3 ms·
What do you do for grounding if your house sits on bedrock? We barely had enough for the "buried in trench, 30" deep" option at our house before hitting the so
by lutorm 7y ago
What do you do for grounding if your house sits on bedrock?
We barely had enough for the "buried in trench, 30" deep" option at our house before hitting the solid lava everything here is built on. (And it's buried in mostly gravel, there is practically no dirt.)
- dangrossman 7y agoApparently, according to an internet source I have not vetted, you lay the 8 foot rods in the bottom of the 30" deep trench.
- supermatt 7y agoThats what parent says they have already done.
- supermatt 7y agoRun a large gauge wire to another location where you can put a better earth. In reality, you are likely on a TN earthing system, so you already have a low impedance earth wire supplied from your local transformer and your local earthing is just a "backup".
- angry_octet 7y agoA ground driven into rock or buried in dry gravel isn't going to be of much use. Typically electrodes are buried in a mixture of bentonite and gypsum, which is pH neutral and provides low resistance. There are also chemical (salt) earth fills which work well but require thicker copper electrodes to deal with corrosion. Various conductor arrangements are used, but in shallow trenches there is always the problem of the wires being cut. A radial or cartesian mesh burial over a larger area would be typical. You can buy electrical mesh and ground enhancement fill for this purpose. Note that you still need it to be below the frost layer in your region -- which varies from 15cm (California) to 300cm (Canada) depending. An earth connected via a distant cable isn't going to be effective against lightning (transients are high frequency and hence conductivity is constrained by the skin effect, and long wires have high inductance even if they have low DC impedance), and additionally is poor practice as it is more lightly to be cut without someone knowing in the future. I doubt any EE would approve it when other methods are available. https://blog.nvent.com/erico/erico-what-is-soil-resistivity-and-how-does-it-affect-grounding/ https://blog.nvent.com/erico/erico-what-is-soil-resistivity-... Cf IEEE 80 & 81
- arminiusreturns 7y agoFun story, in the Marine Corps they pee on the rods to make them ground better. (for mobile CoC's)
- angry_octet 7y agoLet's hope they do that before they power up their gear. Ouch. The mobile radar and HF guys have lots of tricks like this, but also spend lots of time hammering spikes with a sledgehammer.
- deleted 7y ago[deleted]
- dmurray 7y agoI don't see anything that says the rod has to be driven vertically, so burying in 30" or even less of damp soil looks OK.
- ttsda 7y agoThe OP's article has a picture that shows a rod buried horizontally, so it is possible
- mturmon 7y agoThere's a whole story behind that: https://en.wikipedia.org/wiki/Ufer_ground https://en.wikipedia.org/wiki/Ufer_ground This works most easily if you are pouring a concrete foundation and can incorporate the grounding electrode during the pour.