Supply to downlights

[davyj]

Hi - this question is almost answered in a recent thread, but I'm still not sure. I want to run 3x20w LV downlights in a shelf, so is it ok to take the supply from a plug in a ring main socket, instead of from the lighting circuit? I don't understand why I would need a SFCU rather than (or as well as) a 3amp fuse in the plug? What is the CORRECT way of doing this?
And, must I use 2.5 T+E from the plug?
thanks, davy

 

[ban-all-sheds]

Hi - this question is almost answered in a recent thread, but I'm still not sure. I want to run 3x20w LV downlights in a shelf, so is it ok to take the supply from a plug in a ring main socket, instead of from the lighting circuit?

Yes.

I don't understand why I would need a SFCU rather than (or as well as) a 3amp fuse in the plug? What is the CORRECT way of doing this?

You don't - a 3A fuse in the plugtop will be fine.

And, must I use 2.5 T+E from the plug?
thanks, davy

No - you must not use T/E - it's not designed to go into plugs, nor to be moved about in the way that things on plugs are. Use 0.75mm² (and upwards) flex. 2- or 3-core depending on whether the transformer needs an earth.

 

[davyj]

Thanks - happy now!

 

[plugwash]

one final thing

if the transformer doesn't have a cord grip make sure you set up something to stop the terminals being strained by pulling on the flex. the easiest way i can think of to do this would be to put an empty chockbox next to the transformer and use the pair of cord grips inside to secure the flex

 

[ban-all-sheds]

So the flex goes into the chocbox, and under the cord grip, and then it goes to the terminals on the transformer. So what stops it being pulled off those?

 

[Adam_151]

So the flex goes into the chocbox, and under the cord grip, and then it goes to the terminals on the transformer. So what stops it being pulled off those?

The chocbox hitting the side of the wooden box that forms a shelf with lights inside, presumably, becuase the chocbox is too big to fit through the hole that the flex goes through, of course you could push the flex into the box, but thats not going to tear it out the terminals, might allow it to rest on top of hot light fittings though :S

 

[plugwash]

you fix the chockbox close to the transformer on the same surface.

the place that such a flex is likely to get pulled is where it comes out of the plug especially if that plug gets unplugged frequently or if the transformer is attached to something that can be moved.

 

[ban-all-sheds]

What's wrong with a few round cableclips?

Or if it's a box-like structure, just tying a knot in the flex?

KISS.

 

[plugwash]

yeah sufficiant cable clips would work if they were tight but not all cable clips seem to be

i thought tieing knots in flex was extremely frowned upon maybe i'm wrong?

either way the important thing is to do something to ensure the flex doesn't just get pulled out of the terminals.

 

[nstreet]

yeah sufficiant cable clips would work if they were tight but not all cable clips seem to be

i thought tieing knots in flex was extremely frowned upon maybe i'm wrong?

either way the important thing is to do something to ensure the flex doesn't just get pulled out of the terminals.

Put a cable tie round the flex the other side of the clip

 

[ban-all-sheds]

i thought tieing knots in flex was extremely frowned upon maybe i'm wrong?

Don't see what harm it would do, but I guess it is a bit tacky.

Again, if it's box-like you could fit a stuffing gland to the flex just inside - that would stop it being pulled out. Or rummage in the box of bits that might come in useful one day for the cord grip from an old plug and just screw that down over the flex.