1500 Ton York YK No Liquid Level Control

York YK Type G with Hot Gas Bypass and Falling Film Evaporator 1 year old - Once unit starts refrigerant level reaches the setpoint of 50% (verified thru sight glass on condenser) with a variable orifice valve position of 40% (verified). Condenser pressure is 107psig, evaporator pressure is 37psig, PRV position is 40%, VGD is 99.4%, CHW Setpoint is 40 deg and maintained. The liquid level in the condenser starts to rise above setpoint and the VOV begins to open but the level continues rising over a 3 minute window. Once the liquid level is above the sight glass and the valve is 100% open the unit just operates at this condition. The Hot Gas valve is open on start-up but shuts (verified) once it goes into PRV control and does not re-open. Refrigerant charge was removed and weighed to replace the liquid level sensor and was only 187lbs low. No surging or stalling of the unit and no foaming or carryover. The unit ran fine for the first couple of test runs (1 to 2 hours total) to verify sensor calibration and then this happened. Sied note - I have two identical units next to this one and test ran both to see if it had to do with load or operating conditions, which I didn't think it did, and they ran fine. I have never seen this happen and the only thing I can come up with is the VOV butterfly valve or the Isolation butterfly valve had separated from the shaft and is partially closed. Any help appreciated

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