The problem is almost certainly due to the crap method the Wallbox uses to try to detect an open PEN fault. Like a few charge points, instead of doing this properly it uses the cheapskate option of checking to see if the supply voltage goes out of limits, on the false assumption that this always indicates an open PEN fault (it doesn't).

It's pretty common for homes with solar panels, especially those near other homes with solar panels, to have occasional over-voltage events on sunny days. This is never normally a problem for anything connected to the supply, as there is usually a fairly wide voltage tolerance on most appliances. Where this does often cause problems is with charge points like yours, that use voltage sensing as they just false trip thinking there is an open PEN fault.

There is no fix, other than persuading the DNO to drop a tap or two on your local transformer, or changing the charge point for one that uses a more reliable open PEN fault detection method. Sometimes the DNO will change the transformer tap, sometimes they won't. It depends on the measurements from the voltage logger and how much inconvenience changing the tap will cause. They had to change the tap on our transformer a few years ago, meant half the village losing power for about 3 to 4 hours whilst they did it.

You're far from being the first to encounter this false trip problem, there are other threads here where people have had the same problem. I first encountered it about 4 or 5 years ago when the matt-e came out and a chap quite near to us had one fitted to provide open PEN fault protection for his charge point. That also uses the dodgy voltage sensing method and in his case it kept tripping out several times every day. I installed an earth electrode and RCD for him and he sent the matt-e back for a refund. That completely solved the problem for him (and gave very much more reliable open PEN fault protection because doing this removed the PEN altogether).

 

Thanks for the very comprehensive and useful reply Jeremy

 

Anecdotally I had this problem with my original Wallbox Pulsar Plus after about 18 months with the issue most apparent on warm days. I was told the same over voltage BS and to get DNO out. (the voltage here is around 245-248 normally). We had SPEN out for overvoltage testing, who said it was 'in spec.' Eventually the unit went completely unusable, so I involved my installer as well as Wallbox and between them they fitted a replacement unit. The replacement has been fine.