Ingress Protection: The System of Tests and Meaning of Codes

William S. Bisenius

An IP code, correctly determined, should be included in the labeling of many enclosed products intended for international sale.

More and more companies are exporting their products into the world market. In addition, an increasing number of product safety standards are being harmonized to international safety standards. For example, UL 60335-1, CSA 60335-1, and EN 60335-1 are harmonized to IEC 60335-1. One consequence of this trend is a growing need for manufacturers to make sure their products comply with the international standards.

These international standards quite often involve terminology and tests for verifying product safety compliance that are new to designers and manufacturers. For producers of outdoor-rated products, the ingress protection (IP) ratings and tests of IEC 60529 are a big new obstacle to learn how to overcome.

This article explains the relevant terms and test conditions, as well as the rating system, associated with IP compliance, which is known commonly as the product IP code. From this information, compliance engineers should be able to understand what requirements are applicable to their company’s particular products and which associated tests should be used to verify compliance.

Safety Standards

As might be expected, outdoor-rated products are tested to ensure continuing compliance with relevant safety standards when they are subjected to simulated environmental conditions. In the United States, achieving compliance in this regard has previously meant using a suitable National Electrical Manufacturers Association (NEMA)–rated enclosure. Certified NEMA enclosures will have been tested against various outdoor environmental conditions according to established association standards. Industrial control panels commonly carry a NEMA rating. There is no exact correlation between NEMA ratings and IP codes because the tests are completely different. However, NEMA does maintain a summary of approximate equivalencies.¹

For domestic companies that are marketing outside North America today, though, a NEMA rating is insufficient. Compliance now means testing to the international IP requirements—a completely different set of performance levels and tests for outdoor environmental conditions.

The international safety standard for IP is IEC 60529.² This is a reference standard. A reference standard contains general guidelines that pertain to a feature that may be incorporated into many different types of end products. Various end products have their own categorical safety standard that applies to the product according to its overall function. For example, the end-product standard for information technology equipment is IEC 60950-1.

Most international end-product standards reference and require compliance with IEC 60529. (For example, IEC 60335 requires many types of household appliances to be subjected to tests specified in IEC 60529.)

IP Codes

An IP code is a rating assigned to a product that indicates its level of ingress protection, that is, the amount of protection that the enclosure of the product provides against the entry of solid foreign objects (fingers, tools, and so on) and against moisture infiltration (from rain, for example). IP codes have the format IPxx, where the xs represent numerals from the coding scheme. The first number in the sequence signifies the degree of protection against the entry of foreign solid objects. The range of available numbers is 0–6 (see Table I). The second number signifies the degree of protection against the entry of moisture and may be anything from 0 through 8 (see Table II). The letter X may be used as an alternative for zero. The protection is greater as the number is higher.

A few examples of the many possible IP code combinations will suggest how the IP code rating system works. In these, an X appears where a 0 could instead.

• IP23: Protected from solid foreign objects 12.5 mm in diameter and larger, and protected from moisture challenges as aggressive as spraying water.
• IP54: Dust-protected and protected from moisture assault as strong as splashing water.
• IP65: Dust-tight and protected from moisture challenges up to jetting water.
• IPX1: Not evaluated for protection against solid foreign objects, and protected from moisture only in the form of vertically dripping water.
• IP4X: Protected from intrusion by solid foreign objects as small as 1.0 mm in diameter, and not evaluated for protection from moisture.

Of course, the “not evaluated” element of any code can mean any of several things. It might be that the product would be compliant if tested, but has not been tested. Or, the manufacturers might have known that the product would not comply. In many cases, the X or 0 simply signifies an unknown quality for products that were never intended to comply with that particular section of the standard.

Each number in the IP code rating scheme represents a specific test; the higher the number, the more severe the test. Each test has requirements that very tightly control the test procedure and the equipment used. Once the manufacturer has identified the IP code desired for its product—either as required for that type of product by the applicable safety standard or as requested by the company’s marketing department—it can conduct a test program specific to that code.

Tests for Solid Foreign Objects

IP testing pertinent to the first numeral can be usefully considered as two separate sets of tests, one for objects and coarse particles and one for fine-grain solid matter.

Ratings IP1X–IP4X. Tests for ratings IP1X–IP4X address ingress by solid foreign objects of varying size limit (see Table III). These size limits correlate to appropriately sized accessibility probes (see Figure 1). The probes are applied to the enclosure of the product to determine whether they are able to enter any enclosure openings. The standard indicates also a maximum force to be applied to each probe.

Many of the probes specified in IEC 60529 are the same as those required by many end-product safety standards. Therefore, many users already possess this test equipment. For example, the test finger for IP2X is common in most international standards as well as in national standards harmonized with international standards (e.g., UL/CSA 60950, UL/CSA 60601, UL/CSA 60335, and UL/CSA 61010). There are slight application differences, however, that testers need to be aware of (discussed in “Special Considerations” below ).

Figure 1. Accessibility probes for testing for ratings IP1X–IP4X.

Ratings IP5X and IP6X. Unlike IP1X–IP4X, tests for ratings IP5X and IP6X require very specialized and much more complex test equipment. For these tests, the test sample is hung in a dust-test chamber containing specially sized grains of talcum powder in suspension. A calibrated sieve is used to sift the talcum to the proper size.

Depending on the type of product being tested and the associated requirements in the end-product standard, a vacuum line also may be connected to the sample for negative pressure or airflow. The design of the product will determine whether the vacuum line produces negative pressure or airflow. Leaky seals will allow air to flow when the vacuum is applied, and therefore pressure will not build. Likewise, a tightly sealed product will have little to no airflow; consequently, negative pressure will increase. The standard specifies that airflow in the vacuum line should not exceed a rate of 60 volumes per hour.

The test duration is either 8 hours or 80 volumes of air exchanged (if based on air exchange, the test time should in no case be less than 2 hours). The most difficult part of the test might be calculating the internal volume of the test sample for purposes of determining the test time. Unless the testing company has some very good 3-D modeling software and programmers to do this, it might want to employ a simplified calculation that assumes the worst case. Specifically, this involves approximating internal volume from the cube, rectangular solid, cylinder, or sphere that would fully contain the product. It is important here to err on the worst-case side—that is, a longer test is better than one that is too short.

Pass-fail criteria for these dust tests and IP ratings are as follows:

• IP5X (dust-protected): Some talcum permitted inside the enclosure, provided it does not impact safety or operation.
• IP6X (dust-tight): No talcum permitted inside.

Tests for Moisture

IP testing pertinent to the second numeral in the IP code falls neatly into four categories: determining protection against dripping, spraying and splashing, jetting, and encompassing water. For all of these ratings, the pass-fail criteria involve water not being able to enter an area within the product such that it impedes product operation or safety.

Ratings IPX1 and IPX2. Tests for the ratings IPX1 and IPX2 address the possibility of ingress by dripping water. Both tests are conducted using a drip box system and a turntable.

Figure 2. Drip box system for testing for ratings IPX1 and IPX2.

The drip box system incorporates a water box with special drip nozzles oriented in a precise 20 × 20-mm grid pattern (see Figure 2). The drip nozzles are positioned 200 mm above the test sample, and the flow of water through the nozzles is adjusted to control the drip rate (see Figure 3). To test for compliance with IPX1, the sample is rotated on the turntable at 1 rpm and 100 mm eccentricity (the distance between the turntable’s axis and the test sample’s central axis) under water dripping at a rate of 1 mm/min for 10 minutes. For IPX2 testing, the sample is tilted at 15° under water dripping at a rate of 3 mm/min for a total of 10 minutes, 2.5 minutes in each of four positions of tilt.

Ideally, the drip box should be big enough to accommodate the entire product under test. But even a relatively small drip box with a plane area of 500 × 1000 mm has more than 1000 drip nozzles. Therefore, a large drip box can be very expensive. If the sample is larger than the drip box, the standard permits testing the product in sections. The test goes on until all portions of the enclosure have been tested for 10 minutes.

Figure 3. Profile of drip nozzles for testing for ratings IPX1 and IPX2.

Ratings IPX3 and IPX4. Tests for the ratings IPX3 and IPX4 address the possibility of ingress by spraying and splashing water. Two different types of alternative test equipment are described for these tests: a handheld spray nozzle and an oscillating spray test system. The complexity, cost, and ease of use of these two options differ greatly. Compliance engineers should be sure they know which method and test equipment the appropriate end-product standard requires.

Figure 4. Oscillating spray chamber for use in testing for ratings IPX3 and IPX4.

In the oscillating spray test, a spray tube rotates around the test sample, spraying it with water (see Figure 4). The distance between spray nozzle and test sample is to be no more than 200 mm.

The rotation angle of the spray tube depends on the IP rating desired. For IPX3, the sample is positioned under oscillating spray tubes rotating at ±60° from the vertical for 5 minutes. The oscillation rate is two cycles of 120° in 4 seconds. The flow rate depends upon the tube size, which in turn is dependent upon the sample size. For IPX4, the sample is positioned under oscillating spray tubes rotating at nearly ±180° from the vertical for 10 minutes. The oscillation rate is two cycles of about 360° in 12 seconds. The flow rate again depends upon the tube size, which is itself dependent upon the sample size.

Figure 5. Handheld spray tester for use in testing for ratings IPX3 and IPX4.

In the handheld spray test, a precision spray head and shield assembly is used to spray or splash the sample with water (see Figure 5). The distance between the spray head and test sample is to be no more than 200 mm.

Here again, the spray arch varies according to the IP rating desired. For IPX3, the sample is sprayed at ±60° from the vertical and at a flow rate of 10 L/min. Each surface of the enclosure within the spray arch is to be tested for 1 min/m2. Total test time in any case should be no less than 5 minutes. For IPX4, the sample is sprayed at ±180° from the vertical, again at a flow rate of 10 L/min. Each surface of the enclosure within the spray arch is to be tested for 1 min/m2, with no less than 5 minutes of total test time.

Ratings IPX5 and IPX6. Tests for the ratings IPX5 and IPX6 address the possibility of water ingress from a jetting stream. They are conducted using a jet nozzle kit (see Figure 6). Testing to IPX6 requires also a water tank and a high-pressure water source.

Figure 6. Jet nozzle kit for use in testing for ratings IPX5 and IPX6.

To test for compliance with IPX5, the sample is subjected to water jetting from a nozzle with a 6.3-mm-diameter opening at a flow rate of 12.5 L/min. Each surface of the enclosure is to be tested for 1 minute at a distance from the jet nozzle of 2.5–3.0 m. For IPX6 testing, the sample is subjected to water jetting from a nozzle with a 12.5-mm-diameter opening at a flow rate of 100 L/min. Again, each surface of the enclosure is to be tested for 1 minute at a distance from the nozzle of 2.5–3.0 m.

Many test labs can find it very difficult to achieve the 100-L/min flow rate with the 12.5-mm jet nozzle; this is a huge volume of water to move in only 3 minutes (300 L is about 80 gal). This flow rate cannot be achieved through a garden hose or city water source. This test typically requires a storage tank and a high-pressure water pump. Considering the need for a start-up adjustment period and variable test times, it is recommended that the water storage tank have a capacity of at least 130 gal to provide enough water for each test (see Figure 7).

Figure 7. Portable water supply system for use in testing for the IPX6 rating.

Ratings IPX7 and IPX8. Tests for the ratings IPX7 and IPX8 address the possibility of moisture ingress from submersion in water. For IPX7 testing, the sample is submerged for 30 minutes. The lowest point of the enclosure should be 1000 mm below the surface of the water, and the highest point at least 150 mm below the surface. For IPX8, the test time and submersion depth are according to the manufacturer’s specifications and must be marked on the product (for example, “submersible for up to 1 hour at a depth up to 2 meters”).

Compliance with either of these tests does not imply compliance with IPX5 or IPX6 unless the product is marked with both ratings (for example, “IPX5/IPX7”).

Special Considerations

A few other requirements and tips pertaining to the IP test regime are important enough to be worthy of mention here.

Special Pass-Fail Criteria. Most safety standards are concerned only with protecting the user from safety hazards. However, IEC 60529 specifically requires that tests be completed while protecting the user from safety hazards and also protecting the equipment for proper operation. Compliance engineers must remain aware of this important difference in pass-fail criteria.

End-Product Standard. The applicable end-product standard may add further detail to modify or otherwise change the test method or the pass-fail criteria for these tests. The IP standard is only a reference standard; some end-product standards require full compliance with IEC 60529, while others require only partial or modified compliance.

Accessibility Probes. Careful notice should be taken of the requirements regarding the application of probes. Some probes are not permitted to penetrate the enclosure at all, while other probes are permitted to penetrate the enclosure up to a specified depth. Of the probes that are permitted to penetrate the enclosure, a clearance distance must be maintained between the probe and all hazardous parts.

Water Temperature. For some of the moisture tests, the standard requires control of the test water temperature. This necessitates having a storage tank system to allow the water to be maintained at room temperature.

Final Inspection. The test equipment employed to determine levels of IP does not identify and announce a pass-fail conclusion for any of the tests. The probe tests are a hands-on process. And with all the other tests, a compliance engineer must inspect the inside of the product immediately after stopping the test in order to determine whether dust or moisture has entered the enclosure and, if it has, whether the dust or moisture impedes safety or proper product operation.

IP Code Suffixes. Although their use is very rare, one or two suffix letters can be added to the IP code according to a system that exists for the purpose. These suffixes add further detail related to the tests performed. Engineers encountering a suffix letter should check the standard.

Conclusion

This article is intended to provide readers with a good basic overall understanding of the IP coding system and the associated IP tests. Although most of the requirements have been discussed and summarized here, the article is no replacement for use of the safety standard. Anyone to whom the IP requirements apply should be sure to review thoroughly the current edition of IEC 60529. There is no point in performing the IP tests unless they are conducted in exact accordance with the requirements.

References

1. “A Brief Comparison of NEMA 250 and IEC 60529” (Rosslyn, VA: National Electrical Manufacturers Association, 2002); available from Internet: www.nema.org/stds/briefcomparison.cfm.
2. IEC 60529, “Degrees of Protection Provided by Enclosures (IP Codes),” ed. 2.1 (Geneva: International Electrotechnical Commission, 2001).

William S. Bisenius is president of Educated Design & Development Inc. (Morrisville, NC). He can be reached at billb@productsafet.com.