Why black cable with earth

[Bobbya82]

Just changing a light, the old one didn’t need an earth. The new one does, it’s using a greyed sleeved blue for neutral and a brown for the live. I pulled the other 2 cables through and there is an earth cable and black cable put into a connector block. My question is, why is the black cable connected in with the earth and so I can I just connect the earth cable from the fitting into the earth/black cable block. Photo attached.

Many thanks for your help.

 

[AndyPRK]

maybe they are just earthing the spare wire.

I would just carry on and connect the light earth upto that.

In armoured cables, black is used are the earth

 

[Bobbya82]

maybe they are just earthing the spare wire.

I would just carry on and connect the light earth upto that.

In armoured cables, black is used are the earth

Many thanks

 

[JohnD]

It's modern three core and earth cable.

3C+E in houses is most often used for lights with 2-way switching

Incidentally, the use of plastic tape like that is very poor practice.

 

[AndyPRK]

that was my first thought John, but they are already using the bare and sleeved earth for the earth.

Tape is a bit less likely to fall off

 

[EFLImpudence]

My question is, why is the black cable connected in with the earth

It shows that the black wire is not a live conductor.

 

[JohnD]

.

Yes

 

[AdrianUK]

As EFLImpudence correctly states, It is good practice to connect unused conductors to earth.

 

[ericmark]

As @EFLImpudence correctly states, It is good practice to connect unused conductors to earth.

Yes that is the correct method, this is where DIY becomes a problem, we should test, but testers like this are not cheap

at around £80, today with RCD protection any link earth to neutral connection will likely trip the RCD, but pre-RCD use, it was easy to mix up earth and neutral.

As long as you have RCD protection if you do make an error, it will trip, so no worries.

 

[blup]

Yes that is the correct method, this is where DIY becomes a problem, we should test, but testers like this are not cheap View attachment 366871 at around £80, today with RCD protection any link earth to neutral connection will likely trip the RCD, but pre-RCD use, it was easy to mix up earth and neutral.

As long as you have RCD protection if you do make an error, it will trip, so no worries.

Is £80 expensive?

 

[ericmark]

The unit is about the cheapest, it does vary in price

around £65 to £85, I did not need to buy my own until I retried, when I looked at socket testers, they are not much cheaper. The pass figure for a ring is below 1.38Ω and the plug in testers shown will only go down to around 1.9Ω and the RCD should trip in less than 40 ms and the plug in testers don't record the time, and it should not trip at ½ rating (15 mA) and must trip at full rating (30 mA) but the plug in tester does not say how much required to trip the RCD. So getting one which ticks all the boxes for maybe £10 more than the tester never designed to be used on a ring final is if anything cheap.

This is the problem, without the proper tester you are taking a chance, the one I show is a very cheap one, which is not really high enough quality to be calibrated, most are double the price

and this is the problem, the test gear to do a proper job is not cheap.

 

[ebee]

One multifunction tester I bought as Part P had come into place was about £650 back then, it was actually a very good price at the time because as a rule of thumb the testers would cost roughly between £1000 to £1500 approx with separates being the more expensive option than multifunction.
One good side effect of Part P was to make decent-ish testers more plentiful hence cheaper, whether that translates into more actual testing and a better knowledge of the meaning of results is anyone`s guess though!
Another advantage in costs of multifunction testers is the price of regular calibration.
The one I had also did earthing areas and earth rod testing which was viewed as an optional number 6 test after the first 5 "must have" tests.
Can you still get new hand cranked insulation resistance testers these days? they were fairly rare back then! LOL.