i agree with JPL. unless you pipe in cool air from somewhere else, your just circulating hot air. after all, heating air is what a fireplace is meant to do. i have read about tv's melting from being over fireplaces.
Zero clearance is a term used to describe a certain fireplace’s ability to be enclosed completely by combustible building material that can be positioned right up against the body of the fireplace. That is the back, top, bottom and sides. The front area is designed to radiate heat and therefore must be given adequate clearance to combustibles. In this case, objects such as furniture, should be kept a minimum of 48″ away.
ALL electronic components I have ever been exposed to have heat sinks and or fans which dissipate heat to the air. If the air is warm or hot the heat cannot dissipate.