I noticed that the End Y temperature was not recoverling after Robert's HVAC shutdowns. Since it appears the chiller was not working correctly I have started the other one. Water temps are now falling. For the record I turned off Chiller 2 and turned on Chiller 1.This is done indirectly by turning the chiller's water pump off or on.We do not control the chiller remotely. There may be some overshoot on the VEA temperature as it corrects - so don't be surprised if it gets cold before it comes back to normal.
For reference here is a plot showing the temperature excursion which is believed to have caused a lockloss. 7 days shown.
BLUE is the YEND temperature, RED is XEND, and BLACK is the LVEA.
YEND experienced ~ +/- 1degree F of a swing.