SWA earthing

[JohnW2]

EDIT: As I think I've said before, when we leave our installations to someone else, for whatever reason, we leave them to the uninformed in most cases, except the B[coloured]B they have in their hands, leading to 'discussions' or possibly even 'rectification' either for us or someone else in the future. Following best practise as published in that BCB isn't likely, in most cases, to end up in long drawn-out discussions, nor cost a great deal more.

You slipped this in after I replied! In many contexts, I'd be inclined to agree with you, but in this particular case I personally think you are over-interpreting the regulation - by taking what it says about one way of satisfying the regulation to mean that it is the only way of satisfying it.

In my house, there are a good few issues which probably come into the category you mention above, and I've done all I can to avoid the need for any 'discussions' or 'rectifications' by a subsequent owner by documenting the basis on which I believe the installation, as it is, is compliant.

Kind Regards, John

 

[EFLImpudence]

I would agree that 'deemed to satisfy' means, in effect, worst case scenario when, if followed, means that all cases will be compliant.

An example of this is the fitting of 16mm² (domestic) earthing conductors.
This will mean all conditions are satisfied and you don't have to know anything or do any sums when, in fact, 6mm² may be adequate and as such would not be a departure.

 

[JohnW2]

I would agree that 'deemed to satisfy' means, in effect, worst case scenario when, if followed, means that all cases will be compliant. An example of this is the fitting of 16mm² (domestic) earthing conductors. This will mean all conditions are satisfied and you don't have to know anything or do any sums when, in fact, 6mm² may be adequate and as such would not be a departure.

Exactly, as I've said, that has always been my understanding. People who are able, and can be bothered, to undertake proper design calculations (whether in terms of electrical installations, building structure, insulation or whatever) will very often end up with less 'burdensome' answers than they would be stuck with if they took the ('lazy') 'deemed to satisfy' route.

In fact, it produces a few 'anomolies', including in the present context. As you say, the regs can be taken mean that the 3% and 5% VD figures will result in compliance in all cases. However, what then is the position if one has a piece of equipment for which it can be shown that 'safe functioning' is impaired at VDs less than those 'permitted' by the 'deemed-to-satisfy' provision (hence seemingly in violation of 525.100 itself)?

Kind Regards, John

 

[EFLImpudence]

Would that come under manufacturer's instructions requiring additional consideration on already compliant circuits?

 

[JohnW2]

Would that come under manufacturer's instructions requiring additional consideration on already compliant circuits?

Yes, that's quite possible, but I suppose it may not actually be in the MI. It could just be that you 'knew' (by whatever process) that the 'safe functioning' of the equipment in question was 'impaired' by VDs which would satisfy the regs' 'deemed-to-satisfy' guideline.

Of course, this is is all a bit iffy given the permitted variation in supply voltage. In specifying, say, the 3% permitted VD for lighting (I presume that means 3% of nominal, i.e. 6.9V), are they accepting that lighting loads will be OK down to 209.3V (230V - 6% - 6.9V), or what? ... and then what if I 'know' that my supply voltage virtually never falls below 240V - that would allow me a 30.7V VD (13.3% of 230V) before my light got less than 209.3V!

Kind Regards, John

 

[mfarrow]

you are over-interpreting the regulation - by taking what it says about one way of satisfying the regulation to mean that it is the only way of satisfying it.

Now that I'm back at a PC, I just spotted my typo. I meant to say 525.101 is the one you're still departing from . That might meant more sense now.

I'm glad you've the paperwork, but unless you write it in triplicate and put it in/on/under the CU, as with a lot of household paperwork, it will be lost between owners.

 

[JohnW2]

you are over-interpreting the regulation - by taking what it says about one way of satisfying the regulation to mean that it is the only way of satisfying it.

Now that I'm back at a PC, I just spotted my typo. I meant to say 525.101 is the one you're still departing from . That might meant more sense now.

'Fraid not 525.101 is simply the reg which says that one way of satisfying 525.1 (which is rarely going to apply) and 525.100 is to use the guidance figures in 6.4 of informative Appendix 4. ... still doesn't mean that there are not other ways of satisfying 525.1/525.100!

I'm glad you've the paperwork, but unless you write it in triplicate and put it in/on/under the CU, as with a lot of household paperwork, it will be lost between owners.

It's part of a massive 'house manual' that, in it's hardcopy form (and probably also its electronic form), will certainly move between owners, and is sufficiently physically large that it won't get lost. It also exists electronically, including multiple backups, some off-site.

Kind Regards, John

 

[mfarrow]

525.101 is the one you're still departing from.

'Fraid not

So how are you not departing from 525.101 by not following it?

It's part of a massive 'house manual' that, in it's hardcopy form (and probably also its electronic form), will certainly move between owners.

And be shown by those future owners to every electrician who calls, I bet

 

[JohnW2]

525.101 is the one you're still departing from.

'Fraid not

So how are you not departing from 525.101 by not following it?

Not following what? 525.101 is not a 'requirement' which can be 'followed'. It is simply a statement that the requirements of 525.1 and 525.100 are deemed to be satisfied if one remains within the VDs specified in 6.4 of Appendix 4. Try as you may, you will not convince me that by indicating one approach which is deemed to satisfy those requirements, 525.101 is saying that no other way of satisfying those requirements is acceptable.

You seem to have a completely AAF view of 'deemd-to-satisfy' provisions as compared with mine. I was brought up with the view that 'professional design processes and calculations' were the 'proper' way to go, and that 'deemed-to-satisfy' provisions were there for the 'convenience' of those who couldn't be bothered (or did not have the ability) to undertake proper design themselves, and who were prepared to accept that the 'deemed-to-satisfy' approach often resulted in an unnecessarily burdensome design (i.e. 'over-design').

It's part of a massive 'house manual' that, in it's hardcopy form (and probably also its electronic form), will certainly move between owners.

And be shown by those future owners to every electrician who calls, I bet

That's entirely up to any future owner. I will provide him/her with a potential means of avoiding (or, at least, reducing) 'discussion and maybe rectification' in relation to things that may not be obvious to electricians (or other tradesmen) in the future. If the owner chooses not to avail themselves of that, then "that would be their problem"!

Kind Regards, John

 

[mfarrow]

525.101 is not a 'requirement' which can be 'followed'.

No, but it's still a regulation, on its own, with a proper number, not a note/NB/by the way/etc. Therefore if you're not following it, you're departing on it, and that needs to go on the EIC.

you will not convince me that by indicating one approach which is deemed to satisfy those requirements, 525.101 is saying that no other way of satisfying those requirements is acceptable.

You're missing the point, so I'll clarify. I'm talking about departures from numbered regulations. We agreed to disagree on following best practice and possible subsequent raised eyebrows in the future and sure, if the equipment will work down to 120V (a lot can these days) then I'm not saying you can't do that if you feel you will are justified in doing so. If I was installing from scratch, as in RFs case, then I wouldn't be, but that isn't to say I might not come across an instance where it would be prudent to do so, and in that case I'd write the departure down.

Indeed, I "saved" the renewal of a distribution circuit last year because the supply, from a private origin, had a nominal voltage of 240V, not 230V as was originally assumed in the calculations that made it fail the minimum voltage. Was the percentage loss on 240V still a departure from 525.101? Possibly, and if I thought it was then I'd be quite happily to have it put it on the EIC as such and put my name to it if necessary.

 

[JohnW2]

525.101 is not a 'requirement' which can be 'followed'.

No, but it's still a regulation, on its own, with a proper number, not a note/NB/by the way/etc. Therefore if you're not following it, you're departing on it, and that needs to go on the EIC.

Sorry, but I just don't understand you reasoning. I don't understand what you mean by 'following' (or 'not following') 525.101, since it is merely telling you one approach which is regarded as satisfying 525.1 and 525.100.

You're missing the point, so I'll clarify. I'm talking about departures from numbered regulations.

I realise that, and if its a regulation which 'instructs' one to do something, then failing to comply with that 'instruction' is clearly a departure. If it's merely a statement about one way of complying with some other regulations, then I can see no way that one can 'depart' from it - since it's 'information', not an 'instruction'.

We agreed to disagree on following best practice and possible subsequent raised eyebrows in the future and sure, if the equipment will work down to 120V (a lot can these days) then I'm not saying you can't do that if you feel you will are justified in doing so. If I was installing from scratch, as in RFs case, then I wouldn't be, but that isn't to say I might not come across an instance where it would be prudent to do so, and in that case I'd write the departure down.

The reality obviously is that except for (known) lighting loads and other (known) 'fixed' loads, one is essentially stuck with the Appendix 4 VD limits. In particular, one has no other choice with sockets circuits, since one hasn't a clue what equipment/appliances might be plugged in, and what voltage requirements/sensitivities they might have. Indeed, the equipment might be so sensitive to under-voltage that sticking within Appendix 4 VD limits might not be enough to ensure its 'safe functioning' - but that's a separate can of worms (since one would then have a situation which, per your thinking, 'complied' with 525.101, but not with 525.100)!

We obviously know nothing about the nature of the loads in RF's case, so can't comment on that. However, to take a common example, I suspect that you would struggle to find any sensible reason for saying that the 'safe functioning' of a 'simple shower' (no electronics) would be in any way 'impaired' by the voltage supplying it being low, even 'very low'. In other words, I think one could say that a dedicated shower circuit supplying a such a shower (no electronics) complied with 525.100 with almost any degree of VD, certainly a VD which was only moderately above 5%. The same with fixed wired immersions or heaters (without fans) etc. on dedicated circuits. Do you disagree?

Kind Regards, John

 

[EFLImpudence]

If I may -

Section 525 in 525.1 begins with "In the absence of any other consideration, ...".

Therefore "In the presence of other considerations" the subsequent wording in 100,101,&102 is surely nullified and we can do whatever is necessary.

 

[JohnW2]

If I may - Section 525 in 525.1 begins with "In the absence of any other consideration, ...". Therefore "In the presence of other considerations" the subsequent wording in 100,101,&102 is surely nullified and we can do whatever is necessary.

Thanks. That's all true, but I don't know it's really necessary. As far as I am concerned, if one can satisfactorily argue that 525.100 is satisfied (which I believe one can, in the case of loads such as, say, showers, or even many types of lighting), then that's all one needs - and the fact that 525.100 refers to another possibly way (using Appendix 4) of achieving compliance is neither here nor there! However, I suspect that mfarrow will never come around to that way of thinking!

Kind Regards, John

 

[mfarrow]

John

On reflection, I'm probably doing to concede that you may be right. I'm reading the "Any intended departure from these parts... shall be noted on the Electrical Installation Certificate" on page 16, and realising that if I pursue this then it opens a potential can of worms in other part of the book.

I still don't like the wording "deemed to be satified" and its sole context within a Regulation.

You're shower example I would agree with on safety prinicples but I would not install it like that. If I buy a 10kW shower, I want a 10kW shower, not a (for example) 9kW shower.

 

[JohnW2]

John, On reflection, I'm probably doing to concede that you may be right. I'm reading the "Any intended departure from these parts... shall be noted on the Electrical Installation Certificate" on page 16, and realising that if I pursue this then it opens a potential can of worms in other part of the book.

Indeed. Needless to say, I pleased that you now at least understand my view.

I still don't like the wording "deemed to be satified" and its sole context within a Regulation.

It's a concept that has exisisted in the Building Regs (and many other types of regulations) since I first came across them 40 or so years ago. The 'proper' approach has always been to undertake 'proper engineering design calculations' - but for those who don't have the ability, or inclination, 'deemed-to-satisfy' provisions were included as a 'lazy' option. That's true whether one is talking about VD for 'safe functioning' of a load or the required size of a joist to cover a certain span with a given loading. In both cases, the price for using the 'deemed-to-satisfy' approach will often be an unnecessarily 'burdensome' answer - i.e. a larger cable or joist than would be needed if one did the proper design calculations.

You're shower example I would agree with on safety prinicples but I would not install it like that. If I buy a 10kW shower, I want a 10kW shower, not a (for example) 9kW shower.

I suppose I wouldn't usually deliberately design a new circuit like that, either. However, if I wanted to increase the size of my shower, and the existing cable was adequate for the current (but routed such that it would be very difficult to replace with a larger cable), I don't think I would worry about the VD being a little more than 5%, safe in the knowledge that I was confident that I could argue that the VD (whatever it was) was compliant with 525.100. ... and nor am I concerned by the knowledge that if I ever 'fully loaded' the power circuits in my outhouses, the VD seen by the lighting in them might temporarily rise to a little above 3%!

I think there is a lot of scope for the application of 'common sense' here.

Kind Regards, John