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EV Charger Design Advice

NE-ELEC-12

Hi All,

We are currently liaising with a Client regarding a project where they have not been with the D&B contractor in terms of quality of the installation, and ultimately the electrical design. The Client is asking for us via a new D&B Contractor to review the design and current installation to see what can / cannot be utilised going forward.

 One of the items of concern that stands out immediately is the original design is the use of a 5 core SWA cable to supply 2 No. EV charging points. With both charging points being single phase on separate ways within the distribution board. Way L1 using cores 1+2, with way L2 using cores 3+4 we have not yet opened up the EV Charge points to see if core 5 is spare with the SWA being a common CPC, or whether core 5 is used as common CPC. 

We have concerns regarding the use of a cable with multiple single phase circuits within it, and the use of a common CPC for both circuits, is this allowable with in the regulations?

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    NE-ELEC-12 said:
    We have concerns regarding the use of a cable with multiple single phase circuits within it

    Doesn't that happen if you have TPN and split it at the load end into 3 no. SPN circuits?

    In addition, it happens with singles in conduit or trunking?

    It does raise the question as to how the current-carrying capacity was determined, because BS 7671 (and probably manufacturer's data) doesn't cover this use-case for multicore cables (it does for singles in containment, using grouping factors, but there's no evidence that multiple conductors in the same cable can be grouped in the same way using the same factors).

    NE-ELEC-12 said:
    nd the use of a common CPC for both circuits, is this allowable with in the regulations?

    Whilst BS 7671 requires a cpc to be provided at each point in wiring, and, where ADS is used, to be run in the same wiring system (or its immediate vicinity), there is no specific requirement that a cpc is required for each individual circuit. Best analogy is singles of multiple circuits sharing metallic containment where the containment is the cpc.

    If open-PEN disconnection devices are used on each of the circuits separately, and are upstream of this cable, the protection of the OPDD is invalidated. See Regulation 722.411.4.1

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  • 0
    NE-ELEC-12 said:
    We have concerns regarding the use of a cable with multiple single phase circuits within it

    Doesn't that happen if you have TPN and split it at the load end into 3 no. SPN circuits?

    In addition, it happens with singles in conduit or trunking?

    It does raise the question as to how the current-carrying capacity was determined, because BS 7671 (and probably manufacturer's data) doesn't cover this use-case for multicore cables (it does for singles in containment, using grouping factors, but there's no evidence that multiple conductors in the same cable can be grouped in the same way using the same factors).

    NE-ELEC-12 said:
    nd the use of a common CPC for both circuits, is this allowable with in the regulations?

    Whilst BS 7671 requires a cpc to be provided at each point in wiring, and, where ADS is used, to be run in the same wiring system (or its immediate vicinity), there is no specific requirement that a cpc is required for each individual circuit. Best analogy is singles of multiple circuits sharing metallic containment where the containment is the cpc.

    If open-PEN disconnection devices are used on each of the circuits separately, and are upstream of this cable, the protection of the OPDD is invalidated. See Regulation 722.411.4.1

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