An IP rating tells a buyer how well an enclosure or connector resists solids and water. It does not tell the buyer how long a seal will last in service, so it is a starting point, not a guarantee. The chart below explains the ratings most often met on automotive and rail harness connectors.
Common IP ratings
| Rating | Solids | Water | Typical harness location |
|---|---|---|---|
| IP54 | Dust protected, limited ingress allowed | Splashing water from any direction | Interior locations with occasional splash |
| IP65 | Dust tight | Water jets from a nozzle | Exposed locations, washdown with low pressure |
| IP67 | Dust tight | Temporary immersion, 1 metre for 30 minutes | Locations that may be flooded briefly |
| IP6K9K | Dust tight | High-pressure, high-temperature spray (ISO 20653) | Engine bay, chassis and underbody exposed to steam cleaning |
What the rating does not cover
A rating applies to the mated connector with the correct seals, cavity plugs and wire seals fitted. An empty cavity without a plug, or a wire of the wrong diameter in a seal, voids the rating. The rating also says nothing about chemical exposure, vibration or temperature range, so those need their own check.
Using it in a specification
State the rating, the standard it is tested to, and the zone it applies to. Match the wire insulation to the temperature of the zone, and make sure the seal range covers the actual wire outside diameter. For rail, check the connector against the circuit voltage and the vehicle specification.
Connector choice is normally set by the customer drawing, and the harness is built to it. See the automotive and EV harness page, the locomotive harness page, and the wiring harness testing guide for how the finished part is checked.