Discuss EV charger issue - Garo PME trips in the UK Electrical Forum area at ElectriciansForums.net
Tesla Gen 3 chargerElectricallyRandom: please tell us the exact make and model of your ev charger. I want to check its maximum power and power factor and what type and amperage of rcbo is recommended.
If the car is inside the garage there is no need for PEN fault protection. (From the Code of Practice)Are you suggesting an EVCP installed on a non-dwelling doesn't need to comply with BS7671?
The car is kept outside.If the car is inside the garage there is no need for PEN fault protection. (From the Code of Practice)
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.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.
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?
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