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CT Clamp connections inside consumer units

I am looking at how best to terminate EV ultra cable for a EV charger at the consumer unit end.

The data cable for EV ultra has insulation rated at the same voltage as the power cables and therefore can be run inside the consumer unit. If there is space it would be quite tidy to actually mount the CT clamp inside the consumer unit as well. 

I have seen some on you tube do this with some heat shrink to give extra protection and wagos to make connection between the EV ultra and the CT clamp cable. I would probably go for a crimp connector as myenergie at least seem to feel spring connectors are unreliable for data.

 

Just wondering if others view this as an acceptable/good solution

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  • 2no Myenergi Zappi units on a 3pn system. I like having the connections in a separate enclosure rather than in the distribution board where they can be upset should access be required for alterations and the like.

    edit; the board on the left is to be replaced shortly. Had the connections to the CTs been made in there then Heaven knows how some sparky may have left them. Even with EV Ultra, I would arrange breakout of the CT connections before entering the final DB.

  • It is probably permitted in the CU, but unless the only circuit in the CU relates to this load, I'd be tempted to keep the CT in an adaptable box along side if you can, as then it will only be disturbed by folk who know what it is and not to mess with it.  It is remarkable how badly some folk manage in a CU when there is a relay or doorbell supply alongside the MCBs, and this is rather more delicate than that.

    The risk is of changes to an unrelated circuit leading to it being pushed about, at worst compromising your careful LV segregation, or less seriously introducing an EMC issue.

    Mike.

  • This depends on whether the output of the CT is “data” or “current”.

    For “current” types, if the cables on the CT itself are only single insulated, it's not usually safe for them to be outside an enclosure anyway … the output of most CTs is NOT SELV or PELV, but at best FELV.  So, as Lyle and Mike say, in a box is the best option. You can get hold of “guaranteed SELV” CTs, but they are very expensive.

    Data cables should ideally be installed in accordance with BS 6701, and physical separation of at least 50 mm between power and data is required, even with an earthed metallic “divider”. (Which is why I'm not, personally, 100 % convinced at the moment that a combined power/data cable meets BS 7671, by virtue of the fact it doesn't appear to meet BS 6701. Importantly, the physical separation is classed in BS 6701 as an "essential requirement for safety".)

  • For “current” types, if the cables on the CT itself are only single insulated, it's not usually safe for them to be outside an enclosure anyway

    Not sure if the EVSE work in the same way, but with energy monitors the usual setup is to separate the CT from the measured circuit by double/reinforced insulation (e.g. clipping the CT around an insulated & sheathed single core cable) and for the voltage generated by the CT itself to be limited by the burden resistor (often to <<5V for convenient input to an ADC). Thus provided whatever they're connected to (e.g. energy monitor or EVSE control circuitry) provides adequare separation from the mains, they're usually OK in an exposed position.

       - Andy.

  • Thanks all for the responses.

    I ended up bringing the EV ultra in to the CU, dedicated to the EV. Stripping back about a meter of the outer sheath. This left the data cables with an outa sheath which I could run back out of the CU to the meter cabinet for connection to the CT there.

    At the moment it's just connected using wagos with cables held together for strain relief but I need to go back in a couple of weeks and will be looking for a small box to enclose the connections.