Lamp wiring help

[m15try]

Hi folks,

I've been lurking the forum for a little while now, have a few little projects on the go and am in need of some wisdom. First off, apologies if any of this is extremely obvious, I'm largely clueless on these matters.

Long story short, I have a half inch thick steel tube with a two core flex running through it. The flex will be hanging downwards so I think I just need to wire a lampholder on one end and a plug on the other.

So my questions are:
1) Am I ok to use a two core flex with a plastic lampholder even though the tubing is made of steel and screwed into the wall?

2) I'd hazard a guess that the lampholder itself shouldn't just be hanging, it needs to be attached/screwed into the opening of the tube - are there lamp holders/sockets that can screw into the tube opening or similar?

3) Any recommendations for a black lamp holder

Thanks in advance for any help!

Untitled

• m15try
• 22 May 2013
• 1

 

[PrenticeBoyofDerry]

Is there a reason that you are not using a three core cable, so a CPC is offered?
I would always advice continuity of earth between accessories.

 

[m15try]

No reason in particular, I only had two core lying around the house so just went with that for now. Seems sensible to get some three core then. Would I then most likely need a metal lamp holder?

 

[stillp]

I'm confused. What is that "half inch thick steel tube"?
Are you making your own light fitting?

 

[m15try]

Yep kind of, its going to be a wall lamp which is basically a steel tube attached to a wall with a flex running through it.

Something similar to this:
http://assets.inhabitat.com/wp-content/blogs.dir/1/files/2011/05/poorprouve-lamp-537x385.jpg

 

[stillp]

I don't mean to be rude, but if you didn't realise that a CPC is a good idea when making a light fitting, perhaps you should reconsider this project. Do you have any means of checking the insulation resistance of the finished product?

 

[rjm2k]

http://www.ebay.co.uk/sch/i.html?_o....TR0.TRC0&_nkw=insulation+resistance&_sacat=0

I would assume the tube itself needs to be earthed too

 

[stillp]

http://www.ebay.co.uk/sch/i.html?_odkw=meggar&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0&_nkw=insulation+resistance&_sacat=0

I would assume the tube itself needs to be earthed too

Yes, unless the OP has the knowledge and test equipment to make his fitting Class II.

 

[m15try]

I don't mean to be rude, but if you didn't realise that a CPC is a good idea when making a light fitting, perhaps you should reconsider this project. Do you have any means of checking the insulation resistance of the finished product?

Perhaps you're right, but I'd like to learn. I envisaged that the tube would simply provide a means for the flex to run through and with the flex being insulated it would be fine.

Clearly this was a bit stupid. Am I right in saying that I would need to check the insulation resistance from one end of the flex to the other in order to check there's no damage to the insulation?

Thanks all for your help (and patience).

EDIT: I had seen tutorials along the lines of (http://removeandreplace.com/2013/04/01/diy-plumbing-pipe-fittings-desk-lamp/) and figured it wouldn't be an issue to replicate on a larger scale

 

[stillp]

It's not from one end of the flex to the other, it's between all conductors of the flex and the exposed metallic parts. Those metallic parts would need to have a terminal for connection to the circuit protective conductor. You would also need to check the continuity of the connection through the metallic parts, usually at 25 A.

 

[m15try]

Thanks stillp.

I suspect I'm misunderstanding as I'm such a novice on this but I didn't plan on there being any conductors of the flex.

I've got

and have run it through a steel tube

On one end I wanted to put a lamp holder, and the other a three pin plug.

So looking at your post and what I need to do: is the conductor of the flex the steel tubing, and the steel tubing is also an exposed metallic part. So I need to test between the flex and the tubing and have something going from the tubing to the CPC.

 

[stillp]

Thanks stillp.

I suspect I'm misunderstanding as I'm such a novice on this but I didn't plan on there being any conductors of the flex.

It won't be much use if it doesn't have conductors! The conductors are the copper wires.
The insulation resistance test would normally be performed at a high DC voltage. The earth continuity from the CPC to all exposed conductive parts would be at 25 A and a low voltage. Do you have access to test equipment to do that? If you're going to use a metal lamp holder that too is an exposed conductive part, also a metal reflector would be. How is this light going to be switched?

 

[m15try]

Thanks again stillp. Unfortunately I don't have access to any equipment like that. The lamp was going to be switched on and off at the plug. Feels like I've bitten off more than I can chew with this and am risking making something very unsafe.


Why is it that something like this doesn't run into the same issues, as structurally its similar to what I have:
http://removeandreplace.com/2013/04/01/diy-plumbing-pipe-fittings-desk-lamp

 

[stillp]

Why is it that something like this doesn't run into the same issues, as structurally its similar to what I have:
http://removeandreplace.com/2013/04/01/diy-plumbing-pipe-fittings-desk-lamp[/QUOTE]
It has exactly the same issues. I cringe at the sentence "We could not use wire nuts to connect the wires together so we used a solder gun to connect our power cord to the light socket". That's an American web site, and they have appallingly unsafe electrical wiring practices over there.

Thankfully you've used some common-sense and asked for advice.

 

[m15try]

I see,

So if I was to buy the following, which is a dual core flex:

http://www.ikea.com/gb/en/catalog/products/10081557/

And put it through some steel tubing and put a plug on the end, I would still need to test it in the way that we have discussed.

But if I was to simply wire a plug on the end, without the steel tubing, it would be fine?