Earth rods

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TTbangbang

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Do they have a lifespan? (e.g. when in always wet ground)

Are two, placed within 3 feet of each other, that much better than one? If so, is it better to link from each to the MET or link them together and then one earthing conductor to the MET?

Any pearls of wisdom about these for a TT system will be gratefully received.

Thanks :)

TTbb

 
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Copper oxidises but doesn't rot away, so assume a very long lifespan.

Suppose you use however many rods you need to get your Ze(?) low enough. Can't see why if 1 is sufficient 2 would be any better :|

If you are connecting multiple rods why not do it like bonding with 1 continuous length just strip the insulation for the second rod?

I dunno :)

 
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Test often !!!! Never known a rod to disintegrate, but must happen eventually. As for spacing rods there are some complicated recommendations for this, but can't remember what the hell it is - think they should be further apart than 3 feet though.

 

steptoe

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yea, you gotta space them out so you dont get any induced fields surrounding them, personally I always use an odd number, makes it easier to work out the spacing, IMO.

it can be a pretty weird calculation at times, and if you can get away with one rod then just use one.

a good tip I would give if your doubtful on what your readings may be is to run the cable in side a 20mm galv pipe to a toby box(metal inspection box at rod), then tag the toby box to the rod using a 4or6mm bonding link.

9 times out of ten this will be fine to get your rod under 200ohms. :)

 

springcrocus

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a good tip I would give if your doubtful on what your readings may be is to run the cable in side a 20mm galv pipe to a toby box(metal inspection box at rod), then tag the toby box to the rod using a 4or6mm bonding link.9 times out of ten this will be fine to get your rod under 200ohms. :)
Nice bit of info there, Steps Applaud SmileyApplaud Smiley

 

TTbangbang

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Thank you for your comments guys :)

I've put a link regarding earth rods, which I found on another forum, in the Useful Links section.

TTbb

 
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Good link BTW

I have a question, in sandy soil if you fitted a rod now when the ground was went and it passed all your tests, what happens in summer when the ground dries out? Is the installation left at risk?

 
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I would suggest using an extendable rod to dive deeper into soil where it is less likely to dry out - I like to try and hit bedrock if possible!!!! There are also water retaining crystals and other compounds to help maintain moisture, but have never used these so can't really comment. The scenario you have raised here is the reason why Ze at the rod is recommended to be less than 100 ohms so in theory even a drought would not impair performance. The actual allowable Ze is 500 ohms, but have never come a result that is so high so far Pray Pray

 

TTbangbang

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Stupid question, but if there's a natural pond nearby would it be a good idea to stick it in deep into the bottom of that?

...

... wouldn't potentially electrolute the ducks would it?! :p

 

Mr Sworld

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Stupid question, but if there's a natural pond nearby would it be a good idea to stick it in deep into the bottom of that?...

... wouldn't potentially electrolute the ducks would it?! :p
How would you get to it for inspection purposes in the future? ]:)

 

steptoe

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I have been on jobs where the rods have been put at the edges of streams, semi-drowned as such, personally I dont see how that should be needed.

extrendable rods are a good option if the ground isnt too rocky, or slate.

 

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