SWA in Plastic CU from the rear

Discussion in 'Electricians' Talk' started by GeordieKev, Jul 11, 2019.

  1. Philip Hyde

    Philip Hyde Member

    Dont think there will be a massive mechanical load on a cable coming out the back of a fuse board!
     
  2. GeordieKev

    GeordieKev New Member

    I am an electrician, but i work in the industrial side, not a domestic sparky. So I've done all the work myself and getting it signed off for the Part P by the council. That's why i'm asking, I know how to do it, but wanted to see what the thoughts were of doing it this way!
     
    Philip Hyde likes this.
  3. GeordieKev

    GeordieKev New Member

    I asked an opinion of terminating in the CU, not about how I've installed the rest of the circuit. As you stated it's non-standard. which doesn't mean its incorrect just not standard!
     
  4. GeordieKev

    GeordieKev New Member

    Think i need to update this a little as seems although I wasn't clear on what I was asking. I know how to install SWA via glands and earth, and I was planning on doing it that way but rather than have a extra box on the side of the house where i terminated the SWA, then running non SWA into the consumer unit. I thought it would be easier to just go onto the consumer unit. As the reason for glands and connecting it to earth is to stop potential difference due to a short on the SWA, then I couldn't see any issue. Also the building regs are slightly unclear as normal. I also know that attaching the SWA via a gland gives mechanical protection but seeing as it going through a wall and sealed then this isn't an issue!
     
  5. Bazza-spark

    Bazza-spark Well-Known Member

    I would suggest you use an external rated gland for this. If you then use the piranha earthing nut Philip has linked to, you will get a good connection to make your final earth with.

    I am concerned about a few things however.
    1. As this is a new circuit it is notifiable under Part P.
    2. You are using 3 core SWA so I assume you are using the house earth. What is the length of cable run and what is the house earth?
    3. Are you exporting a PME earth to the tub? You may be better using 2 core and installing a rod at the tub. I have read numerous reports of people getting shocks from plug in tubs because the earthing arrangement is incorrect and they are running on nothing much more than a sophisticated extension lead. I know you are using an RCBO, but they can fail.
    Kind regards
     
  6. Coloumb

    Coloumb Well-Known Member

    There is no non standard way. You will have to use a gland and some sort of a box. Despite what @dobbie thinks you will have to connect the swa to it which means it will be on show.
     
  7. GeordieKev

    GeordieKev New Member

    Thank you for the decent reply. This is what I was asking, as i'm not using the SWA as the earth, as it's near enough all underground no chance of being pulled out or a increase in tension to it.
     
  8. peter palmer

    peter palmer Well-Known Member

    I dont see it as that big a deal, twist them neatly together, wrap some earth tape round them and shove it into a couple of earth bar terminals. I wouldn't do it that way myself for a customer but I might at home.

    Why cant you cut the strands flush at the CU end and banjo it at the Isolator near the hot tub. The PME can be exported to there, its just the hot tub bit that needs a rod and I'm not even convinced that's really necessary, suppose it comes under swimming pool rules
     
  9. GeordieKev

    GeordieKev New Member

    Don't be concerned but i understand your reasons so I will answer them.
    1. Yes it is, Which i why I have notified the building control officer and agreed for them to come and inspect my work. Hence the thread.
    2. I am using the house earth, and it a TNC-S the cable run is around 15m.
    3. The run is to a 32 amp sealed unit over 3m away from the tub, this will be connected via a 3 pin 32 amp blue plug to the tub.
     
  10. Coloumb

    Coloumb Well-Known Member

    I’ve never heard of terminating to a bolt. What’s that all about? I hope you don’t mean clamping an earth bonding clamp to the swa
     
  11. GeordieKev

    GeordieKev New Member

    If this was someone else house I would do it that way. In fact I am more likely to install a box and terminate the SWA as normal but thought i would see what peoples opinions are.

    For the OSG, there isn't any rules other than the connection to the tub must be 2m away. i don't require a rod to be fitted and again i could terminate at the isolator but generally this would be exporting the earth as far as i can work out.
     
  12. GeordieKev

    GeordieKev New Member

    It won't all the cables and the SWA will be in the CU as it enters from the rear. The cover over the CU will mean it not on show.
     
  13. Coloumb

    Coloumb Well-Known Member

    Ouch
     
  14. dobbie

    dobbie Well-Known Member

    You really do not have a scooby.I said come into the back of an adaptable box, hence no cable would be showing.I do not know how to explain it any clearer for you to understand.
     
  15. Bazza-spark

    Bazza-spark Well-Known Member

    Thanks @GeordieKev .

    Don't envisage a problem, especially if you gland the armour at the isolator as previously recommended in a post. Just wouldn't want anyone hurt. I also am industrial, but have a few friends that have plug in tubs and have experienced issues. The last were 2 young girls, 8 and 10, screaming in pain as they got out of the tub. Frightening what could have happened if dad hadn't unplugged it quickly (no RCD).

    Kind regards
     
  16. peter palmer

    peter palmer Well-Known Member

    Whats wrong with stripping the SWA back long enough to reach through the wall and into the CU, you could then terminate to a proper gland in a Wiska box outside. No connections inside the Wiska box, the inner bit of the cable would be "passing through" as it were. It would still be sheathed so ok on that score.
     
    ajohn likes this.
  17. peter palmer

    peter palmer Well-Known Member

    What can you touch on a hot tub that is conducive though apart from the water. Sound more like a floating earth than the wrong sort.

    Or maybe the pump or heater are transferring earth leaks through the water and the ground itself is the extraneous bit. Water certainly conducts enough to hurt you.
     
  18. GeordieKev

    GeordieKev New Member

    I understand your concern and I'm glad you flag up anything that you think could be wrong. That's why it's on it's own circuit with an RCBO at the end. I have a little one also and would never cowboy anything.
     
  19. GeordieKev

    GeordieKev New Member

    You don't have a path back to earth if you get a short to the SWA, hence you always terminate at least one end to earth, as this is the end close to the house it means the earth isn't exported all the way and doubling the length of the earth.
     
  20. peter palmer

    peter palmer Well-Known Member

    I'm lost, thought you were trying to find a way of terminating the strands on a SWA on an outside wall back to back with the consumer unit? if so take a single 4mm earth back through the wall to a knuckle or banjo etc.
     

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