NEWBIE - Help please extending 4 core ext armoured cable.

[adie68]

Hi All.

Newbie here, so please forgive me it this has been covered elsewhere, but I couldn't find a relevant post.

I have an external socket in my garden that is served by armored external cabling. It runs back to a 30amp breaker in a consumer unit in the garage that is fed from a 35 amp breaker in the house.

i want to move the socket down the garden to put electricity in the summer house.

I have purchased sufficient 4mm 3 core armored cable to make the run and an external junction box to replace the socket and join the 2 cables together.

On opening the external socket up there are 4 white cores inside numbered 1 to 4.

1 goes to live
2 goes to neutral
3 goes to the earth on the socket
4 goes to an earth point on the socket body

The cable I have purchased is 3 core, black, brown and grey.

I wired the junction box as follows:

Cable 1 to Brown
Cable 2 to Black
Cable 3 and 4 to Grey

On turning the electricity back on this immediately tripped the main breaker in the house although there was nothing drawing load

Removing 1 and then the other of the "earth" wires (cables 3 and 4) resulted in the same thing happening.

I am confused by the 2 earths, I don't really want to open the consumer unit in the garage to find out what is behind the breaker.

Can any one shed any light of provide advice as to what I should do next to resolve this problem?

Many thanks.

 

[Simon35]

Hi All.

Newbie here, so please forgive me it this has been covered elsewhere, but I couldn't find a relevant post.

I have an external socket in my garden that is served by armored external cabling. It runs back to a 30amp breaker in a consumer unit in the garage that is fed from a 35 amp breaker in the house.

i want to move the socket down the garden to put electricity in the summer house.

I have purchased sufficient 4mm 3 core armored cable to make the run and an external junction box to replace the socket and join the 2 cables together.

On opening the external socket up there are 4 white cores inside numbered 1 to 4.

1 goes to live
2 goes to neutral
3 goes to the earth on the socket
4 goes to an earth point on the socket body

The cable I have purchased is 3 core, black, brown and grey.

I wired the junction box as follows:

Cable 1 to Brown
Cable 2 to Black
Cable 3 and 4 to Grey

On turning the electricity back on this immediately tripped the main breaker in the house although there was nothing drawing load

Removing 1 and then the other of the "earth" wires (cables 3 and 4) resulted in the same thing happening.

I am confused by the 2 earths, I don't really want to open the consumer unit in the garage to find out what is behind the breaker.

Can any one shed any light of provide advice as to what I should do next to resolve this problem?

Many thanks.

Get an electrician to do it. Do you know how to make off an armoured cable and maintain the earthing through the box? Got the correct glands etc?

No offence meant, but if you were competent to do the above, then isolating the garage CU and taking the cover off should be within your capabilities.

 

[adie68]

Thanks for the quick reply

In answer to your questions yes I do, yes I have.

didn't say I couldn't take the CU apart, said I didn't want to, as whoever installed it partially covered it when dry lining the garage and to get to it means ripping part of the wall down.

 

[streetlighter]

You need to disconnect the cable inside the garage CU to perform an insulation resistance test to confirm the exisiting cable is clear.
Just a thought but have you stripped back and terminated the other end of the new SWA ?
Generally we use the black core as the CPC ( earth wire ) to break the tradition of Black being neutral in the old colours.

 

[Simon35]

Thanks for the quick reply

In answer to your questions yes I do, yes I have.

didn't say I couldn't take the CU apart, said I didn't want to, as whoever installed it partially covered it when dry lining the garage and to get to it means ripping part of the wall down.

Fair enough...but I think I would be sorting out the access to the consumer unit for maintenance and testing.

As for what the two earths are...what is the new cable connected to at the summer house end?

 

[adie68]

You need to disconnect the cable inside the garage CU to perform an insulation resistance test to confirm the exisiting cable is clear.
Just a thought but have you stripped back and terminated the other end of the new SWA ?
Generally we use the black core as the CPC ( earth wire ) to break the tradition of Black being neutral in the old colours.

Yes the other end of the SWA is stripped and terminated in the junction box but nothing is yet wired to the junction box.

Sounds like I am going to have to get the sledge hammer out then in order to expose the CU fully.

I can change the wiring config easily enough to use black for earth.

The new cable will be connected to standard 3 pin sockets internally to the summer house.

 

[Simon35]

You need to disconnect the cable inside the garage CU to perform an insulation resistance test to confirm the exisiting cable is clear.
Just a thought but have you stripped back and terminated the other end of the new SWA ?
Generally we use the black core as the CPC ( earth wire ) to break the tradition of Black being neutral in the old colours.

Yes the other end of the SWA is stripped and terminated in the junction box but nothing is yet wired to the junction box.

Sounds like I am going to have to get the sledge hammer out then in order to expose the CU fully.

I can change the wiring config easily enough to use black for earth.

The new cable will be connected to standard 3 pin sockets internally to the summer house.

So from the above it sounds like you have powered up the new SWA, via the new JB, to the summer house end, but at the summer house it was bare ends? Or just the chopped cable end, could the ends have been shorted?...or have I misinterpreted what you've said?

As said above, megger out the cable.

 

[adie68]

So from the above it sounds like you have powered up the new SWA, via the new JB, to the summer house end, but at the summer house it was bare ends? Or just the chopped cable end, could the ends have been shorted?...or have I misinterpreted what you've said?

As said above, megger out the cable.

Yes I have powered up the SWA via the new JB. The summer house end of the cable is cut, made up and terminated i a corresponding JB affixed to the summer house. The 3 cores have been stripped back and each 1 fixed into an individual connection point in the JB at the summer house, however the wiring in the summer house for the sockets has not been made up and connected in the JB. Effectively the SWA terminates at the JB in individual terminal blocks ( 1 for each core) with nothing connected to the other side of the terminals.

 

[Simon35]

So from the above it sounds like you have powered up the new SWA, via the new JB, to the summer house end, but at the summer house it was bare ends? Or just the chopped cable end, could the ends have been shorted?...or have I misinterpreted what you've said?

As said above, megger out the cable.

Yes I have powered up the SWA via the new JB. The summer house end of the cable is cut, made up and terminated i a corresponding JB affixed to the summer house. The 3 cores have been stripped back and each 1 fixed into an individual connection point in the JB at the summer house, however the wiring in the summer house for the sockets has not been made up and connected in the JB. Effectively the SWA terminates at the JB in individual terminal blocks ( 1 for each core) with nothing connected to the other side of the terminals.

Does it still trip if the old cable is connected into terminals at the mid-way JB, nothing connecting those terminals together and nothing is connected in the other side of the terminals?

 

[adie68]

Don't know.. didn't try that test.

Can try it tonight when I get home from work though.

 

[Simon35]

Don't know.. didn't try that test.

Can try it tonight when I get home from work though.

Its not much of a test, and is no substitute for testing it properly, but at least it might identify if the fault is in the new cable/gland/terminations or the old cable/glanding/terminations...

 

[londonboy]

Well it looks like Part P is working well down south

 

[dingodeano]

Generally we use the black core as the CPC ( earth wire ) to break the tradition of Black being neutral in the old colours.

I always use the grey. Just sayin.

 

[Scoby_Beasley]

Generally we use the black core as the CPC ( earth wire ) to break the tradition of Black being neutral in the old colours.

I always use the grey. Just sayin.

Must be region thing! When faced with black/brown/grey they become earth/neutral/live (in this situation). Just as well me push bike has a puncture!!

Or even earth/live/neutral.

 

[adie68]

Does it still trip if the old cable is connected into terminals at the mid-way JB, nothing connecting those terminals together and nothing is connected in the other side of the terminals?

Yes is does.

To start with I wired the 2 earths (cables 3 and 4) into the same terminal, then tried with each in a separate terminal and then leaving cable 4 un terminated as it used to be terminated to an earth post in the old socket and there isn't a corresponding earth post in the new junction box.

All 3 variations tripped the breaker.