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Topic Title: Isolation, main switch, multiple 'installation(s)' and EIC etc
Topic Summary: i thought i understood, now not sure
Created On: 24 February 2013 10:00 AM
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 24 February 2013 10:00 AM
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Joined: 18 October 2010

this was the link to my original post on this: ">

I am sorry if i break the rules by reposting as a new topic, but I wonder if this seemingly confused issue has 'progressed' any further than the topic content kindly linked for me to digest which was dated in 2010.

There is a post in that topic that quotes GN2 (it is at the bottom).

Is it accepted by this forum's experienced industry practitioners, that there appears to be a conflict in a Reg 537.1.4 that suggests a 'single main switch is required' and the above GN2 and more over, the difference of opinions on this subject ?

It all came to my mind when looking at an installation as you do, added to over time, that had 4 CUs from a splitter (henley). That's why I asked in a poor way i'm sure, in my last post about Main Switch, Max Demand and all other in the section of 'particulars of installation referred to.." on the EIC; specifically, if a new CU is added (as has been over time) split off using tails from a splitter block, does the term 'installation' and the sections on the EIC 'particulars' (max demand, main switch etc) only get filled in in relation to the new board added ?

To me, all 4 CU's are part of the one installation and not ones in their own right, which means the 'particulars' has to be considered regarding the whole installation and not just the new board added.

However, GN2 quote, lack of one main installation switch being an issue, etc may suggest that it need not be considered like that and that each board could be an 'installation'.

Any views: is it just pedantic regulatory words, or is this just too much a done to death topic not to raise again ?

Thank you.

PS: if there is no single point of isolation, does one leave the main switch bit blank if one takes the view of it all being part of one installation

IEE Guidance Note 2 - "Isolation & Switching", p.40

"It is permitted for a dwelling to have more than one electrical installation. Therefore one 'main switch' is not required to isolate all consumer units simultaneously provided the consumer units have an integral main switch.

"This situation frequently occurs when an additional consumer unit is added, e.g. to supply an electric shower. Regulation 537.2.2.6 requires each device used for isolation to be clearly identified by positional or durable marking to indicate the installation it isolates."

Edited: 24 February 2013 at 12:20 PM by psychicwarrior
 25 February 2013 12:03 PM
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I think the problem dates back to old days and off-peak installations - where you'd typically have one wylex CU for the main circuits and another for the storage heaters, the tails for each being connected directly to the supplier's kit. All in the days before DIN rail modular isolators. The the principle of two intermingled installations within one building/dwelling was set.

The definition of an installation used to include a clause about the origin, by that's been overtaken by events (local generation - stand-by or parallel) and increasingly didn't succeed in exempting off-peak supplies as suppliers moved from two separate supplies to one supply and a pilot wire.

So, yes it's is muddled. I guess the answer to 'what is an installation' to some extent boils down to: what the designer says it is. There could be good reasons for having two completely separate systems (for high availability for instance), but if it gets to the point where a householder doesn't know which switch to throw to make things safe, there's a problem to my mind.

- Andy.
 25 February 2013 06:14 PM
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thanks for your views Andy.

i agree with you on the point you make on the safety aspect considerations.

what's your view on the max, demand, main switch etc regarding the particulars on an EIC in this situation.

ie. if a new board was added (accepting no main switch for the whole), just consider the new 'installation' in relation to the EIC ?

 25 February 2013 06:23 PM
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ie. if a new board was added (accepting no main switch for the whole), just consider the new 'installation' in relation to the EIC ?

Effectively yes, plus a note on the existing regarding the lack of a "main" main switch.



Let the wind blow you, across a big floor.

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