Redundant cables in consumer unit

[SW1970]

Hi, newbie here. Could do with a bit of assistance. I'm doing a PIR on my own property for one of my upcoming assessments.

In my CU there are 2 MCBs that relate to old installations prior to the kitchen and bathroom being renovated. There is an MCB labelled IMMERSION and another HOB. Both are not connected, however the cables for these 2 circuits remain in the CU. The neutrals appear to be connected but the live conductors are not; they are merely folded back into the void in the brick behind the CU. For the sake of my question, let's assume the neutrals are erroneously connected and can be disconnected without upsetting anything.

It can be also assumed as the house is fully renovated the "client" won't be interested in the cables being recovered and the other end of the cables cannot be located without major works. Here's the questions:

1. Which code should I use for the unconnected live cables in the CU?

2. Which regulation clause(s) relates to this issue?

3. If the CU is not going to be replaced, what is the remedial action for the unconnected cables?

4. If the CU is going to be replaced, what is the remedial action for the unconnected cables?

Many thanks to the forum for your help in advance.

Cheers
SW

 

[Deleted member 9648]

Hi, newbie here. Could do with a bit of assistance. I'm doing a PIR on my own property for one of my upcoming assessments.

In my CU there are 2 MCBs that relate to old installations prior to the kitchen and bathroom being renovated. There is an MCB labelled IMMERSION and another HOB. Both are not connected, however the cables for these 2 circuits remain in the CU. The neutrals appear to be connected but the live conductors are not; they are merely folded back into the void in the brick behind the CU. For the sake of my question, let's assume the neutrals are erroneously connected and can be disconnected without upsetting anything.

It can be also assumed as the house is fully renovated the "client" won't be interested in the cables being recovered and the other end of the cables cannot be located without major works. Here's the questions:

1. Which code should I use for the unconnected live cables in the CU? I would code it 2,as the cables are not properly disconnected and identified and whether the cables are safe at the other end is unknown.

2. Which regulation clause(s) relates to this issue? I have no idea,common sense is all I can think of

3. If the CU is not going to be replaced, what is the remedial action for the unconnected cables? Pull them back into a suitable enclosure outside the CU and terminate and identify them.

4. If the CU is going to be replaced, what is the remedial action for the unconnected cables? As above

Many thanks to the forum for your help in advance.

Cheers
SW

Maybe some of the other guys can come up with a reg you could quote but I cant!

 

[Marvo]

If the cables are unknown destination and you can't establish if the 'far end' is safe then wouldn't it be safer to leave the cable in the CU with the L+N disconnected but with the earth still connected. If you remove the earth and pull them back into a separate enclosure and there's ever a voltage fed back from the destination end then this would be hazardous.

 

[domestic spark]

check to see if live, if not chop right back and tape over the ends, push them back into cavity. make sure there not picking up voltage, leakages from the other end.

 

[Deleted member 9648]

QUOTEIf the cables are unknown destination and you can't establish if the 'far end' is safe then wouldn't it be safer to leave the cable in the CU with the L+N disconnected but with the earth still connected. If you remove the earth and pull them back into a separate enclosure and there's ever a voltage fed back from the destination end then this would be hazardous.QUOTE

Seems unlikely if they are disconnected at source.I guess an IR test from them to the rest of the install and exposed/extraneous parts would be worthwhile to check the far ends are not connected to anything.

 

[Deleted member 9648]

check to see if live, if not chop right back and tape over the ends, push them back into cavity. make sure there not picking up voltage, leakages from the other end.

Not good practice,chopped off and stuffed back they can never be re-used...and a test for voltage/leakage would only be valid at the time of chopping off....they should be safely blanked off with a suitable termination.

 

[Marvo]

Couldn't you just make them safe using one of those Wago block things?

 

[Deleted member 9648]

Couldn't you just make them safe using one of those Wago block things?

You could...preferably outside the CU in an enclosure.

 

[SPARTYKUS]

Or a capped end crimp with nylon end, they're good.

I like the idea of leaving the earth in though.

 

[domestic spark]

Not good practice,chopped off and stuffed back they can never be re-used...and a test for voltage/leakage would only be valid at the time of chopping off....they should be safely blanked off with a suitable termination.

why would you need to re use them.

 

[domestic spark]

do nessasary tests, if redundant chop them out.

 

[domestic spark]

wright or wrong thats what i would do, cant stand messey boards

 

[gamblor6]

surely you connect all unused cores to earth, problem solved.?

 

[SW1970]

Thanks for your help folks! So, to answer my own questions with your input:

1. Which code should I use for the unconnected live cables in the CU?

Code 2 because of the neutrals remaining connected and unknown routing and unknown far end termination of the cable; it could be dangerous. I carried out the insulation resistance tests which were ok. As it happens once I had disconnected the cables for the tests I noticed that the outer sheath of one of these cables behind the CU was severely damaged by abrasion against something and the neutral was exposed so it would have been a 2 anyway (could get a finger in there from outside the CU because there is a gap behind the CU - another failure).

2. Which regulation clause(s) relates to this issue?

It looks like several: 611.2 (damaged), 134.1.1 (connections secure), 526 (connections secure).

3. If the CU is not going to be replaced, what is the remedial action for the unconnected cables?

Terminate the L and N conductors using nylon crimp on terminators or similar, label the cable with "unknown routing and termination, believed to be redundant" and tuck behind CU as far as possible. Leave the CPC connected and label similarly, with "L and N terminated behind CU".

4. If the CU is going to be replaced, what is the remedial action for the unconnected cables?

Same as 3.

Any last comments welcome.

Cheers, SW

 

[IQ Electrical]

Code 2-The neutral by definition is a live conductor and should be subject to the requirements of 411.2.

As gamblor 6 suggests, the redundant cores could be labelled as such then terminated into the earth bar assuming there is spare capacity.

If replacing the consumer unit, I think I'd be inclined to still terminate as above, you just never know when that cable could be utilised in the future.