Electrical enclosures are installed in widely varying locations – often your switchboard will be installed outdoors, vulnerable to heavy rain, high levels of humidity, corrosive minerals such as sea salt, dust and sun radiation. Another consideration that is sadly becoming more frequent is the threat of vandalism and sabotage. Carefully choosing an enclosure material is very important. Read on for a quick guide to your options.
Polycarbonate has several benefits over the metallic options, notably its resistance to corrosion and acidic environments. Surprisingly, plastics often have good impact resistance and don’t easily dent and scratch. Its non-conductive nature eliminates the need for earth bonding straps to doors and covers.
Polycarbonate enclosures are generally used for smaller enclosures such as local control stations and marshalling boxes, and rarely used in large sizes due to cost.
Ideal applications: Small enclosures, local control stations, marshalling boxes, chemical environments .
because of its relative cost-effectiveness and strength – some 25 times the strength of plastic.
Unfortunately, raw steel is very vulnerable to corrosion and must be coated using methods such as zinc-coating, galvanising, powder-coating or painting.
Mild steel enclosures are used for everything from indoor switchboards to large MCCs to road side traffic control control boxes. They are generally suitable for all outdoor applications except areas effected by corrosion, such as coastal areas.
As steel is very conductive, care must be taken to earth all steel surfaces to prevent electrocution.
Ideal applications: Virtually all indoor and outdoor uses, particularly in non-coastal and non-corrosive areas.
Like steel, aluminium is susceptible to corrosion, however it very quickly builds up a layer of a whitish substance called aluminium oxide which seals the inside layer of aluminium from oxygen and prevents any further corrosion. Uncoated aluminium can be used for outdoor applications quite safely, but is generally powder-coated or painted for aesthetic reasons.
Aluminium is more lightweight, but not as strong or hard as steel, so thicker sheet is normally used. Another advantage of aluminium is that it is not magnetic, eliminating eddy-currents within the enclosure – this is why aluminium gland plates are commonly used.
Ideal applications: Outdoor switchboards in coastal locations.
Stainless steel is a steel alloy that contains a quantity of chromium and nickel that makes it virtually impervious to corrosion and staining. There are several grades of stainless steel, the most common being 304 (containing 18% chromium and 8% nickel) and 316 (16% chromium, 10% nickel and 2% molybdenum).
Stainless steel is harder than mild steel and is more difficult to cut and work with, but is structurally stronger.
Due to stainless steel’s high resistance to corrosion, it can be and commonly is used completely uncoated, even in outdoor locations. Uncoated stainless steel is generally polished for aesthetic reasons. Uncoated stainless steel is very popular in the food industry as it is easy to wash down without risk of building up grime and bacteria.
Due to its composition of more expensive metals, stainless steel is up to 3 times as expensive as mild steel. Due to the increased content of nickel, higher grades of stainless tend to be more expensive.
Ideal applications: Outdoor locations especially in coastal areas, corrosive environments, food preparation areas.