Is IP67 always better than IP65?
No. The IP67 test is temporary immersion at 1 m depth for 30 minutes; the IP65 test is a water jet lasting at least 15 minutes from a 6.3 mm nozzle at 3 m distance with a flow of 12.5 L/min at approximately 30 kPa. These are different stresses. In an application involving pressure washing, IP67 on its own may not be enough; jet resistance must be looked for separately.
Although the second digit of the IP code looks like a ranking, the immersion and jet tests measure different physical stresses. In immersion the water applies static hydrostatic pressure; in a jet, water leaving a narrow nozzle applies a directed and dynamic pressure to the sealing face, and with some seal geometries a jet is more demanding than immersion.
Practical consequences:
- If the device can occasionally end up under water, a second digit of 7 is meaningful.
- If the device is washed with a pressure hose, a class stating jet resistance must be looked for; IP67 alone does not guarantee that condition.
- If both conditions apply, the manufacturer usually states the two codes together; do not assume that one code automatically covers the other.
For the first digit the situation is different: in both IP65 and IP67 the digit 6 means dust tight, so on the dust side the two are equal. The difference is entirely on the water side.
The point forgotten during installation is this: whatever the class of the enclosure, a gland fitted with a cable of the wrong diameter, an unclosed hole or a crushed seal voids the whole class. Position the entries facing downwards and give the cable a drip loop.
The full topic: Complete guide to IP protection ratings