We were looking into getting our home battery set up turned into an emergency power supply (which will require the fitting of earth rods).
Our battery fitter has suggested fitting them into the soil under the house (which seems counterintuitive to be given how dry it must be). Is this okay (as long as the resistance is low enough)?
Tim
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Thanks, that's reassuring.
A follow question regarding the practical aspects of installing. Our understairs cupboard has limited headroom. A nearby cupboard has plenty of headroom but lots of pipes in the subfloor space. All visible but not much room to work if width is needed. Which would be better?
Tim
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It is probably less dry than you imagine. You will avoid the risk of damage to an external earth rod and its neater as well. A good suggestion I think. John
On 28 May 2025, John R Walliker wrote
FWIW, I was under the impression that the soil under the house was an extremely common position for an earth rod; I'd probably assume that's still the case.
Mine is simply pounded into the clay 2 inches from the wall where the electricity supply comes in
Excuse my igorance but why are earth rods needed? Could the ordinary electrical earth not be used? Is it because the emergency could involve damage to the neutral/earth outside?
I think the usual reason for an outside earth is that most modern houses are built with a solid ground floor, or with a concrete "raft" as he foundations. There should be a barrier membrane, so you can't drill through it without affecting the membrane.
If you have plain soil underneath It would seem the logical place to put it. The moisture content under the house is likely to be more stable, so once a value has been measured, whereas one outside would experience and so perhaps get too high in a drought
Dave
John Ward explains what the possible problems are and the options
As a matter of interest where are the batteries to be installed, or are installed?
I was under the impression they could no longer be installed in a loft space or under stairs for fire access and safety concerns. If installed indoors fire safety and methods of exit in the event of a fire must also be considered. If fitted on an outside wall there is a minimum distance to any window or door.
Would modification to an existing battery fitting also have to consider the above.
Loft
No, it’s just an advisory. As they’re lithium iron phosphate batteries I have no concerns.
Tim
I like John Ward. He is a clear communicator. He would make a good expert witness,
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