Waterproofing Outdoor Enclosures - Cable Gland Alternatives

[Thane of Cawdor]

Hi all,

A quick question: are there any alternatives to using cable glands (like these: https://uk.rs-online.com/web/p/cable-glands/0389599/) for waterproofing the input/output cabling to an outdoor project box/enclosure? Is there a search term for something similar that has a smaller size since the thread on these variants are generally too big to fit onto the side of a small profile hobby box (with a height of ~ 40mm with the lid).

Alternatively, has anyone ever just fitted a silicone sleeve over the wires, drilled a hole between the hobby box lid and main chassis and then screwed together - essentially clamping the silicone sleeve to make the hole watertight (protecting the electronics inside)?

The cable I'm running through is a simple power cable (~5mm in diameter)

[picandmix]

Are you talking about Mains voltages or just low voltage dc ?

There are various small metal ones around  eg brass rust proof -
https://www.ebay.co.uk/itm/Cable-gland-M8-Brass-Brass-LappKabel-SKINDICHT-MINI-M-8X1-1-pc-s-/262436614011?clk_rvr_id=1427597449413&utm_medium=cpc&utm_source=twenga&utm_campaign=twenga&utm_param=eyJlcyI6MCwicyI6OTcyMDIzNywiY2kiOiIwMzJjZWYwZTNhMzlmZmQ3ZjIzZDdmY2VlMGMzNmEwZSIsImkiOiIyNjI0MzY2MTQwMTEiLCJ0cyI6MTUxNzI0MTc0NCwidiI6Mywic28iOjE1MDAsImMiOjI2MjEzfQ%3D%3D&rmvSB=true

[David Hess]

If design considerations allow it, then running the cables through on the bottom should be good enough.  Even with good cable glands, I would use drip loops on the inside.

[james_s]

Sometimes sealing the box completely does more harm than good. I've seen water seep in up higher and slowly fill up a box that tried to be completely sealed. Had it been able to drain out the bottom it would have likely been ok.

[Paul Moir]

You should be able to get those quite small, certainly small enough to fit a 40mm height box.  For example a very common one with a PG9 thread should fit no problem.  The nut's OD is 24mm.

(I would still drill a tiny hole in the bottom at the very least.  I had one application where the moisture transfer though the wire insulation transferred into the sealed unit causing condensation within.  The solution was to drill a tiny hole.    )

[Thane of Cawdor]

If design considerations allow it, then running the cables through on the bottom should be good enough.  Even with good cable glands, I would use drip loops on the inside.

Hmm they probably don't in this case but that's interesting - do you mind explaining how you'd use the drip loop inside the project box?

[Thane of Cawdor]

Sometimes sealing the box completely does more harm than good. I've seen water seep in up higher and slowly fill up a box that tried to be completely sealed. Had it been able to drain out the bottom it would have likely been ok.

Ah I see! Although, wouldn't the hole allow for condensation to occur within the box (and hence the electronics could be negatively affected) even if the box doesn't fill with water?

[David Hess]

If design considerations allow it, then running the cables through on the bottom should be good enough.  Even with good cable glands, I would use drip loops on the inside.

Hmm they probably don't in this case but that's interesting - do you mind explaining how you'd use the drip loop inside the project box?

Immediately after the cable or wires enter the enclosure through the side or top, they are formed into a loop so that any water which leaks in and follows the cable or wires will drip off at the bottom instead of continuing to where the cable or wires terminate.

A drip loops are more often used outside of an enclosure but they work inside as well for defense in depth.

[picandmix]

Given the 40mm height of your box , wonder what its other dimensions are , fairly small ?

Also how much space is taken up with the electronics and are any of them likely to generate any heat at all ?

What kind of outdoor min / max  temps are we talking about as you do not show a country flag.

You will never avoid some condensation etc, so where possible use a protective lacquer coating on your board instead .

Unless your cable is going to be tugged or moved around a lot, a simple rubber cable gland is all thats needed, or just a hole and the cable bedded with some silicone rubber sealant.

[floobydust]

Use cable glands. The plastic ones are low cost, and ensure water/splash/rain storm/melting snow will not get in your enclosure.

Or put your enclosure inside another enclosure which is like a rain hood. You see this in weather stations as a Stevenson Screen.

[james_s]

If the design allows for this, another option is to pot the whole box in epoxy. I normally don't like potted stuff because it makes repair very difficult but it's an option in some cases.