Zs live Testing - does everyone do it?

[sparky999]

Yh that is a good start

 

[cheggers]

upping the scale on the meter sometimes work

I would no change the rcd for a main switch, I would just do R1and R2 + ze

you will get the same reading

 

[SLIPSHOD & SLAPDASH]

nic recomend only live zs testing on sockets only, the rest r1+r2+ze will do nicely thank you.i slill do zs live.

Most of the 'Nic told me this or that' you hear is second hand twaddle. As the more experienced know, the regs are not black & white. Each & every assessor is well versed in the regs, but its their interpretation of a particular example or situation that may not be correct for a different application.

We had our annual inspection last week and one of the tasks i had to demonstrate was where and how to carry out Zs testing on a domestic lighting circuit.

 

[ian932]

I can't see the issue with doing Zs on lighting all you need is a set of these.

NEW Kewtech Lightmates Bulk Buy Offer

Ok maybe your meter sets the RCD off but a changing the RCD for a DP breaker during testing would fix that. IMO EFLI is more important than calculated Zs as its a live function test.

On the topic of Zs being recorded on the form using R1, R2 and Ze you need to also take account of Correction factors for ambient if you are using tables in the red book, its better to use the OSG tables as they are adjusted to around 20% less. The red book figures are for 70deg operating temps.

 

[Andy™]

I can't see the issue with doing Zs on lighting all you need is a set of these.NEW Kewtech Lightmates Bulk Buy Offer

but you still need to remove cover to get at the earth, so not much benefit with that. possibly useful if its a class I fitting though

 

[ian932]

but you still need to remove cover to get at the earth, so not much benefit with that. possibly useful if its a class I fitting though

If you

 

[soakden]

well guys you can always bypass the dimmer with a little link wire then do zs and if you are not on an rcd cct why do you use 3 leads just use 2 zs is earth fault loop remember so go earth to live and test it will be a faster test and saves having 3 hands lol

 

[Apache]

well guys you can always bypass the dimmer with a little link wire then do zs and if you are not on an rcd cct why do you use 3 leads just use 2 zs is earth fault loop remember so go earth to live and test it will be a faster test and saves having 3 hands lol

Thought 3 leads to prevent RCD tripping?

 

[Andy™]

Thought 3 leads to prevent RCD tripping?

yes, but....

and if you are not on an rcd cct why do you use 3 leads just use 2

...there isnt an RCD to trip!

 

[batty]

Most testers I have used will not test unless you have the three leads connected to the right conductor.

Batty

 

[Robojin]

I have and a Kewtech 64 and you have to use 3 leads, I recently bought a set of the lightmates and trust me it makes Zs a very simple task on lighting, just croc clip the earth (change to a probe if it wont clip) put in the lightmate press the button.

Dimmers are still a pain as you need to bypass or you get >1999 max on the KT64

My pennies worth

 

[soakden]

thanks Andyc

common case of speed reading going on there lol

the fluke if set to the right conditions will do a 2 lead test and it makes Zs testing so much faster which when testing lots of lights or skts can save lots of time.

and i think the megger has a lead connector which joins the e-n together so infact making it 2 lead test again anyway

 

[Andy™]

and i think the megger has a lead connector which joins the e-n together so infact making it 2 lead test again anyway

it doesnt. just phase and earth go to it. there are 2 settings - 2 lead and 3 lead

 

[Andy™]

I must confess I always do it no matter what type of fitting is there

do you look like your avatar much when doing this?!

 

[Handy]

If your inspecting a new installation then you should be doing r1+r2 on every point (to prove earth cont and correct connection of accessories ) and then Zs the last point in the circuit to prove the Zs reading will give you 0.4 (0.2 on tt system) disconnection (unless an rcd is in circuit). On a periodic , 10% of accessories (I usually work to 20%) should be Zs tested on lighting circuits , a r1+r2 is not needed if the original test cert is available (this was what the nic man explained to me ).

All this should be noted on the test forms if a periodic is carried out .

Apologies for all the brackets !

 

[tricky01]

i always do a live Zs if possible, proves the cable you have just put back in the terminal is correct, can sometimes show up a dodgy fault your few volts DC on R1R2 dont show, .

Yes always important to do Zs . Either way can be calculated using Zs= Ze + {R1+R2} or by measurement. Remember though Zs soft test if RCD attached.Though best done by calculation .