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Know your enclosure IP ratings

02 September 2010

A lack of understanding of IP ratings is leading to inappropriate specification of enclosures, says Schneider Electric’s Darren Hodson, who also cautions that some IP ratings do not have an international meaning and are not actually relevant to their intended use. Common misconceptions lead to higher costs than are strictly necessary

The common mistake is to assume that the higher the IP rating, the better the equipment inside the enclosure will be protected against weather conditions. This is not always a guarantee and the degree of protection offered by a specific enclosure has to be considered in conjunction with the precise performance requirements of the application.

IP ratings are defined in the IEC 60529 standard “Degrees of protection provided by enclosures”, published in the UK as BS EN 60529. Degrees of protection are specified by the letters IP followed by two or more digits. The first digit, a number 1 to 6, reflects the degree of protection against the ingress of objects as well as the protection of persons against contact with live parts of the equipment within the enclosure. The second digit, a number from 1 to 8, relates to the protection of equipment within the enclosure against harmful ingress of water. Either digit can be replaced by ‘X’ for an unspecified condition.

Specifiers should not automatically opt for a higher IP rating as this does not necessarily mean that the enclosure will perform better in the intended application. For example, an enclosure may pass the test for a high level of protection against ingress of water but in-situ may be subject to environmental conditions, which could cause rusting or other degradation.

One of the most common misconceptions relates to enclosures rated IP69K. This actually stems from a German national standard and has no international recognition. The IP69K test specification was initially developed for electronic equipment on road vehicles as a rating for high-pressure and high-temperature wash-down applications. However, it has no real meaning in the UK as it isn’t defined in a British or international standard and has been found to give different results in different test houses. Thus enclosures rated IP69K can vary between manufacturers and might not even pass the tests for lower IP codes.

To ensure the correct combination of performance and cost-effectiveness, the specifier has to carefully examine the specific conditions that will apply in each application and prescribe the enclosure most suitable for that application, which is not necessarily the one with the highest IP rating. And, of course, the most important thing is to use an enclosure rating that is recognised by IEC or British Standards.

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