Gland Sealing Range
Every cable gland has a cable outer-diameter range within which it can seal, and that range is marked on the product. With a thin cable below the range the seal never closes fully; with a thick cable above it the seal is crushed and tears. In both cases the enclosure's protection rating is void.
The sealing ring narrows inward as it is tightened, but that narrowing has a limit. If the cable diameter is below the range, a microscopic path remains between the seal and the jacket even with the nut fully tightened; the pressure difference created by temperature swings draws humid air in through that path.
- Measure: measure the cable's outer diameter with a caliper and compare it against the gland's range instead of judging by eye.
- Intermediate seal: for thin cable, some glands include an additional inner seal or a reducing ring.
- Glands in different sizes: if cables of different thicknesses enter the same enclosure, pick the correct size separately for each entry.
This detail is the main factor deciding whether the protection rating actually holds in practice on receivers, drivers and junction boxes working outdoors. The IP value on the enclosure label is valid only when every entry is closed with the correct gland, correctly tightened.
Context in which this term is used: Complete guide to IP protection ratings