I have two relatively new realay expansion boxes. they should both be within warrants period. Yesterday I plugged in a small circulation pump, temporari into one of those outlets in the second expansion box, and it immediately started to smoke. I turned that outlet off and unplugged the pump immediately, and immediately plugged it into another outlet on the same expansion box, and it worked perfectly for an extended time.. I'm only using two out of the eight outlets on that expansion box, and those other two devices worked perfectly till now. No interruptions anywhere else in the system.
While the pump was plugged into the faulty outlet, there were popping sounds. The system is properly mounted and no fluids spilled onto the outlets or the system asset all.
Please advise.