Testing lamp is rewired safely

[TheNice]

Full disclosure, my electrical knowledge is close to zero, and despite trying to close the gap by reading up online I'm not much closer to a clear answer on what I imagine is a pretty simple question.

I have some old anglepoise lamps that still need/needed rewiring. I've fitted one and will rewire the rest with three core earthed cable, brass B22 bayonet fittings, and plugs with 3 amp fuses. As far as I'm aware I've done this correctly so far, but I'd like to test that they're safe as all of them are made of metal and are going to see a lot of handling.

I've seen people talking about continuity testing using a multimeter but I'll admit I'm a bit lost on how to go about it and whether it's a function of the cheaper end of multimeters that are within my price range (under £50). I'd be very grateful if someone was able to lend me some advice.

Many thanks.

 

[littlespark]

Professional electricians use calibrated testers rather than multimeters, and they cost way more than £50.00
What we look for is Insulation Resistance... which makes sure each core of the supply flex isnt touching or shorting out with another core.
And continuity. Which tests that each core is continual from point of supply, the plug, to where its going... the lampholder.
Basically it proves that what should be connected, is.... and what shouldnt be, isnt.

If you're not confident in testing, then I would say get someone to test them for you. Will come under Portable Appliance Testing, and most sparks will do it, but a lot of companies want them in some quantity to make it worth their while.

Another option is to use extra low voltage, so the wiring within the lamp is only 12v, say... but then you'de need a transformer/ LED driver and the appropriate lampholder and lamps.

 

[DPG]

If the lamp is earthed then an earth bond test would also be advisable.

 

[TheNice]

Hi littlespark and DPG, thanks for getting back to me.

I'd considered PAT testing but as it'd only be three or so items I imagine it would come in dear. Just to make sure I'm understanding you right - there's no way to test insulation resistance, continuity and earth bond with a more entry level piece of kit?

 

[DPG]

Hi littlespark and DPG, thanks for getting back to me.

I'd considered PAT testing but as it'd only be three or so items I imagine it would come in dear. Just to make sure I'm understanding you right - there's no way to test insulation resistance, continuity and earth bond with a more entry level piece of kit?

You can only do an insulation resistance test and an earth bond test with the appropriate test gear. A multimeter will not be able to carry these out. You could do basic continuity tests, but that's it.

 

[TheNice]

Thank you. Would a continuity test be sufficient to make sure I wouldn't get a shock if something had gone wrong?

 

[Ziggie]

An idea that I haven’t used is that charity shops get items PAT tested( they can’t sell anything electrical ) .

perhaps they might test it for you for a small fee.

 

[westward10]

Some charity shops have a PATesting dept, Oxfam for one but only limited shops. If they are for personal use you could try them.

 

[DPG]

Here's a thought - donate to the charity shop, then they will PAT test it, and you can buy it straight back for a fiver!

 

[TheNice]

Cheeky! ?

On the chance I can't sweet talk my local charity shop, would a continuity test be sufficient to make sure I wouldn't get a shock if something had gone wrong?

 

[DPG]

Cheeky! ?

On the chance I can't sweet talk my local charity shop, would a continuity test be sufficient to make sure I wouldn't get a shock if something had gone wrong?

As has been said already, a multimeter cannot perform the appropriate tests.

 

[TheNice]

Ah, I'm sorry for the confusion. You said earlier that a multimeter couldn't test insulation resistance and earth bond, but would perform basic continuity tests. These basic continuity tests wouldn't be enough to tell if there was a risk of shock?

 

[DPG]

Ah, I'm sorry for the confusion. You said earlier that a multimeter couldn't test insulation resistance and earth bond, but would perform basic continuity tests. These basic continuity tests wouldn't be enough to tell if there was a risk of shock?

As above, the two tests which will confirm the item is safe are insulation resistance and earth bond. A PAT test will cover both of these.

 

[TheNice]

OK great, thanks for your help.

 

[Ziggie]

Let’s go back to when electricians were poor and couldn’t have the MFT tester (not invented) and the trade wasn’t a restricted trade.

when I was 5 this was the test that would be done.

consider the size of the cable (not bell wire )
Buy a cheap multimeter - useful for checking fuses. I had access to an AVO meter.

now:
Unplug lamp and Remove bulb from lamp.
The plug was 3 pins.
The lamp holder has two pins and the metal case.
If the lamp has a switch switch it to the on position.
Check continuity from each of the pins on plug with pins on the lampholder.
There should be one and only one match for each set of pins.
The earth pin on the plug should match with the metal case only .
The other pins on plug should match one of the pins in the lampholder.
Now put the switch off.
At least one of the continuity passes should not work. ( the one that’s the live connection)
Now switch on the switch again and plug in the bulb.
Test the continuity between the two pins on the plug ( not the earth) and you should get a small reading but not 0.

this test is not sufficient for selling the lamp but should be sufficient for your use ( it was for a large number of years)

This sounds like a lot but it would take 3 minutes.

hope this helps

 

[DPG]

Let’s go back to when electricians were poor and couldn’t have the MFT tester (not invented) and the trade wasn’t a restricted trade.

when I was 5 this was the test that would be done.

consider the size of the cable (not bell wire )
Buy a cheap multimeter - useful for checking fuses. I had access to an AVO meter.

now:
Unplug lamp and Remove bulb from lamp.
The plug was 3 pins.
The lamp holder has two pins and the metal case.
If the lamp has a switch switch it to the on position.
Check continuity from each of the pins on plug with pins on the lampholder.
There should be one and only one match for each set of pins.
Now put the switch off.
At least one of the continuity passes should not work.
Now switch on the switch again and plug in the bulb.
Test the continuity between the two pins on the plug ( not the earth) and you should get a small reading but not 0.

this test is not sufficient for selling the lamp but should be sufficient for your use ( it was for a large number of years)

This sounds like a lot but it would take 3 minutes.

hope this helps

I disagree. A lamp that has been rewired by an amateur should be tested properly. Personal use doesn't come into it - are you saying it's OK that his family may receive an electric shock?

 

[Ziggie]

I disagree. A lamp that has been rewired by an amateur should be tested properly. Personal use doesn't come into it - are you saying it's OK that his family may receive an electric shock?

No I’m not but I am saying that if he carries out the tests above , there is a massive reduction in risk than not doing it.
The use of any testing is not without risk. There is a small risk that having tested with the MFT tester recommended that the earth wire becomes loose and the live wire connects to the lampholder. It is a snapshot test.

I would prefer that he did some testing than none.

I attended a house where an old age person had pulled the earth wire out of the lampholder by pulling the standard lamp down to switch it on.

by the way , remember to fit a 2 amp or 3 amp fuse in the plug.
If your house has the circuit on an RCD then you are safer as well

 

[TheNice]

Thank you both for your help. Safety is key for me and something I do my best to take seriously (though none of these will be used by anyone but me!), but I'm also hampered by not having much in the way of funds to spend on them. Rewiring them myself was in the hope of saving money (they were free). So until I can get them PAT tested I'd settle for reducing the risk and not having to work in the dark.

On a worrying note...I got one of the lamps off a family member and opened the plug to discover the earth wasn't connected. She'd been using it for years.

 

[DPG]

Thank you both for your help. Safety is key for me and something I do my best to take seriously (though none of these will be used by anyone but me!), but I'm also hampered by not having much in the way of funds to spend on them. Rewiring them myself was in the hope of saving money (they were free). So until I can get them PAT tested I'd settle for reducing the risk and not having to work in the dark.

On a worrying note...I got one of the lamps off a family member and opened the plug to discover the earth wasn't connected. She'd been using it for years.

It's surprising sometimes the amount of dangerous appliances out there. The example you give is a good one, and would remain unspotted for years since it doesn't stop the lamp working.

It's a shame you're so far away or I would have tested it you for free.

 

[TheNice]

Thanks DPG, that's really kind. I'll do the tests Ziggie suggests and look at finding a PAT tester who won't break the bank in the meantime. Thanks for all your help, and stay safe!