What is the proper way to install a muffin fan in a control cabinet? Are you drawing out all the hot air so you mount it high or do you blow cool air in and exhaust it out?
My view is that any fan that communicates with the world outside the cabinet should be filtered and blowing into the cabinet. If you have a fan exhausting the cabinet, you draw in dust from every conceivable inlet, through conduit, etc. By creating a positive pressure in the cabinet with filtered air a lot of trouble can be avoided. And clean cabinets are safer and nicer to work on. By contrast, PCs were designed with the fan blowing out, which is why they used to suck dust through exactly the parts that couldn't tolerate dust like the floppy drives. It was done to have the power supply fan do double duty saving a fan, but it was a bad design decision. I've seen them nearly full. And it has persisted to this day. If you must have a fan exhausting, you should have a bigger fan pressurizing (through a filter). This kind of thing is easy to overlook on day one, but when you replace a VFD with the heatsink plugged solid, you see the value in keeping dust out. High or low will depend some on what you are trying to do, but, I would lean towards low to take advantage of lower temps near the floor unless that will result in more dirt. And I commend you for thinking before doing.
