P-5 is actually P-S and indicates the station is in the Power Save mode. P-S indicates the station is on but in a "stand by" mode. The power save time can be set to 30 or 60 minutes (see Parameters/Initial Resseting in the manual). When used in the manual mode, the system will go into P-S after 30 or 60 minutes of continuous air flow. To turn the station back on, just press the "S" button on the handle again. P-S will also display after the cool down phase of an Auto cycle. See the attached link to download the 852 Instruction Manual.