Electrics

[Charlotte]

I'm changing the light fittings in my bedroom for wall washer downlights.

First two have gone in fine but the third is causing me a problem.

The wire comes out of the wall in the centre. The wall washer needs to sit in the centre and there is little room for error as it is down from a roof apex.

The wiring hole on the fitting is on the LHS. A lamp holder inserts to a clip, there are no pigtails from a choc block. The simple solution would be to put a chock block on, however, there is no space behind the light fitting and the way the clip is designed, I cannot mount it inside.

 

[RogerS]

Charlotte

How large is the unit? Could you chisel out a bit of the plaster and hide a choc block there?

Failing that, i'd have said crimps but they are just as large as a choc block....have you tried the really small choc blocks?

How good are you with a soldering iron?

Roger

 

[matt]

Sometimes, if you're really careful (both with the cable and the plastering over it, you can tease a little extra wire through - even if the plaster is directly on to cable (i.e. as opposed to the wire run through conduit). Obviously this relies on there being some slack near the other end of the cable but may be worth a try. A few very gentle tugs should give you a clue.

The alternative... If the wall washer is made of plaster, for example, drill a new hole (providing there is clearance).

Or... Is the wall you're fixing too solid brick or studwork? In the case of the latter you could extend the main cable via a junction in the wall space and bring the wire out in the right location for your fitting.

 

[Charlotte]

Crimps are to hand and fit - why didn't I think of that

I don't touch plaster...it's witchcraft and magic that stuff and I'm always terrified that by the time I'm finished, the whole wall will need redoing!

 

[RogerS]

Plastering? Nothing to it! I knocked this up this afternoon.

 

[lurker]

That's a nice ceiling you have in your shed, Rog.

 

[flounder]

I would think a soldered extension with some heat shrink sleeving would be the way to go.

 

[Jake]

Crimping is preferred over soldering AFAIK as the latter needs strain relief.

 

[RogerS]

Crimping is preferred over soldering AFAIK as the latter needs strain relief.

True..up to a point. If the cable was subject to continual flexing then the fracture point would be at the transition between the soldered part of the cable and the rest of the cable and it is good practice to support the cable before the fracture point. But in this instance, once the light has been put up, there shouldn't be any flexing of the cable and so a soldered joint would work fine.

The drawback of crimping is that if the wire is short to begin with then if you fluff the crimp - especially if only at oe end - then life gets difficult having to cut and strip the remaining tiny length of wire so you can have another go.

 

[Jake]

Crimping is preferred over soldering AFAIK as the latter needs strain relief.

True..up to a point. If the cable was subject to continual flexing then the fracture point would be at the transition between the soldered part of the cable and the rest of the cable and it is good practice to support the cable before the fracture point. But in this instance, once the light has been put up, there shouldn't be any flexing of the cable and so a soldered joint would work fine.

True, up to a point. I don't think it is regarded as good practice in mains wiring to rely on a solder joint for the (required) mechanical strength, so you ought to do a soldered joint with strain relief of some sort - e.g. by clamping the cable or by doing a screw connection first and then flooding with solder.

The fact that this joint is behind a light fitting (which might be removed and replaced for painting etc) reinforces rather than reduces this, to my mind. It's more likely to have strain on it when it is crammed in and out than a joint in an ordinary cable run.

 

[Racers]

Hi,

I think a crimp would be better, the light will get hot possibly affecting the solder joint.

Pete

 

[Jake]

The drawback of crimping is that if the wire is short to begin with then if you fluff the crimp - especially if only at oe end - then life gets difficult having to cut and strip the remaining tiny length of wire so you can have another go.

Don't fluff it then!

(I had a couple of these in the kitchen/diner - cut off the grey in 3Y with the PVC (doh) on two occasions (no comment!) leaving myself just a cm or so at the back of the backbox. No slack, and the whole lighting scheme collapses if I can't get it back. With a bit of care and attention they are hard to get wrong, although I won't claim that there were no nerves.)

 

[RogerS]

Crimping is preferred over soldering AFAIK as the latter needs strain relief.

True..up to a point. If the cable was subject to continual flexing then the fracture point would be at the transition between the soldered part of the cable and the rest of the cable and it is good practice to support the cable before the fracture point. But in this instance, once the light has been put up, there shouldn't be any flexing of the cable and so a soldered joint would work fine.

True, up to a point. I don't think it is regarded as good practice in mains wiring to rely on a solder joint for the (required) mechanical strength, so you ought to do a soldered joint with strain relief of some sort - e.g. by clamping the cable or by doing a screw connection first and then flooding with solder.

The fact that this joint is behind a light fitting (which might be removed and replaced for painting etc) reinforces rather than reduces this, to my mind. It's more likely to have strain on it when it is crammed in and out than a joint in an ordinary cable run.

Bending once or twice isn't going to break it. Crimping is better. Soldering in this situation is an alternative.

 

[Jake]

Bending once or twice isn't going to break it. Crimping is better. Soldering in this situation is an alternative.

Getting a bit bored of what seems to be turning into a pissing competition, but your first sentence would be better phrased as "bending it who knows how many times and possibly leaving it under strain isn't very likely to break it in the near future". It might also get pulled out and shoved in while changing the bulb, cleaning the lens if has one, who knows what other reasons - and who can tell how this arrangement is going to be in place - could easily be fifty years.

By the time the casualness is stripped out, it ceases to be a reasonable way of doing electrics at least to my mind.

Agree with the second sentence obviously, and the third if you add strain relief/mechanical strength to the joint.

 

[RogerS]

Whatever, Jake. You clearly are the expert. Certainly you know far more about this than I can possibly know or have experienced in over 40 years of electronics. I bow to your superior knowledge.

 

[Jake]

Temper, temper.

 

[RogerS]

Surprised at you that you mistake sarcasm for temper. You don't really want to see me lose my temper. It's not a pretty sight.

 

[Jake]

I am impressed.

 

[JFC]

Do you turn green or something ?