When waterproof isnt waterproof
This was mounted in an IP68 rated PVC box. So lets talk about expectations of such enclosures. Here are my thoughts on how these should be used. The unit in the picture was mounted in an IP68 enclosure. Two side entry screw glands for 20mm conduit and two screws holding it to a wall which was protected by a skillion awning. The two mounting screws were liberally covered with silastic and the conduit was glued in the glands. Most people would think this is a job well done.
The trouble is that as soon as you cut a cable entry hole the IP rating is out the window. As soon as you put a screw through the back to mount it on a wall the IP rating is out the window. From what I can see water seeped in via the mounting screw holes (about the middle of the box). Now being IP68 rated against water ingress also means being IP68 rated for water egress and the water filled the box up to the lowest mounting screw. You can clearly see the tide mark in the picture.
This is what I have been doing since I first came across this problem about 12 yrs ago. First thing is drill about a 2mm drain hole in the bottom of the enclosure and a 1mm breather hole as low as possible on the side of the box (but at a higher level than the drain hole). Secondly is to have low point for all conduit entering the box and to drill a 2mm drain in the conduit at this low point. It is just common sense.
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That's a fair bit of water, I usually run a bead of silicon over the top of the box to let the water run away so it doesn't go behind. And depending how much room and how important the stuff inside is I fill any holes coming if I have enough cable to play with. But I always put a drain hole in. I've seen it a few times where poor joins in the conduit has let water in and that's gone down and filled the enclosure.
Seen it in Cameras too where they have been mounted under eves and they are filled up from the roof with water running down through cable entry.
IP68 or whatever is good for also keeping the water in too.
I first experienced this at a shopping centre that had a large tinted perspex dome over the camera. This thing was filled to the top ( probably about 6 litres ) and you could not see it from the outside. No need to tell you what happened after removing the first couple of screws that was holding it. No one got a skull fracture but a few rode the wave all the way to the carpark.Originally Posted by MCman
Hahaha...Surfs up!!
Yep. Turns out strobe filaments don't do so well underwater either.
Thats because people overtighten the mounting nuts and crack the base. There is no reason to have it more than finger tight.
I think the design of the most common boxes from electrical suppliers could do with a bit of a rethink.
Some of the smaller electronics boxes have mounting flanges or holes through the box that are outside the sealed section. That solves the penetration through the back issue.
Next is glands or conduit entrys where possible through the base only.
Vertical conduits straight in the top seems a definite no no. Seen that into eaves and it seems to be a case of when it leaks and not if. Even without obvious ways for water to leak in it seems like it just accumulates condensation and drips down.
On that note I have seen some properly sealed equipment come in similar boxes to what you buy off the shelf either with little silica gel bags or breather vents.
Seen breathers on a few cameras as well.
So even if it is completely sealed the moisture in the air inside the box becomes an issue.
I think there is a little breather you can buy, don't know if it's Clipsal. Looks like a conduit hole cap.
Last edited by dmaher; 15-09-15 at 04:09 PM.
I know the one you are talking about.
Here's a different variety.
I had a situation recently where I needed to allow a junction box to "breathe" due to condensation. I drilled 5 x 10mm holes along the bottom of the box, then siliconed some plastic flyscreen mesh on the inside of the box over the top of the holes. Not very elegant, but did the trick.
The ingress of ants can also be a big problem when venting boxes. You can't just drill holes without covering them. The little buggers always find a way in unless the vents are designed properly. I've opened PE beams that have stopped working, only to find thousands of ants inside.
Speaking of PE beams ... What is it with ants and those things. We regularly have sites where thousands of ants have found their way inside rendering the beam useless. Even with the surface spray, they return. Are they attracted to the IR?
No, theyre attracted to the home away from home. For them its an ideal house. Low to the ground, and dry. If you want to keep them out, use Ant powder not spray. The spray dries up, the powder strays as long as its dry.
AdRock (23-09-15)
The couple of spots I have had to put the types of boxes in the open I have snipped a small section out of the rubber washer that goes around the outside and dropped in a couple small sections of mesh to keep critters out like ants. in the 2 years since installed been all good. Condensation, water will always find a way in through the screws or down the conduit or where ever.
Best I have seen is an IP rated outdoor camera used in a kitchen so that they could wash if need be. All good all the washing etc they did no problems at all with water ingress. Fire happened next door and burned the wall in roof that joined the two buildings together so the Fires housed the wall and sections of the roof in this shop. Water got into the camera and filled it up completely to the brim. Nothing burned cable or conduit wise as all was inspected some replaced as a caution yet water got into the camera.
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