This is going to be a long post but here it goes. I have to RTHB 300's on 14 Calamac ice tanks on a building. The glycol is set for 12 degrees. The chillers have the proper charge, tubes clean on both vessels, water flows are good and stable condenser water. Here is the problem. The chillers operate fine during the day in non-ice storage mode. All approaches are good an they maintain 35 degree leaving glycol. It all goes to hell in the ice mode on startup. Since these are RTHB's, they have the EXV that is controlled off of a discharge superheat algorithum built into the UCP2. The EMS sends the signal to built ice. The chiller forces the slide valve to full load for ice production. What is happening is the discharge gas temp. drops causing the exv to shut which in turn drives the evap temp down to 14 degrees tripping the chiller off on low evap temp. The chiller algorithium wants to maintain a calculated 35 degree superheat. The actual superheat will be around 20 degrees causing the exv to go to 0-1 % open, boom down goes the chiller on low evap temp. I have manually forced the exv to 30% on startup but you only get about 10 min to jack with it before it goes off on low discharge superheat but the evap temp be ok at this point. The superheat variable is built into the micro and can not be changed. I have jacked with the control algorithuim settings from 1 -4, no luck! Pueblo has never seen this and they are stumped. I even had a refrigerant sample done to see if there was excess oil in the refrigerant, came back good. I thought about putting a time delay on the load signal only when it goes into ice mode to see if the machine would stablize the exv as it loaded. Has anyone had this problem? It is pretty sad when you know what the problem is but don't know how to correct it! By the way, it also has the most current version software in the UCP 2. And no, changing the chiller is not an option although I wish it was a RTHA!