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

Shop Din Rail Terminal Blocks, 5000+ Products from Trusted Brands like Wago, Weidmüller, Phoenix, Entrelec and RS Pro. Fast & Free Delivery.

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.

 

[Risteard]

"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.

Perhaps.

The other thing which can happen though is if you are not sufficiently qualified/experienced to draw up the specification that you actually force them to erect an inferior installation because you have tied their hands as to how it must be erected.

I mean no offence by this - just a general observation.

 

[davesparks]

"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.

So you get a few electricians round (when that's possible again) and show them where the CU is now and where you'd like it moved to. The electrcian's will then advise you as to what they would do to achieve this and will quote based on that.

All of the answers you get on here are just best guesses based on the information you have provided and a bit of experience. None of us have actually seen the job so our answers here may be completely wrong or inappropriate for your situation.

Trying to over-specify the job may well lead to the electrician's assuming you are a pain in the bum customer and adding extra to the price for the dealing with the expected hassle.

 

[Mike Johnson]

It's all in the difference between being a half empty glass type of person as opposed to being a half glass full person. "Being armed with knowledge" may well make the electrician completing the quote think this chap is really going to appreciate what I am doing, rather than he is going to be a pain.

 

[pc1966]

Rather than fixating on the details of how it might be done, take a step back and consider what you actually want/need out of this.

What you have stated is this is primarily about access - so you can reach the board without trouble. That is a good start and a perfectly valid reason for moving the CU, but is moving it down by a metre or two the best solution? Will it be in the way of anything else in that location, or are there better places that are still within a sane cable-extending reach?

Next thing is you say you are going for RCBO. I think most folk here would agree is the best solution, so that is unlikely to be a contentious point with anyone you get in.

Typically with a new CU most would recommend getting a Surge Protection Device fitted following the guidance in the 18th edition of the wiring regulations. You don't have to get that, but some CU come with it as standard and those that don't it is normally less than £100 more to add a Type 2 SPD (unless you have lightning conductors installed on the building, are rural or otherwise fed from overhead cables, you are unlikely to need a Type 1 SPD). For peace of mind and lower risk to everything downstream of the CU it makes sense.

How many circuits do you currently have? Could you do with any more in the foreseeable future? Generally the cost for a larger CU box is trivial (it is the extra RCBO and effort to test circuits and fit them that would add cost) so for future expansion you should allow a couple of spare slots.

Do you have solar panels or similar local power sources? Are they doubled-up on an existing circuit? That is not permitted (but sadly common) so this would be the time to sort it out properly!

Are there any other things you want sorted as well? Normally before a planned CU change the electrician would do a ECIR to identify any unexpected problems and at that point the cost/effort to complete things properly would be clearer. Given your interest in this I doubt you have any obvious faults that are being ignored (e.g. broken or burned-out sockets, etc).

You might want to look over the best-practice guide #1 on CU replacement, and the guide #4 on inspection report aspects so you are familiar with the sort of things that any competent electrician would be looking to address.

https://www.----------------------------/professional-resources/best-practice-guides/

 

[DefyG]

Probably in a previous post but DIN rail connectors aren't considered 'maintenance free' so would need to be accessible for inspection.