Well, the same exact thing just happened again. It seems something is causing the system to start running on High and high airflow (confirmed via control, despite staging be set to Low+Medium), it runs that way for a very brief period, then falls back to Low. Again there was a 32-Low Pressure Switch Open Event at or about the same time. I'll be calling this in, but would still welcome any thoughts you have or suggestions for information gathering before hand.