For Outdoor mounted controller leave the power on and the dial / switch in the "Off" position. The heat from the transformer will keep the enclosure warm enough to keep condensation from forming inside the controller enclosure. The dial in the "OFF" will keep the controller from activating the solenoids in the field. For Indoor mounted controller You may either leave the power on and the dial/switch in the "Off" position or you may remove the battery backup and unplug the transformer.