Definition
IP Protection Rating (IEC 60529) The first digit indicates protection against dust (0–6), and the second digit indicates protection against water (0–9). Common ratings: IP54 (splash-proof, dust-proof), IP65 (water jet-proof, dust-proof), IP67 (short-term immersion 1m), IP68 (continuous immersion). Outdoor sensors, industrial enclosures, and positioning terminals should be selected according to the installation environment; high humidity or outdoor scenarios are recommended to use IP65 or above.
Detailed Ratings
Dust protection: 0 No protection; 1 Protection against 50mm solid objects; 2 Protection against 12.5mm; 3 Protection against 2.5mm; 4 Protection against 1mm; 5 Dust-protected (limited ingress); 6 Dust-tight. Water protection: 0 No protection; 1 Protection against vertical dripping water; 2 Protection against dripping water at 15° tilt; 3 Protection against spraying water; 4 Protection against splashing water; 5 Protection against water jets; 6 Protection against strong water jets; 7 Protection against short-term immersion (1m); 8 Protection against continuous immersion. IP65 can resist water jets and dust, suitable for outdoor enclosures and sensors; IP67 can withstand short-term immersion, suitable for underground and humid environments; IP68 can withstand continuous immersion, with agreed depth and duration.
Selection Recommendations
Indoor control cabinet: IP20~IP54; Outdoor wall-mounted, pole-mounted: IP65; Underground, tunnel, high humidity: IP67; Underwater, long-term immersion: IP68. Industrial gateways, RTU, DTU often provide specifications like IP30, IP54, IP65. When selecting, installation on DIN rails, wiring method, and heat dissipation requirements must be considered; high protection levels often come with cost and heat dissipation challenges.
Read the dust digit and the water digit apart
The first digit of the code is protection against solid objects. The second is a water test. Neither digit contains the other. Passing a dust test does not imply passing a water spray. Water tests cover dripping, spraying, splashing, jetting, powerful jetting, brief immersion, and continuous immersion. The method, the duration, and the pressure of the later tests are not the same. Brief immersion has an agreed depth and time. Continuous immersion needs a depth and a time agreed separately by the manufacturer and the user. The two codes must not be treated as "one is more suitable than the other for every underwater environment." The test is done on a new sample assembled as instructed, with no extra openings.
The condition is the enclosure in its final assembled state, not the nominal rating of an empty shell. Every added indicator hole, antenna hole, drain hole, and unused expansion port means the original test is no longer automatically valid. The cable has to use a matching gland, and the gland's sealing range has to cover the actual cable diameter. A thin cable in a large gland will not seal even if it is tightened by hand. A vent membrane balances pressure. Its ability to stop liquid water is not the same thing as the enclosure code, and the membrane's rating cannot stand in for a test of the whole unit. A temperature cycle changes the pressure inside the cabinet and draws moisture in through a tiny gap. That path is not the path of a single spray test.
Openings, cable glands, and heat
The most common failure on site is that installation destroys the state that was tested. A missing cover screw, a gasket cut short, a gland locknut left loose, or a spare entry blocked with tape lets water in at those places, and the nominal code on the enclosure has not changed. Using a higher immersion code for long-term soaking, or for an underwater connector that is mated again and again, also goes beyond what a brief test represents. The mistake in the other direction is to seal the device completely in order to raise the code, leave the internal supply with no heat path, and overheat the circuit in a dry room while the ingress test still passes.
A window, a keypad, and a hinge are the weak points. After they age, sealing force falls. The code does not downgrade itself, and the outside still looks new. Condensation forms inside. However high the external code is, internal humidity still has to be considered, with heat or drying if needed, rather than only a higher enclosure code. A wash-down jet may be aimed at a seam. The nozzle angle in the test may not cover that installed orientation. Whether the code on the nameplate is for the whole unit or only for the shell has to be separated in the instructions. Printing a shell code, with no connectors fitted, as the whole-unit code makes the selection too optimistic. Acceptance should check that cable entry, end covers, and installed orientation match the tested state, not only the silkscreen.
The whole unit, and moisture inside it
The code applies to a whole unit assembled as instructed, not to an empty shell. An indicator hole, an unsealed expansion port, and an entry temporarily blocked with tape are not in the state that was tested. The gland's sealing range has to cover the actual outside diameter. If the cable is too thin, a tightened locknut still lets water in. A missing cover screw or a gasket cut short lets spray in at the seam, and the code on the nameplate does not change with it.
Brief immersion and continuous soaking are not the same condition of use. Mating a connector again and again underwater goes further beyond a shell test. A complete seal brings a heat problem. Overheating in a dry room and a passed ingress test can exist at the same time. Internal condensation comes from a temperature cycle drawing moisture into the cabinet. An external spray test will not find it. It needs heat, drainage, or drying, not only a higher code. At acceptance, check that orientation, cable entry, and end covers match the test. If a wash-down jet points straight at a seam, also check whether the test nozzle covered that direction. Write the shell code and the whole-unit code separately in the instructions, so a shell with no connectors is not taken as the unit on site.
The test sample usually has new seals. After ultraviolet light, cleaning agents, and repeated opening, sealing force falls, and the code is not rewritten on the nameplate by itself. The first time the cover is opened after acceptance, restore the screws to the original torque and confirm the gasket has not shifted. If a drain is blocked to meet a dust requirement, condensate pools at the bottom. That trade between dust and water has to be written into the installation instructions. It cannot be read as the highest digit on both sides. If wash-down comes from below, dripping and spraying tests, which come from above, do not cover it. Selection has to look at which side the water actually comes from. After a vent membrane clogs, the pressure difference from a temperature change pushes the seal open at its weakest point. The code is only the start of selection. The list of openings, the gland model, the installed orientation, and whether the cover may be opened are what keep that code on site.