17th stuff, 3rd time lucky

[Pensdown]

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.

I don't really want to get into a conversation about the definition of the word inconvenience because IMO in the context of 314 it’s meaningless.

If for example a N-E fault developed on one circuit which tripped the 100mA RCD at 08:00 on a weekday and it took until 18:00 to get someone out to fault find and fix, IMO that’s inconvenient.

However, if the same fault developed at the same time and took the same amount of time to fix but only this time it happened on Christmas Day, for the occupants it’s a disaster.

 

[NotHimAgain]

BAS has separated this discussion into two main areas.

The first he calls '17th Edition CUs' and the second 'Updating existing installations'

I just want to look at the first of these for the moment.

Why is it called '17th Edition CUs' when all of the discussion seems to hinge around section 314 of BS 7671, which is concerned with division of the installation. Note that it just says installation - meaning any type and size - not just domestic. I am not just being pedantic here - it is an important point.

The discussion also seems to focus on the provision of RCD protection within these 'CUs' - people really must stop calling them Consumer Units - the French think we eat them if we call them that - the term used by the UK in Annex ZA of BS 60439-3 in 1994 was Customer Distribution Board (CDB) .

It would appear then that we are only considering the application of 314 to a limited sub-set of electrical installations when, in fact, it applies to all electrical installations.

No doubt someone will correct me if I am wrong - but the argument appears to be that a single protective device - an RCD in this limited appraisal - must not protect more than one circuit. Further to this, some appear to be suggesting that this is a 17th Edition thing.

Well let's take the last point first - the 'minimise inconvenience' term first came in with the 15th Edition - it was taken out in the Brown copy and it stayed out of the 16th Edition until the Green copy, when it suddenly came back.

Note that the Irish had the term in their 1991 Rules - so it is probably IEC or CENELEC drafting.

BTW the Irish had the equivalent of 314.1 (iii) "take account of danger that may arise from the failure of a single circuit such as a lighting circuit" in 1991 - we are just a bit slow .

Now for those that decide that this, admittedly poorly drafted, regulation should be taken to mean that we cannot use a split bar CDB, and that we must use RCBOs, or should I say those horrible, usually single pole, electronically operated (so they need volts to work!), excuses for circuit protect - not that I am biased mind - then how do you solve this -

A distribution board supplied by a distribution circuit (sub-main in old money) is protected at the main panel by a single overcurrent device, or maybe, in a large T.T installation, a single S Type or fully adjustable RCD . If it operates all of the circuits on the distribution board lose power.

Just think on this a minute - imagine yourself in a very large installation - if you cannot use a single device to protect your distribution circuit you cannot use a distributed system. That OK just wire all of the final circuits back to the main panel - job done (we will forget about the possibility of the main fuse blowing ).

Now what size cable to use - what is the voltage drop on a mile long final circuit .

I think we have a problem here and any solution must work for ALL electrical installations.

 

[ban-all-sheds]

What about adding lights to the circuit?

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

This is like pulling teeth isn't it.

If you were adding lights to an existing bathroom circuit, do you think that you would have to add RCD protection to that circuit?

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.

See above.

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

Then assume you were wrong

OK - so in a topic concerned with what people felt should be done in various scenarios of electrical installation work, I wrote the phrase "as soon as you've opened your toolbox and isolated a circuit" and you thought I was talking about someone turning off an MCB before going on holiday.

Fair enough

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?

That was never my suggestion. My observation was that your comment, "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." was irrelevant to the issues surrounding replacing a CU.

 

[FingRinal]

17th Ed. Consumer Units isn't really about 314. 314 was there before. It's about the increased use of 30mA RCDs - bathrooms, all sockets, buried cables. These can all be sorted with a single 30mA RCD at the origin. It's 314 that then puts the damper on this. The 'inconvenience' is decided on a case by case basis - with the majority of cases falling into the category of splitting circuits across two RCDs.

Manufacturers spotted this and have simply produced an option which will be reasonably cost effective to the client in the majority of cases.

The other part of the argument is what to do with a CU change under the 17th? Rather than make an argument for putting all circuits on a 30mA RCD (by whichever means), perhaps it could be considered from the position of - 'something happened which wouldn't have happend if all circuits were protected by a 30mA RCD (by whichever means) when we paid for a new CU?'

 

[ban-all-sheds]

If you're replacing a CU, I think on balance that you should use RCD devices to comply with the protection rules of the 17th, although I can see some validity in the argument that as you aren't installing the existing circuits you don't have to, but that hinges on whether you think "circuit" includes the OPD or not.

But it can raise ethical and moral dilemmas, as in oharaf's example - to what extent should you refuse to improve safety, or reduce inconvenience if you are not permitted to do the remedial work you think you should, given that it comes down to your interpretation of what the non-explicit regulations require?

If at the other end of the spectrum from replacing a CU is replacing a single accessory for cosmetic reasons, then at that extreme I think it's ludicrous to say that doing it brings with it a need to leave the circuit compliant with the 17th.

And somewhere between those bounds lies the point where you do have to update what's there....

 

[FingRinal]

I can't quite see why anyone would change a CU for cosmetic reasons, but if they did, it comes back to the same thing and the same process of inspection and testing, design and construction in accordance with the current edition of the Regs.

The Regs make no allowance for cosmetic or lifestyle reasons and it's unlikely that stating such things under departures would be accepted.

 

[ban-all-sheds]

Who said anything about changing a CU for cosmetic reasons?

 

[FingRinal]

Who said anything about changing a CU for cosmetic reasons?

Obviously my mistake, but your sentence reads like a dog's dinner which is unusual for you.

 

[holmslaw]

..

 

[FingRinal]

No, what you posted (and in general context) - hence the quote.

 

[securespark]

If at the other end of the spectrum from replacing a CU is replacing a single accessory for cosmetic reasons, then at that extreme I think it's ludicrous to say that doing it brings with it a need to leave the circuit compliant with the 17th.

 

[ericmark]

To fingRinal it is immaterial if it is an MCB which is in turn feed from an RCD or to RCBO’s to cure the problem one way would be to combine both circuits and yes I also think in the main will be the norm in my house all lights from day one have always been on one circuit and to prevent danger should the MCB or RCD trip the stairs/landing and garage both have battery backed lights.
To ban-all-sheds “If you were adding lights to an existing bathroom circuit, do you think that you would have to add RCD protection to that circuit?” yes as it is an addition if the customer does not want the expense he/she has no need to add to the circuit. If however I was replacing a faulty existing lamp then no.
I do see a problem if a new lamp wired in Ali-tube cable is added to a circuit which has some areas where the cable is buried to less than 50mm then since the new bit conforms no you don’t need to add RCD protection.
“If you were changing a fuse or MCB for one of a different rating because the existing one was the wrong size” if you can’t use a RCBO and the MCB was wrong size due to something that happened in the past than changing the MCB for another MCB of different rating is OK. However if the board would take a RCBO or the reason why the MCB required changing was due to some upgrade you had just completed i.e. change of shower size then one does need to upgrade to take a RCD. If good cause can be given i.e. 7kW showers no longer produced then I would say it was OK just to fit a replacement MCB.
“Quote: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?”
I can’t see how this holds true remember we are not just talking about domestic and if I changed a distribution board I would only be concerned with cables directly leaving that board if one of those cables in turn feed another DB then I would not be concerned with the second DB. Returning to domestic a radial wired surface to first socket I would check the first socket before and after and if that’s OK that’s as far as I would go. If the customer wants a PIR he can pay for one it don’t come free with a Consumer unit change. We are permitted to stipulate limitation of work and that is what I would do.
Using a single RCD to protect all is not automatically against the 17th Edition only if it is likely to trip would it be against the 17th Edition and with caravans one is forced to use two RCD in series not parallel one outside caravan and one inside so where a customer is unwilling to pay for multi RCD protection then I see using a single RCD as only option left.
Again there comes a point where one has to use some common sense. If one reads “Best Practice Guide 1” from “The Electrical Safety Council” on lack of earths on lights it goes through a procedure of first trying to persuade the owner to do best option and if this fails it goes through other options one at a time and only if the owner insists on using Class I items does one refuse and walk away. And I think the same applies to every other job we do. First try for best and only if your actions would make the installation more dangerous than existing do you need to walk away from the job.
Eric

 

[ban-all-sheds]

To ban-all-sheds “If you were adding lights to an existing bathroom circuit, do you think that you would have to add RCD protection to that circuit?” yes as it is an addition if the customer does not want the expense he/she has no need to add to the circuit. If however I was replacing a faulty existing lamp then no.

I do see a problem if a new lamp wired in Ali-tube cable is added to a circuit which has some areas where the cable is buried to less than 50mm then since the new bit conforms no you don’t need to add RCD protection.

Those two statements contradict each other.

In the first one you say that adding lights triggers the requirement to update the whole circuit to the 17th standard, and in the second you say that if you add new fixed wiring and the new section complies (which it wouldn't in a bathroom) then you don't have to update the whole circuit.

Anyway - good luck persuading your customers that in order for you to install a couple of downlighters in their bathroom you've got to change some or all of the CU, or add a standalone RCD...

“If you were changing a fuse or MCB for one of a different rating because the existing one was the wrong size” if you can’t use a RCBO and the MCB was wrong size due to something that happened in the past than changing the MCB for another MCB of different rating is OK. However if the board would take a RCBO or the reason why the MCB required changing was due to some upgrade you had just completed i.e. change of shower size then one does need to upgrade to take a RCD. If good cause can be given i.e. 7kW showers no longer produced then I would say it was OK just to fit a replacement MCB.

Again that last statement seems to contradict the earlier ones. Ignoring for now the possibility that the manufacturer's instructions may call for one anyway, are you saying that if a customer chooses a more powerful shower because he wants to then the requirement to add an RCD is there. but if chooses one because he has to then he doesn't have to have an RCD?

Or have I misunderstood?

If one reads “Best Practice Guide 1” from “The Electrical Safety Council” on lack of earths on lights

As is often said, NICEIC don't write the regulations....

 

[FingRinal]

NICEIC technical documents are of a high standard though...but I can't quite understand the approach of their charitable arm - the ESC.

Slight body-swerve into PIRs, but still perhaps relevant to this thread:

Are they assuming that most electricians are a bit dim and can't be trusted with PIRs? Are they assuming that other electricians (in other 'clubs') are as dim as their own members?

All I can think of is a large industrial complex fed by a single supply. There could be a dozen Code 1 defects, but should that warrant an Unsatisfactory? What is the implication of an Unsatisfactory for the industrial complex?

As far as I am concerned, the ESC is geared towards domestic only and their advice should taken within the domestic context only.

 

[FingRinal]

Anyway - good luck persuading your customers that in order for you to install a couple of downlighters in their bathroom you've got to change some or all of the CU, or add a standalone RCD...

I agree with what you are saying... not least because of the potential loss of business for pedantic reasons. But a bathroom is a Special Location (and notifiable) and an electrician has to take special care. What about supp.bonding if none exists?

I know you feel it's nothing to do with them, but NAPIT, Elecsa, NICEIC etc. will have advice for their members and which they might inspect at the next assessment.

At the end of the day, electricians may have to defer to their 'clubs' whether they like it or not - simply for the reason of protecting their own liability and speeding up their decision making.