Radial Zs Testing Question

[Dairyspark]

Just watched one of those videos from college that shows you how to test, and on said video (sponsored by NICEIC

 

[Murdoch]

What a knxb.

I use adaptors that fit in place of the lamp and plug the leads of my tester in.

Anyway, as a competent person, sometimes working live is the only way - in fact how does he suggest you test the Ze?

 

[ProDave]

Well if he thinks you are not supposed to take measurements on live parts, I would go back and ask him just exactly how does he measure Ze?

 

[Dairyspark]

That was my first thought however I like to ask more experienced folks haha, the way we did it at college was to croc clip the earth lead onto its terminal and hold in the neutral then the live lead and have it either set to auto or the lecturer pressed test, oh well, stupid video man haha

Cheers

Bobby

 

[Blue Duck]

Phone the DNO?

:slap

I suspect its an arsee covering exercise from the niceic.

:innocent

 

[Manator]

Measuring Zs on a lighting circuit is classed as a danger. If you were up a set of ladders trying to hold 3 test probes in position on live cables just to do an easily calculated result. Well ?

Ze is a different kettle of fish as you will almost certainly be firmly on the ground and other safety methods can be deployed, like rubber mattting, safety gloves face shields and so on.

Not possible up a pair of step ladders.

 

[Dairyspark]

http://youtu.be/eu2LNgzFUJ0 From 1:35 onwards

 

[Andy™]

he is right in that it is live working, and EAWR does state live working should not be done if other alternatives etc, which there is. you could do Ze though, since its unreasonable to do it dead, and its reasonable to do it live.

in reality though, many will do a Zs with the test probes on whatever terminals

 

[Manator]

he is right in that it is live working, and EAWR does state live working should not be done if other alternatives etc, which there is. you could do Ze though, since its unreasonable to do it dead, and its reasonable to do it live.

in reality though, many will do a Zs with the test probes on whatever terminals

I knew there was an easier way of saying what I did

 

[NozSpark]

Personally I don't Zs test a lighting circuit,,, Zs=Ze+(R1+R2) is a perfectly acceptable alternate method

 

[Murdoch]

Personally I don't Zs test a lighting circuit,,, Zs=Ze+(R1+R2) is a perfectly acceptable alternate method

and the day you forget to terminate the CPC at the CU you leave the circuit unprotected. Doing a Zs is the only way to ensure compliance

 

[Andy™]

one of the reasons i prefer to do Zs, final confirmation that earth is connected properly

 

[Manator]

and the day you forget to terminate the CPC at the CU you leave the circuit unprotected. Doing a Zs is the only way to ensure compliance

I think when safety is an issue forgetfulness is never an option. The only time the cpc would be disconnected is during the continuity and insulation test stages. As this involves all connections to be disconnected I fail to see why anyone would connect two cables ( in any order) and forget to connect the third.

If you carry out a Zs test on a lighting circuit you will be in contravention of the regulations.

BS7671 is only a small part of the regulations, other regulations will have a direct impact on them and safety is paramount.

 

[NozSpark]

Manator ...... Insulation tests should be carried out with all earthing and cpcs connected

 

[kerching]

Just had a quick look on youtube and.......

http://youtu.be/dFPSA19Tknw

....and this is from a college

I seem to recall a missive from NICCY. About calculating Zs but cannot find it

Just sharing

This is the WRONG video BUT....have you noticed how there is NO need to torque up the Connection?!?!

 

[steptoe]

remember,

being a member of NICEIC does NOT mean you are a competent person,

merely that you have met their membership requirements.

 

[kerching]

Whoops, that WAS not what I meant to post!

Now i will have to,try to find it again

 

[pewter]

I find my tester (mft1730) using the 3 wire lo current (non trip) setting is not a reliable result. The 2 wire high current setting is usually not far from what my calculation would be. The low current i find not very good (i have tested same spot with all settings and used calculation and find the low current rubbish. I usually put the calculation on my test sheets.

Whenever i terminate cables i use my long nose (pliers) and give each a tug to make sure its terminated.

 

[SPECIAL LOCATION]

I may be wrong..

But I think you will find one of the points of consideration when doing a Zs that they are referring to is not just your health & safety..

But the safety of others at the same installation where you are working...

You are putting a test voltage down the CPC to all associated earthy parts connected to it...

There is a comment in guidance note 3 about risks of shock hazard to The testing personnel,

Other persons Or Livestock on site.. 

when doing direct live measurement of Zs.

i.e.

An elderly person trying to switch on the light in a room on the same circuit, touching the nice decorative metal light switch while you stick your test voltage down while plugged into the light fitting next door...

May get a bit of a stray voltage as they become a parallel earth path...

(especially if real earth path is a tad faulty and not as low resistance as it should be)

Obviously the Loop Tester should cut itself off if the test voltage is getting to high..

And you should have verified your earth continuity first on your dead tests...

But I think the video comments (I haven't seen it) may be relating to the dangers of just going to an existing live installation & doing a Zs thinking it posses no danger to anyone.

Hence the comments in GN3 & OSG in the Zs testing bit!

It is not only you that has to work safely...  you must also be aware of hazards, risks and dangers you can impose on others that you may not know what they are doing..

opcorn

 

[Blue Duck]

remember,

being a member of NICEIC does NOT mean you are a competent person,

merely that you have met their membership requirements.

Does this apply to Tony fricking Cable?