Installing bathroom fitting with no joist to fix to

[GMjohn]

use the spring toggles. if you can, drill a new hole for the cable entry away from the fixings.

Looking at the fitting, I don't think I could. The space available is about the thickness of the t&e and the grommet at the cable entry is raised. If I offset the 11mm m3 hole a little, and also drill 11mm for the cable directly above the cable entry. I can get around a 10-15mm distance between them.

I am here to help fella, the light concerned was total trash, A new LED is now going in, much better and I will be thanked for it in the end, Experience :smilewinkgrin:

i appreciate it.


Looking at at the spring toggle, and the fact I need to pull on the fitting whilst screwing in to stop the toggle spinning, and given there's 3 toggles, I was thinking it would be easier to do if I put a nut and washer on the toggle and fasten them as I pull on the screw. Then when it's tight I can screw the screw in normally.

I was going to use m3 penny washers, as the head of the toggle is so small. But I can't seem to find them. I can only find m3 light washers. Do they not do penny washers this size?

I was was also thinking of using two m5 spring toggles and one m3 near the cable entry, but it doesn't look like that's necessary judging by the comments and I'll use three m3 instead.

Now a few niggling stupid questions -

With the fitting and screws, there was also 3 metal washers and 3 silicone type washers but with a small membrane type thing instead of a hole. I've never really seen one like it before and it's not mentioned in the instructions. Is it to serve as a washer and I pierce an hole in it with the screw, or is it a kind of cap to cover the screw and seal the indent. Is this an alternative to me using silicone sealant over the screw, as this was mentioned in the instructions? I was just going to leave it out and use silicone as I usually would on ip65 stuff.

what metal are the spring toggles made from? It is zinc coated or stainless steel? I always get confused about which washers and bolts to buy, a2 or bzp. Does it really matter if using internally in a situation such as this?

And a possibly even stupider question, given the potential moisture in the environment maybe getting to the screw/washer etc, does metal of dissimilar materials come into it? I'm thinking a little vague knowledge at the back of my mind is making me overly ---- here and it's not an issue. Feel stupid asking, but it's little things like this that niggle at me without an experienced electrician on hand doing a job.

 

[Richard Burns]

If the spring toggles are a problem then use self driving plasterboard screws

they have a pull out of about 5kg each.
I am not sure about the membrane washers, probably a waterproofing fixture, not really useful here but could have some effect. Use the silicone.
Spring toggles will usually be bright zinc plated, but they do come in stainless as well.
Either would be OK for most uses even outside, but obviously the stainless would be less corrosion susceptible (but significantly more expensive).
I would not worry too much about corrosion from different metals for this situation, not sure where they would be coming into contact mind you.
It is not a high corrosion atmosphere just slightly damp (but hopefully not inside the light fitting!).

 

[GMjohn]

Thanks for the help. One more question before I get to the job over weekend - whilst getting everything ready, I've noticed I need to buy some sealant. Seems to be a lot of choice looking at the screwfix and toolstation catalogues. What's recommended for stuff like sealing screw holes in ip65 fittings, that can withstand the heat and doesn't react if used with cables etc?

Basically a good general sealant or two for an electrician. I'm assuming normal caulk is best between fittings and the wall, but not sure about the type of stuff mentioned above.

Looking at things like everbuild general purpose silicone, it says it can leech things like plasticiser. I can't seem to find anything that stands out as being the one to get. There's acetoxy, neutral, various modulus stuff, stuff with fungicide and other anti fungal etc. What's best? The example I was set was basically use whatever's at hand, but I figure there must be a preference, or maybe ones you shouldn't use.

 

[GMjohn]

I installed this last week. Having done the job. the main question I have is with regards strain relief.

I didn't see any strain relief inside the fitting, (unless the rubber grommet I threaded the cable through also serves this purpose). I left quite a bit of slack on the cable up in the ceiling, and as the cable goes straight through the hole in ceiling right into the grommet, it will likely be looped up in the air directly above the ceiling hole. I'm thinking the downward pressure of the cable weight will mean it will slide further into the fitting over time, eventually putting strain on the terminations. It doesn't feel like I should leave it like that, but I couldn't see what to do to eliminate the potential issue. Maybe I need to go back and do something differently, like remove the slack?

 

[Jamie]

are you a house basher or work in another sector (i.e. commercial or industrial)? as if that where me telling that to my boss he would tell me to get lost and stop wasting time haha

 

[telectrix]

FFS. it's a poxy bathroom light, not NASA'a latest jupiter probe. bang it in, get paid, move on.

 

[pennychew]

I installed this last week. Having done the job. the main question I have is with regards strain relief.

I didn't see any strain relief inside the fitting, (unless the rubber grommet I threaded the cable through also serves this purpose). I left quite a bit of slack on the cable up in the ceiling, and as the cable goes straight through the hole in ceiling right into the grommet, it will likely be looped up in the air directly above the ceiling hole. I'm thinking the downward pressure of the cable weight will mean it will slide further into the fitting over time, eventually putting strain on the terminations. It doesn't feel like I should leave it like that, but I couldn't see what to do to eliminate the potential issue. Maybe I need to go back and do something differently, like remove the slack?

Now that is a good question, i think you what you need to do is post this in the general electrical forum where it will be seen by a few more people as well. I would personally suggest friday evening as there seems to be some knowledgeable guys on at this time

 

[trev]

The grommet, assuming it gives a tight fit round the cable(s) will provide a bit of strain relief. I've never seen a problem like this in well over 30 years mate but it's good that you're thinking this way even though you don't need to.
Think about a normal ceiling rose, what is there in one of those to provide strain relief for the cables entering one of those? Not a great deal is there.
Do we worry about that?