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16mm tails 100A fuse - EV & ESS

vantech

Hi all,

Just looking for a quick sense check.

I currently have job with a 100A DNO fuse with 25mm meter tails feeding the main consumer unit. I’m planning to install an additional external consumer unit via a Henley block to supply:

  • 7kW EV charger
  • 5kW battery storage system (charging) plus 5kW backup circuit (discharge capability) - total 10kW. 

Due to routing constraints, installing 25mm tails to the external CU will be very difficult, so I’m considering using 16mm² tails instead.

The maximum potential simultaneous load on these tails would be approximately 74A (5kW charge + 5kW discharge + 7kW EV). The EV has a 60A load curtailment so the maximum is likely never going to be this high, and the backup circuit on the ESS is supplying sockets (excluding kitchen) and lights, so unlikely ever going to be more than 2-3kW. 

Given that the load is effectively limited by the connected equipment, would 16mm² tails be acceptable on a 100A supply in this scenario, or would 25mm tails be required?

Appreciate any guidance or references to regs / best practice.

Thanks.

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  • 0

    74A (5kW charge + 5kW discharge + 7kW EV).

    Is the battery system physically capable of both charging and discharging at the same time? (Systems I've looked at certainly aren't and Ohm's Law tends to make it a bit difficult if there's a single conductor involved).

    There's a regulation that says anything under 3 meters can be protected by a downstream device.

    Although the 3m limit is for fault protection - overload protection can be anywhere (at the start, at the end, or anywhere in the middle) - as is the case for unfused spurs...

       - Andy.

  • 0 in reply to AJJewsbury

    The ESS has a 5kW coupling (charge and discharge) and a 5kW backup output. 

    If the battery is charging, and the backup loads are consuming 5kW, the total demand for the ESS is 10kW. 

    So presumably if the tails are less than 3m, I can work on the basis that the connected loads (10kW for ESS and 7kW for EV) are lower than the maximum current rating for the 16mm tails? 

    Thanks. 

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  • 0 in reply to AJJewsbury

    The ESS has a 5kW coupling (charge and discharge) and a 5kW backup output. 

    If the battery is charging, and the backup loads are consuming 5kW, the total demand for the ESS is 10kW. 

    So presumably if the tails are less than 3m, I can work on the basis that the connected loads (10kW for ESS and 7kW for EV) are lower than the maximum current rating for the 16mm tails? 

    Thanks. 

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