We recently tried to use an UPS provided from B&R, together with a APC3100. Our hope was that we could do a controlled shutdown (save everything important) if a power failure occurred. But apparently, whenever the main power supply was switched off, then the AR would go to Service mode since all other modules would be shut off and only the APC3100 would remain on since the UPS could only feed the APC with power. And during Service mode, the APC couldn’t run our code. So the only way to make this work is to shut off monitoring off all connected modules to prevent the PLC from switching to Service mode.