Compressor with flooded start control

1. A system comprising:

a compressor for a refrigeration system, the compressor having a suction chamber and a lubricant sump containing a mixture of liquid refrigerant and a lubricant;

a duct assembly, located in the lubricant sump, that includes a duct frame and a sensor unit, the duct frame providing an enclosed path for evaporating the liquid refrigerant from the mixture in the lubricant sump to the suction chamber of the compressor,

the sensor unit having at least one diode, the sensor unit being configured to:

in response to receiving measurement signals, obtain temperature measurements of the mixture within the lubricant sump with the at least one diode; and

in response to receiving a heat signal, heat and evaporate the liquid refrigerant located within the duct frame of the duct assembly with the at least one diode; and

a control module that includes a processor configured to execute instructions stored in a non-transitory memory, wherein the instructions include:

supplying a first measurement signal to the sensor unit;

receiving a first temperature measurement from the sensor unit;

supplying the heat signal to the sensor unit;

supplying a second measurement signal to the sensor unit;

receiving a second temperature measurement from the sensor unit;

determining a temperature change of the mixture based on the first and second temperature measurements;

determining whether the temperature change corresponds to an expected temperature change for the lubricant;

determining whether the liquid refrigerant remains present within the lubricant sump of the compressor after supplying the heat signal to the sensor unit based on the determination of whether the temperature change corresponds to the expected temperature change for the lubricant;

in response to determining that the liquid refrigerant remains present within the lubricant sump, prohibiting operation of the compressor; and

in response to determining that the liquid refrigerant does not remain present within the lubricant sump, operating the compressor.

2. The system of claim 1 , wherein the duct assembly includes an inlet port, an exhaust port, and a mount.

3. The system of claim 2 , wherein the duct assembly is configured to allow the liquid refrigerant to enter the duct assembly from the lubricant sump through the inlet port and to allow evaporated refrigerant to exit the duct assembly into the suction chamber through the exhaust port.

4. The system of claim 2 , wherein the mount is configured to couple a first side of the duct frame to a bottom edge of the compressor.

5. The system of claim 2 , wherein a nozzle assembly is attached to the exhaust port.

6. The system of claim 5 , wherein the nozzle assembly has a converging portion.

7. The system of claim 6 , wherein the nozzle assembly has a diverging portion.

8. The system of claim 7 , wherein the nozzle assembly has an inner cone within the diverging portion.

9. The system of claim 2 , wherein the duct frame is configured to absorb infrared light.

10. The system of claim 2 , wherein the duct frame includes injection molded plastic.

11. The system of claim 1 , wherein the at least one diode includes an infrared light emitting diode.

12. The system of claim 1 , wherein the instructions further comprise supplying the heat signal to the sensor unit using a pulse-width modulation signal.

13. The system of claim 1 , wherein the instructions further comprise determining an actual heat curve of the mixture based on the temperature measurements.

14. The system of claim 13 , wherein the instructions further comprise comparing the actual heat curve of the mixture with an actual heat curve for the lubricant.

15. The system of claim 1 , wherein the instructions further comprise:

in response to a heating period elapsing, (i) discontinue supplying the heat signal to the sensor unit, and (ii) supply a measurement signal to the sensor unit.