Possible overcharged system with EEV

Hello, hopefully someone can assist me.

I have a small system the has a driver controlled compressor and a electronic expansion valve. This system has a temperature probe about the evaporator coil set point is 5.5C. We were receiving alarms from the controller because the temperature could not get below 7.5C. There were bubbles seen in the sight glass, condenser and evaporator pressures were both higher than normal. All sizing and airflow are correct for the equipment design, we have 30+ systems in place that work fine.

We had a refrigeration tech show up, he told us that it was low on charge and added 1kg of 407C to the system, total charge amount is 2.2kg. Now we have to have the EEV at 30-35% to get temperature to 6.0C, the evaporator pressure drops to 0.40Mpa (normal is 0.55Mpa). If the EEV increases to its maximum of 68% the temperature will rise to 11.0C

After the system was charged I swapped the stepper motor and control board, when the system starts up and the valve goes to 17% the condenser pressure jumps to 2.1Mpa and shuts down on high overload. When I put the original stepper motor and board back on I still get a initial jump on the condenser but it only goes to 1.9Mpa.

Is it possible that my original problem was (or is) the EEV, stepper motor, or control board? I have a feeling that the system did not need any refrigerant and only need some simple components changed.


Thank you for your time,
Chad

What about EEV superheat?

Hi Chad and welcome to the forum.
Could you go back to basics and measure your SH, SC, HP, LP and current % then we can help you more