Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 36 replies
  • Subscribers 32 subscribers
  • Views 3005 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

HOT TUBS ANY VIEWS OR ISSUES?

John Peckham
I have been chatting to a mate of mine who is a very experienced sparks who does 10-15 hot tub installs a year. He TTs his supplies to hot tubs which are on PME supplies which is the majority of supplies in Essex other than the odd TT supply in country areas.


He does get called back to hot tubs that he has not carried out electrical installations because people climbing in and out of the hot tub where people have experienced "tingles" ie minor electric shocks. Sure enough these shocks are due to the hot tub being directly connected to the PME earth.


Currently (excuse the pun) BS 7671 701 and 702 do not cover hot tubs only the general rules in Parts 1-6.


Does anyone on the forum carry out hot tub installations and if so how do you do it? Has anyone been called to investigate "tingles"? Does anyone know of any more serious shocks or injuries relating to hot tubs or any other equipment connected to a a PME supply?


Thanks in anticipation.


JP


  • Former Community Member
    0 Former Community Member
    John Peckham:

    Chris


    IET GN5 recommends a plastic insert in water supplies to outside taps that are use metal pipe work connected to a PME earth.


    I have put a plastic joint in my incoming water supply just after the stop valve. I did this as. I have an overhead PME supply that gets thrashed by the local trees as it runs through the village during stormy weather. I have no gas or oil supply. I did this to prevent diverted neutral currents setting light to the house if the PEN became open circuit.


    Hi John, please could you explain a scenario that could set light to your house had you not put a plastic joint in your incoming water supply? Thanks


  • 0
    How about us big koi pond owners. ! .

    i’ve had to go pme, as when i feed my fish if i have a paper cut or similar it was definitely noticeable .


    Rammed a true rod in while still pme and got 26v , and then swapped over to tt island arrangement .
  • 0
    Weardbeard


    When the PEN goes open circuit, and depending on the load on the network and the load balance on the network, current in the neutral will return to the transformer by any route it can. This includes bonded pipe work. These currents can be substantial and in some cases cause pipe work and conductors becoming red hot. Open PENs cause fires due to diverted neutrals and additionally over voltages damage and destroy connected equipment. 


    I have Ave an overhead PME supply to my house in Norfolk. That supply terminates in to the head at the front of the house. The copper water pipe enters my house at the rear of the house . Solid floor so the 10mm bond runs under the 200 year old floor boards. Without the insulated joint diverted neutral current under fault conditions could heat the bond up and set light to the wood.


    Have a look at the virtual IET ELEX show at the PME presentation video and you will see a couple of photos of examples of fire damage due to PME faults.

  • 0
    John Peckham:

    Weardbeard


    When the PEN goes open circuit, and depending on the load on the network and the load balance on the network, current in the neutral will return to the transformer by any route it can. This includes bonded pipe work. These currents can be substantial and in some cases cause pipe work and conductors becoming red hot. Open PENs cause fires due to diverted neutrals and additionally over voltages damage and destroy connected equipment. 


    I have Ave an overhead PME supply to my house in Norfolk. That supply terminates in to the head at the front of the house. The copper water pipe enters my house at the rear of the house . Solid floor so the 10mm bond runs under the 200 year old floor boards. Without the insulated joint diverted neutral current under fault conditions could heat the bond up and set light to the wood.


    Have a look at the virtual IET ELEX show at the PME presentation video and you will see a couple of photos of examples of fire damage due to PME faults.

     


    That is why I do not ever install a main bonding clamp onto a lead gas pipe.


    Z.


  • 0
    Zoom


    Did you watch the IET video on PME?
  • Former Community Member
    0 Former Community Member
    John Peckham:

    Weardbeard


    When the PEN goes open circuit, and depending on the load on the network and the load balance on the network, current in the neutral will return to the transformer by any route it can. This includes bonded pipe work. These currents can be substantial and in some cases cause pipe work and conductors becoming red hot. Open PENs cause fires due to diverted neutrals and additionally over voltages damage and destroy connected equipment. 


    I have Ave an overhead PME supply to my house in Norfolk. That supply terminates in to the head at the front of the house. The copper water pipe enters my house at the rear of the house . Solid floor so the 10mm bond runs under the 200 year old floor boards. Without the insulated joint diverted neutral current under fault conditions could heat the bond up and set light to the wood.


    Have a look at the virtual IET ELEX show at the PME presentation video and you will see a couple of photos of examples of fire damage due to PME faults.

     


    Thanks for the reply! Just to get this straight- you have a 10mm main bonding conductor connected to your water service but have installed a plastic pipe fitting in the service to prevent the 10mm from setting fire to your floorboards?


  • 0
    Yes. Diverted neutral currents cannot flow via my installation to the transformer through the water pipe. And diverted neutral currents cannot flow through the water pipe in to my installation.
  • 0
    John Peckham:

    Zoom


    Did you watch the IET video on PME?




    Do you mean this one?

     








     


  • 0
    I know I have told the story several times before on this forum.


    Around fifteen years ago I was fitting a kitchen and doing the electrical work at a house with an overhead two cable supply and a DIY TNCS earth connection, a big choc-block terminal in the neutral tail after the meter, don’t you just love people who do things like that ?


    In the garden there was a big Koi pond with a brick wall around it bringing the pool up around 18” above ground level, the pool being a lot deeper with a plastic liner along with all the kit and caboodle.


    The lady of the house was sat on the wall feeding the fish and one come up to take some food from her hand, they both jumped back and the lady exclaimed that she had just had an electric shock, I said the fish had as well.


    Her husband insisted there was nothing wrong with the pool equipment saying it had all just been rewired and promptly put his hand in the water to show us that everything was okay, I really would not have surprised me if he had been electrocuted, it was one of those moments where you can see what’s about to happen as he leant forward but you’re powerless to stop him risking his own life due to his own stupidity.


    I measured the voltage of the water at around 90 volts from the neutral tail in the house with a probe dangling in the water. When removed the pump failed an insulation test and was replaced, I also reinstalled an earth rod and did away with the DIY TNCS earthing arrangement.


    So, yes I know you can get an electric shock off water enclosed in a plastic pond liner or container, going back to an earlier comment  does that actually make the water an exposed conductive part? 


    Also commented on before, some years ago I had a conversation on the phone with someone who I understand is one of the countries leading experts on bore hole water pumps, he told me that many year ago people did not bother to earth bore hole water pumps because they considered it pointless as being suspended in water down the bore hole within the general mass of earth they could not be better earthed, but now they always are, because obviously a four foot rod is a better earth than the pump in the bore hole is itself.


    Which sort of leads me in a rambling manner to just how effective is a plastic insert in a metal water pipe?


    We had a discussion some time ago and someone posted an explanation about cows dying in fields and diverted neutral currents, I not sure how to search for that, the search on this forum doesn’t do much, I usually go out to Google in the browser and come back in again.
  • 0
    Here’s one particularly good post:

    https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=41283&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines