I have a waterproof box that I would like to pass a pre-assembled RJ45 ethernet cable into. What is the recommended cable gland size for this application?

Cable glands seem to all be specified with two numbers, for min and max cable diameter, but it seems like the specification should have at least three numbers, i.e. min and max diameters of cable for the part that seals, and a third number for how big a connector you can pass through during assembly.

I am looking for water protection of at least IP *5.

This is the sort of thing you could spend hours hunting through the 600+ results on farnell, but really, someone probably already has a favorite part number that is known to be cheap and just work.


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  • \$\begingroup\$ newark.com/jsp/search/browse.jsp?N=200837+422&ref=lookahead \$\endgroup\$ – DeathBySnuSnu Aug 26 '13 at 16:18
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    \$\begingroup\$ I suspect the solution is not to even try. Just take a plain connectorless cable (or cut the connector off your existing cable), pull it through the cable gland and then crimp on a new connector. That's what I did when I had to run some RJ45 through a wall. \$\endgroup\$ – Ilmari Karonen Aug 26 '13 at 16:35
  • \$\begingroup\$ Cable glands are not designed to have a connector go through them, if they were, then the seal would not be anywhere near as good against the wire. Just assemble the gland before crimping on the end. OR use a waterproof jack on the outside of the box in conjunction with a waterproof connector on the cable. \$\endgroup\$ – Kris Bahnsen Aug 26 '13 at 21:33
  • \$\begingroup\$ Thanks guys. We've had bad experiences with crimping our own cables, and it's a pretty big machine we're building, so reliability is a concern for us. Maybe we will shell out the cash for the waterproof jack, but they're quite expensive. \$\endgroup\$ – Andrew Wagner Aug 27 '13 at 13:56

Converting this from a comment to an answer:

I suspect the solution is not to even try. Just take a plain connectorless cable (or cut the connector off your existing cable), pull it through the cable gland and then crimp on a new connector.

As Kris Bahnsen notes, cable glands are not designed to have bulky connectors squeezed through them. If they were, the wouldn't have anywhere near as good a seal against the cable. The fact that you've found just one part in the Farnell catalog that has almost the necessary size range, and needs extra reducer rings to achieve it (BTW, good luck getting that 5 mm ring over the connector), pretty much indicates that what you're asking for is at the very limit of what's possible, if not beyond it.

Using a waterproof jack and connector, as Kris suggests, is one option, and has the convenient feature of letting you disconnect and reconnect the cable as needed; with a cable gland, the cable would be pretty much permanently attached to box.

However, if you don't need that option, I'd still say the easiest option would be to use a normal ~5 mm cable gland and crimp a new connector on the cable after threading it through the gland. Honestly, people do that all the time, because it's the only practical way to run RJ45 through tight spots (or to get a cable that's exactly the length you want, rather than one of the limited range of lengths available pre-cut). Just make sure to test the cable properly after attaching the connectors, and repeat if necessary. It's not like the connectors cost much.

By the way, I hope your cable's also rated for the conditions you're using it in. In my experience, the outer sheath on cheap Cat5 cables sometimes loses flexibility over time and may crack under mechanical stress. That's generally harmless in an office / data center setting, but it could be a problem if you need things to stay waterproof.

  • \$\begingroup\$ Thanks; response accepted! With crimp connectors, the connectors are cheap, but a quality tool to do the crimping is quite expensive. Our CAT6 cables will not have to flex once installed, and are protected from UV except in a few exposed places that are easy to see. \$\endgroup\$ – Andrew Wagner Sep 4 '13 at 17:04

On my particular cable I'm measuring 13.7mm diagonal on the connector part, and 5.5mm on the cable part, 5mm if you squish it with the calipers.

If on Farnell you choose 5mm as the min cable size, the largest diameter available for the max cable size is 13mm.

HYLEC - 50.620 PA/R7035 Farnell order code: 2056111

This one has two rubber reducer rings to get such a wide cable size range. Note, I have not tried it yet; will post back if it works.

Update: This part did not work well; even if I cut the rubber so I can get the pre-made cable through, it does not fit through the hard plastic part. Also, it does not come with a gasket to seal to the case.


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