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lyledunn
465 Posts
Question
In an effort to separate a new EV installation from the existing installation, it is intended to fit Henley blocks and tail off to a new consumer unit. There are up to twenty similar installations all domestic. The contractor has asked my opinion on his intention as the existing installations have only one consumer unit which, of course, provides a single main switch in compliance with 462.1.201. With his proposal there will be two means of isolation, one in each of the consumer units. This is very common practice in this neck of the woods so ordinarily there would be no concerns raised. However, there is particular scrutiny of EV installations so he is keen to ensure that 7671 is complied with in full. 
There is no space for a separate isolator. My own view is that 462.1.201 does not necessarily demand a single means of isolation but I would appreciate the opinion of others. Even if there was a non-compliance, I do believe that the separate arrangement proposed is a much better alternative.
 
3 Replies
Chris Pearson
2045 Posts
Your wriggle room is to regard your "new EV installation" as being separate from your "existing installation". Each must have a main switch as near to the origin as possible.
AJJewsbury
2163 Posts
In the old days, before the advent of 4-pole REC isolators, it was usual to have two separate CUs (and hence isolation) for the 24-hour and off-peak systems - the argument being they were in effect two different installations within the same building - but that really wasn't ideal for the homeowner hunting for the 'main switch' in an emergency.

It's also common to have two (or more) separate means of isolation where there are multiple sources of supply (e.g. PV systems).

My reading of the regs is that the intent is to have single means of isolation where at all possible, but labelling might suffice in other cases.

How much space is there? If there's room for a pair of Henleys there might be room for some kind of isolator that could feed 2x 25mm²...

    - Andy.
mapj1
2851 Posts
I'm assuming 20 separate installations each with two main switches (not one switch serving 20 properties). Personally, I agree with you, and I'd not blink so long as the switches are close enough that having found one you do not have to go hunting for the other.
It is rather like the common E7 situation with one CU for storage heaters and another for the rest of the site - when they are more or less side by side and well labelled, there is no problem. On the other hand if one CU is under the stairs and the other in the garage I might be more concerned that someone may isolate the wrong thing in a hurry- which is the intention of the regs and what it is all about really.
Perhaps A REC2 before the Henley blocks only if the 2 isolators are remote from the point of split.
regards Mike.

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