Hi,

I've been working at a data center wherein the configuration is n+1, which means there's always a back up in (acmv, electrical systems) in case any power failure.

Our current configuration for acmv is air cooled chillers with a back up of watercooleed. The water cooled side was not running for about three years & lately we tried to run only the chilled water pumps. Due to this we've been encountering expansion tank overflow when we run the chilled water pumps while the air cooled chillers are in operation. (water cooled chiller are not running).

We tried to check if there were open interconnecting valves between air cooled & water cooled but there was none & everytime we run the chilled water pump on water cooled side, we experience overflow of expansion tank.

I hope someone can help me what is the probable cause of this?