Anyone using the Rheem Proterra Heat Pump Water Heater as a finishing heater?  I recently installed such a unit in my home equipped with 6 tons of geothermal heating/cooling with desuperheaters.  The desuperheaters preheat incoming water, in a separate preheat tank situated upstream of the Proterra, to approximately 115F.  But with the preheat running  I am noticing the Proterra is slow to turn on the compressor.  It is set on Energy Saver Mode 130F water temp.

 Is there some maximum entering water temp for the Proterra to operate as a Heat Pump?  Very worst case am hoping I can operate as a standard electric water heater with the desuperheater preheat.