i dont know anything about using tecs but the way they are made can have a very dramatic failure when they go out. if they just fail due to an open circuit in them it is no big deal but if they short out they can blow dramatically and with enough power to zap anything on the same line. think of them as a light socket, when you stick a screwdriver in the socket it will flash pretty good and the fuse will trip but before it does it may or may not melt the wire to the lamp. now think of that in terms of the computer being the lamp wire. i know that tecs are very finiky about having a strong and stable power supply, even minor variations can easily cause them to fail. im not sure but i think they also require a lot of amps to run so it is like double insurance to seperate the power supply for safety in protecting the other computer circuits and also since it has its own power supply it has very strong amps and a stable power supply for running. the other parts of the computer cause fluctuations in the power supply as power demands change so it is always fluctuating.