A cooling tower is used to cool water and is a massive heat exchanger, expelling building heat into the atmosphere and returning colder water to the chiller. A water cooling tower receives warm water from a chiller. This warm water is known as condenser water because it gets heat in the condenser of the chiller. The paired water-cooled chiller is typically at a lower level, like in a basement. The cooling tower’s role is to cool down the water, so it can return to the chiller to pick up more heat.

Fig 1. Line diagram of condenser loop from EnergyPlus

By default, a Variable Speed cooling tower is added to the condenser loop once a water-cooled chiller has been added to the project. The user has the ability to switch it to a Single Speed cooling tower.