Two identical BEopt residential designs, one with a gas furnace and the other with an electric furnace, behave the same with one exception. Regardless of whether the electric furnace is sized or autosized, there are a few times, even days, when its output goes to zero. There are never any unmet hours. In DView the delivered energy is exactly the same except for these few periods when delivered energy from the electric furnace drops to zero. These are not periods of extreme cold although they are during periods of low temperatures. Delivered energy from the gas furnace, on the other hand, seems plausible--no such "dropouts." As a result, annual delivered energy for heating is always 65.1 for the electric furnace, but 74.8 MMBtu for the gas furnace. Again--no unmet hours ever show up and the living space remains at the setpoint despite delivered energy temporarily dropping to zero.
Any thoughts on this?
