Can you do a PAT on the iron - i,e, strap all 3 phases and neutral and test insultion with respect to CPC or chassis at 250V DC to begin, maybe 500V later

Any DC fault that will fire an RCD of 300mA rating should show up pretty smartly as a few thousand ohms, I imagine there is either a construction fault - pinched insulation that has now squeezed out, or there is something like a water heater element leak,

The way you damage an RCD that quickly  is to make it break far more than its nominal rating, not a gentle trip at a a few times the nominal. Or it has been breaking and being reset far more then the user has reported.

Mike.

it is operating under zero load ♀️

imbalance or neutral issue. I’m off to bed. Let me know if you sort it , I am interested

nanight duck

it is operating under zero load ♀️

imbalance or neutral issue. I’m off to bed. Let me know if you sort it , I am interested

nanight duck

1) your current RCD is stuffed.

2) your Iron may (proabably does) have a problem,

We need to try to test if these effects are independent bad luck, or as I think we both fear if  problem 2 has caused problem 1 - though it is hard to see how.

I'd start by PA testing the iron.

M

Operating with nothing connected