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Earth rod, RCD tripping fault

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Discuss Earth rod, RCD tripping fault in the UK Electrical Forum area at ElectriciansForums.net

J

Jel

1st question:
Had to install a earth Rod in rural area today because the Ze on the current TN-S system was too high.
All the circuits are brand new, but for some reason a circuit with LED Haler downslight on seem to trip when the systems earth is changed to the earth rod. The Ze of the system is 11.1ohms.
Every other circuit is fine.

2nd Question:
As my Ze is higher, all the readings im getting for my Zs are too high, but would i be right in thinking they circuits meet the disconnection times because of the RCD, so the high Zs does not matter?
 
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Also another thought, the circuit did sometimes work, but if i went to turn the circuit off then back on again from switch it would trip. Could it be that i have too many halers on the circuit and the inrush is causing the MCB and RCD to trip? Maybe stepping up to a C type breakers.
Just seems strange when i connect old earth back in, lights seem to be ok?
 
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Max Zs for TT system is 1667 ohms, the quoted figures are for TN systems. 11.1 ohms Ze is more than acceptable for a TT system.
I can't see why changing the earth to TT would give problems, so further investigation of the circuit in question would be my choice of action.
 
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tony mc said:
What trips the RCD or the MCB?

What was the high ZE reading you had with the TNS system.

And yes the RCD will cover your high ZS readings. Is it lower than 11.1 ohms with the bonding connected?

I take it all your dead tests R1 + R2 readings were as expected !
Click to expand...


Well if i split the lights up they work, but when they are all connected it trips.
I have IR circuit and each light and all seem to be fine.
I though it was too high start up for Btype MCB, but the lights work fine on TNS system, just get all this tripping with TT.

There is no main earth bond to gas and water because the mains are plastic and most of the other pipes. All plastic under floor heating pipes aswell.
 
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Yes well this is actually an outbuilding at the back of someones house.
We have run supply there from house, but the earth is not good enough, so we have installed earth Rod as they did not want to pay for DNO to come out.
 
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GLENNSPARK said:
IR that circuit....if its the RCD thats letting go...then go line-earth.....and neutral-earth....at 500v...if its clear then try it at 1000v...just to be sure....
Click to expand...

IR is all clear, its all brand new cables.

The other strange thing is when i do my Ze that same RCD seems to trip, but i still get my reading?
 
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I would say something is not right in the wiring, as it "sometimes" works shouldn't be the case. If you are talking about LED Halers downlighters how many on the circuit?
Have you checked no caught wires in switch?
 
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the earthing arrangements for the distributers equipment is their responsibility.....further more as they have allowed it to be used as a means of earthing for the consumers installation.....the DNO then has a duty to maintain that earth........PERIOD!!!
 
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Jel said:
Yes well this is actually an outbuilding at the back of someones house.
We have run supply there from house, but the earth is not good enough, so we have installed earth Rod as they did not want to pay for DNO to come out.
Click to expand...

Makes a bit more sense then.
I'm assuming you have the correct sized cable for the load/length running to the outbuilding?
 
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Being stupid, as their was no main earth bonds connected thought it would be ok.

Have not been able to test inside the house yet as owner are away till next week, but i have had major issues with DNO lately and Ze being too high and they will not do anything about it as they say they do not maintain the earth?
 
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