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IP ratings: what you need to know

IP ratings: what you need to know When it comes to enclosures, what do IP ratings mean and how can you be sure you have made the correct choice? Chris Lloyd of Spelsberg offers an insight.

Technically, IP stands for International Protection, but is more commonly known as Ingress Protection and is a set of ratings designed to provide a reliable standard for determining the level of protection offered by an enclosure against solid objects and water. These ratings are defined by the international standard EN 60529.

The first digit in an IP rating is the protection against contact with dangerous parts and solid bodies. The second digit in the rating is the level of protection against the harmful ingress of water. In some cases there may be a third digit which relates to the protection of an enclosure against external mechanical damage; this classification is not covered by EN 60529 but is covered by EN 50102.

The letter 'X' is used in place of the first or second numeral by equipment manufacturers to indicate that tests are not applicable to the product. It is also used in standards to indicate that for the range of products covered such protection is not required. For example, IP4X specifies that protection against the 1.0mm probe is required and that there is no requirement for the protection from the ingress of water. According to current IEE Wiring Regulations, BS7671, an enclosure, which is readily accessible, must maintain an IP rating of IP4X for horizontal top surfaces, in order to prevent small items falling through and coming into contact with live equipment.

For the purpose of most applications the rating system goes up to IP68, which provides complete protection from ingress when fully submerged (though statically fixed) in water of up to 10m in depth. However, a specialised IP69K rating is available for applications which require protection against not only the ingress of dust but also high temperature, high pressure water - making products with this certification ideal for use in conditions where equipment must be carefully sanitised.

The adoption of this classification system promotes uniformity in methods of describing the protection provided by the enclosure and in the tests to prove the various degrees of protection. The product's IP rating ensures that the person specifying a project knows that the product is protected from particles of dust or water that may be present in the environment.

Despite the rating system giving an accurate and reliable indication of the level of protection an enclosure supplies, it is very common to see enclosures being over specified, 'just in case'. Not only is specifying a higher degree of protection often more expensive, it can also be less suitable for a particular application. For instance, ventilation or pressure compensation devices can reduce the possibility of internal condensation caused by changes in air temperature and humidity. Drainage holes may be sufficient to disperse the condensate, but these apertures may reduce the IP rating, however, if correctly designed, drainage holes can enhance the weatherproof capabilities of an enclosure.

Then there is ventilation, which can provide an important contribution to the satisfactory operation of enclosed equipment, for example where significant heat is generated in an enclosure. Too high an IP rating can compromise the ventilation, and so shorten the life of the equipment.

It should be noted that IP ratings are for ingress only and that tests are comparative and are conducted with fresh water. Therefore, they in no way indicate the enclosure's ability to withstand the effects of corrosion from salt water, chemicals, acid rain and other special environments as well as the normal expected weather conditions.
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