Settings
Pressuretrols have 2 settings: A main cut-in or cut-out setting (depending on model), and a differential setting (which is either additive or subtractive, and usually stated on the controller). The main setting is accessible from the outside of the controller, but the differential is often located inside the controller box, and typically the cover must be removed by removing a screw to access the differential control. If the main setting is a cut-in setting, then the differential setting sets the cut-out setpoint by adding to the cut-in setting(additive), and if the main setting is a cut-out setting, then the differential sets the cut-in by subtracting from the cut-out setting (subtractive).Domestic hot water
Note that in systems in which the boiler providesReferences