Back in the late 90’s....I worked in a Air Force office where we had to put up a rack (one single) with a UPS and a couple of raids attached to a server. As winter came, we came to discover that the radiator in the room was totally unnecessary. In fact, the one rack was putting enough heat that we opened the window five or six times a day to cool off the room. The negative came in the summer, as room temp got pretty excessive and we had to buy a second AC unit to help keep the office cool enough.
Back in '89 I was assigned to a unit in Korea where we had a huge mainframe system that was kept cool by huge a/c units. We worked directly in line of the vents (both above and below us). It was funny, because you would see many of the folks working with the system bringing their winter parkas to work on a summer day with temps in the high 80s and humidity to match.