dual row 17th cu ?

[RossR]

I see we still have the problem that you will not recognise that a house with 2 CUs has 2 installations.

I'm afraid not. I can see how it is convenient to consider them as two installations, but I have yet to see a logical argument why.

How does that change when the same protective devices are housed in multiple enclosures?

You then have multiple assemblies of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes, and need multiple main switches as per 537.1.4, one for each installation.

Why is an installation not allowed to have protective devices spread between multiple enclosures? If it includes the circuits that originate from it, which are in many enclosures and may incorporate further protective devices?

Are the henley blocks before multiple CUs not part of an electrical installation?

 

[RossR]

Well - maybe one of those who disagrees could try and change your mind, from wrong to right.

I'm willing to change me mind, but your silence isn't going to convince me.

 

[ban-all-sheds]

Sorry - for some reason the topic wasn't showing as having a new post until this morning's

I see we still have the problem that you will not recognise that a house with 2 CUs has 2 installations.

I'm afraid not. I can see how it is convenient to consider them as two installations, but I have yet to see a logical argument why.

Installation. An assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes.

 

[RossR]

Why is an installation not allowed to have protective devices spread between multiple enclosures? If it includes the circuits that originate from it, which are in many enclosures and may incorporate further protective devices?

Are the henley blocks before multiple CUs not part of an electrical installation?

 

[holmslaw]

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[holmslaw]

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[RossR]

I work in buildings that have multiple overlapped supplies and it requires complicated procedures and multiple isolations to switch off any major part of the installation.

Interesting that you still refer to it as a single installation.

I'll happily admit I'm wrong, but only if I someone can show me a logically consistent interpretation of the regs. I agree that the regs need to be applicable to all sorts of installations. For simplicity I'm concentrating on a particular scenario for now. That's a domestic situation with a single supply from the DNO. This feeds some Henley blocks that in turn feed two consumer units. Each CU has a single RCCB "main switch" feeding a selection of MCBs.

How many installations is this? BAS says 2. I think 1. What do you think?

Do the Henley blocks form part of an electrical installation? I'm yet to get an answer for this.

 

[holmslaw]

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[JohnD]

In a ordinary "house" it seems to me self-evident that the "house" has "an electrical installation" and ought to have one main switch to turn it all off.

You might or might not have multiple CUs in your house for the garage, shed, shower etc. That doesn't affect my opinion.

What you do in an industrial site may well be differerent.

 

[RossR]

Take a block of 100 flats you might have installed all the mains and sub mains, all the landlords services and wired each individual flat, its one big installation containing lots of smaller installations.

A block of flats was an example I had in the back of my mind too. I think I like your description of one big installation containing lots of smaller installations. If you apply the first half of 537.1.4, that implies a big switch that would isolate the whole lot, as well as an isolator for each flat.

Probably simpler to understand if you think of the building and the installation as completely separate.

Completely agree. A building might have multiple installations, and an installation might span multiple buildings.

Also see the definition of 'distribution circuit' in part 2.

I don't have my BRB handy, but I'd guess it backs up your "big installation containing lots of smaller installations" interpretation.

I say its at least two installations, if you take a supply to a garage thats another installation, that makes three. But the Henley blocks are feeding the installation, or, an installation.

I could go for three - one encompassing everything including the henleys' and two within that. "as near as practicable to the origin" of the big installation would surely be before the henleys'.

Now have a look at 537.1.6, you could argue that the henley blocks have split the single supply source into three supply sources. So therefore you should fit a label advising that all three switches must be operated to isolate the installation. Not surprisingly, unhelpfully the regs don't define what source means.

I think that's perhaps a bit tenuous, but the regs don't seem well written for situations with multiple sources, which is becoming more common with renewables. Take the definition of Origin for example. For now I'm trying to keep things relatively simple by only considering a single source. I believe there is a new special location in amendment 1 for medical locations. Perhaps that considers redundant sources?

 

[holmslaw]

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