Lowering Consumer Unit & Extending Cables

[slartybartfast]

• I want to replace my consumer unit and move it down the wall so don't need a chair to get at it.
• However the wires leading to the Consumer Unit are not long enough and would need extending
• I gather that compliant way to extend is to use a suitably encased DIN rail with DIN terminal connectors and use as a means to extend the cables.
• Clearly each Live cable would need to be routed to the new Consumer Unit.
• However could the Neutrals be connected to a bus bar, and then use a meter tail to connect to the new Consumer Unit below? Same for earth? Or would each L, N & E need to terminate at the CU?
• BTW: Planning on populating the new CU exclusively RCBOs.

Just want to be "armed" ready for a discussion with electrician.

Thx !

 

[telectrix]

you'd find that the N and E bars in the CU will not accept anything over 10mm. I'd not do it. I'd extend all 3 conductors of each cable to the corresponding CU terminals. one thing to beware of is the easrth din rail connecors. use plain ones, not the ones that are electricall connected to the din rail.

 

[pc1966]

All of the cables need to be extended to the new CU.

You cannot common the neutrals if using RCBOs as they need to monitor the outgoing (live) and returning (neutral) current per-circuit to see if anything has gone astray that should trip the protection. For extending normal T&E type cables here it is fairly simple, you can use DIN rail mounted terminals, or the Wago spring-loaded ones, so long as they are suitable protected.

Normally you would not "extend" the tails if practical, you would replace them to avoid necessary high-current joints. But it can be done with Henley blocks if really needed.

But there are other limits for long tails, specifically they need to be physically protected and if longer than 3m then they should have a fused switch or similar at the sending (i.e. meter/cut-out) end.

 

[telectrix]

All of the cables need to be extended to the new CU.

You cannot common the neutrals if using RCBOs as they need to monitor the outgoing (live) and returning (neutral) current per-circuit to see if anything has gone astray that should trip the protection. For extending normal T&E type cables here it is fairly simple, you can use DIN rail mounted terminals, or the Wago spring-loaded ones, so long as they are suitable protected.

Normally you would not "extend" the tails if practical, you would replace them to avoid necessary high-current joints. But it can be done with Henley blocks if really needed.

But there are other limits for long tails, specifically they need to be physically protected and if longer than 3m then they should have a fused switch or similar at the sending (i.e. meter/cut-out) end.

well spotted, I missed the RCBO bit.

 

[pc1966]

Another minor point is it is not a good idea to use the earth terminals for the DIN rail (i.e. the green/yellow ones that actually connect to the rail). Not because of any functional limitation, but it makes testing the circuits harder to do (really the electrician has to separately check each circuit's earth and so they would need then to isolate at the extending box, not at the CU where it is more obvious and accessible).
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Ah, just spotted that Telectrix has already mentioned this!

 

[slartybartfast]

So DIN terminal connectors for each L, N & E of each cable it is then. I've just watched a video on RCBOs and now understand how they work, so thanks pc1966 for pointing that out.

 

[pc1966]

DIN terminals make for a very neat and ordered way of doing things. You can get different colours as well to make it easier to keep track of things, but typically what is easily available is grey for most and blue for neutral, as you choice.
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Actually RS have a range of colours in the 4mm max size:

1SNK506020R0000 | Entrelec Blue ZS6 Feed Through Terminal Block, 6mm², ATEX, 1 kV ac | RS Components

uk.rs-online.com

1SNK506061R0000 | Entrelec Green ZS6 Feed Through Terminal Block, 6mm², ATEX, 1 kV ac | RS Components

uk.rs-online.com

1SNK506064R0000 | Entrelec Brown ZS6 Feed Through Terminal Block, 6mm², ATEX, 1 kV ac | RS Components

uk.rs-online.com

You might need bigger ones for cooker/shower though, as often that is 6mm or even 10mm T&E cable.
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A more limited range taking up to 10mm cables:

DIN Rail Terminal Blocks | RS

Non-fused DIN rail terminals are modular plastic blocks used to connect electrical wires and provide protection from overcurrent and short-circuits.

uk.rs-online.com

 

[davesparks]

• I want to replace my consumer unit and move it down the wall so don't need a chair to get at it.
• However the wires leading to the Consumer Unit are not long enough and would need extending
• I gather that compliant way to extend is to use a suitably encased DIN rail with DIN terminal connectors and use as a means to extend the cables.
• Clearly each Live cable would need to be routed to the new Consumer Unit.
• However could the Neutrals be connected to a bus bar, and then use a meter tail to connect to the new Consumer Unit below? Same for earth? Or would each L, N & E need to terminate at the CU?
• BTW: Planning on populating the new CU exclusively RCBOs.

Just want to be "armed" ready for a discussion with electrician.

Thx !

Why do you need to be 'armed' ready for a discussion with an electrician? You're getting a few quotes for a job, not going to war.

The best thing to do wherever possible is to replace the cables that aren't long enough so that there aren't any joints.
If this is not possible for some or all of the cables then a joint box will be needed, depending on the number of cables involved this could be a small joint box or an adaptable box with din rail as you suggest.

 

[pc1966]

Why do you need to be 'armed' ready for a discussion with an electrician? You're getting a few quotes for a job, not going to war.

Yes, very true!

 

[slartybartfast]

"Armed" as in "armed with knowledge". Knowledge helps inform your requirements. The better your specification, the more focused the quotes are, and easier to compare.