Resistors cressall.com


 ELECTRICAL ENGINEERING | MARCH 2020 9


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