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

 

[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).

 

[marconi]

It may still be just a faulty RCBO as others have mentioned. You could reasonably ask the electrician who did the work to contact GARO to obtain a replacement. Or you could contact GARO...

What is the first half of your postcode?

I have just sent a missive to GARO technical desk on this problem.

 

[ElectricallyRandom]

It may still be just a faulty RCBO as others have mentioned. You could reasonably ask the electrician who did the work to contact GARO to obtain a replacement. Or you could contact GARO...

What is the first half of your postcode?

I have just sent a missive to GARO technical desk on this problem.

SO22. I will give them a ring myself as I've bought thw Garo myself to be installed.

 

[marconi]

Just spoken on the phone with GARO technical desk. They will do the swap of the RCBO no problem. You need to take proof of purchase to the retailer/wholesaler and ask them to order a replacement RCBO - may even have one in stock. GARO do not deal direct with the public he said.

When wholesaler informs you that replacement has arrived you can collect it. You will have to pay for it until you return the original and get a credit. Or, one could remove the original and exchange for the replacement at the same time. Whatever happens the suspect RCBO has to be sent back to GARO for testing. Or something like this ;-)

The email I used was [email protected] (very helpful).

Please let us know the outcome because we all learn this way.

 

[marconi]

ElectricallyRandom: Don't be shy. Have you now resolved the problem?

 

[Risteard]

My guess is either a faulty Garo unit or a regular supply voltage fluctuation that is too short to be picked up by the sampling the car charger is doing hence you can't see it on the app.
Leaving a decent multi-meter connected on min and then max might prove the point, failing that a voltage data logger could be hired and connected for a few days.
Even if you prove that, getting the DNO to do something about it can take effort and endurance.

To be honest I don't highly rate the methodology used by the Garo Pen protection devices as they aren't guaranteed to detect an open PEN conductor in all circumstances (subject to what loads your neighbours are pulling at the time) and they can be triggered by supply issues (as you may be seeing).

If it were me I'd be seriously considering banging an earth rod in and changing the earthing arrangements in the garage, removing the need for the PEN protection device completely.

I don't want to cause additional concern but a couple of unrelated things jump out at me too:
-you may have a PV system on a shared RCD in the house CU. This is a no-no as there's no point the RCD tripping to save your life if the PV system continues to deliver power until it notices it should shut down.
-the RCD topology isn't ideal - I think there's three 30ma type A RCD's in series. A Type B would normally be fitted for an EV charger.

Also the EVSE must not be on a shared RCD which it is.