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Hot tubs and PME

vantech

Hi, 

I am planning a hot tub install, and we circle back to the question of earthing arrangements! 
 

I am thinking of 3 different approaches to this as follows: 

 

  • PME to the isolator next to the tub, gland off and convert the output to TT creating an island.

 

Q: by doing this, how far away from the tub does the rod need to go? 

 

  • PME to the tub, and install a rod that is then supplementary to the PME.

 

Q: can this rod be next to the consumer unit or cut out, or does it need to go next to the tub? 

I understand the issue of touch/step voltages, but if a rod is installed next to the consumer unit and the tub is perhaps 10 metres away, would this be sufficient? 
 

  • PME to the tub, with a local rod as described in point 2 above, but with a Matt:e device that also protects for open PEN faults.

 

It isn’t possible to install an earth mat or grid, and the tub is likely going to be installed directly onto a concrete base, possibly with wooden decking surrounding the edges but not confirmed. 

I know this is a subject that is debated frequently but this is my first and I wanted to get some feedback. 

The TT solution would likely resolve many of the issues however the suppliers earth is better and isn’t dependent on weather and the soil! 
 

Thanks. 

 

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  • 0

    vantech: 
     

    I understand the issue of touch/step voltages, but if a rod is installed next to the consumer unit and the tub is perhaps 10 metres away, would this be sufficient? 
     

    • PME to the tub, with a local rod as described in point 2 above, but with a Matt:e device that also protects for open PEN faults.

    BS 7671 only recognises open-PEN detection and disconnection devices for EV charging installations.

    One issue is that, downstream of the device, if you have supplementary bonding or accidental contact with anything connected to PME, the device is rendered ineffective.

    Secondly, the voltages etc. in Section 722 are not suitable for someone in a bath or shower.

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  • 0

    vantech: 
     

    I understand the issue of touch/step voltages, but if a rod is installed next to the consumer unit and the tub is perhaps 10 metres away, would this be sufficient? 
     

    • PME to the tub, with a local rod as described in point 2 above, but with a Matt:e device that also protects for open PEN faults.

    BS 7671 only recognises open-PEN detection and disconnection devices for EV charging installations.

    One issue is that, downstream of the device, if you have supplementary bonding or accidental contact with anything connected to PME, the device is rendered ineffective.

    Secondly, the voltages etc. in Section 722 are not suitable for someone in a bath or shower.

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