Live Or Dead Testing - A Question For Members

[says-les]

Sirs

I have asked, on another forum, if the sparks agree that they should be and are, testing Zs dead except for Ze which can only be tested live.  By measuring R1 + R2 and adding it to the measured Ze, our local college advocate this is the recommended way. 

The only loop test to be done live, is the Ze test and all socket outlets.

This question was rejected by most of the members, saying that they feel competent to test Zs live at any point, using the loop tester probes.

What is the official method?

Do you consider it optional as to which method is used?

Thanks

Les

 

[sellers]

I would think along the lines that the official method is whatever the H+S and Risk assesment allows at the time.

 

[Doc Hudson]

Sirs

I have asked, on another forum, if the sparks agree that they should be and are, testing Zs dead except for Ze which can only be tested live.  By measuring R1 + R2 and adding it to the measured Ze, our local college advocate this is the recommended way. 

The only loop test to be done live, is the Ze test and all socket outlets.

This question was rejected by most of the members, saying that they feel competent to test Zs live at any point, using the loop tester probes.

What is the official method?

Do you consider it optional as to which method is used?

Thanks

Les

Official methods can be found in the various BS7671 publications and guidance notes such as; On Site Guide, Guidance Note 3  and obviously referring to BS7671 itself as to what permissible values are for the types of circuits tested. Your question does not mention whether you are considering new installation, additions and alterations to existing installation, inspection and testing or domestic/commercial work. Care must always be taken when doing a Zs tests, as exposed metalwork can become live for a short period. In a domestic property that you know is empty, this risk can be minimal and safely controlled. Whereas in a commercial environment when the premises are still a working environment, with unknown quantities of persons, who could be in contact with exposed conductive parts on the circuit you are trying to test, then the risk becomes harder to control. So as Sellers suggest, the contractors risk assessment will establish which of the available methods can be safely performed without any risk to any 3rd parties also in the premises or to the person undertaking the work. In my personal opinion there is no one size fits all answer to your question.

Doc H.  

 

[Doc Hudson]

A further comment re the title of your question "Live Or Dead Testing - A Question For The Moderators". The moderators function on this forum is primarily to ensure that the forum T&C's are followed and all members respect all other members input. e.g identifying Spam posters, Trolls, or just plain bad language or disrespectful comments. They do not carry any superior wisdom or knowledge of BS7671 or industry standards, methods good practice or legal obligations. It is the pool of wisdom from the membership as a whole that has the greater knowledge. So your question should be out to the forum membership en-mass, not specifically aimed at moderators.

Doc H.

 

[Technician]

I would agree with the above, especially with respect to the point

raised by Sellers on the risk assessment.

Some believe that testing is not complete until a live Zs test

has been carried out and, to this end, a method statement on

agreed procedures should be available, along with precautions to be

taken.

It looks like more paperwork etc. but it would demonstrate that due

diligence has been followed.

 

[a3]

A further comment re the title of your question "Live Or Dead Testing - A Question For The Moderators". The moderators function on this forum is primarily to ensure that the forum T&C's are followed and all members respect all other members input. e.g identifying Spam posters, Trolls, or just plain bad language or disrespectful comments. They do not carry any superior wisdom or knowledge of BS7671 or industry standards, methods good practice or legal obligations. It is the pool of wisdom from the membership as a whole that has the greater knowledge. So your question should be out to the forum membership en-mass, not specifically aimed at moderators.

Doc H.

I have changed the title to better fit

 

[says-les]

Thank you

 

[SLIPSHOD & SLAPDASH]

My view is calculating does not prove anything.

 

[sellers]

My view is calculating does not prove anything.

I agree, and if an electrician cannot test Zs live safely then can they call themselves a competent electrician?

 

[says-les]

No one questions that and R1+R2 is measured dead and added to the measured Ze. I think the Guidance note 3 accepts this. How would you measure Zs at a FCU?

 

[sellers]

open up plonk testers on and wait for the magic number?

 

[says-les]

I think the IEET want us to avoid loose exposed live terminals being probed behind such an item whereas no danger plugging into a socket.

 

[kme]

Done correctly, there is NO danger attached to live Zs testing at an FCU, or indeed a light fitting. 

100% with sellers on BOTH his above points - if someone deems themselves incapable (or is deemed by a 3rd party) of safely carrying out what I personally consider an essential part of an electrician`s regimen - then that person is "not competent".

How to test? Again, if this isn`t known by the testee, then they aren`t competent to DO the test, ergo incompetence again........

IMHO

KME

 

[philbas]

I agree with sellers, if you can;t do the risk assessment and test it live, you should not be doing it anyway

 

[Doc Hudson]

As an additional thought to this debate, Where an installation is live and working and has essential services that cannot be turned off, then it can be impossible to safely measure Ze as you cannot remove the installations CPC and bonding connections to get a reading down only the suppliers earth facility (or the Ra of the rod). So if you cannot get an accurate Ze you certainly cannot add R1+R2 to a guessed Ze. In this case the most reliable and accurate verification that your max Zs limits are not exceeded is a live Zs test reading of the circuit  in question.

Doc H. 

 

[says-les]

Very true, but this is not about best method, but about what is acceptable, and it is acceptable even to measure R1+R2 and add to the distribution company's enquiry figure for Zs. This method can be noted on the relevant form.

 

[Sidewinder]

Try doing that with a circuit on a D63 & see if what you get is comlpiant?

 

[says-les]

Sorry but what is a D63?

 

[davetheglitz]

My experience is that live Zs readings inevitably come out lower than calculated. To that end if the R1+R2 + Ze method is within limits I'm quite happy to put this down. With lighting in particular this allows you to do measurement at switches where there is a loop in during EICRs - which saves having to swing from chandeliers - and also is the longest earth path.

 

[says-les]

Thanks for pointing that out.