Which grommet/gland for exterior electrical socket?

[Lobster]

I'm about to install an outside socket. Have bought this box for it:

...but am annoyed to find it arrived with no form of grommet/gland for the incoming cable; you have to buy this separately it seems.

I'm not sure exactly which component I need - can someone point me in the right direction please? The cable (2.5mm T&E) will be entering the box from the rear, via a hole through the wall.

I can see this grommet on the same site:

looks about right to me; however it's IP55 rated whereas the box is IP65 so presumably by using that I'd be downgrading the IP rating of my box, which seems poor practice if nothing else.

The socket will be used for power tools / lawnmower, ie never used when raining or left with an appliance plugged in while raining, so maybe I'm overly concerned? Just want to make sure I'm doing the job properly, that's all...

Thanks David

[Dave Plowman (News)]

If fitting flush to the brick with a rear cable entry, a grommet may cause more problems than it solves. I'd just used some silicone sealant between box and wall.

--

*I didn't say it was your fault, I said I was blaming you.

Dave Plowman [e-mail] London SW To e-mail, change noise into sound.

[Ian]

Hello David.

I'd prefer to use a gland such as

I can't see, from the web site, if the box will accommodate a gland or only the grommet.

Selling the box and glands.grommets separately makes sense to me. I had an outdoor switch box which had built-in glands. This wasn't a good idea because the glands were designed for larger cable than I was using. Moisture got into the box through these glands despite packing the cable with sleeving to make it larger.

Have a look at

and to see the difference between IP55 and IP65.

Good luck, Ian.

[Andrew Gabriel]

They both use 20mm knockouts (and 25mm sometimes). That type of gland needs a rubber seal with a stretched hole for use with T&E PVC, and these are not easy to find. The one you have identified there is for circular cables, as indeed most of these glands are.

Moisture will always get into such a box, even just condensation. You need a drainage hole in the bottom, and bend the wires inside so there's a drip loop before each goes into the wiring accessory, so any water which leaks in on the cable drips off before it can run into the back of the wiring accessory.

Alternatively, run the wire into one of the bottom knock-outs, where making it waterproof is not so important unless you are going to be spraying water jets at it. MK do a grommet for T&E which you could use in this case.

[ARWadsworth]

Oh dear. I have stopped fitting those. They are the Eterna range

They turned out to be utter s**te and probably not UV resisatant.

[Lobster]

That's useful, seeing the actul difference between IP66 and IP65 - protection from "jets of water" and "powerful jets of water". Certainly for my application I can't see any problem with using an IP65 grommet at the back, especially if I select a bottom knockout hole as AG suggested.

Thanks all David

[Ian]

Hello David.

Thank you for raising the topic. I'll be doing something similar later this summer for the power feed to pond equipment.

Regards, Ian.

[John Rumm]

Where is the incoming cable coming from, and what sort of cable?

If you are brining T&E through a wall into the back of the box, then silicone will be fine - forget the gland since you don't really need strain relief in the circumstances, and the silicone will protect from chafing (or place a standard 20mm knockout ring grommet round the annulus of the hole).

If connecting to a surface run cable, then T&E won't really be suitable anyway unless run in some conduit (in which case a conduit knockout termination will solve the problem). Alternatively you could use a plastic gland with rubber seal with exterior grade round cable like hi-tuf, or a metal three part gland with SWA.

You probably want a small drain hole drilled in the bottom anyway - that means that if water (or condensation) gets in, it also has a way out).