Chrome Sockets and Switches

[TheFew]

Thanks for the analogy. I did no realise initial that the earth was more for failure cases as opposed to normal operation.

I will buy 50m of T&E and test the continuity between the CU earth straps and the faceplate. Hopefully this will give some assurance.

 

[securespark]

I've been driving for over 40 years

Aren't you knackered?

 

[ban-all-sheds]

No - I'm on the M25 - loads of opportunities to have a kip.

 

[ianniann]

Thanks for the analogy. I did no realise initial that the earth was more for failure cases as opposed to normal operation.

I will buy 50m of T&E and test the continuity between the CU earth straps and the faceplate. Hopefully this will give some assurance.

Just connect a live wire to the faceplate and see what happens. Simples.

 

[TheFew]

Just connect a live wire to the faceplate and see what happens. Simples.

How would that help? What would i be looking for?

 

[ianniann]

How would that help? What would i be looking for?

Well it wasn't a serious suggestion, but it would either result in a blown fuse/breaker or a very dangerous live faceplate depending on whether your supposed earth wire was actually connected to earth.

 

[SimonH2]

That sounds do-able if I can find about 50m of wire to run from the CU and the furthest switch

50m ? That's a long way - veeery big house ?
How about a cable reel extension lead - connect the earth pin of the plug to the MET, and wire a short piece of single flex into the earth pin of a plug for the other end.
You need to measure the resistance of the long lead and your test leads, then subtract this from all your readings to get the resistance of the earth connection to each fitting. The sort of multi-function testers used by electricians (basically a specialised multi-meter) will do this subtraction automatically - as will many multimeters with a zero function.
You are looking for all the readings to be consistent with distance (as the cable runs). Someone else should be able to suggest the maximum value you should see, but with a general purpose multimeter you'll probably not be able to measure such low values accurately.

 

[TheFew]

Well it wasn't a serious suggestion, but it would either result in a blown fuse/breaker or a very dangerous live faceplate depending on whether your supposed earth wire was actually connected to earth.

Ah ok. So if earth worked the fuse would trip. I'll keep that as a backup plan

 

[TheFew]

50m ? That's a long way - veeery big house ?
How about a cable reel extension lead - connect the earth pin of the plug to the MET, and wire a short piece of single flex into the earth pin of a plug for the other end.
You need to measure the resistance of the long lead and your test leads, then subtract this from all your readings to get the resistance of the earth connection to each fitting. The sort of multi-function testers used by electricians (basically a specialised multi-meter) will do this subtraction automatically - as will many multimeters with a zero function.
You are looking for all the readings to be consistent with distance (as the cable runs). Someone else should be able to suggest the maximum value you should see, but with a general purpose multimeter you'll probably not be able to measure such low values accurately.

Yeah the house is an awkward shape and the fuse box is a long way from the furthest light switch. So i have bought 50m of 1mm t&e to to the test.

My multimeter is basic, but i could measure 1.5 ohms over about 2m of 2.5mm t &e. So it should be able to measure longer lengths.

I will have a play tomorrow and see where i get to.

Thanks

 

[EFLImpudence]

If you mean a single length of 2 metres of 2.5mm² wire, that should be about 15 milliohms (0.015Ω) - 7.3mΩ/metre.

1mm² (which you have bought) will be about 18mΩ (0.018Ω) per metre. 50m - 0.9Ω.

 

[TheFew]

If you mean a single length of 2 metres of 2.5mm² wire, that should be about 15 milliohms (0.015Ω) - 7.3mΩ/metre.

1mm² (which you have bought) will be about 18mΩ (0.018Ω) per metre. 50m - 0.9Ω.

Ah ok. I suspect that i have deluded myself somehow then, as the multimeter i have is not that sensitive!

So i guess i can do a basic continuity check. But measuring the resistance with a device that is probably only accurate to 20 ohms is clearly out of the question..

 

[flameport]

But measuring the resistance with a device that is probably only accurate to 20 ohms is clearly out of the question..

Even the worst, cheapest, lowest quality multimeter available should be able to get within 1 ohm or so.

 

[ban-all-sheds]

I will buy 50m of T&E

Which will be unmanageable, and will probably need chucking away when you've done with it. 3-core flex wouldn't have been a PITA to unwind and rewind, and you would have been able to use it in the future.

 

[SimonH2]

Of course, the easier way to do a basic continuity check would be to use the nearest socket to get an earth. it would upset the measurements if trying to measure Ze, but since the OP doesn't have kit sensitive enough to take meaningful measurements for that, it would be "near enough".
And T&E is manageable - it's a right PITA, but with care it can be unrolled and rolled up again. It won't go back on the reel without a lot of care to keep the layers even, but it can be done. 16mm² T&E is "fun" to use as a temporary circuit (we needed it urgently at work, and they don't stock SY round the corner)

 

[ban-all-sheds]

And T&E is manageable - it's a right PITA, but with care it can be unrolled and rolled up again. It won't go back on the reel without a lot of care to keep the layers even, but it can be done.

The house is an awkward shape, which I take to mean twists and turns, he actually needs quite a long piece to reach the furthest point, and he's going to be dragging it around from switch to switch and socket to socket, upstairs and down. By the time he is done it will be a mess.