Chiller 2 at EX had its Low Ambient Lockout enabled at 14 degrees. Early this morning, once the temperature dropped below 14 degrees, it went into inhibited mode. Because this chiller is running as the lead unit, Chiller 1 attempted to come on and cool the loop because its Low Ambient Lockout was disabled. There is an apparent issue with the second refrigerant circuit in Chiller 1 which caused it to fault. I disabled the Low Ambient Lockout on Chiller 2 which caused it to run again, since it is the lead unit, and this has cooled the loop back to where it had been running the last several days. 

I checked the chillers at EY as well and found that Chiller 2 also had its Low Ambient Lockout enabled at 14 degrees, and I disabled this as well. I will continue troubleshooting Chiller 1 at EX next week when the weather is less severe. Currently all chillers are set to run regardless of how cold it is outside.