Star-design/CCM problems

GG

Its very urgent, if you know it, please help , thanks very much indeed.

Basicly i am modelling the ventilation flows in a small room with a heat source placed in the middle.

I made a single room with a lower opening (about 0.2 m2)as inlet with vel. mag 0.2m/s with temp 15 degree) and upper opening as outlet , and applied an area of 1x1m face as heat flux 1200w/m2 at floor level of the room, in order to form heat-driven flow in the room, however after running it , the temperature is very big >1000k , how come ? i tried many times, still cant fix it.