I have a ground to water heat pump for my home heating/cooling (scroll compressor). The 3-phase 15kW-peak motor can be soft started but this option is off by default.

I'm aware of all the positive effects of a soft start but I cannot find any negative, are there any? In general or specifically for scroll compressors? Why would the option be off by default?

  • $\begingroup$ I understand that there is a softstart installed but turned off? What kind (star delta, FI, other ...)? What is the typical power consumption of the motor? $\endgroup$
    – mart
    Jul 29, 2020 at 12:21
  • $\begingroup$ I'm not sure and don't have the time to properly check right, but I'd look at the torque the motor produces at low voltage, is there enough torque to do the volumetric work? Remember, a scroll compressor is a positive displacement machine! $\endgroup$
    – mart
    Jul 29, 2020 at 12:35
  • $\begingroup$ @mart if the motor wouldn't produce enough torque at low voltage, I guess there would be no softstart installed in the first place. Typical consumption of the motor is between 1,8 and 3,0 kW. Kind of softstart: no idea, here a picture of the power board: heatingspareparts.com/image/vaillant/0020150124/011/… $\endgroup$ Jul 29, 2020 at 13:53
  • $\begingroup$ The picure doesnt tell me much, maybe others. You should be able to edit it into the question. $\endgroup$
    – mart
    Jul 29, 2020 at 14:02
  • $\begingroup$ I was rewiring a centrifugal lift pump the other day and found that it had no soft start wiring. My guess is that the pump characteristic vs rpm of a centrifugal pump is sufficiently benign that they don't need soft start. $\endgroup$ Dec 4, 2022 at 4:41


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