I'm in a 2ft deep by 2ft wide by 4ft tall box using a 250 without an air cooled hood and my temps average 5-7 degrees warmer than the room it's in. It's a pain to keep the heat under control. But if you can find an air-cooled hood to fit in your space it'd be easier to control the heat and you shouldn't have a problem with the correct ventilation. There are a lot of factors that play into keeping it under control. What are the room temps like that the closet is in?