Impedance testing

[johnnyjb]

Why is it neccasary to remove equipitential bonding when doing a test on Ze
Is it true that you can leave them connected for final circuits inside a house this is the way we do it at work !!!!

 

[Adam_151]

When testing Ze, you should have the main switch off and diconnect the earthing conductor and clip onto that, to ensure the ze is the impedance of the earthing facility and not parallel paths, remember to reconnect earthing conductor before closing switch!

When doing Zs, you leave everything connected (removing main bonding while energised is not a good idea!), you accept that the figure you obtain will be affected slightly by parallel paths

 

[RF Lighting]

I have only had it once, but I have been on a job where the suppliers main earth had failed, but the house was still receiving a good earth through the parallel paths provided by the earth bonding / incomming services.

Had I carried out the Ze test with the bonding in place, it would have appeared that all was well.

 

[dingbat]

RF, I get that with lots of houses in LS6.

But it's okay... it's only for students, after all!

 

[RF Lighting]

Mine was all the way over in Morley.

LS6 has featured on Picture of the week! on more than one occasion though

 

[securespark]

I have only had it once

Poor you!

Seriously, I've had poor (or even atrocious) Ze's loads of times, even on PME.

I had one on PME that was high. I rang Central Networks & told them I had a poor Ze on PME.

"What is the value?" she asked.

"The highest value I'm getting is 15...." I began.

"Gosh that is high for PME!"

"...hundred", I finished.

[Klaxon going off in background]

The house was built in 1975 & it turned out the N/E link screws had never been tightened properly, hence the fluctuating values.