Sparking on earth cable

[rob_em]

Hi

I have changed one of my mcbs and were connecting earth back to main terminal and saw a small spark. What could it be ?

Thanks

 

[flameport]

A combination of someone putting their life at risk by working live inside a consumer unit and one or more faults on the circuit(s) concerned.

 

[Diver Fred]

Which earth connection is it?

The main one to the earth spike/mains water?
Or to an in-house circuit?

 

[rob_em]

It's ring mains earth

 

[rob_em]

House circuit Diver Fred

 

[ericmark]

DNO earth and real earth are not the same, the home should be bonded to DNO earth, but if items have been incorrectly bonded, then there can be a voltage difference between two earth types, also if not RCD protected there can be an earth fault. But also capacitive linking can cause a small spark when connecting, but this should not show a second time.

So you have highlighted a potential fault, so now you need to used the test equipment to find out why, so get out the loop impedance tester, and insulation tester, and see what has caused it. May want to clamp on an ammeter to see how much current is flowing, and it the current still flows with the isolator switched off.

I do check back ground leakage, once you know how much current is flowing and the voltage difference you will have some idea as to what is causing it.

However, since you have asked the question, it seems likely you need to employ a proper electrician to investigate further.

 

[rob_em]

This is connected to pme

 

[CountryFan]

Looks like cpc to me, but as above fault on a circuit likely

 

[endecotp]

I have changed one of my mcbs

Why?

I’m going to guess that maybe it was tripping, and so you decided it was faulty and should be replaced.

and were connecting earth back to main terminal

Why did you disconnect it in the first place?

and saw a small spark. What could it be ?

A warning of imminent death. Frankly I’m amazed that you got your phone out to capture the image of the spark with your thumb on the wire, rather than retreating to a safe distance.

Was the isolator that is shown in your later picture turned off?

One thing that’s not clear in any of your photos is whether there is bonding to the water & gas supplies. Is there a main earth terminal? Are they connected inside the CU?

 

[pete01]

One thing that’s not clear in any of your photos is whether there is bonding to the water & gas supplies. Is there a main earth terminal? Are they connected inside the CU?

Good spot, also the earth by the isolator and the earth in the consumer unit look like different cables....must/might be an earth terminal somewhere.

 

[rob_em]

Same earth cable goes to pass and connects to main terminal in cu

 

[rob_em]

pete01 mcb was on and the earth cable from this ring sparked when connected to terminal in cu

 

[flameport]

mcb was on

Do you want to die?

As that's exactly what will happen if you continue to work on live circuits.

 

[Highway Man]

You should get an electrician to sort that out for you, I take it that you are not a registered electrician and you should not be inside the consumer unit. You have an earth fault on your system, possibly isolated to one circuit but quite possibly on them all. Have you been doing any other alterations or changing light fittings or light switches by any chance?

 

[rob_em]

No i havent but live to earth test when disconected from earth block showed me 130v