The correct procedure for resetting a TRU is just to switch it off, then on again.
There are some "hidden" reset functions within the DC master box which involves switching the bus tie to Open, moving the battery master switch to OFF and then back to Reset. However that is not the sort of thing you want to be doing in flight!
I have on occasion done it when ground power has upset the DC master box such that the aircraft won't come to life at all. Moving the battery master switch to reset with bus tie to NORM is a "small reset" whilst doing same with the bus tie set to OPEN is a "mega reset" (my terminology!).