Discuss Earth Rod install in the Electrical Forum area at ElectriciansForums.net

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Hi all
Having to install a earth rod In for a hot tub, hot tub just installed outside the house. I am planning on installing earth rod 100mm from edge of house what are the chances that there will be services below this line. The gas pipe and water pipe are further along the wall about 2M away I wouldn’t think the pipes will be running right along side the house would they ?
 

telectrix

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too close to house. allsorts of builders crap there. 1m min. from house. and then suss out where other services are. what reason needed for rod?
 
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Hi thanks for reply. Installing hot tub and the current earthing system is TNC-S. so planning on installing earth rod ?
 
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Well it was previously a hire hot tub came with a 13amp plug top but looking at spec says 16amp supply required and they are from Spain ?
 

pc1966

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If you are worried and have the patience then hand-dig down by 1m or so like putting in a fence post and then if no services it is unlikely to be below that, so then a long rod (2m or so) can be driven in and back-filled with the soil that came out.
 

pc1966

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This site will do a search for you for free, though you need to sign up and give the area details. Won't catch everything but at least gas mains and HV cables will be shown:

Give some margin around them as not all services are quite where the map shows them to be.
 
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I have looked for info regarding earth rod but no luck with it just says 16amp supply. But would have thought hot tub would be better on TT earthing system anyway ? Don’t think it’s good idea having it on TNCS . I’ll just dig down about 600mm should be clear of all services in my garden then ?
 

Strima

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I have looked for info regarding earth rod but no luck with it just says 16amp supply. But would have thought hot tub would be better on TT earthing system anyway ? Don’t think it’s good idea having it on TNCS . I’ll just dig down about 600mm should be clear of all services in my garden then ?
And if the network neutral develops a fault potentially your rod will be the only path for the neutral currents from your installation and possibly your neighbours back to the transformer.
 

timhoward

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But would have thought hot tub would be better on TT earthing system anyway ? Don’t think it’s good idea having it on TNCS
Some manufacturers do say it should be TT'd.

Here are some rambling disorganised thoughts: (EDIT related to just leaving it TNCS)
Extraneous metalwork from the house should be already dealt with, otherwise even before the hot tub arrives there's a problem.
The houses equipotential zone would be extended to a 16A socked on an external wall.
The hot tub probably doesn't have any exposed conductive parts as is effectively a double insulated plastic class II item.

What could go wrong...
-cable supplying it could lose earth connection + fault conditions + exposed conductive part (unlikely 1st two at same time, and most hot tubs wouldn't have 3rd)
-broken PEN on supply and all earthed conductors become live (hot tub probably class 2, safe inside it and around it, dangerous if you can touch a garden tap but that applies anyway)
-neutral return currents could be near buried extraneous conductors causing tingle - (GN7 advocates applying section 702 to outdoor hot tubs which would include earthing mat to tackle this ). Unless hot tub is a good distance away from building and any extraneous parts and the earth rod wouldn't help much
Have I missed anything?
 

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