Zs

[Sparky Ninja]

This threads never gonna end



You will notice that the illustrations in the OSG & GN3 have only one circuit in the consumer unit, hence no parallel paths, hence no need to illustrate it disconnected. They also appear to be thermoplastic multicore cables and not steel conduit or any other potentially parallel path providing wiring systems.....

 

[snowplough]

Thanks for replying widdler,

I was wondering that and you have just confirmed it with the illustration,

I never thought that you could get parrallel paths effecting your reading when you do the Dead test R1+R2 (method one) connecting to the earth bar, and i thought it was just when you had metal conduit etc protecting the cable .
I wonder why we are not told at college then to discoonect cpc from earth bar when doing metod one?.

Many thanks for your feed back ,i must speak to my tutor after the holidays

regards

Locket

 

[pushrod]

If you are testing in the workshop and you can see you just have T&E everywhere, then putting a little test lead on to the earth bar or clipping onto the earth bar can save you quite a bit of time disconnecting and reconnecting, especially if you are in some form of timed assessment.

 

[snowplough]

Hi Pushrod,

I appreciate that but ii would have never thought i could be getting incorrect readings and i would have tesred like that in real life, because surely you would always disconnect to be on safe side and just test cpc disconnected knowing nothing else can encourage your readings.

All this gives me more questions then answers, It might be an incorrect R1+R2 reading on a all, but if it helps to keep the Total Zs reading lower, hence keeping within disconnection times to prevent electric shock ,does it really matter?

Thanks for your constant feedback

Locket

 

[pushrod]

Sorry locket have read that a couple of time times but not really sure what you're saying.

 

[snowplough]

Sorry push should read what i write,

I started off saying that i would never have thought you can obtain parrallel path readings by using the test method two with croc clip on earth bar on a R1+R2 dead test, which would give you a lower reading .
Then i was thinking well it might be an incorrect R1+R2 measured reading by not disconnecting the cpc from earth at test, but does it really matter when overall, it can only contribute to a lower Zs reading, which means disconnection times can be met, lowering the electric shock risk.

Many Thanks

lOCKET

 

[pushrod]

Got you now.

R1+R2 readings are fundamental when designing and installing. Checking them allows you to compare to design/check quality of installation. If you are doing an R1+R2 you would want it to be accurate.

When you have an existing installation ie you are doing a minor works or a like for like replacement/repair that is where the emphasis moves more to your Zs reading.

 

[snowplough]

Thanks pushrod for your input,

Ive loads more questions ,but ill save them for another day

akaind Regards

Locket