I noticed last night that it was getting very warm in my house so I went to mechanical room to discover the heat pump was running non stop. The line sets were very hot and the only way to shut it down is to turn off the breaker. As soon as breaker is turned back on the heat pump starts even if furnace is off. This is a 4.5 ton ten year old system with the variable speed blower and all the bells and whistles...any ideas??