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

[ban-all-sheds]

As I've said elsewhere, the BS7671 definition of "installation" is so vague and all-encompassing as to be totally useless. Anything from a switch+lampholder+bit of cable to a highly complex industrial electrical 'set-up' would satisfy that definition!

Maybe that's the point.

Maybe the perceived "vagueness" is actually the flexibility people need to organise the totality of their electrical stuff into a meaningful and manageable number of "installations"?

You, for example, would have fewer problems (none??) if you had multiple installations instead of one.

"An assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes". So if you have such an assembly to fulfil the specific purpose of providing electrical power to (for the purposes of argument) Ground and First Floors, would that not be an installation?

Imagine your situation writ a bit larger. You have a big detached house, and in the grounds you have a separate workshop, a swimming pool and poolhouse and a bungalow for granny. Somewhere a 3-phase supply enters your demesne and gets split into a single-phase for the house, a single-phase for the workshop, a single-phase for the pool and poolhouse and a single-phase for the granny house.

What characteristics are there of either the phase going to the workshop, or any of the protective devices or final circuits within it, which are co-ordinated with those going to and in the main house to fulfil a specific purpose? You've already agreed that the independence of such separate parts is such that neither is affected by the other, and the presence of the other could not be detected in either, so what kind of co-ordination is going on?

I suppose I would agree that "a block of flats" has one installation - but I'm also inclined to think that each of the flats within the block has its own separate installation.

This is getting surreal.

Either it has one installation or it does not.

Either each flat has its own separate installation or they each have a fragment of one.

 

[ban-all-sheds]

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"

That's not necessarily true, and is not explicit in how I voted.

I don't know how many CUs you have, how each is supplied, and how their final circuits are divided. I voted for "more than 3" for two reasons:

1) I don't think you have only 3 CUs, one on each phase.

2) I do not think that the rule is a 1:1 relationship between a phase and an installation.

 

[JohnW2]

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. ...

I did say "in the situation concerned". In that context, there are two possible regulatory outcomes (dependent upon the applicability of 530.3.4 to my house) as a result of different interpretations of the meaning of "installation". One of the outcomes requires all the devices within my CUs/DBs to have, in their own right, a breaking capacity of 16kA. The other outcome potentially allows me to have devices which, in their own right, have a breaking capacity less than 16kA.

Which of those two outcomes would you say was 'erring on the side of safety'?

Kind Regards, John

 

[ban-all-sheds]

At the moment, how many contraventions of the 16kA requirement do you have?

 

[JohnW2]

Maybe the perceived "vagueness" is actually the flexibility people need to organise the totality of their electrical stuff into a meaningful and manageable number of "installations"?

I think we are moving progressively away from the point. I don't really care, per se, about how BS7671 regards/defines an "installation". All I want is to ascertain whether or not the electrical setup in my house does, or does not, satisfy the requirements for 530.3.4 to apply to it. However, as currently worded one cannot ascertain whether or not it applies to my house, because it uses a word which (in this context) a few people regard as having a different meaning from what most seem to think.

This is getting surreal. Either it has one installation or it does not. Either each flat has its own separate installation or they each have a fragment of one.

I think that most people subscribe to the same 'common sense' view that I do - that the entirety of the electric happenings [meter(s), CUs/DBs & final circuits] relating to one dwelling constitutes that dwelling's (one) 'electrical installation'. On that basis, each flat has it's own (single) installation.

If, for some reason, one also wants to talk about a whole block of flats, then it is IMO again not unreasonable to talk in terms of it having a single 'installation', the installations within individual flats then being sub-installations of the block's installation. There is nothing I can see about the BS7671 definition of an installation which precludes the possibility of having 'installations within installations'.

Kind Regards, John

 

[JohnW2]

I don't know how many CUs you have, how each is supplied, and how their final circuits are divided. I voted for "more than 3" for two reasons: 1) I don't think you have only 3 CUs, one on each phase.

Indeed not, and I gave you the facts recently - 2 CUs on Phase 1, 3 CUs on Phase 2 and 2 CUs on Phase 3 - i.e. 7 in total (ignoring one for genny-only circuits, which has nothing to do with the DNO supply). All of the CUs/DBs are fed from the incoming supply - i.e. no CU is fed from another CU.

Do I take it from this comment that your view is that each CU/DB and associated final circuits constitutes "an installation"?

2) I do not think that the rule is a 1:1 relationship between a phase and an installation.

As you know, nor do I.

Kind Regards, John

 

[JohnW2]

At the moment, how many contraventions of the 16kA requirement do you have?

Are you asking 'how many devices' I have? If so, I'll have to do some serious counting!

Of course, the irony is that, since all my CUs are essentially 'type-tested' ones, all the devices within them will presumably have passed the "conditional short-circuit test" (guaranteeing safe breaking of a 16kA load when there is a BS88-3 ≤100A in series with it).

Kind Regards, John

 

[ban-all-sheds]

I think we are moving progressively away from the point. I don't really care, per se, about how BS7671 regards/defines an "installation".

It is the problem of the definition of "installation" which is at the root of the problem of not knowing how many/what type you have.

All I want is to ascertain whether or not the electrical setup in my house does, or does not, satisfy the requirements for 530.3.4 to apply to it.

Surely that hinges on what the definition of installation is.

However, as currently worded one cannot ascertain whether or not it applies to my house, because it uses a word which (in this context) a few people regard as having a different meaning from what most seem to think.

But you don't really care about what that word means, and therefore don't really care whether or not it applies to your house?

I think that most people subscribe to the same 'common sense' view that I do - that the entirety of the electric happenings [meter(s), CUs/DBs & final circuits] relating to one dwelling constitutes that dwelling's (one) 'electrical installation'. On that basis, each flat has it's own (single) installation.

I cannot see any sense in the notion that social arrangements of ownership and occupation of a building are electrical engineering factors.

For those who do think they are I would point out that there is no difference, electrically, between [one CU and final circuits] in one part of the block and [one CU and final circuits] in one part of your house.

If, for some reason, one also wants to talk about a whole block of flats, then it is IMO again not unreasonable to talk in terms of it having a single 'installation', the installations within individual flats then being sub-installations of the block's installation. There is nothing I can see about the BS7671 definition of an installation which precludes the possibility of having 'installations within installations'.

Can you see anything which precludes the possibility of having installations within one dwelling?

 

[ban-all-sheds]

Indeed not, and I gave you the facts recently - 2 CUs on Phase 1, 3 CUs on Phase 2 and 2 CUs on Phase 3 - i.e. 7 in total (ignoring one for genny-only circuits, which has nothing to do with the DNO supply). All of the CUs/DBs are fed from the incoming supply - i.e. no CU is fed from another CU.

Do I take it from this comment that your view is that each CU/DB and associated final circuits constitutes "an installation"?

I cannot see any way in which that conflicts with the definition of "electrical installation" in the regulations.

 

[ban-all-sheds]

Are you asking 'how many devices' I have? If so, I'll have to do some serious counting!

So in other words, a lot.

I don't see how you are erring on the side of safety by creating lots of contraventions.

 

[JohnW2]

It is the problem of the definition of "installation" which is at the root of the problem of not knowing how many/what type you have.

With 530.3.4 as it is, that is true. The 'root of the problem' could also go away is 530.3.4 itself used wording which made it clear what it applied to, without using words whose meaning (in that context) was not clear. However, my point was that, even with the definition as the root of the problem, discussing whether it is 'deliberately flexible' is not going to help to get an answer.

I cannot see any sense in the notion that social arrangements of ownership and occupation of a building are electrical engineering factors.

I agree that there is no engineering sense in such a notion. However, I strongly suspect that it is roughly how the great majority of people think about it, maybe even the authors of BS7671.

Can you see anything which precludes the possibility of having installations within one dwelling?

As I've said, no I can't (since the definition could mean almost anything) - but that does not necessarily mean that is what is intended.

Kind Regards, John

 

[JohnW2]

I cannot see any way in which that conflicts with the definition of "electrical installation" in the regulations.

As said repeatedly, it doesn't. Nor do any of the other views about how one should count how many "electrical installations" there are in one house. Your view is just your view, and it doesn't seem that many other people think the same way.

Kind Regards, John

 

[JohnW2]

So in other words, a lot.

Indeed so. I've just done a quick mental tot-up, and I think the answer is about 44 (4 main switches, 9 RCDs {in CUs/DBs}, 29 MCBs and 2 RCBOs).

I don't see how you are erring on the side of safety by creating lots of contraventions.

You don't seem to understand what I said. Making a decision as to how to interpret the regs which resulted in lots of contraventions obviously would not constitute 'erring on the side of safety'. However, until you raised it a few days ago, I hadn't even thought of this potential issue, so I never made such an interpretation/decision. You essentially believe that (in relation to the matter we are discussing) I have no contraventions. What I said is that if I were actually making the decision, I ideally would (but probably wouldn't!) 'err on the side of safety' by interpreting the regs not only in a way that seems to have a lot of support but one which resulted in my having to use 'safer' devices.

"I probably wouldn't" primarily because, in electrical terms, IMO there really isn't a significant safety issue (i.e. 'erring on the side of safety' doesn't significantly favour either approach). Whatever we say about the number of "installations" I have, the PFC at any one of the CUs is going to be the same as it would have been if I had a 'simple' (one CU) single-phase installation, and the service fuse is <100A. In other words, there is nothing 'less safe' about my CUs than would be the case if I had a very simple one-CU, single-phase, installation.

As an aside, if I wanted any more 'reassurance', no part of my house is closer than about 40m from the boundary of my 'property'. Even if they built a substation on the verge just outside my property, they would have to use ludicrously fat supply cable to get the PFC at the origin of my installation anywhere near 16kA, even for the 'closest' CU - and, of course, the PFC at most of my CUs will be a lot lower than the figure at the 'origin of the installation'.

It is probably worth remembering that this discussion has only happened because you raised the issue!

Kind Regards, John

 

[ban-all-sheds]

You don't seem to understand what I said. Making a decision as to how to interpret the regs which resulted in lots of contraventions obviously would not constitute 'erring on the side of safety'.

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.

However, until you raised it a few days ago, I hadn't even thought of this potential issue, so I never made such an interpretation/decision. You essentially believe that (in relation to the matter we are discussing) I have no contraventions. What I said is that if I were actually making the decision, I ideally would (but probably wouldn't!) 'err on the side of safety' by interpreting the regs not only in a way that seems to have a lot of support but one which resulted in my having to use 'safer' devices.

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.

"I probably wouldn't" primarily because, in electrical terms, IMO there really isn't a significant safety issue (i.e. 'erring on the side of safety' doesn't significantly favour either approach). Whatever we say about the number of "installations" I have, the PSC at any one of the CUs is going to be the same as it would have been if I had a 'simple' (one CU) single-phase installation, and the service fuse is <100A. In other words, there is nothing 'less safe' about my CUs than would be the case if I had a very simple one-CU, single-phase, installation.

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

It is probably worth remembering that this discussion has only happened because you raised the issue!

Bit of an exaggeration - all I did was say I hoped your devices were 16kA after you declared that you did not have an installation(s) with a single-phase supply.

 

[ban-all-sheds]

That obviously depends upon what one regards as an "installation", and your opinion obviously differs from that of a good few others. When I last looked at my Poll, your view was outnumbered 9-2 (and that's without a vote from myself, so effectively 10-2) - the majority believing that my house has just one "installation".

Kind Regards, John

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