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

[JohnW2]

Single point of isolation is I would say drawing the DNO fuse.

I find it hard to agree with that . The requirement, at least in a domestic property, is surely that there should be a single point of isolation available to the householder/occupier - and I wouldn't say that pulling DNO fuses qualifies as that.

In fact if we consider what is entered on an installation certificate then that seems a more reasonable way to define it. So re-thinking it all, I would say it is all down to how many installation certificates cover the house, if you have 5 certificates then it is 5 installations, even if only one consumer unit. .... So how many installation certificates cover the house? if more than one, I will change my vote.

That approach surely would make no sense. Installation certificates (I presume you mean EICs) are issued in relation to all sort of works, many of which are not particularly 'major', and it would surely be crazy if each time one was issued the number of 'installations' in the building was deemed to have increased. I find it hard to believe that many people would agree with this approach.

Kind Regards, John

 

[ban-all-sheds]

The requirement, at least in a domestic property, is surely that there should be a single point of isolation available to the householder/occupier

That's not a requirement which I can find in BS 7671.

But given that the compilers of its index regard their role as creating a treasure hunt, I might have missed what you're referring to - got a reg number?

That approach surely would make no sense. Installation certificates (I presume you mean EICs) are issued in relation to all sort of works, many of which are not particularly 'major', and it would surely be crazy if each time one was issued the number of 'installations' in the building was deemed to have increased. I find it hard to believe that many people would agree with this approach.

It might be useful to consider EICRs.

The model form for those in Appendix 6 has space to record the details of just one main switch.

 

[JohnW2]

That's not a requirement which I can find in BS 7671. But given that the compilers of its index regard their role as creating a treasure hunt, I might have missed what you're referring to - got a reg number?

I confess that when I wrote "...should be..." I was thinking more about the 'spirit of safety' than of any specific regulatory requirement - i.e. it seems to be to be highly desirable that an 'ordinary person' should have the means of de-energising the entirety of his/her installation (or whatever!) without having to pull a cutout fuse (if they even know that it exists, and know how to do so relatively safely).

Off the top of my head I cannot think of any specific regulatory requirement, but I'll see if I can find anything when I'm next close to my BYB!

It might be useful to consider EICRs. The model form for those in Appendix 6 has space to record the details of just one main switch.

I'm not sure how you're suggesting that this would help in determining the number of 'installations'. I presume that you're not talking about 'counting EICRs', since I think that would be even less appropriate than eric's suggestion of 'counting EICs'!

Kind Regards, John

 

[ban-all-sheds]

I confess that when I wrote "...should be..." I was thinking more about the 'spirit of safety' than of any specific regulatory requirement - i.e. it seems to be to be highly desirable that an 'ordinary person' should have the means of de-energising the entirety of his/her installation (or whatever!) without having to pull a cutout fuse (if they even know that it exists, and know how to do so relatively safely).

Indeed - but all installations require a device for isolating - pulling a cutout fuse is not compliant. The difference for ordinary persons is that the device must work on all line & neutral conductors.

Off the top of my head I cannot think of any specific regulatory requirement, but I'll see if I can find anything when I'm next close to my BYB!

537.1.4 A main linked switch or linked circuit breaker shall be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

A main switch intended for operation by ordinary persons, e.g. of a household or similar installation, shall interrupt both live conductors of a single phase supply​

Interestingly - when searching using part of that, to find something I could copy & paste, I came across this (with my emphasis)

537.1.4 A main linked switch or linked circuit breaker shall be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

For households this would need to be a double pole switch.


The point being that there should be one switch which is capable of de-energising the installation.


Regards

That is, indeed, true, but it seems to be commonly violated, and I can't recall having noticed people complaining about that. 'Secondary' CUs or switchfuses for submains to outhouses etc. seem to be commonly fed from post-meter Henleys without any upstream isolator which covers the whole of the "installation" (as you and I would probably regard it - but see below). I wonder what people think about that?

Perhaps one issue is the BS7671 definition of "an (electrical) installation" could be taken to indicate that it does not necessarily mean 'what we would think'. If there are, say, multiple CUs or submains, one could argue that, although they shared a cutout and meter, they could be regarded for the purpose of BS7671 as being separate 'installations', each of which had its isolator as required by 537.1.4?

Kind Regards, John

I'm not sure how you're suggesting that this would help in determining the number of 'installations'. I presume that you're not talking about 'counting EICRs', since I think that would be even less appropriate than eric's suggestion of 'counting EICs'!

I'm suggesting that if an E Installation CR has provision to record only one main switch, then maybe BS 7671 regards N CUs with, therefore, N main switches as N installations.

 

[securespark]

I want two, I want two, I want twoooooooooooooooooooooooooooooooooooooo...............................................

 

[JohnW2]

Indeed - but all installations require a device for isolating - pulling a cutout fuse is not compliant. The difference for ordinary persons is that the device must work on all line & neutral conductors.

Fair enough - that's essentially consistent with my 'spirit of safety' view, then.

Interestingly - when searching using part of that, to find something I could copy & paste, I came across this (with my emphasis)

Yes, very interesting. I confess that I don't recall writing that - but it does indicate that this is not a new discussion!

I'm suggesting that if an E Installation CR has provision to record only one main switch, then maybe BS 7671 regards N CUs with, therefore, N main switches as N installations.

OK, I understand that. However, it's a pretty indirect way of trying to get an indication of what BS7671 regards as "an installation", so I think we have to continue to regard that as speculation.

As far as I am aware, there is no effective way of obtaining meaningful clarification from BSI and/or IET as to how one is meant to interpret BS7671. Maybe stillp can suggest an approach?

Kind Regards, John

 

[stillp]

As far as I am aware, there is no effective way of obtaining meaningful clarification from BSI and/or IET as to how one is meant to interpret BS7671. Maybe stillp can suggest an approach?

You could try using that rare substance, common sense. Why do you think you need clarification? What is/are the problem(s) caused by what you perceive as a need for clarification?

 

[JohnW2]

You could try using that rare substance, common sense. Why do you think you need clarification? What is/are the problem(s) caused by what you perceive as a need for clarification?

Well, I suppose the reality is that I'm not going to do anything about it (and am not particularly concerned about it), even if my suspicions are well-founded, but it would still be nice to know.

On the basis of 'common sense' I have always believed that I have one, 3-phase, "installation", and the majority of those who have so far voted in this Poll seem to agree. If that is the case BS7671's reg 530.3.4 does not apply to my installation. BAS pointed out that, if that is the case, it would seem that I cannot take advantage of the provision to invoke the "conditional short-circuit test" of 61439-3 (Annex ZB) which would allow me to have CUs with devices which, in themselves, have a breaking capacity less than 16kA. In other words, if my installation doesn't satisfy the conditions for 530.3.4 to apply, I am stuck with 432.1 - which would effectively mean that I should have 16kA devices.

In a gesture to 'get me off that hook', BAS expressed the view that I don't actually have 3-phase installation (which is what would 'disqualify' me from 530.3.4) but, rather, that I have three (or more - see **) single-phase installations. I didn't really buy that, but he was so insistent that I started this Poll to canvas opinion, and it seems that most people who have voted agree with me. I see that you have not yet voted - what is your view?

[** BAS not only feels that the three phases represent separate "installations", but also that each of my distributed CU's/DBs (with associated final circuits) constitute separate "installations"]

Kind Regards, John

 

[stillp]

This is the introductory test to the conditional s/c test: "The following test procedure is intended to verify the performance of the incoming device and its connections, and any other item in the CDB not separately rated in excess of 16 kA, when the complete CDB is protected by a fuse-link complying with BS 88.3".
So, if you don't have devices rated to withstand a 16kA fault, you have to hope that your CU manufacturer has performed (and passed!) the test.

I haven't expressed an opinion on the number of installations you have, because I don't feel that it matters. The term is used across a wide variety of documents, and more precision would lead to even more questions as well as circumstances where that new definition was wrong.

 

[JohnW2]

This is the introductory test to the conditional s/c test: "The following test procedure is intended to verify the performance of the incoming device and its connections, and any other item in the CDB not separately rated in excess of 16 kA, when the complete CDB is protected by a fuse-link complying with BS 88.3".

Yes, I understand the nature and purpose of the test.

So, if you don't have devices rated to withstand a 16kA fault, you have to hope that your CU manufacturer has performed (and passed!) the test.

Maybe they have - I don't know. I can't say I recall ever having seen claims about this in device documentation.

Do I take it that compliance with 61439-3 does not require that 'Annex ZB' test to necessarily be undertaken and passed?

However, even if the devices have passed that conditional test, I'm not sure it changes anything I've said ... as I said, if I do have "a 3-phase installation", then 530.3.4 does not apply to my installation, in which case 432.1 would appear to require my devices, themselves, to have a 16kA breaking capacity.

I haven't expressed an opinion on the number of installations you have, because I don't feel that it matters. The term is used across a wide variety of documents, and more precision would lead to even more questions as well as circumstances where that new definition was wrong.

Fair enough. In that case I would suggest that 530.3.4 itself should perhaps be a bit more explicit as to what situation it applies to - since, as currently worded, there is no way one can determine that without a clear understanding of the meaning of an "installation".

Kind Regards, John

 

[ban-all-sheds]

OK, I understand that. However, it's a pretty indirect way of trying to get an indication of what BS7671 regards as "an installation", so I think we have to continue to regard that as speculation.

I disagree that it is indirect - it seems to be a pretty firm indication of what the granularity of "installation" is regarded to be.

If you interpret the regulations in a way which immediately creates the problem that the model forms can no longer be used, then IMO that's a pretty strong hint that your interpretation is flawed.

As far as I am aware, there is no effective way of obtaining meaningful clarification from BSI and/or IET as to how one is meant to interpret BS7671. Maybe stillp can suggest an approach?

I can suggest an approach.

I suggest that one should exercise reasonable skill and care when reading the regulations and do what is to the best ones knowledge and belief in accordance with BS 7671...

If there's potentially more than one "meaning" which can be read, I would always say go with the one which minimises inconsistencies, conflicts and other problems. If "meaning A" creates real issues which simply do not exist with "meaning B" then prefer B over A, particularly when B only gives rise to potential issues only of concern if B is wrong.

 

[JohnW2]

.... If there's potentially more than one "meaning" which can be read, I would always say go with the one which minimises inconsistencies, conflicts and other problems. ...

In such a situation, my inclination would be to go with the one which is most 'conservative' in the situation concerned - i.e. 'err on the side of safety'.

Kind Regards, John

 

[ban-all-sheds]

You could try using that rare substance, common sense.

That might be a plan. But too often people don't apply it. Too often they eschew the principle that if "meaning A" creates real issues which simply do not exist with "meaning B" then B should be preferred over A, particularly when B only gives rise to potential issues only of concern if B is wrong.

 

[ban-all-sheds]

In such a situation, my inclination would be to go with the one which is most 'conservative' in the situation concerned - i.e. 'err on the side of safety'.

Interesting.

I would say that in all cases, an "interpretation" which creates more doubt, more inconsistencies, more broken rules, and more contraventions than another is not conservative, and does not err on the side of safety. BS 7671 is a regulatory/engineering document. It is not erring on the side of safety to deliberately make it unstable.

 

[ban-all-sheds]

In a gesture to 'get me off that hook', BAS expressed the view that I don't actually have 3-phase installation (which is what would 'disqualify' me from 530.3.4) but, rather, that I have three (or more - see **) single-phase installations.

I'm touched.

But I have not done anything in order to get you off any hook. If you are on one, it is a hook entirely of your own making, and one which you willingly climbed onto.