They don't recommend it, for reasons of safety (FIRE!) and efficient disspation of heat - but I have done this , without a problem.
Do at your own risk, but ensure that there is PLENTY of room (at least 3 or 4 ins, I wld suggest) around the unit - tops, sides, front - for air to circulate. (Preferably, air should be able to enter near the bottom and escape from near the top, to give a convection current of airflow.)
Also, I did not turn the heater on fully.
Hope this helps.
MS, August 2008
