Discuss Max Ze for TT system in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
How about this:
Will a RCD work even without a main earth!
We know what it say's, but i'll guarantee you, that virtually every poster that comes on this and other forums, that isn't knowledgeable on TT systems, take that figure in BS 7671 as being the stated maximum and that's what they inevitably will work too!! ...And why i always Poo it off!! lol!!
The whole section on TT earthing needs a thorough sorting out and a bit more guidance wouldn't go amiss either!!
I'm going home (Cyprus) for Xmas this year, and while home, i'll be checking my own TT system. Earlier this year (early summer) it was around 0.93 ohms which has been steadily dropping year on year from around 4'ish ohms.
Here on site, our earth fields were tested middle of last month and recorded 0.17 ohms and 0.21 on the other. The highest value recorded this year was 0.28 and 0.30 respectively, which corresponds to similar test results conducted last year.
It's surprising what can be achieved when you know what you're doing!! lol!!
In a word, no. Fault current needs a path to earth for an RCD to operate. If that path is through you then yeah, it will operate if your bodily resistance combined with the resistance of whatever you happen to be standing on is low enough to allow more than the rated current of the RCD to flow. That said, the requirements of fault protection will not be met if a fault can occur leaving an exposed conductive part live and ready for you to become the earth path!
Im assuming that I'm providing an answer to a genuine and not a rhetorical question
Here on site, our earth fields were tested middle of last month and recorded 0.17 ohms and 0.21 on the other. The highest value recorded this year was 0.28 and 0.30 respectively, which corresponds to similar test results conducted last year!
If you touched a live cable and you was not earthed, you would not get a shock as there is no path to earth. If you make a path to earth then rcd opens simple.
But the whole point is that the system should disconnect before you can touch what is live!
Just to clarify,
the max recommended values I gave earlier were for run of the mill and domestic type circuits and not for the more specialised installations.
Edited last post. Not necessarily!
ADS doesn't rely on the customer being the earth! lol
My question was only 'will it work!' :devilish:
Do not need to discuss all the diferent scenarios.
Then the right answer would be - Not always! lol
Final answer?
What about class 2 lighting circuits that have no earth?
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