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IP rating confusion `leading to incorrect specifications`

10 July, 2010

Schneider Electric is warning that poor understanding of IP ratings is leading to enclosures being specified inappropriately. The company also points out that some IP ratings – notably IP69K – have no meaning internationally, and are irrelevant to their intended use.

“The system of IP ratings is misleading many specifiers and resulting in higher costs than are strictly necessary,” argues Schneider’s Darren Hodson. “The common mistake is to assume that the higher the IP rating, the better the equipment inside the enclosure will be protected. This is not always a guarantee, and the degree of protection offered by a specific enclosure has to be considered in conjunction with the performance requirements of the application.”
 
IP ratings, defined in IEC 60529 (published in the UK as BS EN 60529), specify degrees of protection by the letters IP followed by two or more digits. The first digit – a number from 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 inside the enclosure. The second digit – a number from 1 to 8 – relates to the protection of equipment in the enclosure against the ingress of water. Either digit can be replaced by an X for an unspecified condition.
 
Schneider says that specifiers should not opt automatically for a higher IP rating because this does not necessarily mean that the enclosure will perform better. For example, an enclosure may pass the test for a high level of protection against the ingress of water but in situ may be subject to environmental conditions which could cause rusting or other degradation.
 
According to Hodson, one of the most common misconceptions relates to the IP69K rating. “This actually stems from a German national standard and has no international recognition,” he points out. “The IP69K test specification was initially developed for electronic equipment on road vehicles as a rating for high-pressure and high-temperature washdown 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. The result is that IP69K-rated enclosures 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 examine carefully 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,” says Hodson. “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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