17th stuff, 3rd time lucky

[ban-all-sheds]

IMHO this argument ....

IMO when we started it was a worthwhile discussion.....

Well let's continue/try again, and see if we can progress without snide comments, accusations of lying and misdirection, dismissal of questions as tedious and irrelevant arguments etc.

There seemed to be two strands to the discussion; what is a "17th edition board" and to what extent an existing installation has to be brought up to 17th Edition compliance when working on it.

17th Edition CUs

People are never going to agree on this one, for exactly the same reason that they never agreed on what complied with the 16th. The issue of circuit separation is more acute now given the requirement in practice for almost everything to be on an RCD, but the problem about what complies with 314 is essentially the same.

Every installation shall be divided into circuits as necessary to:

(i) avoid danger and minimize inconvenience in the event of a fault
.
.
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
.
.
.

"Minimize" is an unfortunate word to have used, as it means to reduce to the least possible degree or amount, and the least possible amount of inconvenience in the event of a fault would be a CU with several 10's of RCBOs, with each individual socket, light, FCU and fixed appliance on their own dedicated circuit. And that's never going to happen.

"avoid danger and take account of inconvenience in the event of a fault" would IMO have been much better, for in reality it is the user of the installation who is best placed to judge what inconvenience he is prepared to suffer when circuits are lost because of a fault on a different one.

If you're going to take the literal meaning of "minimize" then not even circuits arranged as per normal with RCBOs for each one complies, so with that meaning you're never going to comply with the 17th.

Once you back off from that position, and inject practical reality into your design I'm not sure that a dual RCD board is necessarily non-compliant, not for a domestic dwelling.


Updating existing installations

There seems to be agreement that the regulations are not retroactive, yet there also seems to be an insufficiently thought-through belief about "taking responsibility" for what's already there, particularly when replacing a CU.

I say "insufficiently thought-through" because ask about EIC'ing an installed circuit and the usual position is "can't do that because I can't see it", so whatever "taking responsibility" means it cannot mean "ensuring that it complies with BS 7671:2008".

Some of the compliance issues can be addressed in some circumstances - when replacing a CU for example it's reasonable to say that you have to put existing circuits on RCDs, but with other work it isn't so reasonable to insist that what's already there has to be changed.

For example, if you were replacing a light or a switch in a bathroom, would you expect to add RCD protection to the circuit?

Unlikely I know, but if the lighting circuit was long and VD was over 3% but < 4%, would you want to rewire it?

If you were changing a fuse or MCB for one of a different rating because the existing one was the wrong size would you expect to add RCD protection?

There are all sorts of other "what ifs" - no point trying to compile an exhaustive list.

I don't believe that 131.8 means that as soon as you've opened your toolbox and isolated a circuit you're not allowed to turn it back on and leave until it complies with BS 7671:2008.


And I would welcome constructive comments and rational, relevant debate on all of this.

 

[oharaf]

I think what BAS is getting at is how comfortable we are with dealing with existing installations and then certification of them.

Let me try this example and see what people think.

I recently went to an elderly gentlemans house he wanted his 'fuse board' looked at.

On arrival, there is the classic wylex on wood with a wylex sub board for 2 30A rings, a shower from henley block to a 30A metal clad MCB.

Now he is 68 in poor health as are many and worried about money.

TBAH the house could do with a complete re-wire - he knows that

Now I can offer him several solutions


1. Leave it alone - mmmmmmmmmmmmmmmmm!!!!!!


2. Install dual RCD and split circuits over

3. Single RCD board all on the RCD?!?!?!?!?

4. Split load single RCD - all sockets and shower on RCD lights on none
RCD.

5. All RCBO's!!!


My feelings

1. Not even an option

2. I would prefer this but the cost element may put him off

3. Can do, but lights out and a dead man possibly

4. I can more than live with this, it is safer than what is there and the
lights would remain on

5. The cost would kill him



I would happily do option 4 for him, yes it would not meet current BS7671, but and this is the moral question and answer for me. By departing from BS7671:2008 is he safer?

Answer yes, is he happier yes, can he afford this? Yes

So what do we all feel???

 

[FingRinal]

"Minimize" is an unfortunate word to have used, as it means to reduce to the least possible degree or amount, and the least possible amount of inconvenience in the event of a fault would be a CU with several 10's of RCBOs, with each individual socket, light, FCU and fixed appliance on their own dedicated circuit. And that's never going to happen.

In my opinion, you're focusing on the wrong word. 'Minimize' is attached to the word 'inconvenience'. It is the word inconvenience that is the main thrust of things. Once we have established what the inconvenience is or could be, we can decide what to do about it. The Regs would like us to 'minimise' it.

So, first of all we need to define what 'inconvenience' is. Inconvenience will change from installation to installation and from use to use.

Inconvenience to me is likely to mean something different to someone else. Also, in 10 years time, inconvenience may mean something different to me. But by then, a PIR will be due and the Inspector should take this into consideration.

For example, if you were replacing a light or a switch in a bathroom, would you expect to add RCD protection to the circuit?

Not at all. Assuming the replacement is of the original specification, the replacement can't be considered to be an addition or an alteration.

If you were changing a fuse or MCB for one of a different rating because the existing one was the wrong size would you expect to add RCD protection?

This would depend on the type of circuit, its use and other factors.

I don't believe that 131.8 means that as soon as you've opened your toolbox and isolated a circuit you're not allowed to turn it back on and leave until it complies with BS 7671:2008.

It doesn't state that at all. It refers to making additions and alterations and not to switching an mcb on or off (which you might do if you went away on holiday for example).

yet there also seems to be an insufficiently thought-through belief about "taking responsibility" for what's already there, particularly when replacing a CU.

Insufficiently thought-through by whom? It's insufficiently through-through if someone thinks responsibility can be ignored for reasons of convenience. If someone hasn't inspected 1st fix (i.e most of Cables and Conductors), it hasn't been signed for and it hasn't been done. I suppose the solution would be to amend the standard forms of BS7671 to include extras that the constructor could sign for as Inspector - assuming he is competent to do so.

 

[mobileman]

Option 4 but with lights on RCBO?

Only adds thirty quid to option 4.

 

[oharaf]

I know what you're saying, but £30 is still a lot to a pensioner!!

I am going to speak to help the aged I think they have some sort of assistance grant for the 'unvalued' members of our society.

If it comes to it i may just stand some of the cost myself!!

I think I'm to soft hearted at times

 

[FingRinal]

I would happily do option 4 for him, yes it would not meet current BS7671, but and this is the moral question and answer for me. By departing from BS7671:2008 is he safer?

Answer yes, is he happier yes, can he afford this? Yes

So what do we all feel???

You have changed the protective device on very circuit and have failed to change the protection to one which complies with the current edition of BS767. Therefore you cannot certify that the work you have done complies with the 17th Edition. And you have taken payment for a professional service and notified it for compliance with the Building Regulations.

Perhaps the only time you could do this is as a straight like for like swap as an emergency replacement.

 

[holmslaw]

..

 

[holmslaw]

..

 

[FingRinal]

An "alteration" is a substantial change ie a new cu or new circuit, what you are doing that must comply with the 17th. Nothing else has to comply with the 17th, except for main bonding.

Why stop there? What about tails or earthing conductor?

A PIR is carried out on what you can see, so you would list all actual and suspected 17th non-compliances. If everything else is ok and passes a test, then installation is acceptable and you have done all that could be reasonably expected.

How unreasonable is it to implement a significant safety change of the 17th by installing RCD protection?
To follow this to it's extreme, if a house was wired in 1946, then it would be OK to 'replace' the old installation with an exact replica of the original installation and simply note it as a departure.

 

[Pensdown]

From my POV is not all about reg numbers, it more about the basic principles of circuit design. Each circuit should have its own protective device and the down stream device should discriminate with the up stream device.

The circuits should be arrange to minimise inconvenience in the event of a fault, make inspection and maintenance straight forward and take into account any dangers that may arise from the failure of one circuit.

In general, when referring to over current protection, most domestic installations have evolved to meet these basic principles. We now have independent lighting circuits for up & down. Independent ring circuits for up and down and in some case another for the Kitchen. We have separate circuits for the boiler, outside lights, alarm, the list goes on.

However, if we applied diversity to the average domestic installation, in most cases we could go back to a single lighting circuit and in some cases a single ring circuit with spurs for the heating, alarm etc. But we don’t because we have learnt that multiple circuits are much better than single circuits. They reduce the inconvenience in the event of a fault. They reduce the dangers that may arise from the failure of one circuit and multiple circuits make inspection and maintenance possible.

But it seems all the benefits of independent circuits are now being ignored just because some circuits also require additional protection.

If the trade is going to follow the CU examples in the OSG we may as well go back to fewer circuits because the benefits of multiple circuits now only applies to over current protection. We can no longer work on a grouped RCD circuit without tripping the others and one earth fault will take out multiple circuits. We’ve gone backwards.

As for the cost of RCBO’s, I can remember when MCB’s were first introduced. We all thought because they were so expensive they would never be for the mass market. But when the customer had the options in front of them, most went for the more expensive CU’s with MCB’s rather than the much cheaper CU’s with re-wirable fuses. And the customers that chose the re-wirable CU’s went out and brought plug-in MCB’s to replace the fuses.

As said above, a lot comes down to customer choice and IMO at that moment they aren’t getting that choice. "Here is a 17th board, that's the way all it's always been done"

And if anyone is still on a TT supply I would suggest they get converted to TNC-S before trying to conform to the 17th.

As for alterations and additions I generally agree with what holmslaw has said so far...so that may change....

Edit....Thanks to FR my post is now in the correct decade

 

[ban-all-sheds]

In my opinion, you're focusing on the wrong word. 'Minimize' is attached to the word 'inconvenience'. It is the word inconvenience that is the main thrust of things. Once we have established what the inconvenience is or could be, we can decide what to do about it. The Regs would like us to 'minimise' it.

So, first of all we need to define what 'inconvenience' is. Inconvenience will change from installation to installation and from use to use.

Inconvenience to me is likely to mean something different to someone else.

Which is basically what I said when I talked about the user being the one who should decide what inconvenience is acceptable, but I appreciate the problems of having an informed discussion.

But if the idea is to "avoid danger and reduce inconvenience to a level acceptable to the user in the event of a fault", then if the user is happy with a dual RCD board it complies.

Not at all. Assuming the replacement is of the original specification, the replacement can't be considered to be an addition or an alteration.

What about adding lights to the circuit?

This would depend on the type of circuit, its use and other factors.

It's a circuit with cables concealed in walls or partitions at a depth of less than 50mm in an installation not under the supervision of a skilled or instructed person.

It doesn't state that at all. It refers to making additions and alterations and not to switching an mcb on or off (which you might do if you went away on holiday for example).

Was I wrong to assume that in the context of this topic people would take "opening your toolbox and isolating a circuit" to mean that they were doing some kind of work on it, not going on holiday?

yet there also seems to be an insufficiently thought-through belief about "taking responsibility" for what's already there, particularly when replacing a CU.

Insufficiently thought-through by whom? It's insufficiently through-through if someone thinks responsibility can be ignored for reasons of convenience. If someone hasn't inspected 1st fix (i.e most of Cables and Conductors), it hasn't been signed for and it hasn't been done.

That's nothing to do with a CU replacement.

 

[FingRinal]

But it seems all the benefits of independent circuits are now being ignored just because some circuits also require earth leakage protection.

I agree with all your points, but I think you've inadvertently slipped here. It's impact protection that is causing this gnashing of teeth with the 17th. Leakage is the main concern for bathrooms.

And if anyone is still on a TT supply I would suggest they get converted to TNC-S before trying to conform to the 17th.

There has never been a guarantee of discrimmination with Type S RCDs for all faults (i.e. high leakage in bathroom). But there are no guarantees with anything. With increased risk, there is a pay-back, with TT it is with loss of inconvenience - which still complies with the 17th's requirements to only minimize the inconvenience.

 

[FingRinal]

In my opinion, you're focusing on the wrong word. 'Minimize' is attached to the word 'inconvenience'. It is the word inconvenience that is the main thrust of things. Once we have established what the inconvenience is or could be, we can decide what to do about it. The Regs would like us to 'minimise' it.

So, first of all we need to define what 'inconvenience' is. Inconvenience will change from installation to installation and from use to use.

Inconvenience to me is likely to mean something different to someone else.

Which is basically what I said when I talked about the user being the one who should decide what inconvenience is acceptable

Then we agree.

But if the idea is to "avoid danger and reduce inconvenience to a level acceptable to the user in the event of a fault", then if the user is happy with a dual RCD board it complies.

The Designer takes on an assumed responsibility to minimize to a reasonable level. He is the comptent person and can't ignore it altogether so a reasonable distribution of circuits in a dual RCD boards should suffice in many situations.

Not at all. Assuming the replacement is of the original specification, the replacement can't be considered to be an addition or an alteration.

What about adding lights to the circuit?

Then your addition must comply with the current edition of the Regs.

This would depend on the type of circuit, its use and other factors.

It's a circuit with cables concealed in walls or partitions at a depth of less than 50mm in an installation not under the supervision of a skilled or instructed person.

See above.

It doesn't state that at all. It refers to making additions and alterations and not to switching an mcb on or off (which you might do if you went away on holiday for example).

Was I wrong to assume that in the context of this topic people would take "opening your toolbox and isolating a circuit" to mean that they were doing some kind of work on it, not going on holiday?

Then assume you were wrong

yet there also seems to be an insufficiently thought-through belief about "taking responsibility" for what's already there, particularly when replacing a CU.

Insufficiently thought-through by whom? It's insufficiently thought-through if someone thinks responsibility can be ignored for reasons of convenience. If someone hasn't inspected 1st fix (i.e most of Cables and Conductors), it hasn't been signed for and it hasn't been done.

That's nothing to do with a CU replacement.

You've made an alteration to every circuit. It has everything to do with a CU change. The paid job you have taken on is to change the protection of the entire installation, so what excuse can there be for changing the protection to not comply with the 17th?

 

[ericmark]

Thank you Ban-all-sheds you have put a lot of thought into what you have said and in the main agree with you.
Oharaf has made a very good point and to follow regulations could put the client at more risk.
Holmslaw comment or repair and up-grade is getting close to what I think.
Pensdown also had some good points.
And I do not disagree with anything strongly but where I see a problem is not the planned up-grade or even repair but where some one in the past has got it wrong.
I will give an example.
Borrowed Lines: I will not call it borrowed neutrals although it ends up the same but we have all seen where two way switching has been used and instead of using triple and earth between both switches twin and earth has been used and the live is taken from another switch in a multi gang switch. This means the Line can come from two sources and on a stairs it is likely a different MCB.
In theory we should have done a PIR first in practice we are unlikely to have found this until after a board change.
Our options are:-
1) Run another cable between the two switches.
2) Connect to lights to a non RCD supply.
3) Connect both lighting circuits to the same MCB.
In most cases we would pick the latter. And does not really matter if anything is put down on paper why but we have done a risk assessment and balanced this against cost. That’s why we are tradesmen we use the regulations as a guide not a fixed set of rules. Each case should be considered in isolation and just because you did it that way last time does not mean you should always do it that way.
The problem arises when one is asked the question as a remote observer and you can’t see it’s wired surface in trunking and it is very easy to renew the twin and earth for triple and earth.
It is very easy on here to quote the regulation that says you can’t do that and I have done just that. And instead of giving sensible answers going completely by the book. And it only takes one complaint where someone says my son was injured following your advise and we all and I am guilty become over careful in what we say.
We are tradesmen and have to act like tradesmen and make that executive decision. Although would I enter it on a installation certificate likely to be scrutinised by a jobs worth?
And if you say you always follow the rules you’re a liar. And if you say you don’t you’re a fool! We may admit it in the Pub over a drink but never on a forum like this.
Eric

 

[FingRinal]

3) Connect both lighting circuits to the same MCB.

I think you mean RCD, not mcb. Unless the customer is willing to pay for more, this is going to be the only option. And I think it looks like becoming the norm.