If we used a 700 with a vector cassette, we could do it. That not being an option, the Plus II needs external help to deal with this. We don’t need to disable the PI. Assuming he is maintaining a pressure in a pipe, simplest answer is a pressure switch. A pressure switch has two settings. The high setting opens the contacts, the low setting closes them. So, by running the start input to the drive through the pressure switch, we can control when the drive starts and stops. As the demand falls off the drive tries to go to a minimum speed. However, because the demand is so low, the pressure continues to build because the drive is at a minimum speed. At a certain point, the pressure switch will open up (some pressure just above the setpoint). The drive stops. Then, when usage picks up, the pressure falls off. When it drops to the low level setting on the pressure switch the switch closes again providing a start input to the drive. The drive goes back to maintaining the setpoint.