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Matt.e, hot tubs and PME

Farmboy

Q1. According to Guidance Note 7, when installing hot tubs, section 702 should be applied in full. The note to regulation 702.410.3.4.3 recommends that when PME is used, a mat or electrode of 20 ohms or less be connected to the supplementary bonding.



So, if no supplementary bonding is present because there are no extr/exp.c.parts, does an electrode/mat still need to be installed (anywhere on the system)?



Q2. A Matt.e device (https://matt-e.co.uk/single-phase-connection-units/), as used in EV charging to comply with Regulation 722.411.4.1 (iv), of Amd 1, is installed on a tub supply, on a PME system.



So, given it's a hot tub, does the electrode/mat still need to be installed as per the note to regulation 702.410.3.4.3, when:


a) supplementary bonding is present, and,


b) when no exp/extr.c.parts are present, hence no suppl bonding?



(and no, this isn't work I've done).



 



F


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  • 0
    So, given it's a hot tub, does the electrode/mat still need to be installed as per the note to regulation 702.410.3.4.3, when:

    a) supplementary bonding is present, and,

    b) when no exp/extr.c.parts are present, hence no suppl bonding?

    To pick op on that point - in my mind the mat itself would count as an extraneous-conductive-parts - so there'd be no getting way from supplementary bonding even it it was only between the mat and the hot tub's c.p.c.


    As an aside, if you've got something with a low impedance to earth such as a mat  connected to a PME system you might expect quite large diverted N currents to potentially have to be carried by its connecting conductors - applying the normal rules might suggest that the mat or buried grid should be connected to the MET via main bonding conductors (in addition to the hot tub's c.p.c. locally by supplementary bonding conductors as demanded by 702).


       - Andy.
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  • 0
    So, given it's a hot tub, does the electrode/mat still need to be installed as per the note to regulation 702.410.3.4.3, when:

    a) supplementary bonding is present, and,

    b) when no exp/extr.c.parts are present, hence no suppl bonding?

    To pick op on that point - in my mind the mat itself would count as an extraneous-conductive-parts - so there'd be no getting way from supplementary bonding even it it was only between the mat and the hot tub's c.p.c.


    As an aside, if you've got something with a low impedance to earth such as a mat  connected to a PME system you might expect quite large diverted N currents to potentially have to be carried by its connecting conductors - applying the normal rules might suggest that the mat or buried grid should be connected to the MET via main bonding conductors (in addition to the hot tub's c.p.c. locally by supplementary bonding conductors as demanded by 702).


       - Andy.
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