I have some pretty thick hospital grade extension cords. Just that I turn my electric heater up as if I were running a 400w system which caused the overload. Things are normal now that I lowered the heater as if I were running a 600w system. Temps are a stable 65 lights off and 70 lights on.

But thanks NoDrama. I'll look for the 30amp rated ones. I never really read the labels. I just usually get the thick ones with the lil light on the end if you know what I'm talking about. Someone told me those are "hostpital grade" whatever that means. I just explained the deal (electric heater heating up cords) to my local hardware guy and he showed me those.

If I'm not mistaken, its the length of the cord that had something to do with it as well.