Why aren’t heat collector tubes/pipesof fireplace heat exchanger blower mounted on upper surface of fireplace?
Since I am not, and never have been, in the design and manufacture of these devices, my answer is a 'best guess.' I suspect that those pipes are not put over the fire for two reasons: 1. So as not to deflect, or impede the flow of combustion gasses [smoke] which could cause it to be deflected back into the room possibly causing a dangerous environment due to toxic compounds in the flue gasses. 2. The significantly greater amount of heat above the fire, combined with the acids in the flue gasses would rapidly eat out the pipes making them look like a piece of lace and allow toxic flue gases into the airflow in the pipes and into the room, again creating a dangerous condition for occupants of the room.
The blower blows air into the pipes. If they were on top the hot air would pass through the blower, heating it up. The components of the blower would overheat.
