Has David Cockburn disappeared from this forum?
Has he Gone
- Thread starter ebee
- Start date
He is still upsetting them on the IET!!!!!
Ho Heck - just when you thought it was safe .................
I dont think he was for real he was just trying to wind people up!
Prince of Darkness was my fave what happened to him/her??
Prince of Darkness was my fave what happened to him/her??
Holmslaw seems to have taken a break as well !
I, Bernard Green, assure you and others that I have formed my opinons about earthing and bonding and equipotential areas from 40 years of electronic and electrical design. fault finding and consultancy.
An important part of my decision process is the history of how true earthing to ground via the lead sheath of the supply cable became obsolete for economic reasons and was replaced for many customers by supplying the "earth" via the neutral. One less conductor in the network so almost 1/3 removed from the cost of cables. Because over head twin wires could break leaving the neutral open circuit it was sensible to retain the earth rod to ground as in TT supplies. voltage operated circuit breakers between the internal earth wire ( the CPC ) and the ground rod would detect a fault and disconnect the power. That was OK until immersion heaters and and boilers connected to metal water supply pipes became common and introduced parallel paths for earth currents to true ground. These currents could then by pass the coil of the circuit breaker. ( Although called voltage operated the trip mechanism actually operated like all device on the current in the coil of an electromagnet, the voltage had to be great enough to drive enough current through the impedance of the coil. ) The CPC would still not rise above the trip voltage of the breaker but the fault current in the parallel path could be very high and dangerously high if the path was not capable of carrying the current that the fuse would allow to pass.
Current operated RCDs that operate on the difference between current in Live and Neutral are probably the best way to detect and react to faults and electric shocks involving a current flowing to earth or ground from the Live and/or Neutral.
Provided a true ground to anything but ground floor buildings, such as flats on the first or higher floor is not easy or reliable using a ground rod. Ground floor properties need the ground rod to be checked from time to time and may be in-effective in drought conditions. So the TN-C ( PME ) supplies became common as they were generally seen as more reliably safe than using a ground rod.
But all this is a compromise and the fit all (all = 99% ) regulations and terminology do not fit the 1% of non standard situations.
That's why you can still request a TN-S supply or convert to TT for the 1% of non-standard installations.
I don't think anyone is saying you don't understand earthing. It's bonding you seem to struggle with. What it's for, when to install it and why it's different to earthing.
I don't think anyone is saying you don't understand earthing. It's bonding you seem to struggle with. What it's for, when to install it and why it's different to earthing.
I think he's gone for good - he took almost all of his posts with him when he went.
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