Never seemed to work very well, although that may be as much due to people opening all the windows as much as anything else.
The windows should all be locked after the current installers/maintainers claimed the air con units themselves worked fine, the failures were being caused by the windows being opened. The depot locked the windows put the ball back in their court for the next move!
It was maybe two years they had a management meeting with the contractors. The two management teams went round a set that was signed off days before as being a ok. They opened up the vents and found them clogged with dead leaves!