Amd3 Transitional Period

[EFLImpudence]

Yes, I know that but the OSG ( blanket x 0.8 ) and a lot of people carrying out EICRs will take the figures as gospel.

I refer the honourable gentleman to his original question:

but what about EICRs during that period - would one mention (or even code) things which were currently compliant but which would not be compliant with Amd3?

I am just trying to say that it may still be compliant if the trouble is taken to think about it.

 

[ericmark]

To have another means to ensure disconnection is very different to having another means to ensure disconnection within a time limit.

So the question is if 12 seconds is too long? So for say a B20 supplying a 2.5mm² cable over 100A the magnet will work so looking at less than 100A for 12 seconds will this cause a danger? If so then clearly the whole idea of a MCB is flawed as one may not have a direct short and it is considered that the thermal part of the MCB will trip before damage to cable so all you are worried about is the danger of 12 seconds rather than the 2 seconds it would take a fuse to disconnect with same load and rating.

Without RCD protection yes I see there is a problem. With RCD protection I can't see any problem so where protected by RCD I would not worry if the loop impedance is exceeded which is required to trip the magnetic part of a MCB.

I would agree in real terms you could fail it on volt drop but I don't see volt drop as a danger.

 

[PrenticeBoyofDerry]

I don't think you should hold your breath too much in waiting for the price to become sensible, at least from mainline suppliers. Two years down the road, Amazon are currently still selling the BGB (Amd1) for £60.45, as compared with £76.50 for BYB.

I recall when the BGB first came out, it was selling for about £80.00. I waited a short while and managed to purchase it for £55.00 on Amazon.
Therefore saving me enough money to then purchase the on-site guide, which I recall was published some time later than the BGB and have a wee bit left over for a pint of the black stuff!

 

[JohnW2]

Yes, I know that but the OSG ( blanket x 0.8 ) and a lot of people carrying out EICRs will take the figures as gospel.

Sure - but that is the 'problem'/fault of the OSG and those people, not of the regs.

I refer the honourable gentleman to his original question:

but what about EICRs during that period - would one mention (or even code) things which were currently compliant but which would not be compliant with Amd3?

I am just trying to say that it may still be compliant if the trouble is taken to think about it.

Indeed, and I'm not disagreeing with that. As it said, my question related to any installations (if they exist) which are compliant under current regs but which would (really) be non-compliant under Amd3.

Kind Regards, John

 

[JohnW2]

I don't think you should hold your breath too much in waiting for the price to become sensible, at least from mainline suppliers. Two years down the road, Amazon are currently still selling the BGB (Amd1) for £60.45, as compared with £76.50 for BYB.

I recall when the BGB first came out, it was selling for about £80.00. I waited a short while and managed to purchase it for £55.00 on Amazon.

That's interesting, having fallen to £55 after a short while, it appears to have risen again in the ensuing 2 or 3 years. The BYB was £85 when I pre-ordered it, a little down at £76.50 by the time I paid for it.

Therefore saving me enough money to then purchase the on-site guide, which I recall was published some time later than the BGB and have a wee bit left over for a pint of the black stuff!

The new OSG is due to be published on 31st January, at at Amazon pre-order price of £24.30. If one is to believe what it says, it is going to be a 'paperback', rather than spiral bound - which, if true, will be a bit of a pain.

Kind Regards, John

 

[JohnW2]

To have another means to ensure disconnection is very different to having another means to ensure disconnection within a time limit.

It is, indeed, very different, but my interpretation of 415.1.2 ("The use of RCDs is not recognised as a sole means of protection and does not obviate the need to apply one of the protective measures specified in Sections 411 to 414") is that (unless impossible) one should not rely on an RCD to achieve required disconnection times, not just 'disconnection'.

So the question is if 12 seconds is too long?

Are you talking about L-E or L-N faults? If the former, then 12 seconds is clearly far too long, since the required disconnection time is 0.4s for TN or 0.2s for TT.

Kind Regards, John

 

[scousespark]

There is no difference between this amendment and any previous. We install and test to the current edition until July 1st and this applies to jobs started or designed up to July and completed afterwards. From July we switch to AMD3.

Until the regs are in front of us, nobody knows which changes made the cut from the DPC. In the last amendmennt, we expected a relaxation of the rules around RCDS but this never materialized. If a currently compliant circuit becomes non-compliant from July, it will be suitably coded from the on.

 

[JohnW2]

There is no difference between this amendment and any previous. We install and test to the current edition until July 1st and this applies to jobs started or designed up to July and completed afterwards. From July we switch to AMD3.

Many thanks. We're well into page 3, but you are the first person who has given a clear and straightforward answer to the simple question I posed in my OP!

Having said that, if I were a householder commissioning work to be undertaken by an electrician during the next few months, I would be very annoyed if, during that 'transition period' the electrician failed to inform me if (s)he was designing/undertaking work which (s)he knew would be non-compliant with the regs which would be in force in a few months' time. In that situation, I would have expected to have been appraised of the situation, so as to give me the option to ask for the work to be undertaken so as to be compliant with the (known) 'upcoming' regulations.

Until the regs are in front of us, nobody knows which changes made the cut from the DPC.

That's obviously true, but it would seem incredibly unlikely that the main specific issue which has been discussed in this thread (the introduction of the concept of "Cmin", as they have decided to call it) will not appear in Amd3. The only real question is whether the value of Cmin will be 0.95 (as in the DPC) or whether, as suggested to them by myself and others, it will have changed to the seemingly-more-logical 0.94.

Kind Regards, John

 

[martinxxxxxx]

I don't think you should hold your breath too much in waiting for the price to become sensible, at least from mainline suppliers. Two years down the road, Amazon are currently still selling the BGB (Amd1) for £60.45, as compared with £76.50 for BYB.

I recall when the BGB first came out, it was selling for about £80.00. I waited a short while and managed to purchase it for £55.00 on Amazon.
Therefore saving me enough money to then purchase the on-site guide, which I recall was published some time later than the BGB and have a wee bit left over for a pint of the black stuff!

One of the Wholesellers is giving these books away if you register and spend enough product from them, I think it is about £8K...

 

[ban-all-sheds]

Having said that, if I were a householder commissioning work to be undertaken by an electrician during the next few months, I would be very annoyed if, during that 'transition period' the electrician failed to inform me if (s)he was designing/undertaking work which (s)he knew would be non-compliant with the regs which would be in force in a few months' time. In that situation, I would have expected to have been appraised of the situation, so as to give me the option to ask for the work to be undertaken so as to be compliant with the (known) 'upcoming' regulations.

And how annoyed would you be to find that post-June you may not have that socket installed because your existing circuit is non-compliant?

 

[JohnW2]

Having said that, if I were a householder commissioning work to be undertaken by an electrician during the next few months, I would be very annoyed if, during that 'transition period' the electrician failed to inform me if (s)he was designing/undertaking work which (s)he knew would be non-compliant with the regs which would be in force in a few months' time. In that situation, I would have expected to have been appraised of the situation, so as to give me the option to ask for the work to be undertaken so as to be compliant with the (known) 'upcoming' regulations.

And how annoyed would you be to find that post-June you may not have that socket installed because your existing circuit is non-compliant?

If, as I would expect to happen, I had been fully appraised of the situation (both pre- and post 1st July), I would presumably have then made an informed decision as to how I wanted the electrician to proceed, and therefore would have no basis for being annoyed by what course had been taken (on my instruction).

I might want to get something 'slipped in' before regs changed which would make it non-compliant OR I might want things to be done in a manner which would result in a 'clean' EICR a year down the road - but the important point is that I would expect to be given the information to enable me to make that choice.

Kind Regards, John

 

[westie101]

I would expect most house owners to not actually care less one way or the other as they will have little knowledge of the changes.
Most folk just want it safe, it will be - unless you are saying the present regs. are unsafe and at a reasonable cost, I'm fairly certain given the choice the majority will opt for the cheapest option.

As a comparison, how many folk too action against car dealers when the requirement for DLRs came into force because the car they had just bought had none? And those are clearly visible!

 

[JohnW2]

I would expect most house owners to not actually care less one way or the other as they will have little knowledge of the changes. ... Most folk just want it safe, it will be - unless you are saying the present regs. are unsafe and at a reasonable cost, I'm fairly certain given the choice the majority will opt for the cheapest option.

Some will obviously think like that. Others (like me) wouldn't. Given the information, I might well end up choosing the cheapest option, but I would like to be the one making that decision.

As a comparison, how many folk too action against car dealers when the requirement for DLRs came into force because the car they had just bought had none? And those are clearly visible!

"DLRs" ???? Whatever, there is a difference between 'being annoyed' and 'taking action'. I would certainly be annoyed if someone sold me something, knowing that it would soon be 'behind the times' in terms of regulations (which might, for example, affect resale value, and perhaps even safety), without bringing that situation to my attention.

Kind Regards, John

 

[ericmark]

Having said that, if I were a householder commissioning work to be undertaken by an electrician during the next few months, I would be very annoyed if, during that 'transition period' the electrician failed to inform me if (s)he was designing/undertaking work which (s)he knew would be non-compliant with the regs which would be in force in a few months' time. In that situation, I would have expected to have been appraised of the situation, so as to give me the option to ask for the work to be undertaken so as to be compliant with the (known) 'upcoming' regulations

Kind Regards, John

Can't see how any work complying with the volt drop requirements of today can fall foul of the reduced loop impedance values. If it does not comply with volt drop then it's just non compliant end of story.

When it dropped for a B32 MCB from 1.5Ω to 1.44Ω we did not have any problems as at 1.5Ω it was also 4% not 5% volt drop.

The problem as I see it is still accuracy of measurement. Without taking into account bunching, temperature and the corrections where volt drop can move from 18 mV/A/m to 16.5 mV/A/m when corrected just moving the readings by one digit on Ze and Zs readings and volt drop moves 0.35 volts so the calculations at best are +/- 0.7 volts.

Use a loop impedance meter twice and the reading can change by 0.02Ω so add that and one realises that +/- 2 volt error is possible. So until the calculated reading is 13.5 volt you really don't know if it's an accuracy issue or if the installation is really out of speck.

So looking again at final ring on a TN-S system then 1.39Ω Zs will just about fall into the volt drop requirement assuming Ze = 0.8Ω so in this case it could after the amendment fail but would be so close one in real terms could only advise that the ring final was at maximum length rather than say it's non compliant.

But if one looks as a shower supply at 45A then 0.9Ω with a TN-S incomer of 0.8Ω although in theroy 16 meter of cable (10mm²) can still be used I would say your right on the edge and in real terms disconnection times are more down to RCD than the MCB.

Although the regulations say we can't rely on just a RCD since the RCD is tested and we can't test a MCB I am more inclined to trust the RCD for rapid disconnection times.

As to industrial situation the reduced low voltage transformer is often provided with only a 12A trip (thermal only) on the incomer so with a line - earth fault at 230 volt in and 55 volt out then 50A can be delivered from a 16A socket before that 12A thermal tip will auto disconnect the supply. Compared with that the rest hardly seems to matter.

 

[JohnW2]

Can't see how any work complying with the volt drop requirements of today can fall foul of the reduced loop impedance values.

I agree that it would be unusual, but it could happen, even with today's 'max Zs' figures (let alone the expected reduced Amd3 ones), if Ze was high and one had a fairly long high-current circuit. As an example ...

... consider a 45A shower circuit (B45 MCB) using 25m of 6mm² (Method C) cable, in a TN-S installation with a Ze of 0.8Ω. On today's figures, that would mean a 'maximum Zs' of 1.02Ω (falling to 0.97Ω if we end up with Cmin=0.95). By my reckoning, VD at 45A (at 70°) would be only 8.215V (3.57%), but Zs would be 1.12Ω - hence 'non-compliant' even with today's limit, let alone the expected reduction, despite VD being well within guidelines. With a longer circuit, this would become much more dramatic - Zs would have to rise to about 1.24Ω (cable length ~35m) before VD hit 5%.

If it does not comply with volt drop then it's just non compliant end of story.

As often discussed, a circuit is not necessarily "non-compliant" just because VD (at maximum load) exceeds the 'deemed to satisfy' figures (3% or 5%) in the Appendix of the regs. It is compliant provided that it is considered that the voltage supplied to the supplied equipment is not so low as to "impair the safe functioning of the equipment" (which, I would suggest, would very rarely be the case, particularly in a domestic installation).

Kind Regards, John