Comfort Control for Central Electric Heating Systems

Central electric heating systems typically consist of a number of low-mass heating elements. Due to this low mass, fast rates of temperature rise and fall will occur in the furnace. The end result can be large and uncomfortable temperature swings in the living space. In order to provide good comfort, the control system used must take into account the characteristics of an electric furnace. An analog computer study was conducted to determine the best method of controlling an electric central heating system. The analog computer optimized the thermostat design parameters to provide the required end result of homeowner comfort and long heat equipment life. Since mechanical thermostats have practical limitations on minimum switching differentials and only solid-state electronics could overcome this difficulty, the computer optimized controller was built using integrated circuit electronics. A field test compared the performance of a conventional ON-OFF mechanical thermostat system with the new solid-state controller. The conventional system produced excessive room temperature swings of 3°F, while the new controller produced small swings of less than 1°F.