In an answer to another question, @FredWilson made the following comment:
At idle expect to see the fans off much longer than they are on in a normal system. The ratio of off to on depends on outside air temperature and humidity. At 75 degrees F and 50% humidity we expect to see 10 to 20 percent on time. On a hot, low humidity day fan on times of up to fifty percent are sometimes seen.
I was wondering if there might be somewhere a generalized table of fan on / off ratios by temperature and humidity which could be useful as an indicator of cooling system health.
