When I had my home rewired I was told that 'earth-rods' were no longer used and the electrician earthed everything back to a connection on the incoming line before the company fuse and meter. A friend mentioned that he had fitted an earth-rod when he had his water supply changed to plastic piping. Is one of the above wrong or are both OK?
Depends. It seems your earthing system was a TT, but is now a TN arrangement. If there is a green 'PME' sticker on the DNO fuse housing, then no problem.
Your friend should not be using the water pipe as an earthing conductor, unless it is a private supply. Some older houses do have their main earthing through the water pipe, but it really shouldnt be left like that. So he was probably right in changing it to an earth rod.
As a general statement it is complete crap.
However in a specific case, (which is what he may have meant) perhaps the elect-co decided to provide a TN-C-S earth (which is connected to the neutral at the incoming cutout). This is dependent on there being MEN (multiple earth-neutral) protection points along the distribution path - which they may have added, upgraded or even decided what they had was OK.
His earth may have always been TT and been derived from the metal water pipe - something which is no longer allowed.
As a general statement its incorrect to claim earth rods are no longer used. However for any given supply its possible that an upgrade on the supply side, has ments that you no longer need your own earth rod, and that the supplier can now provide a main earth connection.
In times past it was not uncommon for properties that had no provision of earth from their supplier to use incoming metal services to provide one. The practice is not allowed now, however as with practices of this nature existing installs do not necessarily get upgraded until there is some material change that forces them. The change of service provision to plastic being a common cause.
Both are ok (with the note that the statement about earth rods is incorrect taken as a general statement)
The different earthing types are explained here:
and TT here:
So why not have all of the above for safety, or would that start earth currents if an earth further back went dicey? I remember that when I was young, we always buried something like a copper pan with an earth wire on it at the ent of a long cable to make the earth locally good. I'm still alive. Brian
Why not?
Its allowed, and there's lots of it about, but not allowed to be installed that way any more. Trouble is if a water supply pipe is replaced with plastic, you no longer have a good earth.
NT
completely untrue. Its called TT earthing.
supplier's earth feed
normal/sensible
NT
That doesn't sound right to me. Everything up to the output of the meter is either the responsibilty of the DNO or the company you pay for electricity. IMHO a "domestic spark" shouldn't be messing with anything pre the meter output or Main Earth Terminal.
Did the spark connect to a DNO provided a MET or just put an earth clamp around the armour of the incomer? If that latter you may or may not have a properly earthed system.
Because the water co says so :)
It is actually that...
Plastic water pipes, innit.
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