System and method to maintain evaporator superheat during pumped refrigerant economizer operation

A method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system is able to operate in either the pump mode or a compressor mode of operation and includes an electronically controlled expansion valve (EEV), the method comprising:

• using a controller to obtain a stored, predetermined pump differential pressure range able to be produced by a pump of the refrigeration system;
• using the controller to obtain a stored, predetermined superheat temperature range;
• detecting a superheat level;
• determining that the detected superheat level is outside of the predetermined superheat temperature range, and then using the controller to command adjusting at least one of the EEV and a speed of the pump based on whether the superheat level is above or below the predetermined superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range;
• and
• further comprising detecting that the superheat level is within the predetermined superheat range, and that a pump pressure differential is below a lower threshold of the predetermined pump differential pressure range, and then closing the EEV by a predetermined percentage and maintaining a current pump speed to maintain a current value of the pump differential pressure.

A method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system is able to operate in either the pump mode or a compressor mode of operation and includes an electronically controlled expansion valve (EEV), the method comprising:

• using a controller to obtain a stored, predetermined pump differential pressure range able to be produced by a pump of the refrigeration system;
• using the controller to obtain a stored, predetermined superheat temperature range;
• detecting a superheat level;
• determining that the detected superheat level is outside of the predetermined superheat temperature range, and then using the controller to command adjusting at least one of the EEV and a speed of the pump based on whether the superheat level is above or below the predetermined superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range;
• and
• further including detecting that the superheat level is above a predetermined upper threshold of the predetermined superheat range, and that a pump pressure differential is within the predetermined pump differential pressure range, then opening the EEV by a predetermined percentage and reducing a speed of the pump speed to thus reduce an upper threshold of the pump differential pressure range by a predetermined fixed value.