Bob and Tim are at lunch and discussing the last service call that they had which was a spring start up on a 100 ton chiller. Tim has some questions about how a chiller operates and Bob is filling him in on some blank places that he has in his knowledge base.
Bob explains, “All mechanical refrigeration systems work basically alike. As we discussed in the last service call a chiller cools water and circulates water through the building and back to the chiller. Typically a chilled water system will operate at about 45°F water leaving the chiller and returning to the chiller at 55°F, thus a 10° drop through the chiller. This only occurs when the chiller is working at full load. Most chillers have the ability to run at partial load so that they won’t have to stop and start so many times. If you can imagine a 100 ton system that would reduce the building temperature to the setpoint and then shut down, and then stand idle until the building warmed up a little bit and then start back up again. That’s a large piece of equipment that is stopping and starting on the electrical line. Manufacturers have developed several ways to offer capacity control.