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EVCP connections within an EV consumers unit.

Andrew Dyke

Hi all,

I’d like to open a discussion regarding the use of Eastron DIN rail-mounted SDM (sub-distribution meters) within EV consumer units.

On a number of installations I’ve encountered, the meters have been supplied with what appear to be undersized conductors—typically 1.5 mm²—taken from the load side of a double-pole BS EN 61009 C40 RCBO. Upon reviewing the manufacturer’s documentation, I have been unable to find any guidance relating to additional overcurrent protection requirements for the meter supply.

I contacted the manufacturer directly, and they advised that a DIN rail-mounted fuse holder with a 1 A fast-blow fuse should be installed. However, this requirement does not appear to be documented in their published instructions or technical literature.

Bearing in mind the following from BS 7671:

134.1.1 Good workmanship by one or more skilled or instructed persons and proper materials shall be used in the erection of the electrical installation. The installation shall take into account of manufacturers instructions. 

510.3 Every item of equipment shall be selected and erected so as to allow compliance with the regulations stated in this chapter and the relevant regulations in other parts of BS 7671 and shall take into account of manufactures instructions. 

I’d be interested to hear others’ experiences or interpretations on this, particularly in relation to compliance, best practice, and how this is being approached in the field.

  • If there is no credible failure mode of the meter internals that can overload the wire without tripping the 40A MCB, then its probably OK - the length is short enough to allow a decent short-ciruit current to flow. It may be less than 3m and contained , and then rather like the 5A lighting circuit tap from a 1000A bus-bar, we dont really care as its protected at the other end.

    It may look a bit odd, but it sounds regs compliant if the meter cannot draw more than the 1.5mm2 can supply - probably about 16A all day or a lot more for very short periods.
    Mike 

  • Are these 1.5mm² conductors carrying the full EV load, or just a supply to the meter itself?

    If the latter, it's plausible that's it's OK - BS 7671 allows overload and fault currents to be handled individually - if the meter only draws a fraction of an amp then overload isn't and issue and 1.5mm² may well be OK on a C40 MCB for faults once the manufacturer's energy let-though data is consulted. Consider domestic ring circuits in T&E where a single 1.5mm² c.p.c. is considered fine on a 32A MCB.

       - Andy.

  • Andrew Dyke said:
    I contacted the manufacturer directly, and they advised that a DIN rail-mounted fuse holder with a 1 A fast-blow fuse should be installed. However, this requirement does not appear to be documented in their published instructions or technical literature.

    By a 1 A fast-acting fuse, are these in all cases suitable for the prospective fault current? The IEC 60127 high breaking capacity (HBC) fuses are only suitable for 1.5 kA ... smaller package fuses, either general purpose or for electronic equipment protection, to BS EN [IEC] 60269 series are available with higher breaking capacities, but they are often 32 mm fuses.

  • in reply to AJJewsbury

    good point, 40A whole current metering is not so clever on 1.5mm2, I was assuming this is the remote current transformer  type, so the thin wires just monitor voltage
    Mike.

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