TT Earth Electrode indoors?

[George Miles]

Is there any reason not to have an earth rod indoors? TT system.

I've got 2 earth rods outdoors, can I keep them and add a third indoors so there's less resistance?

[george]

[Alan]

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.

[Cursitor Doom]

Should really be earth loop *impedance* tested at 50Hz.

[Max Demian]

Do you live in a mud hut with an earth floor?

[George Miles]

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 i hope

[George]

[John Rumm]

No reason why not, although you may find it harder to get a low impedance in what will likely be drier soil.

[Andrew]

So, not a problem for those with 'internal wells' that are now 'features'.

[John Rumm]

I feel I have missed something?

[Andy Wade]

Access for inspection and testing? You might not want an earth pit [*] visible FVSO "indoors".

[*] e.g.https://www.screwfix.com/p/plastic-inspection-earth-pit/59527#_=p

[John Rumm]

ISTM if you have a slab floor, having one you can lift for access to your inspection pit[1] would not be unreasonable.

[1] or more typical terminal cover:

[Iggy]

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.

[Cynic]

Citation please

[Brian Gaff]

Also of course when dealing with such low impedance systems the way you connect them together will matter as well. some very thick copper? Brian

[The Natural Philosopher]

[Roger Hayter]

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.

[Roger Hayter]

I was momentarily surprised that your URL gave the stock position at my local Screwfix; until I remembered the miracle of cookies.

[John Rumm]

That seems unlikely. You may make little or no improvement, but so long as you are not disconnecting the existing electrode its not going to get worse.

That really depends on the local soil conditions.

The benefit it sounds like the OP is aiming for is that of better redundancy and fault tolerance, since the connection to the existing electrode is vulnerable to damage.

(Protecting the existing main connection better would seem prudent also)

Multiple rods are ok (and are commonly used in the supply side of PME installations for example), but ideally don't want to be too close together such that they are in overlapping resistance areas.

You can't say that with any certainty. More rods "may" not be better - but then again they might. It will depend on the circumstances and local soil conditions.

I suspect if you have a lightening strike or fallen power line *inside* your property, you have other things to worry about.

[tabbypurr]

You sure do talk cobblers

[Iggy]

1 - Seems unlikely? What if there's a plumbing leak, rain flooding into the basement or an overflowing washer? Thanks but no thanks for that "fun" in a lightning storm.

2 - Yep, that's why I said "could".

3 - Of course, I don't disagree with better protection, but there's absolutely no such thing as redundancy. A 2nd rod and connection would send power into 1 earth, through the entire building's appliances and out the other earth...you just fried every device and person in contact with any device.

4 - Again, the more rods and distance just becomes further reach and obtaining what was missed before. You unwittingly turn the system into a lightning arrestor and melt the incapable earthing entirely.

5 - I just demonstrated the more rods failure. But how is saying, find out what you have before doing any such nonsense, nonsense? He very well could be extremely low already and doesn't know it. Earthing of only a certain resistance range is needed, anything more kills its operation and anything less changes nor improves nothing...he, uncommonly, has 2 for a reason.

6 - Sorry but, that's absolutely wrong. A rather large area (bigger than the whole house) will be energized by lightning or even a power-line. Why do you think they say to stay off corded telephones, earthed appliances and that's including computers during lightning storms? Not new stuff.

7 - I appreciate your points, but you desperately need an Earthing Refresher. You have some very bad information. Thus why, PME's are banned for broad area situations.

[Andrew]

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 ?.