Mercer provided a replacement unit which was installed the same way and 16 days later on Boxing day, 3 minutes into load shedding it went up in smoke again. This time my friend was in the kitchen and noticed that plugs that are not on UPS output were still ON. Very strange to see two units fail in the same way. He has had the electrician out and checked everything and had a second person check and all is wired correctly.
It is almost like the inverter was pushing power back to the DB and the neighborhood for that matter via the AC input side. I have the older Axpert 5kVA RCT unit from 2015 and at this time managed to download a service manual for my unit. This has a block diagram figure 2.1 which seems to show a safety relay and an inverter relay.
