Outside junction Boxes, switches

[WolvesJon]

Hi all Is it ok to fit conduit into the top knockout of an outside switch or junction box. I was always told to only use side or bottom knockouts for outdoor fittings but noticed they all come with a knockout at the top. I've got a job to do next week and it would be easier to bring conduit straight down into the boxes but was worried about water ingress. Many thanks Jon

 

[DNS1]

Can't see a problem, as long as the conduit, adaptor and box are all compatible and seals are fitted where appropriate.

 

[D Skelton]

Of course it is. I always add a little silicone too for peace of mind. Just make sure your PVC is properly welded together or if it's galv then some PTFE tape works a treat.

 

[micknew]

Make sure you drill a drain hole in the bottom of the box in case the seal fails.

 

[DNS1]

Make sure you drill a drain hole in the bottom of the box in case the seal fails.

I know why you'd suggest this, but I wouldn't personally... You'd be making a modification to a rated and certified fixture...

 

[D Skelton]

The drain hole will be needed anyway because of condensation.

 

[Rockingit]

I know why you'd suggest this, but I wouldn't personally... You'd be making a modification to a rated and certified fixture...

I can't off hand think of a single commonly found make that doesn't have a 'drain hole drill here' option - you need to drill it yourself as they can't foresee orientations etc.

 

[D Skelton]

I know why you'd suggest this, but I wouldn't personally... You'd be making a modification to a rated and certified fixture...

Most come with drain holes or at least areas set aside for drain holes. I have seen many a time an RCD tripping because of a switch or some galv full of water due to condensation. I agree though, it is hard to strike a balance between sealing a unit completely from the elements yet at the same time allowing free air flow within the accessory.

Edit: beaten to it!

 

[DNS1]

Fair points chaps!

 

[Silly Sausage]

Good point re drain holes...my thinking has always been, because these enclosures aren't gas tight, moist air gets in then condenses out. No hole, they fill up with water.

 

[WolvesJon]

Hi Guys Thanks for the quick replies. Its plastic conduit I will be using with a female adapter. Does anyone know if there are any rubber seals available I could use between the adapter and the box to give a water tight seal or is a bit of silicone my best bet

 

[D Skelton]

PTFE tape for the thread, silicone around the edges, solvent weld for the adaptor.

 

[Silly Sausage]

If it's PVC to PVC, I'd use solvent cement.

 

[guest119]

Or 2 angle boxes and go in underside (oops, nearly said go in the bottom).

Boydy

 

[SPARTYKUS]

Or 2 angle boxes and go in underside (oops, nearly said go in the bottom).

Boydy

nothing wrong with that, just a bit of a trickier entry point.

 

[Guitarist]

There is no way you will ever keep moisture out of an enclosure of this kind, regardless of how much silicone you use. As already pointed out, condensation alone will make it damp inside. The only solution is to have a small drain hole. We had a saying back in the food factories..."You can't keep it out, so give it a way of leaving".

 

[Andy78]

Hi Guys Thanks for the quick replies. Its plastic conduit I will be using with a female adapter. Does anyone know if there are any rubber seals available I could use between the adapter and the box to give a water tight seal or is a bit of silicone my best bet

Yes you can get 20mm rubber seals, they are usually used with stuffing glands. Can't see them being very effective with conduit adapters though.
As has been said, pvc solvent and silicone are your best bets.

 

[WolvesJon]

Thanks Everyone

 

[telectrix]

in this situation, you need a plumber to assist.he'll drill a 22mm hole in the bottom of the box, then install a condensate pipe all the way round the house to feed into the furthest drain.