Post by pinkie on Nov 2, 2016 15:47:33 GMT
Good thread
Its revealed 2 scary safety issues here - while I checked some things with my UK electrician. I know this is only obliquely relevant to balanced mains, but I feel a lot of ownership in this thread
1) I have a TT system, which is not what my French sparky told me. And the earth spike was dug up when doing the pool landscaping. The electricians measured the loop impedance at under 100 ohm so concluded the cable running through the ground to the spike was adequate without the spike itself. Now I realise that is my only earth, I am conscious that I have just covered 90% of it with waterproof terrace. I have just ordered a loop tester - but the RCD's are still firing , so whilst that is hardly a full test, the impedance can't be grotesque. They can fit a new spike for me when...
2) My connection to the house from the meter (60A control switch) is loose in the open roadside meter cabinet made with a large junction block. 2 unprotected wires flapping around in a box which a meter reader expects to open, and any member of the public could. And, although not me who did it - my responsibility since it is house side of the sealed box. F*&%!
Back on balanced mains - well grounds and noise - I am led to believe that noise does not bleed away to earth. However, super duper mega earth beds can do no harm if connected to the earth at the incoming supply earth bonding point. The danger comes from having different parts of the system connected to different earths. Earth is not a great conductor. The soil impedance can allow high voltages to develop between earth points. So all earth points should be connected by low impedance cable of sufficient diameter.
This is one of the reasons the water pipes are bonded to the earth system. The incoming metal water pipe is an earth connection. Bonding it to the electrical supply ensures it does not become a separate earth connection at a different potential to the main one. Cleaning the connections on it will ensure a really good safe low impedance connection to the main earth, but is not intended to improve your earthing. Of course, in effect it gives another earth spike (except here my water supply to the house is plastic pipe!)
Its revealed 2 scary safety issues here - while I checked some things with my UK electrician. I know this is only obliquely relevant to balanced mains, but I feel a lot of ownership in this thread
1) I have a TT system, which is not what my French sparky told me. And the earth spike was dug up when doing the pool landscaping. The electricians measured the loop impedance at under 100 ohm so concluded the cable running through the ground to the spike was adequate without the spike itself. Now I realise that is my only earth, I am conscious that I have just covered 90% of it with waterproof terrace. I have just ordered a loop tester - but the RCD's are still firing , so whilst that is hardly a full test, the impedance can't be grotesque. They can fit a new spike for me when...
2) My connection to the house from the meter (60A control switch) is loose in the open roadside meter cabinet made with a large junction block. 2 unprotected wires flapping around in a box which a meter reader expects to open, and any member of the public could. And, although not me who did it - my responsibility since it is house side of the sealed box. F*&%!
Back on balanced mains - well grounds and noise - I am led to believe that noise does not bleed away to earth. However, super duper mega earth beds can do no harm if connected to the earth at the incoming supply earth bonding point. The danger comes from having different parts of the system connected to different earths. Earth is not a great conductor. The soil impedance can allow high voltages to develop between earth points. So all earth points should be connected by low impedance cable of sufficient diameter.
This is one of the reasons the water pipes are bonded to the earth system. The incoming metal water pipe is an earth connection. Bonding it to the electrical supply ensures it does not become a separate earth connection at a different potential to the main one. Cleaning the connections on it will ensure a really good safe low impedance connection to the main earth, but is not intended to improve your earthing. Of course, in effect it gives another earth spike (except here my water supply to the house is plastic pipe!)