I have a 1000 w MH 2 feet above it at first (maybe 2 1/2 feet)
I have one fan blowing hard right on the bulb and another lightly across the top of the soil (plants).After they're a week old about I move the light to about 18 inches.Or 2 feet at the most.Depends on the heat yours turns out.and the temp of the room and control you have over that.
Window ac units are great for getto grows ...they help with temp and bring in fresh CO2 every time it's on .And it replenishes the room with fresh cool air.Just make sure you don't have light leaks because of it.(You need to build a light baffle)