Hot tub electric shock

[Samhhh]

Hi I'm looking for some advice, yesterday when exiting my hot tub I felt a slight electric shock when my foot made contact with the ground around the hot tub. I work as a cable jointer so a tingle is second nature to me so I double checked when in contact with ground and water I can feel a slight tingle in my fingers when isolated from ground I feel nothing. Today I put my multimeter onto a nearby earth terminal and probed the water to get a reading of 0.2volts. Im on a pme supply and have a cable running from a rcd to a isolated and then a feed to the tub. Any idea where this voltage could be coming from? And if installing a seperate earthing point with rods would solve the issue? Thankyou

 

[marcuswareham]

A voltage operated ELCB, as we used years ago, but breaking the supply earth as well.

thats the one

 

[Mark Wright]

what was the outcome of this? I couldn't be bothered to read all 7 pages.


In America where they have more swimming pools they make more fuss about stray voltages

"In our case, stray voltage is coming from the grounded conductors of an electrical system nearby and the surrounding “earth” ground. When you are dealing with a pool, stray voltages usually feel like a small tingling sensation when you touch a puddle of water on the pool deck or a handrail/ladder attached to the pool. In the most extreme of cases, electricity in pools can cause paralysis and ultimately lead to drowning."

The shocking truth | Megger

Electricity in Swimming Pools

us.megger.com

 

[LastManOnline]

A voltage operated ELCB, as we used years ago, but breaking the supply earth as well.

I have long advocated a similar type solution. I don't understand why this option has not being explored more

 

[UNG]

what was the outcome of this? I couldn't be bothered to read all 7 pages.


In America where they have more swimming pools they make more fuss about stray voltages

"In our case, stray voltage is coming from the grounded conductors of an electrical system nearby and the surrounding “earth” ground. When you are dealing with a pool, stray voltages usually feel like a small tingling sensation when you touch a puddle of water on the pool deck or a handrail/ladder attached to the pool. In the most extreme of cases, electricity in pools can cause paralysis and ultimately lead to drowning."

The shocking truth | Megger

Electricity in Swimming Pools

us.megger.com

I would suggest you read the whole thread rather ask for a synopsis

I would also suggest you read the link you posted which clearly highlights the differences between the UK and US electrical systems and the differences in test equipment used and obviously the installation tests that are carried out

 

[pc1966]

I have long advocated a similar type solution. I don't understand why this option has not being explored more

Until EV came along in large numbers no one really bothered much about the open PEN problem.

But the flaw with the idea of opening the supply CPC is many houses will end up connected to the neighbour's PEN by virtue of bonded pipes, etc. Unless everyone on your "extraneous conductive neighbourhood" uses such a device it might well fail in practice to avoid high metalwork potentials.

Really the most practical routes are either very good additional earths, such as building foundations or a decent sized mat, or putting the tubs on a TT supply. Of the two, the local good earth is better as it ought to save you from over-voltage damage to equipment, but the TT option is likely to be easier to implement in practice.

 

[Mark Wright]

Sorry can't remove above box?

I would suggest you read the whole thread rather ask for a synopsis

I would also suggest you read the link you posted which clearly highlights the differences between the UK and US electrical systems and the differences in test equipment used and obviously the installation tests that are carried out

stray voltage is sill relevant relevant in the UK.

Stray voltage occurs when voltage exists in the ground. Meaning, loose electricity has “escaped” from a cable, a transformer, or other power source. It’s now traveling through the ground, trying to dissipate.

So I would suggest you tell me how this is not relevant in any country?

there also more aware in Australia, where they have a very similar system and more swimming pools.

 

[Samhhh]

I thought I would post and update (sort of) so the hot tub technician came out and said he knew what the issue was straight away.. Stray voltage coming from the uv light connected to the water feed that helps sanitise the water flowing through the system. He disconnected and the shocks continued, he then checked every single circuit individually spent over 2 hours testing the tub and said everything on the tub was as it should be. So I'm still stuck with the issue. I have since been out to try and get to the bottom of it, I check the eli at the rotary isolater and it was all good, i tested from earth to neutral and had 0 volts. I turned the tub off and still got the same shock, placed one end of the multimeter in the water and one in the soil at the side of the tub and it was reading 5v, moved the prong around to different areas of ground all within a couple of meters of the tub and it fluctuated from 2v to 5.8v. I ran a flying leaf from my earth terminal to the hot tub and checked from water to the flying lead and got 0v. So it has to be potential difference right?

 

[stevethesparks]

"Hot tub technician" did he witness the problem you have as well as the the tick sheet tests for the hot tub alone? IMO as an on-site technician, he should be advising what steps to take.

 

[brianmoooore]

This is looking like the problem is nothing to do with the actual hot tub. other than you are placing something connected to your supply's earth connection in the middle of your garden.
suggest that you connect a long lead to, or near, the incoming earth terminal, switch off your consumer unit, then check for voltage between the soil and the lead.

 

[Samhhh]

This is looking like the problem is nothing to do with the actual hot tub. other than you are placing something connected to your supply's earth connection in the middle of your garden.
suggest that you connect a long lead to, or near, the incoming earth terminal, switch off your consumer unit, then check for voltage between the soil and the lead.

I tried this but I don't know if I was doing something wrong, so I tried testing from the live on the rotary to the earth in the rotary and it would read 246v, I then went from the neutral to the earth and got 0v, the hot tub was obviously off at this point, so I then went from the water to the ground outside near the rotary getting 5-6v. This proves that the hot tub isn't the problem I think? I also ran a lead from the top earth terminal as close to the hot tub as I could get it I ran an eli to make sure that it was in fact working as earth and I got >1. This threw me right off as I thought my supply earth/neutral had gone down so I tested at the incomer and everything was good 246v 0.3 eli. Would the >1 reading be because I still had the consumer unit on? Or is it just the fact that it was a tiny lead and the fact it was running for around 20 metres?

 

[Samhhh]

"Hot tub technician" did he witness the problem you have as well as the the tick sheet tests for the hot tub alone? IMO as an on-site technician, he should be advising what steps to take.

So he did witness it but he couldn't feel it himself, though he did test to earth and agreed there was something amiss, he spent 2 hours outside and when he spoke to me he said he had tested every single circuit in the hot tub and everything was fine with it. The only thing I can really do at the moment is take his word for it, but the fact that the issue still persist even when the hot tub is turned off surely means it has to be external? He didn't have any advise to give he just asked me to let him know what the outcome is so he can look out for it in future, I've spoken to me electrician and he's installed plenty of hot tubs on pme systems and never had an issue so is it just me that's unlucky ?

 

[pc1966]

Simplest solution is to have a TT supply for the tub. You need a DP RCD (or RCBO) and a local earth rod or similar located close to where the pool is.

Biggest risk with TT supplies are a failed RCD (less of an issue if your CU already has a RCD there, so you have two in series) and, more practically, the risk of hammering a rod in to a utility cable or pipe!

While two 30mA in series have no selectivity, for this case it does not really matter. Disconnecting on a fault if wet REALLY matters!

It need not be a rod, you could have several meters of 16mm bare copper wire buried in a narrow trench 0.5m deep or similar, if hand-dug with care no risk to any (sane) utilities. Such wire sold by the metre here:

Superlec 1X16 BARE SOFT DRAWN CU STRAND BS6360/81

Non insulated, non sheathed, flexible stranded bare copper cable for use in earthing electrical systems and power distribution networks.

www.superlecdirect.com

 

[marcuswareham]

So he did witness it but he couldn't feel it himself, though he did test to earth and agreed there was something amiss, he spent 2 hours outside and when he spoke to me he said he had tested every single circuit in the hot tub and everything was fine with it. The only thing I can really do at the moment is take his word for it, but the fact that the issue still persist even when the hot tub is turned off surely means it has to be external? He didn't have any advise to give he just asked me to let him know what the outcome is so he can look out for it in future, I've spoken to me electrician and he's installed plenty of hot tubs on pme systems and never had an issue so is it just me that's unlucky ?

Surprising the hot tub specialist didnt think/aware of the relevance of the earthing arrangement used as its quite important for hot tubs.

The fact your electrican has fitted loads of hot tub on PME without issue doesnt mean the voltage drop on the PEN conductor is not the issue as this will change alot depending on the length and type of cables feeding your house, so in other locations/houses there could be no issue likewise what the hot tub is sitting on will change the outcome (timber deck or soil etc), so it could be coincidence that any other hot tubs the electrician has installed which might have higher volt drop on the PEN conductor just happen to be on some decking

I am sure your electrican knows what he is doing although, there is still a very dangerous risk if in the unlikely event your supply PEN conductor would go open circuit which is why it seems most people favour TT for hot tubs

 

[marcuswareham]

It need not be a rod,

Or check out earthingservices.com, they have an electrode which is a round disc they also have conductive concrete which can help increase surface area or make it possible to get an electrode in a tricky location

 

[pc1966]

Or check out earthingservices.com, they have an electrode which is a round disc they also have conductive concrete which can help increase surface area or make it possible to get an electrode in a tricky location

Their web site is utter crap!