Calculated Zs on an EICR

[Blaspark]

The code breaker book advises a C2 code for tails that are not the minimum required 25mm.
I mean where in bs7671 states that tails must be 25mm?
What if you have 16mm tails? Why is that a C2 if they are acceptable for the load they are connected to and satisfy the requirements for fault protection?

I'm not sure. Why is 25mm specified at all?

I agree that example seems counter intuitive

 

[Ian1981]

I'm not sure. Why is 25mm specified at all?

That’s my point.

 

[Blaspark]

That’s my point.

Maybe it would be good to know why the 25mm is specified, if we understood that we might understand why the c2 is in the book.
The iet do have a phone number. If they can't give a straight answer I might think they are talking sh*t but if you don't ask you won't know

 

[Blaspark]

Is it not actually better for various reasons. You can't do a live test for zs without bonding connected which will give you a lower value. However building works may permanently remove that parallel path.
If you use ze + r1 + r2 you get the highest possible value which will be more resilient.
No?

Anybody going to contradict this?

 

[Blaspark]

Personally speaking I always prefer to measure Zs as this is the only test that confirms the complete circuit including protective devices. There’s always a possibility that you can have a high resistance accross a device that would result in a high impedance at the end of the circuit. This will never be found by calculation.

I think that what you're saying is reasonable however we always test sockets with a plug, at least I do, so that covers that. Then you have lights, switches and other devices which are tested at the terminals to test the connection not the device.
So ze + r1+r2 is still best because it prevents parallel earth paths.

 

[cliffed]

GN3 states that calculating you Zs is perfectly acceptable. Almost seems to advise it over live testing.

Agree but to get your r1 + r2 reading-the curcuit needs to be switched off,so why not a zs test

 

[Blaspark]

Agree but to get your r1 + r2 reading-the curcuit needs to be switched off,so why not a zs test

Zs test is a live test. It also includes parallel paths which might be removed. There can be parallel which shouldn't be removed and there's a procedure for managing them.
Live tests are discouraged for obvious reasons as should be taking Zs values that include paths that may be removed.

 

[Ian1981]

Maybe it would be good to know why the 25mm is specified, if we understood that we might understand why the c2 is in the book.
The iet do have a phone number. If they can't give a straight answer I might think they are talking sh*t but if you don't ask you won't know

Dno on our new build sites stipulate 25mm conductors with a 16mm earthing conductor as they fit a 100amp fuse.

 

[cliffed]

Zs test is a live test. It also includes parallel paths which might be removed. There can be parallel which shouldn't be removed and there's a procedure for managing them.
Live tests are discouraged for obvious reasons as should be taking Zs values that include paths that may be removed.

It’s also an eicr zs should take place,leaving all Main bonding connected,how are you suppose to get the pfc & ze measured @ origin

 

[Blaspark]

Dno on our new build sites stipulate 25mm conductors with a 16mm earthing conductor as they fit a 100amp fuse.

In that case the c2 seems wrong.
Could it be that the codebreakers codes are only for installations done to the bs 7671 that the codebreakers book is for.
My codebreakers book for the 18th edition its codes probably may only make sense on an 18th edition installation.
However rcd for protection against shock is a general thing and it's ratings on that may apply retrospectively. I'd have to think about it.

 

[Blaspark]

It’s also an eicr zs should take place,leaving all Main bonding connected,how are you suppose to get the pfc & ze measured @ origin

Pfc/pscc are measured with bonding connected. Ze isn't. Zs is best always calculated.
I think so at least

 

[Blaspark]

If you can't switch off supply to take a Ze correctly maybe that should be a limitation on a eicr. Otherwise people might wonder why the Ze has dropped since the eic though it'd be obvious to the old hands here.

 

[cliffed]

Pfc/pscc are measured with bonding connected. Ze isn't. Zs is best always calculated.
I think so at least

Agree on the Ze,Zs can be cakculated this usually happens @ the design stage.
Are we actually saying no live testing.

 

[westward10]

I maybe incorrect but the calculated Zs test which seems to be coming prevalent is due to the possible risk of exposed live parts. This begs the question how Ze will be performed which is a required test and exposes the individual to similar exposed live parts.

 

[Ian1981]

I maybe incorrect but the calculated Zs test which seems to be coming prevalent is due to the possible risk of exposed live parts. This begs the question how Ze will be performed which is a required test and exposes the individual to similar exposed live parts.

That’s the likes of the Niceic sticking their beak in and quoting the EAWR for live working which is nonsense in my opinion

 

[cliffed]

On the Eicr tests we do,it’s a live test,with necessary risk assessments.
I’m getting confused here,waithing for the Eng v Wales match to begin,bbq at local pub.
Its hot,& in Uk ha ha
,

 

[Blaspark]

That’s the likes of the Niceic sticking their beak in and quoting the EAWR for live working which is nonsense in my opinion

Eawr allows live working.

 

[Ian1981]

Live testing is impossible to avoid.
Even if you obtain the Ze measurement from the dno, you should still verify it’s connection to earth externally by live testing

 

[cliffed]

Live testing is impossible to avoid.
Even if you obtain the Ze measurement from the dno, you should still verify it’s connection to earth externally by live testing

Defo

 

[Blaspark]

On the Eicr tests we do,it’s a live test,with necessary risk assessments.
I’m getting confused here,waithing for the Eng v Wales match to begin,bbq at local pub.
Its hot,& in Uk ha ha
,

Ok so you Zs live but how do you do Ir test?

Live testing is impossible to avoid.
Even if you obtain the Ze measurement from the dno, you should still verify it’s connection to earth externally by live testing

Yes you should and if you can't that's a limitation. To do so requires disconnected bonding which requires power off