Connecting series of bulkhead lights with conduit... waterproof too

[SimonB27]

I need to replace a very old lighting system in my cellar. Part of the problem is the cellar is damp and part of it passes outside the house so water actually drips through the ceiling when it rains.

I have envisaged a series of IP65 bulkhead lights mounted in the ceiling (the cellar is 100ft long) connected with conduit but now I'm thinking it's not so straightforward. I have had a number of thoughts...

If I connect the conduit directly to the luminaries (one in then one out the other side) with male adapters then am I making a future problem for myself if I ever need to change the light fitting as it will be difficult to extract the fitting from the installed conduit system? Or should I terminate the conduit before each light fitting to a gland then run cable a few inches to a gland in the the light fitting and then the same in reverse on the other side of the light fitting?

If I go the adapter route and connect everything directly together, how do I make the connections to the light fitting as waterproof as possible? IP65 luminaries are easy enough to come by but how waterproof are the adapters to connect the conduit? Is silicone grease or similar going to be enough?

Any thoughts gratefully received.

 

[ban-all-sheds]

Could the lights be on the walls instead?

 

[bernardgreen]

Conduit that runs from lamps in a cold room to an open end in a warm room can result in condensation appearing in the lamps. Water vapour from the warm area is drawn into the conduit when the lamps cool down. That water vapour condenses in the lamps and this draws more water vapour into the conduit.

 

[securespark]

I would be tempted to use anti-corrosive fluorescents, wall mounted on either side of the cellar.

 

[flameport]

Conduit, with T box adjacent to each light, and short piece of flex from the box into the light fitting using suitable glands.

 

[SimonB27]

Thanks for the comments guys.

The cellar is barrel-vaulted so the walls are low at the sides - maybe 4'6" - but the ceiling is about 7'-odd in the middle. I've always thought the light would therefore be better higher up. I've also got shelves / wine racks in places (much of the cellar is not fit for much else but keeping wine in!) and they come pretty much up to the top of the walls, and higher. So it's better to have the light above you rather than on far side of the cellar even if there were wall space (if that makes sense). I'll give that some more thought but given the ceiling curves down to the walls so the walls are damp too, especially in the bit under the garden, I'm not sure lights on the walls would actually deal with my water-resistance issue.

When I say drips through the ceiling, it's not a cascade so the waterproofing doesn't actually need to withstand a spray as in IP65. The system I'm replacing had galvanised metal conduit but regular domestic bulb holders and bare bulbs(!!!) including one directly under the garden! They survived for the 20 years I have lived here but it has all corroded now and it needs to be re-done properly.

On Bernard's comment, that's an interesting point. I'm not sure what I can do about it except hope it won't be a problem. The whole installation is underground and so it will all be cool. Our fuse box is actually in the cellar, which never gets warm, so that's where the conduit would start. That is under the house so it is drier though. The house used to be a brewery and the cellar starts under the house for a large part of it. It's reasonably dry, so long as you don't try to put say a cardboard box on the stone floor, but a section goes under the garden for about 20 feet where (I presume) a chunk of what was an attached barn has been removed at some point in the building's history. That's the bit with incoming water. The rest of the cellar is under the remaining barn (now no longer attached).

The whole installation won't need to be as waterproof even as something outdoors because it won't need to withstand wind and rain. My main concern is sealing the joints so water doesn't get into the light fittings and go all yukky (and maybe needing to swap out a light fitting at some point in the future - hence the question about cementing it all together). I'm surprised that the male adapters you seem to be able to get to attach conduit to junction boxes and luminaries don't seem to come with o-rings to make them a bit more waterproof.

 

[canduit]

Why not do away with conduit and use these http://www.screwfix.com/p/tower-male-comp-gland-white-20mm-pack-of-2/45943 with round flex? I'm not sure if Screw fix glands come with a rubber seal but I know some brands do. You will also have to consider potential water entry into the light fittings via your fixing method.

 

[ericmark]

I know that SWA can still allow moisture to transfer but far less likely.

 

[Iggifer]

You will also have to consider potential water entry into the light fittings via your fixing method.

Big blob of silicone over the screwhead/hole will deal with that, no drama.

I would be more worried about piercing any tanking that might be in the wall tbh

 

[canduit]

As se

You will also have to consider potential water entry into the light fittings via your fixing method.

Big blob of silicone over the screwhead/hole will deal with that, no drama.

I would be more worried about piercing any tanking that might be in the wall tbh

As securespark suggested, anti corrosive fittings. These clip onto the supplied brackets so no holes to be made in fitting.

 

[SimonB27]

Thanks again guys

I know that SWA can still allow moisture to transfer but far less likely.

SWA? - sorry not sure what you mean.

Big blob of silicone over the screwhead/hole will deal with that, no drama.

That's what I thought - thanks for that. There's no tanking LOL (that's my problem) but I don't think there's any tanking solution that's going to deal with rain from above - short of lifting the entire paved terrace above the cellar and putting a membrane underneath it. That would be fun but is unlikely to make it onto page 2 of my current list of DIY priorities.

Why not do away with conduit and use these http://www.screwfix.com/p/tower-male-comp-gland-white-20mm-pack-of-2/45943 with round flex?

Good question. I guess the conduit is to provide impact protection as well as neatness. The ceiling is easily within reach and I just feel exposed cable is more likely to get knocked / pulled. I had also thought that conduit would give me a better seal into the luminaries than a gland. But then that's why I'm asking the question. I'm grateful for others' thoughts.

Conduit, with T box adjacent to each light, and short piece of flex from the box into the light fitting using suitable glands.

So you're suggesting running the conduit past the luminaries and having flex come out of a box via a gland for a few inches to bridge the gap to each light? Interesting thought.

I had envisaged running the conduit into one light and out of the other side to the next one. It seemed the neatest solution but it seems no-one thinks that's a good idea.

 

[Iggifer]

As securespark suggested, anti corrosive fittings. These clip onto the supplied brackets so no holes to be made in fitting.

Those brackets are the biggest pile of dog do-do ever. I NEVER use them to hang a light fitting. The slightest knock and down comes the fitting.

As for which method to use for the conduit. Something to consider with the straight through conduit idea, is that the chances are that the hole in the bulkhead/flourry, will not be at the same distance from the ceiling as the conduit saddles stand it off the ceiling at, so you will need to bend the conduit to suit - not a problem now, but if you do ever need to replace a fitting you could end up having to replace lengths of conduit.

You can use the T box idea, I would run the conduit behind the fittings, out of view (if possible)

If you wanted to stop the conduit short of the fitting, you'd just use a female conduit adapter - compression gland - flex - compression gland into the fitting. It's not as tidy, but it does make for easier fitting replacement.

As for waterproofing the adapters, so long as you use a bit of solvent weld and get a good seal - if it's good enough for plumbers, it's good enough to stop a bit of condensation. If you do decide to use T-Boxes, make sure you get a gasket for them and you can also fill them with a water repelling compound, or again, just silicone them (need to be confident of your connections with this method though!)

And finally, SWA = Steel Wire Armoured - armoured cable, would do the job, without the need for conduit, boxes, tees, bending etc. it's just a heavy duty cable that you gland into each fitting. If you haven't worked with it before, probably not the cable for the job, but does look nice when done properly

This stuff.....(that's not properly, but google failed me)

 

[SimonB27]

SWA - ah of course!

All very helpful stuff - many thanks. The issue of the standoff from the ceiling - saddles vs light fitting - had occurred to me too.

I'll give all this some more thought.

Many thanks to all for your quick replies.

 

[Adam_151]

Instead of focusing on ensuring that the lights will not suffer water ingress (which if installed on a cellar ceiling which is constantly dripping is going to be quite a difficult task), one could simply accept the water ingress and design around it.... ELV supply, drain holes, etc

 

[ban-all-sheds]

I'm not sure lights on the walls would actually deal with my water-resistance issue.

My thinking was that it's easier to manage "water resistance" if cable entries are at the bottom of things.[/QUOTE]

I'm surprised that the male adapters you seem to be able to get to attach conduit to junction boxes and luminaries don't seem to come with o-rings to make them a bit more waterproof.

You're talking abut PVC conduit, aren't you.