As a follow up to Stefan's alog, we closed the MSR doors and turned the fan off at 2:20pm to see what temp the room would reach while running with the nominal two cooling units. The attached plot shows a quick increase in about 30 mins from 25.5 to 27.5 degC. At this point the polarizer located in the MSR1 rack drifted and caused problems with the commissioning work. We abandoned our tests and returned the MSR back to its original doors-open-and-fan-running configuration. The temp came back to its 25.5 stable state in about 30 mins.