EV charger issue - Garo PME trips

[ElectricallyRandom]

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

 

[loz2754]

Are you suggesting an EVCP installed on a non-dwelling doesn't need to comply with BS7671?

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

 

[ElectricallyRandom]

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

The car is kept outside.

https://www.tesla.com/sites/default...ng/Gen3_WallConnector_Installation_Manual.pdf

Would you look at the link and page 36 - 'Wall Connector LEDs'.

When you first start up the charger from powered off what is the pattern of vertical green LEDs you see which records the mcb size the charger believes it is connected to? By selecting the mcb size the charger then knows at what level to limit the maximum output current and thus input current. This is done during first commissioning of the charger. Do you know if it was done?

When you next charge car would you feel the 4 mm2 cabling or the conduit in which it is contained. Do this after an hour and then two hours. Is the cable/conduit noticeably warm? Stick a thermometer on if you have one and take a reading. Also feel the surface temperature of the GARO RCBO and the 32A circuit breaker in the garage board.. You do not need to open up anything to do this and the previous test.

I am wondering if your Gen 3 charger has been incompletely/incorrectly commissioned such that it 'thinks' it has a power supply feed sufficient to deliver its maximum or near maximum current output of 48A. See page 6 of link above.

After it was installed, I did the commissioning myself - all it is is setting the charging current and a couple more basic settings. It is set to 32A. When I charge, the Tesla app does show 32A and my smart meter reading goes up by a little over 7kW. I will check the temps when I charge next.

 

[marconi]

Thank you for the information. A quick analysis.

If charger input terminal voltage is 222 V as you measured and output is 32A delivering 7.6kW from the table of page 6 of manual and assumed power factor is 0.9 (the tesla Gen 3 includes some power factor correction technology) then apparent input current is:

I = 7600/(0.9 x 222) = 38A

The apparent input current waveform is not a pure sinewave and will be peaky ie have a high crest factor which the ratio of its peak value to its rms value. A higher crest factor is indicative of the presence of harmonics and distortion.

See: Crest Factor - https://www.sunpower-uk.com/glossary/crest-factor/#:~:text=Crest%20Factor%20(peak%2Dto%2D,has%20a%20CF%20of%201.414.

At face value 38A is higher than than the rating of the type B 32A mcb in the garage DB. For the GARO 40A RCBO, 38A is 95% of its rated amperage - good practice is to derate the amperage rating of an mcb when it passes a continuous current such as several hours of high current ECV charging. For one MCB in an enclosure with a continuous load a typical derating is 80%. Thus the GARA 40A has a derated rating of 40 x 0.8 = 32A which is below the apparent input current of 38A.

Further derating may be required - I cannot be certain - because the GARO 40A RCBO is next to a warm contactor which would derate the continuous current handling further to below 32A.

See the IET article you should find if you google 'Derating grouped circuit breakers within a consumer unit'. I cannot post a link because the EF forbids it.

All in all then it seems to me that a maximum EV charging current of 32A is too high. A figure of 24A for maximum charging current is within the continuous current carrying capacity of the 32A mcb and 40A rcbo when each is derated. (32A mcb derated by 80% is 26A).

You can see now why I would like you to feel and if possible measure the temperatures of the rcbo and wiring. So, once you have done this, could you change the maximum charging current to 24A by telling the charger the mcb size is 30A - check the LED lights show this change has been made. And then see if the GARO trips over say the next 10 charges. Hold fire for now on changing the 4mm2 cabling as I suggested earlier.

Where are you in the country - just for my interest please?

 

[ElectricallyRandom]

Thank you for the information. A quick analysis.

If charger input terminal voltage is 222 V as you measured and output is 32A delivering 7.6kW from the table of page 6 of manual and assumed power factor is 0.9 (the tesla Gen 3 includes some power factor correction technology) then apparent input current is:

I = 7600/(0.9 x 222) = 38A

The apparent input current waveform is not a pure sinewave and will be peaky ie have a high crest factor which the ratio of its peak value to its rms value. A higher crest factor is indicative of the presence of harmonics and distortion.

See: Crest Factor - https://www.sunpower-uk.com/glossary/crest-factor/#:~:text=Crest%20Factor%20(peak%2Dto%2D,has%20a%20CF%20of%201.414.

At face value 38A is higher than than the rating of the type B 32A mcb in the garage DB. For the GARO 40A RCBO, 38A is 95% of its rated amperage - good practice is to derate the amperage rating of an mcb when it passes a continuous current such as several hours of high current ECV charging. For one MCB in an enclosure with a continuous load a typical derating is 80%. Thus the GARA 40A has a derated rating of 40 x 0.8 = 32A which is below the apparent input current of 38A.

Further derating may be required - I cannot be certain - because the GARO 40A RCBO is next to a warm contactor which would derate the continuous current handling further to below 32A.

See the IET article you should find if you google 'Derating grouped circuit breakers within a consumer unit'. I cannot post a link because the EF forbids it.

All in all then it seems to me that a maximum EV charging current of 32A is too high. A figure of 24A for maximum charging current is within the continuous current carrying capacity of the 32A mcb and 40A rcbo when each is derated. (32A mcb derated by 80% is 26A).

You can see now why I would like you to feel and if possible measure the temperatures of the rcbo and wiring. So, once you have done this, could you change the maximum charging current to 24A by telling the charger the mcb size is 30A - check the LED lights show this change has been made. And then see if the GARO trips over say the next 10 charges. Hold fire for now on changing the 4mm2 cabling as I suggested earlier.

Where are you in the country - just for my interest please?

Hi. I really appreciate such a comprehensive reply - must say it was a very interesting read (my inner geek approves ). Preferably I'd really like to charge at a higher current than <32A in the future if possible, but I'll try it for testing purposes.
As I can change the charging current in the Tesla app, I may just do that - it normally slowly ramps up the current to whatever it is set to.

I'm in Hampshire (are you anywhere close?).

Thanks!

 

[marconi]

Not far from Dartford Crossing.

 

[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.