I recently bought a house with a dual heating system and have been having issues with heat pump. HVAC guy came out to help today and he was trying to explain that you want your heat and cool within 3 degrees of each other. Not sure I understand why. If I have my cool on 74 and my heat on 55 my assumption is that my heat pump would come on when the temp is above 74 to cool and that my heater would not come on until the temp dropped below 55. What am I missing?