The Main Controller (UMC-117), also known as the Kitchen Controller in residential models, lets you set temperatures in 2-degree intervals between 100 and 120 F. (With professional adjustment of dipswitches in the controller, you can even go higher on the 28-R and 28-C Series models. However, Paloma recommends never making this adjustment unless you have a specific requirement for doing so – hot water causes serious burns)Temperature settings can be changed by touching in new settings at any time, even while the water is running.A Main Controller should be installed in the kitchen, laundry room or near the Paloma itself (but never outdoors).