Zs tests.

[madeinengland]

hi i have my 2392 exam coming up in a couple of weeks and we need to do a full set of tests on a composite board. i have conflicts between my notes and what i find in books. for the Zs test does all bonding and earthing need to be in place or do you disconnect the bonding for extraneous parts?

my tutor told me (and therfore in my notes i have) that you disconnect the bonding for the water and gas pipes as you will send a small current through this bonding and therefore could shock someone in a real life situation.

but i've just read in a book that in order to do the Zs test it says "ensure all earthing and bonding is in place"

headbang

 

[PoorFish]

As far as I am aware you keep all bonding in

With Ze you take the main bonding out

However there will be more experienced answers to follow this one ......

 

[Zeespark]

Main Bond is the only cable to be removed from the main earth bar, other earthing cables (CPC's etc) to stay put, otherwise you will get readings from parallell paths. Apologies if I have got the cable names wrong .

AndyGuinness

 

[madeinengland]

cool so if i remove the bonding to the water pipe and gas pipe that will be like removing the main bond??????????

 

[Zeespark]

No you leave those alone, no need to remove them, just the cable between the consumer unit and the cable head/rod.

AndyGuinness

 

[bulmer]

If you remove your earth conductor from the earth bar, how are you going to get a zs reading?

Also as zs is a live test, i've been taught that all bonding is to be in place.

 

[ADS]

If you remove your earth conductor from the earth bar, how are you going to get a zs reading?Also as zs is a live test, i've been taught that all bonding is to be in place.

This is correct

Zs - everything left in place and connected.

Ze - Remove the earthing conductor from MET, croc clip on end, probe on incomming Line conductor.

 

[Zeespark]

Ze and Zs are different tests.

AndyGuinness

 

[ADS]

Ze and Zs are different tests.AndyGuinness

But he was asking about Zs

 

[Zeespark]

DOH My mistake I apologise, for that test ALL bonding in place.

AndyGuinness

 

[madeinengland]

i know how to do the tests. Ze is done with green lead connected to incoming earth which is disconnected from earth block/M.E.T and blue and brown probes to incoming phase and nuetral respectively in top of main switch.

Zs is done for example at a mains socket using the plug lead.

If you remove your earth conductor from the earth bar, how are you going to get a zs reading?Also as zs is a live test, i've been taught that all bonding is to be in place.

i'm not removing the earth conductor from the earth bar to do a Zs test.i'm talking about the bonding that goes to the gas and water pipe on the test rig.

if this is connected and you do a Zs are you sending a current down all the bonding?

therefore potentially livening up all metalwork like water pipes and radiators etc.anyone who touches these items during this test will get a bolt. or have i got my wires crossed.so to speak

 

[m4tty]

I think the bonding is connected when doing Zs test which includes parallel paths which is the reason measured Zs is less than calculated Zs=Ze+(R1+R2)

I await to be corrected

Cheers

 

[madeinengland]

thanks for the responses guys. the general view is that ALL bonding is to be in place and that's good enough for me.

the tutor definately said that you should disconnect the water and gas bonding for Zs. he also said it should be done for insulation resistance too as we've been taught to do it on the earth block in ccu.

but he could have meant something else as a couple of times he's said one thing but meant another. but i guess that's what you get when the course is 6-9 at night, concentration is hard.

 

[bulmer]

All bonding is kept in place as the installation will be now live and on a live installation, you wouldn't disconnect any bonding would you?

Plus with it in place, the installation is as it would be under fault conditions.