Freddie Posted May 18, 2021 Share Posted May 18, 2021 Started my build in 2008. Single handed to complete shell in 2017, in between working and injuries. Pushing on with internal fit out at the moment and will post photos later, but for now I have a problem I need to resolve. The house is built on rock. the metre box is on the external wall of the garage. Rock to ground level is 525mm. I have a boundary wall, which runs parallel with the garage, 1500mm from the metre box. I have built up a 600mm raised flower bed 500mm wide attached to boundary wall 5 metres long, leaving a path 1 metre wide between the garage and the flower bed. The standard earth rod 1200mm x 5/8 inch has been placed in the raised flower bed. It goes right down to the rock and backfilled with topsoil. Earth cable is run in a length of 25 mm pipe under the path. My electrician can only obtain an electrical reading of 285 at every socket inside the house. This has to be brought down to below 200 to comply with regs. I don't think he has come across this situation before as I haven't seen him for a month. So, the question is :- Has anyone come across this situation before and how did you reduce the reading to below 200 ? I would appreciate any advice given. Thank you all for your kind attention. Freddie Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 18, 2021 Share Posted May 18, 2021 (edited) 6 minutes ago, Freddie said: Started my build in 2008. Single handed to complete shell in 2017, in between working and injuries. Pushing on with internal fit out at the moment and will post photos later, but for now I have a problem I need to resolve. Oh dear @ToughButterCupI think you have just lost the forum's diyMax crown. @FreddieI suggest you post your earthing rod resistance question in the electrical forum topic because resident experts are more likely to monitor their specialist subject topic Edited May 18, 2021 by epsilonGreedy Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 I don't understand Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 18, 2021 Share Posted May 18, 2021 3 minutes ago, Freddie said: I don't understand Just an in-forum joke @Freddie. Members here represent a broad spectrum of self build projects from hands-off cheque-book builds to personally laying every brick and roof tile at the other extreme. You sound like a hands-on self builder. Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 7 minutes ago, epsilonGreedy said: Oh dear @ToughButterCupI think you have just lost the forum's diyMax crown. @FreddieI suggest you post your earthing rod resistance question in the electrical forum topic because resident experts are more likely to monitor their specialist subject topic Okay. thank you for the message. Just learning to get around the site. doh. Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 2 minutes ago, epsilonGreedy said: Just an in-forum joke @Freddie. Members here represent a broad spectrum of self build projects from hands-off cheque-book builds to personally laying every brick and roof tile at the other extreme. You sound like a hands-on self builder. That's me ... extreme hands on " proper" self builder lol. Link to comment Share on other sites More sharing options...
ToughButterCup Posted May 18, 2021 Share Posted May 18, 2021 Welcome @Freddie. Sounds like you have forgotten more about self building than I'll ever know. See you over on the electricians forum. @Onoff will know the answer. Added to that he's tame and has a sense of humour. What more can a fella need? Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 Multiple rods to get the reading down, correctly spaced (there are guidelines)...or a copper earth tape in a long trench...or a bfo copper earth plate like an old HW cylinder run over a few times with the digger... ? Nothing to stop you combining the above. Increase the surface area of copper to earth is the key. (Dungeness power station had similar issues. They basically built it on a big metal mat). 1 Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 You might glean something from this: https://www.electrical-installation.org/enwiki/Installation_and_measurements_of_earth_electrodes Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 18, 2021 Share Posted May 18, 2021 4 hours ago, Onoff said: (Dungeness power station had similar issues. They basically built it on a big metal mat). My electrician said he struggles to get a good earth connection in an area of sandy soil nearby. Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 42 minutes ago, epsilonGreedy said: My electrician said he struggles to get a good earth connection in an area of sandy soil nearby. How hard has he tried? Seriously. Every electrode will likely have a resistance to earth even if really high. If you can't get depth then put more in, go horizontal etc. Double up, triple up whatever and the resistance should lower. Link to comment Share on other sites More sharing options...
Nickfromwales Posted May 18, 2021 Share Posted May 18, 2021 16 minutes ago, Onoff said: How hard has he tried? Seriously. Every electrode will likely have a resistance to earth even if really high. If you can't get depth then put more in, go horizontal etc. Double up, triple up whatever and the resistance should lower. +1. It's just down to x amount of increased cross sectional area. Some jobs I've had to whack 3 rods in to get something reliable. Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 Make sure your rod connections are clean and accessible. Tighten up and give a coat of something if fussy. Grease, Vaseline etc. A bit like when keeping car battery terminals in good nick. You can get earth inspection pits. https://www.tlc-direct.co.uk/Products/TLPT205.html? https://www.toolstation.com/earth-pit-plastic/p15291? Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 8 hours ago, ToughButterCup said: Welcome @Freddie. Sounds like you have forgotten more about self building than I'll ever know. See you over on the electricians forum. @Onoff will know the answer. Added to that he's tame and has a sense of humour. What more can a fella need? Thanks @ToughButterCup appreciate the help Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 One option is bentonite but that can shrink. You can buy moisture retentive clay to go over the top. Marconite is electrically conductive gravel. Some you just mix with cement. Then there's even more exotic conductive cement that in effect increases the rod diameter thus surface area. A bit ott for domestic. Not a bad shout if ever you have piles done to do an extra one for a deep rod. Saying that a mate's concession to earthing at his workshop is the earth conductor affixed by a pair of old mole grips on a scaffold tube banged into the ground! ? Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 41 minutes ago, Onoff said: Make sure your rod connections are clean and accessible. Tighten up and give a coat of something if fussy. Grease, Vaseline etc. A bit like when keeping car battery terminals in good nick. You can get earth inspection pits. https://www.tlc-direct.co.uk/Products/TLPT205.html? https://www.toolstation.com/earth-pit-plastic/p15291? Thank you @Onoff for your advice . The article on wiki is very interesting and I have learnt a lots from there. I will start off with 2 rods and keep adding if the reading does not come down. will let you know Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 3 minutes ago, Onoff said: One option is bentonite but that can shrink. You can buy moisture retentive clay to go over the top. Marconite is electrically conductive gravel. Some you just mix with cement. Then there's even more exotic conductive cement that in effect increases the rod diameter thus surface area. A bit ott for domestic. Not a bad shout if ever you have piles done to do an extra one for a deep rod. Saying that a mate's concession to earthing at his workshop is the earth conductor affixed by a pair of old mole grips on a scaffold tube banged into the ground! ? Now that's a thought. I still have galvanised scaffold so just drill a hole in it and connect it up. Dig flower bed soil back out, lay down 4 metres of tube on soil and cover back over. Will I still need to keep earth rod and tube apart as stated in wiki ? I assume so. Will try the easy stuff first then only try the exotic stuff if all fails. Interesting lessons for me . Much appreciated for your help. Thanks Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 9 hours ago, ToughButterCup said: Welcome @Freddie. Sounds like you have forgotten more about self building than I'll ever know. See you over on the electricians forum. @Onoff will know the answer. Added to that he's tame and has a sense of humour. What more can a fella need? Thanks for the welcome, and reference to Onoff. Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 8 minutes ago, Freddie said: Now that's a thought. I still have galvanised scaffold so just drill a hole in it and connect it up. Dig flower bed soil back out, lay down 4 metres of tube on soil and cover back over. Will I still need to keep earth rod and tube apart as stated in wiki ? I assume so. Will try the easy stuff first then only try the exotic stuff if all fails. Interesting lessons for me . Much appreciated for your help. Thanks I was just pointing out ref the scaffold pole, don't do that. If you're going to dig the flower bed up then lay a proper earth tape. Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 Just now, Onoff said: I was just pointing out ref the scaffold pole, don't do that. If you're going to dig the flower bed up then lay a proper earth tape. LOL. no I wasn't , first multiple rods. If no joy add earth tape if no joy add Marconite . Hopefully will get it with the rods. Cheers. Link to comment Share on other sites More sharing options...
Onoff Posted May 18, 2021 Share Posted May 18, 2021 If that 285 Ohm reading is recent it might be way high in Summer once (if ?) the ground dries out. 500mm of soil isn't much. Try the bfo flattened HW cylinder if you can get one...and flatten it...loads of area on that. Link to comment Share on other sites More sharing options...
Freddie Posted May 18, 2021 Author Share Posted May 18, 2021 16 minutes ago, Onoff said: If that 285 Ohm reading is recent it might be way high in Summer once (if ?) the ground dries out. 500mm of soil isn't much. Try the bfo flattened HW cylinder if you can get one...and flatten it...loads of area on that. Sounds good. Been thinking of soil make up and how to make it wetter, although it will be in the shade most of the day. The reading was taken on 26th April , 3 weeks back. We also spent 15 minutes saturating the soil with water via hose pipe with same reading. Link to comment Share on other sites More sharing options...
Onoff Posted May 19, 2021 Share Posted May 19, 2021 More reading: https://professional-electrician.com/technical/selecting-and-installing-earth-electrodes/ Link to comment Share on other sites More sharing options...
TonyT Posted May 19, 2021 Share Posted May 19, 2021 If you have trenches rather than rods use copper tape, bare copper 25mm wide by 3mm thick in the trench and terminate it into an earth rod chamber, there join it to a 16mm earth conductor. This allows the joint to be inspected. Link to comment Share on other sites More sharing options...
TonyT Posted May 19, 2021 Share Posted May 19, 2021 With rods you have to watch the zones of influence so if you hit a rod 1.2 metres into the ground the next rod if you decide to add another needs to be 2.4metres away So sometimes it’s worth just throwing the tape into a trench , backfilling with bentonite if necessary and away you go. Link to comment Share on other sites More sharing options...
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