Is there any reason not to have an earth rod indoors?
I've got 2 earth rods outdoors,
can I keep them and add a third indoors so there's less resistance?
On Mon, 25 Dec 2017 04:20:13 -0800, George Miles wrote:
What is your earth rod resistance now?
Adding an extra rod is not guaranteed to lower the total resistance.
If you are currently getting 10 ohms than adding another rod will not
really help, however if you have 150ohms or so, then an extra, or deeper
rod may well help.
AC is preferred for earth electrode testing since it avoids any
electrolytic effects on the electrode when using DC. (you can test with
DC, but its good to take a few readings reversing the polarity for each
I don't think domestic earth systems are as low impedance as one might
think. Someone said between 10ohms and 150ohms, and these are the sort
of figures attainable without burying huge amounts of copper. Conductor
diameter is more governed by possible fault currents than anything else.
Also mechanical strength may be relevant if exposed. You won't go far
wrong in a house using 16mm^2 and that may be unnecessarily big.
There are, of course, regulations you can look up if necessary. But
huge bus bars are probably not useful.
The Earth Impedance has been tested and is OK,
but the plastic casing covering the earth wires clipped to the wall has been broken,
it's where it can get knocked by wheelbarrows etc,
it would be so much neater to not have wires clipped to outside walls
but to have the earth rod under the consumer unit indoors.
The floor is flagstones on earth,
(its a Victorian house)
so I should be able to put an earth rod indoors
even if it means drilling through some footing
On Monday, December 25, 2017 at 12:20:16 PM UTC, George Miles wrote:
ISTM if you have a slab floor, having one you can lift for access to
your inspection pit would not be unreasonable.
 or more typical terminal cover:
Well I was thinking of those programs like Homes Under the hammer, which
was one situation where a house bought at auction turned out to have
an old well inside the property.
It was dry-ish but with some nice ferns growing so the new owners
installed some wall-washer lights and put an inch thick slab of
glass over it as part of their new kitchen floor. It looked quite
interesting, but I would have thought at a wine store would
have been a better use for it.
Being not-dry, I presume they could have stuck their TT earth
rod down there at the bottom ?.
replying to George Miles, Iggy wrote:
Yes, you bring unregulated and unwanted electricity into the building and you
may SEVERELY worsen your earthing. Close lightning strikes energize the earth
and would energize your earth rod. Poor earthing conditions are dry soil, so
being under the building's footprint could mean little to no earthing actually
happens. The 3rd rod should NOT be a replacement of the existing 2 and MUST only
be added to the existing 2 by a jumper conductor...ONLY IF determined to be
needed or beneficial.
This addition or by driving your existing rods deeper, is the ONLY way to reduce
your resistance. But, what is your current resistance? If you're already at very
low resistance, then you likely can't make it any better because you're down to
the conductor's own resistance. Don't do anything unless and until you know what
your resistance is. More rods IS NOT better and WILL only extend your reach to
pick up static electricity, fallen power-line or lightning energy...a deeper
single rod is factually best.
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