What's your lowest Ze recorded on a TT system

[rodney12]

Hi all,

As above really, just wondering the best Ze reading you've ever got on a TT system. Best i've found to date is 21 ohms.

Just how low is it possible to get? i'm intrigued...

 

[Guest123]

4 ohms.

On a construction site, 120mm earth and LOTS of copper in the ground.

 

[AA410]

Hi all my latest is 2.96 ohms with a 20ft scafold poll put in the ground with a jcb

 

[pennywise]

Sorry dragging this thread up from the dead but today managed to get a reading of 0.51 on the earth rod for a garage only a 3/8in 1m rod into soft wet ground couldn't believe what i was seeing (tested with an earth loop impedance tester).

 

[Mr Mark Sparks]

tested to stake cpc only?? or connected to cu

either cpc on feed cable is still connected or there is a n-e fault and the efli is gettig away that way

 

[pennywise]

Test was done at earth rod in the pit just after it was driven in, there is no neutral earth fault within the installation, and the supply has just been commissioned by the LEB.

 

[Des 56]

These extra low readings may be because of close proximity to a Tnc-s stake earth and commuting that way
The supply transformer earth resistance would account for greater readings

So a proper guiness book of records low TT reading is not awarded as far as I'm concerned
,thats because my best must be in the mid twenties only

 

[steamboatwilly]

Test was done at earth rod in the pit just after it was driven in, there is no neutral earth fault within the installation, and the supply has just been commissioned by the LEB.

If the test was done at the pit that's not a REAL Ze then is it? Mind you, I'm only jealous as my best is a mere 47 Ohms. I've had a Zs of 7 Ohms on a TT system before but alas that doesn't count either!

No Guinness Book of Records entry for me then....

 

[Darkwood]

If you wee on the earth rod i bet you can knock a few more ohms off

 

[empress]

If you wee on the earth rod i bet you can knock a few more ohms off

for dramatic results pour a bucket of water round it and watch the Ze drop like a stone.
backs up the old dry conditions for earth rod test..

 

[legge]

0.51 ohms by pennywise? - sure you haven't driven the rod againsed the incomming supply cable or gas pipe? a colleague of mine did exactly that (near miss!). BTW, my best reading is 15.6 ohms

 

[Sintra]

I am going to have to but in here and claim the all time record low for Ze on a TT system.

In Paris last week testing a new installation tested 0.14 ohms for a Ze on a TT (couldn't believe it).

The installation is a large office complex with a 3 phase TT supply. Main incomming cables are 240mm with 120mm main earth. This part of the installation was existing. After a lot of investigation as to the type of electrode used it was established that the 120mm main earth was conected to an earth plate buried in the courtyard of the building. From this plate a tape was run underground around the perimiter of the building and back to the earth plate in a ring.

Hope this gets me into the guinness book of records for lowest Ze on TT.

 

[Guest123]

After a lot of investigation as to the type of electrode used it was established that the 120mm main earth was conected to

THE EIFFEL BLOODY TOWER!!! to get a Ze like that on a TT.

 

[Sintra]

THE EIFFEL BLOODY TOWER!!! to get a Ze like that on a TT.

Wouldn't surprise me in 25 years of sparking never seen a set up like this. Would be interested to know if this type of earthing is common practice in Paris or France in general.

 

[Guest123]

I thought my 4 ohms was pretty dam good!!!!

 

[Sintra]

4 ohms is pretty darn good. Think my previous lowest was about 28 ohms.

 

[AA410]

It knocked the nuts of my 2.96 with me scaffold pole

 

[pennywise]

I thought that I had gone through something at first, but i've been on the job before the garage was biult ie. when they were digging the foundations and preparing the ground for the garage there was nothing there and the supply comes into the grounds of the property on an over head line so I haven't hit that.

 

[jimmus]

Wouldn't surprise me in 25 years of sparking never seen a set up like this. Would be interested to know if this type of earthing is common practice in Paris or France in general.

Did a lot of installation work at euro-disney and yes this is commonplace in France.
They love their TT and run loads of tapes round everything, at E-D every ride/stand etc had its own tapes run round it - dont ask me why, I was just there chucking these things in the ground because they were paying a fortune and it was no brain donkey work
Will have fantastic scrap value for whoever gets to rip it all out in the future!

 

[Phil Mumford]

I regularly get less than 0.2 Ohms on TT. Maybe its because I forget to disconnect the main bonding conductors