Chilled Water System Staged Shutdown

Setting up a staged shutdown of a chilled water system can help reduce the chance of the chiller tripping due to excessive cold water or surging.

Most chilled water systems are designed to provide a large amount of chilled water within a short amount of time.  The larger the chiller the more water it can cool.  One issue within many systems is the effects of sudden loss of demand for chilled water which can result in a safety trip of the unit.

Depending on the way a system is configured and the time it takes for a chiller to completely shut down, the water within the entire system could become excessively cold and the pumps alone will not keep problems from happening. 

Another option to help with shutting down of the system is to shut it off prior to shutting down the air handlers.  This will keep a load on the chilled water system and dissipate the extremely cold water and avoid unnecessary safety trips of the unit. 

There are many ways to accomplish a staged shutdown.  If your chiller system is scheduled along with the air handlers, setting up a separate schedule for the chiller would allow the shutdown time to be adjusted.  If your system uses some type of logic to start the system whenever the air handlers are running you will need to set up a sequence in the programming. 

Whatever type of system you have, shutting off the chiller prior to the air handlers and allowing the water time to warm slightly before shutting down air handlers will significantly reduce stress on the chiller.  The lower stress on the chiller translates into lower maintenance costs.