TT earth cable small and god knows where the rod is

Diver233 · Mar 31, 2019

Just started to test a TT system, so found the earth and thought that cannot be it for the size of the house. (See pic). So tested the Ze and got 94 so less than a 100 but I thought I’d check the connections to the earth rod. Cannot find it anywhere. I can see a new main electric feed has been put in at some point because the old one is still there.
So my question to the more knowledgable is, how long ago was a 2.5mm cable for a TT earth allowed and also should the installers of the new main (aprox 2005) into the building have picked that up ? At that point.
Turns out around that time the garage where the inlet is was connected to the house and I’m guessing they concreted over the earth rod.

[ElectriciansForums.net] TT earth cable small and god knows where the rod is

Top Cat · Mar 31, 2019

I am Olllllllllllld and we didn't use a black earth wire in 1900 and frozen to death! so it was probably a DIY install!
Mind you it could have been me when i had no green and yellow, or just green as it was in the 'good old days'!

Diver233 · Mar 31, 2019

I only go as far back as the 16th, but it has surprised me when the New main cable was installed it wasn’t changed then.

buzzlightyear · Mar 31, 2019

Diver233 said:
I only go as far back as the 16th

try the 17th century .

Deleted member 26818 · Mar 31, 2019

2.5mm2 currently the minimum CSA allowed.
So any time since about 1900 to present day.
As for the colour black, again any time from about 1900 to about 1966.

Top Cat · Mar 31, 2019

I started when the 14th edition was out and believe me, we didn't give a sh*t!

Diver233 · Mar 31, 2019

Top Cat love the honesty

TJ Anderson · Mar 31, 2019

2.5mm min if not buried and protected against corrosion and mechanical damage.

You need to locate that earth electrode

Diver233 · Apr 1, 2019

Going to put a new electrode in with new cable, hoping to lower the reading a bit.

davesparks · Apr 1, 2019

I suspect it would have originally had a VOELCB which that black earth would have connected in to.

Sparky Pat · Apr 1, 2019

Agree with davesparks, I believe black was an accepted colour for an earth wire back in the distant past.

davesparks · Apr 1, 2019

Top Cat said:
I am Olllllllllllld and we didn't use a black earth wire in 1900 and frozen to death! so it was probably a DIY install!
Mind you it could have been me when i had no green and yellow, or just green as it was in the 'good old days'!

How old are these old days? If you go back far enough you'll find that green was once a phase colour.

bill01803 · Apr 1, 2019

My fathers house had a water bonding wire dating back to when the house was build in 1936 which was a red VIR 7/044

FatAlan · Apr 1, 2019

Save yourself some digging and check with DNO to see if they can give you a PME connection.

Taylortwocities · Apr 1, 2019

Diver233 said:
but it has surprised me when the New main cable was installed it wasn’t changed then.

Not suprising. As it is a TT, the earth connection is the responsibility of the customer, not the DNO.

TJ Anderson said:
2.5mm min if not buried and protected against corrosion and mechanical damage.

You need to locate that earth electrode

Yes. That electrode needs finding. Its a screwed termination, so should be accessible. (Its probably under the floor of that new extension!).

And a small weedy cable to the earth electrode isnt suprising. After all, its only required to carry enough current to trip the RCD.

FatAlan said:
Save yourself some digging and check with DNO to see if they can give you a PME connection.

Absolutely!!

static zap · Apr 1, 2019

Taylortwocities said:
And a small weedy cable to the earth electrode....
Enough to trip RCD

And survive some mechanical damage / corrosion ....!

Diver233 · Apr 7, 2019

So an update.
Installed a new earth rod and cable, ze now down to an amazing 0.29.
We pleased and well worth the effort

Taylortwocities · Apr 7, 2019

Is that 0.29ohms just the rod? All other earths disconnected?

Lucien Nunes · Apr 7, 2019

ze now down to an amazing 0.29.

0.29 ohms, or kilohms? What did you drive the rod into... the water pipe or the service cable neutral?

Diver233 · Apr 7, 2019

Just read my post lol,note to self read what you write before clicking post, 29Ω was reading 99Ω when I started.
First earth rod I have replaced so was not sure what to expect, thought maybe 45-50Ω, but was really pleased with 29Ω.
Is that about right ?.

Deleted member 26818 · Apr 7, 2019

29 Ohms is very good.
Especially when you consider the line, transformer windings and the rod at the transformer is supposed to be 21 Ohms.

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