A system comprising: a compressor for a refrigeration system ; a duct assembly that includes a duct frame and a sensor unit (97-1, 97-2), the duct frame providing a path for evaporating refrigerant from a lubricant sump of the compressor, the sensor unit (97-1, 97-2) being configured to obtain temperature measurements corresponding to at least one of the refrigerant and a lubricant within the lubricant sump ; and, in response to receiving a heat signal, the sensor unit (97-1, 97-2) being configured to heat and evaporate the refrigerant located within the duct frame of the duct assembly ; and a control module using a processor configured to execute instructions stored in a non-transitory memory : supply the heat signal to the sensor unit (97-1, 97-2); receive the temperature measurements from the sensor unit (97-1, 97-2); determine a temperature change of the at least one of the refrigerant and the lubricant based on the temperature measurements; determine a presence of liquid refrigerant within the lubricant sump of the compressor in response to a determination that an actual temperature change does not correspond with an expected temperature change for the lubricant; and in response to a determination that the actual temperature change corresponds with the expected temperature change for the lubricant, operate the compressor . a compressor for a refrigeration system ; a duct assembly that includes a duct frame and a sensor unit (97-1, 97-2), the duct frame providing a path for evaporating refrigerant from a lubricant sump of the compressor, the sensor unit (97-1, 97-2) being configured to obtain temperature measurements corresponding to at least one of the refrigerant and a lubricant within the lubricant sump ; and, in response to receiving a heat signal, the sensor unit (97-1, 97-2) being configured to heat and evaporate the refrigerant located within the duct frame of the duct assembly ; and a control module using a processor configured to execute instructions stored in a non-transitory memory : supply the heat signal to the sensor unit (97-1, 97-2); receive the temperature measurements from the sensor unit (97-1, 97-2); determine a temperature change of the at least one of the refrigerant and the lubricant based on the temperature measurements; determine a presence of liquid refrigerant within the lubricant sump of the compressor in response to a determination that an actual temperature change does not correspond with an expected temperature change for the lubricant; and in response to a determination that the actual temperature change corresponds with the expected temperature change for the lubricant, operate the compressor . supply the heat signal to the sensor unit (97-1, 97-2); receive the temperature measurements from the sensor unit (97-1, 97-2); determine a temperature change of the at least one of the refrigerant and the lubricant based on the temperature measurements; determine a presence of liquid refrigerant within the lubricant sump of the compressor in response to a determination that an actual temperature change does not correspond with an expected temperature change for the lubricant; and in response to a determination that the actual temperature change corresponds with the expected temperature change for the lubricant, operate the compressor . <EOS>