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Commando socket charging

Glan gluaisne

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Sep 11, 2019
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I had a similar issue with our transformer at the farm.
My Combined Heat and Power (CHP) generator (56kw continuous 3 phase) was tripping off and recorded voltages of 255v and higher.
If you can show the DNO that they are supplying voltages over 253v, they are in breach of regulation and they HAVE to reduce it on the transformer tap. But they don't like doing it. After producing the data, they changed it in a week, but before that they weren’t interested.
Once it gets over 253v it can't be good for equipment onsite surely.

Our supply went over 260 VAC today, until I isolated it. After that I saw it hit 285 VAC at times. It seems a tree damaged a cable, almost certainly taking out the PEN conductor, causing the line voltage to float around all over the place, as well as pushing the PEN local voltage up to around 80 V above true local earth. This thread relates the tale: Open PEN faults . First time I've witnessed an open PEN fault first hand, and it's convinced me that the IET were right to make open PEN protection mandatory for any outlet installed to supply a car charge point.
 

Glan gluaisne

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Out of interest, why didn’t you get a 3ph supply to the house if the cable was literally already there?

I did think about it, but decided to go with single phase to start with, and see if we ever needed any more power. It would be very easy to upgrade to three phase, as the cable joint is literally 6ft below where our meter is. As it's turned out, I can easily run two charge points overnight and all the loads in the house, so I can't see that we're likely to ever need any more.
 

26ct2143

Member
Nov 22, 2020
206
84
Burton-on-Trent, UK
Our supply went over 260 VAC today, until I isolated it. After that I saw it hit 285 VAC at times. It seems a tree damaged a cable, almost certainly taking out the PEN conductor, causing the line voltage to float around all over the place, as well as pushing the PEN local voltage up to around 80 V above true local earth. This thread relates the tale: Open PEN faults . First time I've witnessed an open PEN fault first hand, and it's convinced me that the IET were right to make open PEN protection mandatory for any outlet installed to supply a car charge point.
Wow that's high, I've heard people hitting 260v before, but not over that.
If it's a regular thing, I'd complain (loudly) to the DNO, damaged equipment is surely going to be an issue.
Do the car chargers trip off to protect the car? That would worry me greatly.
 

Glan gluaisne

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Sep 11, 2019
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Wow that's high, I've heard people hitting 260v before, but not over that.
If it's a regular thing, I'd complain (loudly) to the DNO, damaged equipment is surely going to be an issue.
Do the car chargers trip off to protect the car? That would worry me greatly.

It seems that it was probably an open PEN fault. The DNO (SSEPD) confirmed on the phone that a tree had damaged a cable nearby, and although our power didn't fail it seems likely that the tree damaged just the PEN conductor, and left the phase conductors undamaged. At times the measured line to neutral in the house went up to 285 VAC, believe it or not, but it was fluctuating like mad, going up and down tens of volts in less time than my meter takes to display the reading. I isolated the supply, as we had a phone charger go bang, rather dramatically, so there was a very real risk of damage to other appliances in the house.

Charge points must have open PEN protection, if the installation has a PME supply, so this should have tripped to prevent the car bodywork rising to an unsafe voltage had the car been charging. Not sure what the voltage tolerance of the chargers (which are built in to the car, under the rear seat in the Model 3) is, but pretty much every switched mode supply I've seen has an upper limit of between 265 VAC and 285 VAC, and I suspect Tesla may have erred on the side of caution and included over-voltage protection. As far as the charge point goes, then the voltage it can tolerate depends on the power supply to the EVSE circuity. I would be surprised if there isn't some form of over-voltage protection built-in to most charge points.
 

GRiLLA

Member
Jul 5, 2020
819
776
UK
Like a few others on here I can’t claim the OLEV grant. In addition I already have a portable charger that can plug into a 32A commando socket. Therefore for my particular predicament there does seem an opportunity to save money with a commando socket vs buying a proper charger.

Having researched with the objective of minimising both component cost and on-site installation labour, it appears I need:

A) A 32A blue commando socket, which needs to be interlocked to comply with regs as it will be located outside, fairly simple to buy for £20 or so

B) PME fault detection in the consumer unit, which removes the need for an earth rod

C) Type A RCD plus additional >6ma DC leakage detection and auto shutoff in the consumer unit to avoid having to use an expensive (£120+) Type B RCD/RCCB. As I understand it all RCDs upstream of a Type-B (if present) also should be converted Type B which further calls for avoiding a Type B if possible

Plus minor sundries such as wire etc.

My issue is there doesn’t seem to be a consumer unit on the market which has both (A) and (B) included. Nor are the >6ma DC protectors in (C) available as a separate item which you could combine with a regular Type A RCD/RCCB*, so you can’t assemble the components into your own mix & match consumer unit either.

Rolec do an “O-PEN:EV” consumer unit which appears to do (B) but not (C), since (C) is built separately into their chargers.

There are a few units (eg SP-EVCP-B from Matt-e) which combine (B) with a Type B RCD/RCCD, but they are >£300 which negates any real saving vs a proper charger.

So, my question is, has anyone come across a product which combines (B) and (C) at a genuinely cheap price?



* apart from one provided by Rolec as a replacement for a component inside their wall charger - I don’t think you can use this as a standalone inside a consumer unit

Seen this one? EVSE Connection Centre with PEN Loss detection - IP65 | ecoHarmony
 

mr_e

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Dec 26, 2020
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0
London

Glan gluaisne

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Sep 11, 2019
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This looks spot on. Seems like you can spec the IP30 version with both earth fault detection and >6mA DC detection and a Type A RCBO for £234. Then if I’m not wrong you could hook it up as a 2nd consumer unit off the meter, wire a 32A interlocked commando socket directly into it, at a total equipment cost of £260+sundries and meeting all the latest regs?

If this was fitted at the supply end, then it just needs tails connected to a Henley tapped into the incoming supply to the CU (that avoids having to run hefty cable into the existing CU, rearrange the bus bar etc to make a non-RCD protected way, etc). Because the cable from such a protection box will have RCD protection it doesn't need to be armoured unless it's going to be in a location very prone to damage, so NYY-J, or even T&E in conduit, could be used, making the wiring simpler (terminating SWA isn't difficult, but it takes a bit of skill to do a neat job). If it were me I'd probably do surface runs of cable in NYY-J, as that fits standard plastic cable glands, is tough, UV resistant, etc (so doesn't need conduit outside) and it's as easy to terminate as T&E.
 

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