Has anyone had any experiece with creating unloading curves for TRANE GSHP units.  I have calculation the compressor kW/ton, and kW/MBh values but do not know how to plot the curves at different loading capacities.  My initial review back from USGBC commented on providing a curve. 

The units I have are single compressor, according to the sales rep they are ON or OFF at 100%, I don't think this is accurate but could be wrong.

Is there a standard equation to create these curves?  I went through AHRI 330 but could not find any significant information on part load calculations for ground source heat pumps, they mention it, but just the testing method.