Recently had a Carrier 3-ton 2 stage heat pump installed. The temperature difference (cooling) between the supply air and the return for stage 2 is 19 degrees which I understand is OK. When it is running in stage 1 which is most of the time the difference is only 14-15 degrees. I know the compressor in stage 1 is only about 2/3 of stage 2 but since the the fan (FV4 air handler) runs at a lower CFM shouldn't the delta be close to if not the same. Wouldn't this make stage 1 less efficient.