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

 

[Robson689]

Has the electrician tried replacing the GARO unit?

How come he decided to use this device vs an earth rod?

 

[ElectricallyRandom]

Has the electrician tried replacing the GARO unit?

How come he decided to use this device vs an earth rod?

No, not replaced (yet). Garo vs Earth rod - price and simplicity I suppose.

 

[timhoward]

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.

 

[ElectricallyRandom]

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.

Thanks for this. Before we commit to an earth rod, are there any PEN devices you'd rate better than the Garo? Perhaps a simple swap would suffice?

As far as solar - that's the wiring the house came with (new build), I suspect the same as the rest of the large new development. But I take your point and may raise it with the builders.

Thanks

 

[marconi]

After awhile I've noticed that the PME fault device trips every now and again

What actually trips in the GARO? The contactor, the RCD or both?

 

[timhoward]

After awhile I've noticed that the PME fault device trips every now and again

What actually trips in the GARO? The contactor, the RCD or both?

That is a great question and I did make an assumption there.
I assumed the contactor tripped as there are 2 other 30ma Type A RCDs upstream and I suspected one or both of them would also trip if it was the RCD tripping.

Before we commit to an earth rod, are there any PEN devices you'd rate better than the Garo?

Unfortunately I'm not aware of any better standalone ones that aren't integrated into charge points.
I believe the Matt:e one works the same as the one you have. Some charge points also monitor current on the earth conductor as an additional factor in their decision making. @Gavin John Hyde is the resident expert.

( See

)

Ultimately the point of this thing is to make sure that if there is a supply fault your car body cannot become live. This method of protection was added to the regs based on the laws of averages to make it easier to fit charge points. My personal opinion is that it's better to make sure the car body isn't connected to supply earth in the first place, and bang a couple of £10 earth rods in.

 

[ElectricallyRandom]

That is a great question and I did make an assumption there.
I assumed the contactor tripped as there are 2 other 30ma Type A RCDs upstream and I suspected one or both of them would also trip if it was the RCD tripping.

Unfortunately I'm not aware of any better standalone ones that aren't integrated into charge points.
I believe the Matt:e one works the same as the one you have. Some charge points also monitor current on the earth conductor as an additional factor in their decision making. @Gavin John Hyde is the resident expert.

( See

)

Ultimately the point of this thing is to make sure that if there is a supply fault your car body cannot become live. This method of protection was added to the regs based on the laws of averages to make it easier to fit charge points. My personal opinion is that it's better to make sure the car body isn't connected to supply earth in the first place, and bang a couple of £10 earth rods in.

Might not be the answer to your question, but the only thing that trips is the switch on the Garo itself.

 

[EricMark]

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

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.

If in a garage why does it need any loss of PEN detection?

 

[timhoward]

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

If in a garage why does it need any loss of PEN detection?

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