EV charger issue - Garo PME trips

[sparkymark77]

I fitted one of these Garo units with a Tesla charger last year. All worked fine for a few months and then started doing exactly the same as yours with the rcbo tripping. I re-tested everything and all fine so contacted Garo and they sent a replacement rcbo. I swapped it over and it’s been fine since so in my case it was a faulty rcbo.

 

[hasel5]

Garo have had a issue with the RCBO units not being able to take up to the full rating of the device have swapped out loads of these RCBOs so just replace the RCBO and all will be fine

 

[Gavin John Hyde]

Hi. Not sure if it's the right place to ask, so won't be upset if it gets removed. Apologies if the terminology (PEN/PME/etc) is used inaccurately.


I had an EV charger installed in December on my detached garage by a local electrician. The charger is one that doesn't have a PEN fault detection device (Tesla), hence we agreed I'd get it separately (Search Results - Detail - https://www.garo.co.uk/product-details/All/G6EV40PME).


Armoured 10mm^2 cable (from main circuit board to garage - approximately 32 meters) has been used to the garage where a smaller consumer board and the PME fault device was fitted. From there there's around 4-5m of 4mm cable to the actual charger.


After awhile I've noticed that the PME fault device trips every now and again - always late in the evening or at night, although that's mostly when I charge. It is quite sporadic, although in reality probably happens every 5-6 charges, which can be annoying in the morning if I miss the message on the car's phone app.


Interestingly the Tesla charger integrates with my Home assistant, so I can see the voltage at the charger, which seems to significantly drop on some evenings/nights (expected under load?), although never below the PME device's 207-253V range.


I have raised this with the electrician several times and he's not sure why this is happening. Also everything seemed fine on the 2 occasions he's tested it - once after installing and later when I raised the problem with him. However the test was never done by him at the time when voltage significantly dropped.

I did measure the voltage myself once when the voltage seemed low, soon after the PME device tripped and I reset it. In the house - ~232V, in the garage's consumer unit - ~230V, meanwhile Tesla charger in Home Assistant reported approx 222V while charging.



Question - where would I go from here ? Is there anything obvious another electrician would perhaps notice.. ?

Some photos attached.

Thank you

Apologies for the late response.. I am exceptionally busy these days with solar pv installs galore. not so much EV charging but approaching teh wider renewable sector with same determiantion to consumer the mundane through to interesting knowledge. Dont fit anything I do not fully understand. Not been on the forum as much the last few months. not had time. Business has tripled in size.
I am not a fan of Garo RCBOS, went through a spell using them but found them too prone to nusinace tripping - oddly enough normally a tesla involved.. i had one install with a similar issue albeit in the end we got the dno out who fitted a bit of kit to measure the supply voltage and we could show that as he was fed from an overhead line - with pole 2 metres from his garden fence that as he was end of the line his voltage would drop to just over 200V in some cases. long story short they replaced transformer on the pole and now everything is fine.
I have been told by some planners for the dno that as so many people are now on octopus go and similar tariffs for evs that kick in at 00:30 every night they can actually see the effect on ev chargers kicking in at this time on the local parts of grid and the voltage level drops. It is in some areas causing some headaches in balancing the grid supply.

Had another customer with similar issue of car stopping charging due to detection of low voltage (sub 220V), flashed up on esla central dash. this could happen day or night and occur majoirty of time. it was only when he took it to the Tesla rangers over by Avonmouth and showed them on a 7kw charger that they then relented from saying it is your supply. they replaced the charging port and a wiring loom even thought there was supposedly nothing wrong with it. so read into that what you will

 

[marconi]

https://www.digikey.be/htmldatasheets/production/2996418/0/0/1/dua55-datasheet.html

ElectricallyRandom - Please would you look at the section 'Range Settings' in the link above and tell me what voltage window and measuring range have been selected by the four little switches on the voltage monitoring relay behind the flap.

 

[marconi]

ElectricallyRandom: Do you have an electric shower? What power is it? Is it fed by right hand rcd?

 

[marconi]

ElectricallyRandom: Questions, questions, questions!

1. Is you leccy supply from overhead cables?

2. Where are you along the line of poles between the transformer and your tap off?

3. In the voltage plot was it your EV starting to charge that caused the very significant voltage drops at 8pm and 10pm? I have assumed it was which is why I am checking. Or something else?

 

[marconi]

ElectricallyRandom - good morning Sir.

Just wondering if you have resolved the problem and how? We like to learn from what advice was useful or otherwise.

 

[ElectricallyRandom]

ElectricallyRandom - good morning Sir.

Just wondering if you have resolved the problem and how? We like to learn from what advice was useful or otherwise.

Been really busy, so no, I didn't yet. In the mean time it has happened at least twice again. Garo tripped in the evening, I've reset it and the charging completed by early morning. I'm very tempted to just swap the garo for a matt:e as per several similar stories online.

 

[marconi]

Did you lower maximum charge current?

 

[ElectricallyRandom]

Did you lower maximum charge current?

Only just. Need to charge today - dropped the current from 32A to 26A. Will see how it goes.

To answer your questions a few posts above:

1. No overhead cables around here - all underground.
2. Not sure I understood the question, but I have no idea whereabouts the main transformer is in this neighbourhood (new development, dozens of new houses). It's definitely not in the vicinity if it makes a difference.
3. Yes, voltage drops quite noticeably when I start charging.

 

[ElectricallyRandom]

https://www.digikey.be/htmldatasheets/production/2996418/0/0/1/dua55-datasheet.html

ElectricallyRandom - Please would you look at the section 'Range Settings' in the link above and tell me what voltage window and measuring range have been selected by the four little switches on the voltage monitoring relay behind the flap.

Apologies for a late answer - busy time. I've just checked and here's the settings. That should mean 230V +-10% according to the datasheet. What do I make of it... ?

 

[marconi]

Apologies for a late answer - busy time. I've just checked and here's the settings. That should mean 230V +-10% according to the datasheet. What do I make of it... ?

We will move on to this aspect after trying a lower maximum charging current.

 

[HappyHippyDad]

If the car is inside the garage there is no need for PEN fault protection. (From the Code of Practice)

I don't think its quite as simple as that. I think it's more along the lines of if the vehicle cannot be charged outside then there is no need for PEN fault protection (on PME or TNS system (as you have to assume TNS is actually PME and not a proper TNS) ). If the EVCP is installed in the garage and the car could still easily be charged outside due to the position of the charger then you still need PEN fault protection.

 

[loz2754]

I don't think its quite as simple as that. I think it's more along the lines of if the vehicle cannot be charged outside then there is no need for PEN fault protection (on PME or TNS system (as you have to assume TNS is actually PME and not a proper TNS) ). If the EVCP is installed in the garage and the car could still easily be charged outside due to the position of the charger then you still need PEN fault protection.

Indeed. You worded it in a less ambiguous way.

 

[ElectricallyRandom]

We will move on to this aspect after trying a lower maximum charging current.

Charged at 26A instead of 32A tonight - went without the Garo tripping. Will try a few more times, see how it goes.

 

[marconi]

For your interest, the heating effect of a 26A current is 66% of the heating effect of a 32A current since the heating effect of a current is proportional to the square of the current. So {26/32}exp2 = 0.66 x 100 = 66%

The RCBO contains an electro-thermal-mechanical trip which uses the current flowing to perform its overcurrent detection function.

 

[marconi]

ElectricallyRandom: Where are we going? If we find that the RCBO holds with a charging current of 26A then there is some evidence that a factor in the problem is the magnitude of the current and its heating effect. I suspect - don't know for certain - but either the RCBO is faulty as others' experience has suggested - in which case it is a simple one for one replacement, or that even with a new RCBO in place the real problem is that for the high long term charging current of 32A, the operating current of the RCBO is derated to a lower value than its marked 40A and less than 32A. If this is indeed the case what I would try next is to re-arrange the voltage relay, contactor and RCBO on the rail of the GARO box so that from left to right we had RCBO-Voltage Relay - Contactor. By doing this we move the warm coil of the contactor away from the warm electro-thermal-mechanical trip mechanism of the RCBO and thereby allow the RCBO to operate at a lower temperature which in turn reduces the amount of derating. We can then trial a charging current of 32A again. Does this seem like a plan if we find that at 26A the RCBO holds closed? You will have to call back the electrician to do the re-arrangement. It would be no more than an hour of his time.

I still think the 4mm2 cabling is too thin because the voltage drops as measured by the Tesla charger point are in my view excessive and power is being wasted warming them up. Typically 6mm2 would be used. But a simple solution is to double up the 4mm2 cabling.

 

[miladenaa]

I can understand not wanting to knock in a meter of earth rod, but to detect loss of PEN it really only needs to be 6 inches. However

 

[marconi]

ElectricallyRandom: ?????????? Did I contribute as others have in vain?

 

[ElectricallyRandom]

ElectricallyRandom: ?????????? Did I contribute as others have in vain?

Oh yes you have I have dropped the current to 26A and last night on 3rd charge at lower current my pen device has tripped again. Just lowered the current down to 22A, but this is clearly not sustainable. I totally take your point on reshuffling the pen fault device's modules to help with heat, but it feels like a bit of hit and miss. I am very tempted to swap it altogether (would gladly just remove it tbh, but that's not quite right).