With an ACSC100 set for spot/discrete mode, please check the system pressure. Please note standing pressure of R410a @ 70 degrees is approx 201 psi. Therefore, if the standing psig reading on the unit is 41 psi, for example, refrigerant obviously fractionated to be at 41 psi. Per the units firmware if the pressure is below 90 psi the unit will not start compressors, nor annunciate any alarms to the contrary. A couple of things that will keep the SC compressor from starting are: If the Suction Pressure is below 92psi then the compressor will not start, and there are no alarms reported on this.
If the pressure difference between the suction and discharge pressure is above 7psi then the compressor will not start, and no alarms are reported. The unit will log an event that reads ""Start up Line Pressure Imbalance."" "