Can I please check that an IR test can be performed by disconnecting the ring legs from a socket - whilst everything is connected in the CU?As you imply, even if applied between L&N, 250V DC is very unlikely to damage anything used to experiencing 230V (RMS) AC. However, we're talking (well, I think we are!!) about the situation with L and N joined together (and testing between them and earth - in which case, as I said, I can't see any credible test voltage damaging anything other than possibly input filter (L-E and N-E) capacitors.
Kind Regards, John
This saves having to locate these in a busy CU.
I think the recommendation is to test at 250v across L&N to Earth when we are concerned about connected or vulnerable loads?