Hope the weather improves soon!
My heat pump compressor is also a big hit on the watts.
The funny thing is, after the initial start inrush, the compressor and air handler only need 2-3kw to run.
The LRA for the Copeland scroll compressor I measured @ 132A.
I thought by adding a second Schneider XW Pro 6848, I could start the compressor.
After reviewing a new document:
XW Pro Multi-unit Design Guide
990-91373A
April 2021
It is apparent the second inverter only adds a small amount of capacity, and I can’t find a spec on the inrush surge capacity for two inverters.
So plan “B”, I bought one of the soft start devices you mentioned.
hypereng.com
SS1B16-32SN (230V, 60/50Hz, 16-32 FLA)
I contacted HyperEngineering, and they said the device would allow the compressor to start w/ the single inverter capacity of 52A.
They told me to remove the "hard start" kit I installed when I put in the new heat pump in 2017.
It was completly destroyed & non-functional anyway from the LRA load, and I now understand the difference between "hard start" and "soft start".
I have not installed the HyperEngineering device yet, not sure I completely understand the wiring diagram, and if I toast the heat pump compressor during hot weather, the wife will be unhappy.
So I’m waiting until the weather cools off to do the install. Might be in the 70’s here by December-January.