Although I don’t have my CQ-20B in a rack as that would be counterproductive to have something so small housed in a rack. I wouldn’t be concerned about it overheating unless you had it sat in direct sunlight, however, that would be the same for any digital board. I have both my QU-SB and AB168 in a shallow 6u rack and neither of those suffer with the heat, especially the SB as that is fanless.