Main switch position on CU

[KeenPensioner]

As I've said many times I'm not an electrician but still learning at 73 years old. I watch a lot of YouTube videos on electrical topics, just for the sake of it. I've just watched a video by Artisan Electrics where he was fitting a new CU and had a problem when the length of the existing tails were not long enough to reach the main isolating switch (which was on the RHS of the new board but came through a wall on the LHS of the existing board.) He had a nightmare trying to pull new tails through from the meter cupboard outside and eventually drilled though the wall and used trunking.

Sorry for the long preamble, but the video generated lots of comments on why he couldn't just move the main isolating switch (Eaton Version) from the RHS to the LHS of the new CU. The easy answer (as suggested in the comments) was just to buy anther CU with the main switch on the LHS but he didn't do that and accepts he should have done an EICR beforehand.

Can someone kindly explain why moving the main switch is a bad idea, as many comments suggested.

I expect that the busbar would need to be adjusted to accommodate the the L incomer being on the left now and outgoing side of the N incomer would be (perhaps) too close to the busbar and not reach the N bar. Also could you explain why polarity of the RCBOs would be a problem?

 

[Marvo]

It's not uncommon for an isolator switch to break the live before the neutral and vice versa when reset it will connect the neutral before the live. This is why many isolators have L and N sides marked on them and shouldn't be connected the other way around. This means that when moving the isolator from one side of a CU to another you couldn't use the original busbar that connects between the isolator live and one side of the other circuit breakers.

There's also an issue where a CU is given a short circuit rating that's actually higher than the rating of some of its internal components. Without getting too in depth this is called a 'type tested' rating of 16kA (BS EN 60439-3) whereby as long as the CU is installed exactly as it's supplied it carries this higher rating. As soon as you make any fundamental chances to the CU it loses its 'type tested' rating and may be unfit for purpose. The liability would fall on the person who made the changes.

I uploaded a document here that outlines changes in the regulations surrounding type-tested assemblies. https://www.electriciansforums.net/...guide-to-the-requirements-of-bs-en-61439.194/

 

[KeenPensioner]

Thank you for your prompt reply, I appreciate that. I understand what you explain and the consequences of altering the "type tested" configuration of the CU. For the sake of a purely hypothetical argument (bearing in mind that I'm not an electrician) would it be possible to move the isolator to the left, and configure the busbar to fit by remove a couple (say) of the busbar connections to accommodate the N coming from the bottom of the isolator? Many electricians who commented on the problems he had suggested that. I understand it could invalidate the manufacturer's warranty but could it be done?

 

[Marvo]

Even if you removed a couple a couple of the connection tabs from the busbar wouldn't that mean the busbar is still running very close underneath the neutral connection of the isolator? I think it might be a separation issue.

I'm not a UK sparky so I'm not intimately familiar with the exact layout UK consumer units, maybe one of the UK members has a better theory.

 

[westward10]

Even if you removed a couple a couple of the connection tabs from the busbar wouldn't that mean the busbar is still running very close underneath the neutral connection of the isolator? I think it might be a separation issue.

I'm not a UK sparky so I'm not intimately familiar with the exact layout UK consumer units, maybe one of the UK members has a better theory.

You hit the nail on the head in #2.

 

[littlespark]

The solution is, you get a Cu with a left hand mainswitch, or install longer tails to reach.

Technically, if everything is connected as it should, and nothing is touching that shouldn’t, then it is possible to rebuild a Cu as you need, but as explained, it could go against type testing, and could be very confusing for the next spark to work in it

 

[KeenPensioner]

Thank you all for your replies, appreciated. "littlespark" has obviously described the correct way to do it. I realise that anything other than that would be dubious at best but I just wondered if it could be done by moving the isolator switch and rejigging the busbar. The video by Artisan Electrics is here and as can be seen from some comments (by electricians) they suggested doing that. Thanks again for taking the time to reply.