High Zs values (Just)

[Nigel]

Don't get where you are coming from Essex....why does the cost of rectification affect the code applied?

For me it does not. I would code it as per 7671. But the op is concerned and if the remedial works are relatively easy then I cannot see why he is even considering fudging it.

 

[Deleted member 9648]

For me it does not. I would code it as per 7671. But the op is concerned and if the remedial works are relatively easy then I cannot see why he is even considering fudging it.

You've lost me mate, does that mean you'd code 2 or 3? Absolutely everything I code on an EICR is 'as per 7671'......don't you?

 

[Richard Burns]

I have not actually come across this yet, though it has been close at times. If this were found then I would expect that some careful retermination of connections would resolve the problem, you are talking a fraction of an ohm here.
Unfortunately with circuit breakers if the resistance level were exceeded then the disconnection time could jump from practically instantaneous up to 13s (if the circumstances were just right, the type B CB is on the upper limit of design(5In) and the supply voltage is down to 218V) this tends to mean that non compliance could be significantly dangerous, though as you say it was deemed safe three years ago, only the definition of dangerous has changed.
If it were a fuse then a faction of an ohm increase would not significantly increase the danger as the time would be 0.401s instead of 0.4s and this might be suitable to be coded as improvement recommended. I think (silly as it sounds) if it is a circuit breaker then a potentially dangerous situation by the new definition of dangerous is now in place.

 

[Nigel]

You've lost me mate, does that mean you'd code 2 or 3? Absolutely everything I code on an EICR is 'as per 7671'......don't you?

I would code it a 2.

 

[Toneyz]

If you take a 32A type B circuit breaker the max Zs under 15th was 1.50 under the 16th the voltage was based upon 230V and was 1.44 now with Cmin reduced further to 1.37 the reduction being 0.13 ohms you can see how this has come about.

 

[Deleted member 9648]

Thanks for the replies everyone.
I'm sticking to a code 3 with an explanatory note but will discuss the issue with my NICEIC inspector on his next visit and go with his interpretation. I understand the reasoning behind a code 2, but I think it would be very hard to explain to a client that his fully compliant installation wired 3 years ago is now deemed potentially dangerous.

 

[Nigel]

Thanks for the replies everyone.
I'm sticking to a code 3 with an explanatory note but will discuss the issue with my NICEIC inspector on his next visit and go with his interpretation. I understand the reasoning behind a code 2, but I think it would be very hard to explain to a client that his fully compliant installation wired 3 years ago is now deemed potentially dangerous.

It will be in harder to explain why you think you can just ignore parts of BS7671.

 

[Deleted account]

Essex,
I don't believe wire puller has ignored bs7671.

He has made an informed decision and given a code.

I actually agree with you and would give the C2, but I agree it's a bit unfair considering the changes in the book.

The individual spark doing the EICR must code appropriately to how they personally view the issues with suitable explanation.

 

[Nigel]

Essex,
I don't believe wire puller has ignored bs7671.

He has made an informed decision and given a code.

I actually agree with you and would give the C2, but I agree it's a bit unfair considering the changes in the book.

The individual spark doing the EICR must code appropriately to how they personally view the issues with suitable explanation.

Maybe he will write down that it is only just a little bit dangerous.

 

[static zap]

EU & harmonization , a simple idea goes and gets all complicated .
( have DNOs got 230V for a rainy day ? )

 

[Intoelectrics]

I have not actually come across this yet, though it has been close at times. If this were found then I would expect that some careful retermination of connections would resolve the problem, you are talking a fraction of an ohm here.
Unfortunately with circuit breakers if the resistance level were exceeded then the disconnection time could jump from practically instantaneous up to 13s (if the circumstances were just right, the type B CB is on the upper limit of design(5In) and the supply voltage is down to 218V) this tends to mean that non compliance could be significantly dangerous, though as you say it was deemed safe three years ago, only the definition of dangerous has changed.
If it were a fuse then a faction of an ohm increase would not significantly increase the danger as the time would be 0.401s instead of 0.4s and this might be suitable to be coded as improvement recommended. I think (silly as it sounds) if it is a circuit breaker then a potentially dangerous situation by the new definition of dangerous is now in place.

As you stated if the readings are very close to the stipulated maximum values then it could be just a matter of checking the terminations at accessories. I have had this situation many times especially on RFCs, which can flag up when you do end to end measurements and you get high or inconsistent readings. Many times it has turned out to be a loose connection or a poorly terminated conductor.
I think "wirepuller" is in a tricky spot as he has to explain to the client that prior to AMD3 there was no problem but now it doesn't comply. Then explaining to the client that the installation is potentially dangerous will be awkward also because they will likely not understand how it can be completely safe a few years back but now dangerous, yet there have been no alterations or deterioration?
Electricians these days have to be highly skilled consultants, negotiators, teachers and salespersons.

 

[Intoelectrics]

Duplicate post

 

[telectrix]

so, this Cmin. causes problems. samewith the temp.0.8. never ever seen a supply voltage as low as 218V, never seen a cable reach 70 deg.Cunless overloaded.just justification for the IET trough feeders high earnings.

 

[Ian1981]

so, this Cmin. causes problems. samewith the temp.0.8. never ever seen a supply voltage as low as 218V, never seen a cable reach 70 deg.Cunless overloaded.just justification for the IET trough feeders high earnings.

I think the point is that it could happen.
Cables designed for maximum operating temperature of 70 degrees can be allowed to reach this temperature and thus allowances must be made for this scenario.
The voltage matter......same as you never recorded at voltage so low before but again it’s erring on the side of caution and above all else, safety

 

[Deleted member 9648]

It will be in harder to explain why you think you can just ignore parts of BS7671.

Maybe he will write down that it is only just a little bit dangerous.

Not all non-compliances with current 7671 will attract a code 2. For example the recommended code for a cable buried at <50mm deep without RCD protection and compliant with recent previous editions of 7671 is a code 3.
That's not 'ignoring' BS7671, it is recognising that while it does not comply with the latest edition, it complied with a recent but previous edition and was deemed safe then so cannot suddenly be dangerous.
If your logic applied then any code 3 would be 'ignoring' Bs7671, there would only be a code 1 or 2 permitted.

 

[Nigel]

Not all non-compliances with current 7671 will attract a code 2. For example the recommended code for a cable buried at <50mm deep without RCD protection and compliant with recent previous editions of 7671 is a code 3.
That's not 'ignoring' BS7671, it is recognising that while it does not comply with the latest edition, it complied with a recent but previous edition and was deemed safe then so cannot suddenly be dangerous.
If your logic applied then any code 3 would be 'ignoring' Bs7671, there would only be a code 1 or 2 permitted.

You understanding of a C3 is not correct I am afraid.

 

[Ian1981]

Thing is we are required to inspect and test to the current edition of the wiring regulations and for us to achieve ADS as well as the protective bonding to be in place, then the formula
Zs x Ia must be equal to or less than 230v x cmin (0.95).
If the circuit(s) can’t fulfill that formula then I can only see a C2 option as ADS can not be guaranteed at all times, at least not according to bs7671.

 

[Deleted member 9648]

You understanding of a C3 is not correct I am afraid.

Kindly explain it to me then.

 

[davesparks]

Not all non-compliances with current 7671 will attract a code 2. For example the recommended code for a cable buried at <50mm deep without RCD protection and compliant with recent previous editions of 7671 is a code 3.

Compliance with previous editions, recent or not, does not affect the code given.
The code given is in accordance with the current edition.

 

[davesparks]

so, this Cmin. causes problems. samewith the temp.0.8. never ever seen a supply voltage as low as 218V, never seen a cable reach 70 deg.Cunless overloaded.just justification for the IET trough feeders high earnings.

Out of interest how often have you measured the temperature of the conductors within a cable in service?