Calculated Zs on an EICR

[Blaspark]

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.

Similar =/= same. Is the dB on the ceiling? Is the light on the ceiling?
Is Ze a necessary and unavoidable live test? Is Zs at light fitting an unavoidable live test?
And still... Parallel paths and consistent test reports. You don't want the eicr different to the eic and you don't want the eicr done differently each time a different company shows up.

 

[TJ Anderson]

Live working and live testing are two different things.

Also in my opinion (and we can all have them as Inspectors)....

Calculating Ze + R1 + R2 to give you recorded Zs value is not satisfactory and should only be used during initial verification of new install or changes to a circuit to give you a predicted value of Zs which you then confirm by measurement. By doing both tests, you also can highlight parallel earth paths just for you own sanity. Yes, sometimes Zs will be considerably less than Ze + R1 + R2, so what, if you understand parallel paths. When you do and R1 + R2 test you are making temporary changes to install (a link) and after it is put back it should be confirmed by a measured Zs. If only an R1 + R2 test is carried out then added to Ze and recorded as Zs, this creates the possible scenario that an installation gets left less safe following a EICR than when it started if a cpc was to be broken and not noticed.

Zs only is perfectly suitable for EICR as the system has already been commissioned and is operating.

 

[Blaspark]

Live working and live testing are two different things.

Also in my opinion (and we can all have them as Inspectors)....

Calculating Ze + R1 + R2 to give you recorded Zs value is not satisfactory and should only be used during initial verification of new install or changes to a circuit to give you a predicted value of Zs which you then confirm by measurement. By doing both tests, you also can highlight parallel earth paths just for you own sanity. Yes, sometimes Zs will be considerably less than Ze + R1 + R2, so what, if you understand parallel paths. When you do and R1 + R2 test you are making temporary changes to install (a link) and after it is put back it should be confirmed by a measured Zs. If only an R1 + R2 test is carried out then added to Ze and recorded as Zs, this creates the possible scenario that an installation gets left less safe following a EICR than when it started if a cpc was to be broken and not noticed.

Zs only is perfectly suitable for EICR as the system has already been commissioned and is operating.

"after it is put back it should be confirmed by a measured Zs."
Visual inspection is fine for that according to the rules.

"Calculating Ze + R1 + R2 to give you recorded Zs value is not satisfactory"
Every inspector can have his opinion. My opinion is that that statement is false.

"By doing both tests, you also can highlight parallel earth paths just for you own sanity."
If you want pal

"Zs only is perfectly suitable for EICR as the system has already been commissioned and is operating."
Do it differently each time and you don't get to see how the system changes over time, which is very valuable info.

You shouldn't do live tests if they aren't needed. You need to Ir test the circuit therefore you need to switch it off. Therefore you can do your r1+r2 at the same time.

If you can switch the whole dB off you can take a Ze if not its a limitation.

I'm repeating myself. It's boring

 

[westward10]

I think you are over complicating an EICR. The Zs reading whether there are parallel paths or not is the realistic value of the circuit in service. I understand on an IV you need to verify protective conductors and polarity before energizing the circuit but not on an EICR.

 

[Blaspark]

I think you are over complicating an EICR. The Zs reading whether there are parallel paths or not is the realistic value of the circuit in service. I understand on an IV you need to verify protective conductors and polarity before energizing the circuit but not on an EICR.

It's only complicated if you think about it. If you just do it the way is recommended by me and others you get all the benefits I seem to have to repeatedly state

 

[westward10]

I often do two readings at something like a water heater or boiler and have found on a couple of occasions no continuity of the cpc when disconnected but aside from that on an EICR I am not complicating matters after all I have 100 circuits a day to do

 

[Blaspark]

You guys seem so determined to do it live. I highly suspect that you do eicr on business that don't organise scheduled maintenance properly and don't understand the benefits and how easy it can be.
Are you guys doing eicr without ever switching anything off and with tons of limitations? It's how it seems.
I have no problem with live work when it's sensible

Doing 100 tests a day instead of 50 good ones is fine for earning cash but not good for the clients if they were half way wise

 

[westward10]

The 100 circuits was a joke. If you are removing all parallel paths what is your opinion of a circuit which has had supplementary bonding deliberately connected to it with the aim of reducing the Zs value so fault protection is maintained because this has effectively become part of the circuits fault path.

 

[Blaspark]

The 100 circuits was a joke. If you are removing all parallel paths what is your opinion of a circuit which has had supplementary bonding deliberately connected to it with the aim of reducing the Zs value so fault protection is maintained because this has effectively become part of the circuits fault path.

I think that's quite dodgy but allowed. I remember something specified like there has to be documentation for the duty holder so he/she is aware of the risks and isn't going to have it removed during building modifications and such. I suppose in such a case you can't use calculated values, which are deliberately worst case (a worst case building management is preventing happening) and should document it on your certs since on going management of that risk is necessary

 

[Blaspark]

Do you know where I find out about that in the regs or legislation? I can't remember right now

 

[Blaspark]

The 100 circuits was a joke. If you are removing all parallel paths what is your opinion of a circuit which has had supplementary bonding deliberately connected to it with the aim of reducing the Zs value so fault protection is maintained because this has effectively become part of the circuits fault path.

Also we're not removing all parallel paths. Think of a few metal light fittings attached to a metal beam. You still need cpc but will always have parallel paths. Or a boiler.

 

[Blaspark]

542.2.6

 

[Blaspark]

The 100 circuits was a joke. If you are removing all parallel paths what is your opinion of a circuit which has had supplementary bonding deliberately connected to it with the aim of reducing the Zs value so fault protection is maintained because this has effectively become part of the circuits fault path.

Actually I can't find where that example is allowed and I consider it dangerous. Under fault conditions current is going to flow on something not designed for the purpose. It could arc and start a fire. I say no until someone shows me why it is not dangerous and preferably explicitly permitted in bs 7671

 

[Ian1981]

Supplementary bonding is considered to supplement fault protection, that is it maybe utilised between circuits and local accessible exposed conductive parts to reduce the touch voltages if the earth fault loop impedance for a circuit is exceeded.
Another more common used method for this is rcd protection of the circuit
It’s all in chapter 41 protection against electric shock part 4 of bs7671
See 419

 

[westward10]

Actually I can't find where that example is allowed and I consider it dangerous. Under fault conditions current is going to flow on something not designed for the purpose. It could arc and start a fire. I say no until someone shows me why it is not dangerous and preferably explicitly permitted in bs 7671

I am not sure it is still permitted but is was once acceptable so there are instances of where it may be still in play.

 

[Blaspark]

I am not sure it is still permitted but is was once acceptable so there are instances of where it may be still in play.

I guess if it's still in play but does pose a risk I might be forced to C2 unless I could FI it and make sure it's sound. Arcing was the risk I could imagine . That risk could be mitigated.

 

[TJ Anderson]

You guys seem so determined to do it live. I highly suspect that you do eicr on business that don't organise scheduled maintenance properly and don't understand the benefits and how easy it can be.
Are you guys doing eicr without ever switching anything off and with tons of limitations? It's how it seems.
I have no problem with live work when it's sensible

Doing 100 tests a day instead of 50 good ones is fine for earning cash but not good for the clients if they were half way wise

Chil out mate! Have you ever heard of earth leakage monitoring and thermal imaging for a kick off? There is life beyond GN3 you know!

 

[Bait Account]

Why so harsh on the book. It's very difficult to decide what to put on the eicr personally I like to avoid that bs and defer to an "authoritive source"

Anybody going to contradict this?

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.

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

It's only complicated if you think about it. If you just do it the way is recommended by me and others you get all the benefits I seem to have to repeatedly state

What a jerk lol.

 

[westward10]

Actually I can't find where that example is allowed and I consider it dangerous. Under fault conditions current is going to flow on something not designed for the purpose. It could arc and start a fire. I say no until someone shows me why it is not dangerous and preferably explicitly permitted in bs 7671

Bit late but it was Regulation 413-02-15 of the first 16th Ed, deleted in the amendment 2 copy.