Spa shock issue and competence to install

[TrevorM]

Hi all

I have an issue with a spa installation we had a few months ago.
Just as a bit of background info, I am a TV engineer and run a TV engineers forum, I have also completed many of my own electrical installations at home before things got a tricky without the relevant qualifications etc.

The install consisted of splitting the tails, installing a new metal clad fuse box with appropriate fuse and RCD and running the larger of the applicable sizes of armoured cable around the house to a 32a rotary isolator, then there is a length of armoured cable into the spa.
This was completed by a qualified electrician prior to the spa arriving.

The was fitted and has been OK.

Last night I decided to check the chemicals in the spa before getting in, this is highly unusual for me, checks are usually performed earlier.
I was barefoot on an outside block paved patio, I dipped the test meter in the water and got a good tingle through a few days old cut in one finger.

Put a non injured finger in and you feel nothing, put my shoes on and put the cut finger in and you feel nothing.

I have read through any posts referencing spa shocks on this forum but the solution isn't entirely clear to me. As I recall the armoured cable was three core and I can't remember what the electrician said or did about the earth conductor and the armoured outer, are they joined together????

Anyway, I have contacted the spa installer and they are coming out tomorrow.
I asked the following question, which probably didn't go down well.

Can you tell me what qualifications your installer has please?

The answer was "years of experience, knows hot tubs inside out etc etc" & "was approved as competent by the NICEIC"

It seems strange that a qualified electrician must install everything but someone with proof of nothing can be left to make the final connections to the spa given the current legislation as I understand it.

Can anyone tell me what the situation is regarding who can or can't make the final connections and should any tests have been completed on the installation before or after the installation of the spa. Should a record of installation have been left for us?

Considering the longish run of armoured cable around the house was there a more appropriate method to install it, I read a lot about rods being driven in the ground near spa's in the other threads.

Thanks for any advice offered. This is a little different to what my forum members normally deal with.

regards
Trevor

 

[Octopus]

Thats not a bad idea, I know if someone called me to say that about my install I'd be round there like a shot as I would hate for something bad to happen and get the blame!

Precisely my point & exactly what I would do

 

[Leesparkykent]

Lee, what's your preference when it comes to hot tubs? I have connected a few, not many, and I normally connect it back to the supply earth as it's going to be better than any rod, however these were all sitting on decking limiting the risk. I know sticking rods in would be nice and cut off the supply earth but it's never going to compete.

however, I suppose you could always put a rod in local to the tub and connect it back to the met, gives you redundancy in the event of fault.

It depends really..using the suppliers earth or making the hot tub TT both have there pros and cons Imo. When using the suppliers earth pme/tncs you could have a healthy installation but experience "tingles" like the OP suggests but this isn't going to do wonders for the relationship between you and the customer so to speak. When Making the hot tub TT 99/100 you are going to be relying on an RCD for earth fault protection. In an ideal world I suppose you would use the suppliers earth with a rod/s connected to the MET with a very low Ra and have the hot tub either sat on or have wooden/composite decking built around it where you are likely to be in contact with the tub and ground at the same time

 

[sparksburnout]

Hi
The electrician is customer of mine and did the work for me one weekend so I do not have a certificate.
I am going to call him for a chat but only got the answer phone tonight.

Yes, I am absolutely sure it is a shock, the cut provides a lower resistance to the rest of the skin.
I even popped my Fluke probes in the water and onto my skin and get a 2-3 VAC depending on pump speed.
And it doesn't happen with shoes on.

It might be interesting to try the same thing with bare feet and the metal kitchen sink.

Is weekend work exempt from certification then?

 

[BES]

Is weekend work exempt from certification then?

After the pub opens , yeh

 

[Midwest]

Op not sure if you've have the search facility on this forum. If you have, you'll find a lot of posts on this subject. No expert myself in this area, but the advice you've been given by Lee appears spot on from what I've researched. Putting on shoes increases your resistance, thus prevents you receiving a 'shock', in your described scenario. In addition to what Lee suggested (if it proves to be the case), I would also consider putting down some materials, to prevent you stepping on bare earth or ground, when getting in and out of your tub. Stuff I've read about outside spa baths etc, I wouldn't be using one as you have installed (the tub, not necessary the electrical installation). Composite decking might be an idea?

 

[uksparks]

Have you ever considered extending the equipotential zone as well as rodding, this would give the best of both worlds, excellent low earth resistance with local equalised true earth to provided earth.

Yed well I was just thinking you could run an additional 10mm from the MET to the hot tub with a local rod, it's going to help, I think next time I will do this.

 

[Darkwood]

The issue here is the ground under and around the hot-tub can become very wet, and as the OP had a cut its like having little resistance to voltage (like sticking a 9v on your tongue).... I do wander though how are the pumps controlled for speed on these hot-tubs, is it common to have an inverter to control the motor? The comment of the voltage changing reletive to pump speed could be a red herring but also it could be very relevent as it may indicate poor earthing to the drive or motor - the designed leakage may be sourcing an alternative route.

 

[keniff]

I had this with my hot tub at home, leesparkykent is spot on. I knocked in 2 X 1m rods (near the hot tub, got it down to 20ohms) now I don't get the tingles, it's was on a tncs earthing arrangement before, I disconnected the cpc at the hot tub end though

 

[TrevorM]

Thanks for the replies, yes I did use the search feature and gained some useful info. I can't reply quickly as my posts are moderated.
I also note similar readings from Kettles and other Class 1 appliances in the kitchen with bare feet on a slate and concrete floor.

I will inspect the spa carefully with the installer tomorrow and then get the electrician back to cure the problem as suggested here.

Many thanks.

regards
Trevor

 

[PEG]

Hi dude,try measuring that voltage again,between the floor and your tingly solution...let's see if we can beat 3v AC :vanish:

 

[davesparks]

Hi
The electrician is customer of mine and did the work for me one weekend so I do not have a certificate.

Then I would have refused to connect the spa, and in my opinion so should have the installers if they were on the ball.