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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 ?
 
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?
 
Hi thanks for reply. Installing hot tub and the current earthing system is TNC-S. so planning on installing earth rod ?
 
all depends on the hot tub. is it plug and play,like ezy-spa? what do the mnufaturers instructionds specify? may not wnt a rod.
 
Does the manufacturer recommend and earth electrode?
 
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 ?
last thing tat came from Spain was squashed by Drake. 1588.
 
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.
 
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.
 
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 ?
 
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.
 
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?
 
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?
prophet of doom strikes again,. just plug it in, don't use mains radios and hairdryers in the tub. ensure sunlife policy up to date,
Earth Rod install 1620148927080 - EletriciansForums.net
 
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?

I believe most have metallic heating element housing which are earthed meaning there is a chance the water can rise in potential should a PEN fault occur, although depends on the conductivity of the water and distance to the heating element to dictate how bad the concicences are

Yes earth mat under and around the hot tub i think is the best way connected to the TN-C-S earth , if i was to put one at my house I would go that way, although its a different story if you told a client you need to dig up a massive section of there garden to install an earth mat not sure how well that would fly
 
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 ?

Are the gas and water pipes metal?, if so they will be connected to the TN-C-S earth

2m is too close too buried TN-C-S potential metal work, meaning making it TT will not get rid of the risk due to PEN fault voltage appearing on the TT earth rod.

The TT rod wants to be a decent distance from anything TN-C-S (most DNOs recommend around 10m)
 
I believe most have metallic heating element housing which are earthed meaning there is a chance the water can rise in potential should a PEN fault occur, although depends on the conductivity of the water and distance to the heating element to dictate how bad the concicences are
I appreciate this discussion, as there seem to be many views out there about this topic. Good to know about the earthed housing.
Yes earth mat under and around the hot tub i think is the best way connected to the TN-C-S earth , if i was to put one at my house I would go that way,
Has this actually created a new problem in broken PEN situation that you step out with wet feet and now have a directly connected potential of 230v underneath where you are standing? In normal circumstances this certainly adds value, in worst case it probably makes things even worse?

The TT rod wants to be a decent distance from anything TN-C-S (most DNOs recommend around 10m)
And there lies the problem - many properties don't have that much space.

My internal conclusion (that I welcome constructive debate on) is that if enough space TT wins, but TNCS with no rod/mat is 2nd prize subject to a careful assessment.
 
So looking at most of the posts around my post. Everyone will just keep it on the TNC-S system earthing ? Which has gone away from how I have thought hot tubs should be installed. On my thinking it’s not that the even the PEN having a broken neutral and causing the system earth to become live. But as on a TNCS system the neutral and earth combined and ure standing with wet feet on earth then u can get tingles from the water and could potentially rise to a dangerous level. With installing a earth rod, u are taking away that potential danger. I can’t think how being 1m 2m or 10m away from house would make any difference as if broken PEN then most of the time in your house u are insulated from any danger. Or has hot tub installs changed as I don’t do a lot of these installs now ?
 
Ultimately the risk is the open PEN fault and somehow anything on the house CPC being elevated in potential compared to the Earth.

But what matters is potential difference, what someone in contact with the pool can observe compared to the ground around it. So a buried set of wires/mesh connected to the CPC/earth circuit around the pool area would bring that difference down to low levels. It need not be very deep, just enough not to get damaged/brought up be any gardening activities, so 30-50cm probably OK.

The connection from the house to any external earthing arrangement should be in 10mm^2 cable due to the risk of high diverted neutral currents in the event of a fault, but the actual grid/loops/fingers of copper could be a little smaller, something like "1kg 3.25mm Bare Copper Wire" from here:
Better still would be 16mm copper as fully meeting BS regs for burial such as this whicxh is sold per meter:
With a decent MET style terminal block in a plastic box to link the insulated 10mm wire to a set of 4 or so lengths arranged to cover the area of the tub and a meter or two beyond in all directions.
 
Last edited:
So a buried set of wires/mesh connected to the CPC/earth circuit around the pool area would bring that difference down to low levels. It need not be very deep, just enough not to get damaged/brought up be any gardening activities, so 30-50cm probably OK.
Out of interest, would this arrangement typically achieve a lower impedance than a rod?
I noticed section 702 mentioned 20 ohms earlier.
(Appreciating this thread btw)
 

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