Poll: How Many Installation(s) do I have?

[JohnW2]

Sorry - I thought you said that making a decision that you had a single installation with a 3-phase supply was erring on the side of caution.

Well, it is, isn't it? If I regard my installation as a single 3-phase one, that 'decision' means that I should have 16kA devices, whereas if I felt that I had multiple single-phase installations, I could invoke the provision to have 'less safe' devices. That surely means that deciding that it is a 3-phase installation 'errs on the side of caution", doesn't it? The fact that I do not have 16kA devices does not alter that - it simply means that if I make 'the 3-phase decision', all my CUs are, strictly speaking, non-compliant.

If you want to use "safer" devices you may. Just because there is an exemption available that doesn't mean that you have to take advantage of it. You could determine that you have 7 installations with single-phase supplies but still use 16kA devices because you wanted to. There's no need to decide that you have a single installation in order to be "forced" to use "safer" devices.

Of course not - but that's not the point. The point is that making the other decision (3-phase) seems to remove the option to have the 'less safe' devices.

Also in other words there is no electrical reason to have, or difference between, 1 installation vs 7.

Exactly - none of this is about electrical considerations, it is only about regulatory compliance. For some reason (which appears to have no electrical/engineering basis), 530.3.4 has chosen to exclude 3-phase installations from the provision which allows the lower breaking capacity devices to be used.

I would imagine that the same was in your mind when you started this by saying that you hoped I had 16kA devices if I did not have "an installation with a 3-phase supply". I presume that you understood that, electrically speaking, the number of phases was irrelevant (when each is used separately), so I presume that, just like me, your concern was solely about compliance with a regulation which appears not to be based in engineering or physics.

Kind Regards, John

 

[JohnW2]

Logically those (now) 13 people would say that it is impossible for anybody to have more than one installation.

Well, as I've said, in the absence of an imposed (and meaningful!) definition, I would indeed say that it was impossible for a single dwelling to have more than one electrical installation, since I would regard that dwelling's "electrical installation" as consisting of 'all fixed electrical things' within that dwelling.

Kind Regards, John

 

[EFLImpudence]

I know it won't prove anything one way or the other, as it is just written by someone else, but what about Part P (c)

The requirements of this part apply only to electrical installations ... [that] are -

(c) in a building that receives its electricity from a source located within or shared with a dwelling.

That would seem to say that, for example, an office is a separate installation from the dwelling although the electricity originates in or even is shared with the dwelling in the same building.
Building three phase, dwelling and office single phase.

 

[JohnW2]

" .... (c) in a building that receives its electricity from a source located within or shared with a dwelling."
That would seem to say that, for example, an office is a separate installation from the dwelling although the electricity originates in or even is shared with the dwelling in the same building.

I don't think it says, or necessarily even implies, "...in the same building".

I would think that (c) relates to a pretty uncommon situation. To have a dwelling deriving its electricity from a source located in a non-dwelling is probably not all that uncommon - but the other way around [as per (c) above] seems far less likely.

I really am not sure what this means in terms of the meaning of "an installation" (in the eyes of the authors of Part P)but, as you say, there's no reason to assume that the authors of Part P have the same ideas/views as do the authors of BS7671!

Kind Regards, John

 

[ban-all-sheds]

Well, it is, isn't it? If I regard my installation as a single 3-phase one, that 'decision' means that I should have 16kA devices, whereas if I felt that I had multiple single-phase installations, I could invoke the provision to have 'less safe' devices. That surely means that deciding that it is a 3-phase installation 'errs on the side of caution", doesn't it? The fact that I do not have 16kA devices does not alter that - it simply means that if I make 'the 3-phase decision', all my CUs are, strictly speaking, non-compliant.
..... The point is that making the other decision (3-phase) seems to remove the option to have the 'less safe' devices.

Well, yes, it does.

But I still cannot get my head round the idea that that's the reason for making the decision. It's like being on a French motorway, not being happy driving at 130kph, so deciding to pretend that it is raining so that you have to drive slower.

 

[ban-all-sheds]

Well, as I've said, in the absence of an imposed (and meaningful!) definition, I would indeed say that it was impossible for a single dwelling to have more than one electrical installation, since I would regard that dwelling's "electrical installation" as consisting of 'all fixed electrical things' within that dwelling.

Well - I would indeed say that within the dashed line is "an assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes".

 

[JohnW2]

But I still cannot get my head round the idea that that's the reason for making the decision.

It sounds as if you don't understand exactly what I've been saying, so I will attempt to spell it out again ...

There is a regulation. There is a difference of opinion as to whether or not it should be interpreted in such a way that it applies to 'the electrics' in my house. One of those interpretations would result in a regulatory requirement for me to have higher-rated devices. The other interpretation would allow me (regulation-wise) to have lower-rated devices (although I would obviously be free to use higher-rated ones if I so wished). It is surely apparent that the more 'cautious' approach ('more conservative', 'erring on the side of safety') is the former of those?

Put another way, if (like me) one has lower-rated devices, then one interpretation would cause one to believe that one's CUs were compliant, whereas the other interpretation would cause one to believe that they were non-complaint. Again, it seems obvious to me which of those interpretations would be the 'more cautious' (etc.).

Don't forget that the need to discuss this 'decision' only arose because of a desire to determine whether 530.3.4 applied to 'the electrics' in my house. Prior to that, I would not have thought that a 'decision' was necessary, since it would never have occurred to me to even consider suggesting that my house had anything other than one, 3-phase, installation.

Kind Regards, John

 

[JohnW2]

Well - I would indeed say that within the dashed line is "an assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes".

Indeed so. As I've said, almost anything would satisfy that definition, but that doesn't make me think that it would be sensible to describe almost any group of related electrical items within a building(e.g. lampholder switch and cables) as being an "electrical installation".

Kind Regards, John

 

[ban-all-sheds]

It sounds as if you don't understand exactly what I've been saying, so I will attempt to spell it out again ...

There is a regulation. There is a difference of opinion as to whether or not it should be interpreted in such a way that it applies to 'the electrics' in my house. One of those interpretations would result in a regulatory requirement for me to have higher-rated devices. The other interpretation would allow me (regulation-wise) to have lower-rated devices (although I would obviously be free to use higher-rated ones if I so wished). It is surely apparent that the more 'cautious' approach ('more conservative', 'erring on the side of safety') is the former of those?

But it is such an arbitrary decision, and seems to be done AAF. If you don't want to use lower-rated devices, you are, as you say, free to use higher-rated ones. You don't need to decide that an exemption does not apply to you to be able to not take advantage of it.

Put another way, if (like me) one has lower-rated devices, then one interpretation would cause one to believe that one's CUs were compliant, whereas the other interpretation would cause one to believe that they were non-complaint. Again, it seems obvious to me which of those interpretations would be the 'more cautious' (etc.).

But you've chosen a definition to make your installation non-compliant and you do not care to rectify that.

I'll go back to the French motorway analogy - what you have said here is thinking that it would be safer to do 110 instead of 130, deciding that it was raining and therefore you had to do 110, but then carrying on driving at 130.

Don't forget that the need to discuss this 'decision' only arose because of a desire to determine whether 530.3.4 applied to 'the electrics' in my house. Prior to that, I would not have thought that a 'decision' was necessary, since it would never have occurred to me to even consider suggesting that my house had anything other than one, 3-phase, installation.

A strange desire to have, given that it doesn't matter to you whether it applies or not.

 

[ban-all-sheds]

Indeed so. As I've said, almost anything would satisfy that definition,

True.

but that doesn't make me think that it would be sensible to describe almost any group of related electrical items within a building(e.g. lampholder switch and cables) as being an "electrical installation".

Indeed not, but I think it hardly senseless to describe a CU and all its devices and final circuits originating at it as an assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes.

 

[stillp]

The other interpretation would allow me (regulation-wise) to have lower-rated devices

But only if the assembly of those devices can pass the conditional s/c test at 16kA.

 

[JohnW2]

But it is such an arbitrary decision, and seems to be done AAF. If you don't want to use lower-rated devices, you are, as you say, free to use higher-rated ones. You don't need to decide that an exemption does not apply to you to be able to not take advantage of it.

There seems to be some misunderstanding here.

I do not "want to use higher-rated devices". The umpteen devices I have are all 'lower rated' and, regardless of regulations, I do not intend to change them.

If you believed that my devices were strictly non-compliant (which I don't think you do, now) you might criticise me for saying that I have said that I would knowingly 'ignore' a regulation. However, I am perfectly comfortable to do that, by 'common sense extrapolation' from non-contentious aspects of the regs. The one thing that no-one disputes if that if I did have a simple single single-phase installation, it would be deemed acceptable for me to have a 'type tested' CU which contained devices which, in themselves, had a breaking capacity <16kA, so long as they passed the "16kA conditional short-circuit test" in the presence of a fuse ≤100A. As I am sure you would agree, there is nothing about having a 3-phase installation (with the phases used separately) which changes anything about that, so the regs 'should' deem those same type-tested CUs with the same "conditionally tested" devices as being just as acceptable as in a simple single-phase installation.

It was you who started this by saying that you "hoped I had 16kA devices", the implication I took to mean that you (then) thought that my CUs would be non-compliant if they did not have 16kA devices. I had never thought about that before you mentioned it and, as you know, I now am inclined to think that what you then implied was correct - although, ironically, you now seem to have reversed your opinion (albeit you appear to be in somewhat of a minority.

Kind Regards, John

 

[JohnW2]

But only if the assembly of those devices can pass the conditional s/c test at 16kA.

Indeed - but they do (I hope) since they exist in what I assume to be 'type-tested' CUs (they never come with such a 'label', so I'm not sure how one can be certain!). That presumably implies that they pass that test, doesn't it?

Kind Regards, John

 

[ban-all-sheds]

There seems to be some misunderstanding here.

I do not "want to use higher-rated devices". The umpteen devices I have are all 'lower rated' and, regardless of regulations, I do not intend to change them.

So why seek to determine that you have an installation which requires them rather than a number of installations, none of which do?

If you believed that my devices were strictly non-compliant (which I don't think you do, now)

I never did.

you might criticise me for saying that I have said that I would knowingly 'ignore' a regulation.

Surely I can criticise you if you think you are ignoring a regulation? Surely no matter what my opinion is, if you believe that X is required and then you chose not to do it so you are choosing to do what you believe is non-compliant?

However, I am perfectly comfortable to do that, by 'common sense extrapolation' from non-contentious aspects of the regs.

I fear that "common sense" is not something we can fruitfully discuss, since to me it makes perfect, common, sense to say that a CU and all its devices and final circuits originating at it is an assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes, and that it is anything but common sense to say that it is not because nobody can have more than one such assembly.

The one thing that no-one disputes if that if I did have a simple single single-phase installation, it would be deemed acceptable for me to have a 'type tested' CU which contained devices which, in themselves, had a breaking capacity <16kA, so long as they passed the "16kA conditional short-circuit test" in the presence of a fuse ≤100A. As I am sure you would agree, there is nothing about having a 3-phase installation (with the phases used separately) which changes anything about that, so the regs 'should' deem those same type-tested CUs with the same "conditionally tested" devices as being just as acceptable as in a simple single-phase installation.

IMO they do, because IMO if you use the phases separately you do not have any assemblies of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes which have a 3-phase supply.

It was you who started this by saying that you "hoped I had 16kA devices", the implication I took to mean that you (then) thought that my CUs would be non-compliant if they did not have 16kA devices.

No - I said that because I (it seems mistakenly) thought that you would ensure that you complied with the regulations, and would not take the attitude that you did not care what the breaking capacity of your devices was.

I had never thought about that before you mentioned it and, as you know, I now am inclined to think that what you then implied was correct - although, ironically, you now seem to have reversed your opinion (albeit you appear to be in somewhat of a minority.

It was correct in the sense that my position was, is, and always will be that if you think you do not have any CUs which are in single phase installations ≤ 100A yada yada then you ought to have 16kA devices.

I have not changed my mind regarding that, nor have I changed my mind that you actually have a number of single-phase installations, all of which can be compliant with type-tested CUs which comply with 61439-3 including the annex about conditional 16kA ratings.

 

[JohnW2]

No - I said that because I (it seems mistakenly) thought that you would ensure that you complied with the regulations, and would not take the attitude that you did not care what the breaking capacity of your devices was.

As I said, I "do not care" so long as it as high as would would be acceptable in a type-tested CU in a simple single-phase installation - which it is.

Kind Regards, John