I have an Evolution system (355CAV042060, 186BNA018000, CNPVP2417ATA, and SYSTXBBUID01-C). While I've owned this system I've seen a small number of 32-Low Pressure Switch Open events. IIRC, they've always occurred during heating season. ATM I can't remember what my contractor said about these but my impression was that they are nothing to be concerned about.

A little while ago I heard unusually high air flow coming out of a supply register. Higher than I've ever heard before. I suspect it was the type of airflow that would be produced by the system running on High. My home doesn't require high output and my system is actually set to Low+Medium. The setpoint for heating is 72, all the time, and the system rarely even needs Medium. It isn't that cold out tonight, a bit windy at times but nothing that would challenge my furnace running on Low, nothing had caused the house to drop significantly below 72 to begin with, so this period of high air flow seemed very much out of place.

It took me maybe 2-3 minutes to get to the room where the return intake and Evolution control are. As I got there the blower had just finished ramping down to a level consistent with Low. It remained on Low for a short period than turned off. Curious, I went into Last 10 System Events and saw what appeared to be an entry from just a few minutes earlier:

FN 12/21/2012 1:55A F
32-Low Pressure Switch Open Events
6 Events

Which leads me to believe that event and the period of unusually high airflow may have been related. The system has been operating OK since then, on just Low. However, I'd like to know what happened there. Any thoughts on this? Thanks, happy holidays.