IP (Extended Environment) Ratings for Equipment

Moe Lamothe, P.Eng, Lamothe Approvals Inc.

IEC 60529, 2^nd edition describes the ratings for enclosure Ingress Protection (IP) covering water, foreign objects and access to hazardous parts. The IP rating has been in use in Europe and other countries outside of North America for many years, and has just recently been added to the Canadian Electrical Code (for hazardous locations). They are similar in intent to the NEMA ratings but there is no direct relationship. These ratings are widely used on portions of enclosures and components, as well as complete enclosures.

In North America, the common practice has been to use NEMA enclosure ratings for both water and dust resistance. As the name suggests, these standards were originally developed and published by the National Electrical Manufacturer’s Association (NEMA) and have been adopted by UL, CSA and other standards bodies in North America. International Standards use the IEC IP ratings instead of the NEMA ratings.

For example, 61010-1 and 60950 uses these requirements for ‘Protection Against Liquids’. Typically these standards reference IP X0 where the ‘X’ indicates that there is no rating for entrance of objects or dust. The ‘0’ indicates that there is no protection against water.

The IP rating is written as IP followed by the 1st and 2nd characteristics optionally followed by letter qualifiers. The qualifiers are rarely used and are beyond the scope of this article. Typical markings with their meaning:

IPX0 – Protection against entry of objects and prevention of touch not rated, no protection against entry of water. This is the most common rating.

IP2X – Protection against solid objects up to 12.5mm and accidental touch by fingers, no rating for protection against water.

IPX5/IPX7 – Dual rating indicating protection against jetting water and temporary immersion.

Cross Reference to NEMA

There is no direct relationship to these ratings but some guidance can be gained from the following table.

A common rating for outdoor equipment is IP56. The ‘5’ for limited ingress of dust is not much of a problem but the ‘6’ requires a well gasketed enclosure. Remember that the jet of water is 12.5mm (1/2”) in dia. with sufficient volume to fill a 3.5 cu. ft. volume in one minute. It doesn’t sound like much but the stream of water at 3m distance has only dropped a few centimeters. Because of the pressure it will enter enclosures that will stay dry inside even when immersed in water!

For IP ratings concerning ‘Protection Against Solid Objects’ and ‘Protection of Persons’, any lower rating than the one obtained is considered to be covered. For example, if you have a rating of 5, all ratings from 1 to 4 are also covered without additional testing. For ingress protection against water, the jetting water ratings are separate from the immersion ratings. A rating of 6 will cover you for ratings 1 to 5 but ratings of 7 or 8 are separate.

We strongly recommend that you purchase a copy of IEC 60529 if you have any equipment that needs to meet ingress protection specifications. This is particularly true for the water ingress tests.

The table on the next page summarizes the important ratings and the basic tests required.

IP Test Summary

Note - For voltages not exceeding 1000Vac or 1500Vdc – no contact with hazardous parts. For higher voltages, must pass dielectric test specified for voltage.

Difference between dust tests for IP5X and IP6X

The dust test for IP5X and IP6X (dust rating of 5 and 6) is conducted in a dust chamber for 8 hours, with talcum powder (2kg per cubic metre of the test chamber) circulating, so it continually falls down onto the equipment under test.  IP5X testing may be conducted either with or without underpressure - depending on the equipment category (see below).  IP6X is tested with underpressure, regardless of the equipment category. 

The following is a description of the two enclosure categories:

Category 1 Enclosures - Enclosures where the normal working cycle of the equipment causes reductions in the air pressure within the enclosure below that of the surrounding air, e.g. due to thermal cycling effects - if the equipment will or may be installed near a heater (or other heat source) which will cycle the temperature of the equipment.

Category 1 equipment must be tested with underpressure - which means that the enclosure will be maintained below the surrounding atmospheric pressure by a vacuum pump for the duration of the dust test. 

Category 2 Enclosures- Enclosures where no pressure difference relative to the surrounding air is present. 

For IP6X testing, the equipment is assumed to be Category 1- regardless of what it actually is.  A pass for this test is only if NO dust is observed inside the equipment after the test. 

IP5X testing can be conducted for either Category 1 or Category 2 type enclosures.  A pass for this test (regardless of which category is used) is if the powder has not accumulated in a quantity or location such that it could interfere with the correct operation of the equipment or impair safety. 

Moe Lamothe is the president of Lamothe Approvals Inc. (Georgetown, ON, Canada). He can be reached at info@lamotheapprovals.com.

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The copyright for all of the text, tables and illustrations remains with Lamothe Approvals Inc. Permission is granted to print or reproduce this document provided that it properly attributed to Lamothe Approvals Inc.

Prepared May 2003