I ALWAYS shut turn the power off on my older HR22 and H21 receivers, and always tell my customers to do so as well for anything up to an HR24...do an info test on your temp and you'll see why...my HR22 is at around 90 degrees off, but runs as high as 117 degrees when the power is on. Also, a laptop fan connected to the usb port works great when a receiver is inclosed in a glass cabinet.