Hmmmh. I just can't figure this out. Perhaps someone can tell me the answer to this mystery. I have a Carrier 2 speed condenser (38TDB) and 2 stage variable speed gas furnace 58cva and a Carrier thermidistat. How does the thermidistat determine what stage should operate? I looked at all of the Carrier literature and it indicates that no higher stage will operate until the preceeding stage has operated for at least fifteen minutes. But if the setpoint on the stat is only one degree from the room temperature, how long would the lower stage operate until switching to a higher stage (in both heating and cooling modes)? There is absolutely no way to know from the stat whether high or low is in operation unless you look at the circuit board on the furnace or condenser! It would be somewhat nice to be able to determine if high or low stage is operating for economic reasons. I have looked at every schematic, diagram, pamphlet, operating guide and technical manual--nothing indicates what the stat logic is in regards to staging. help someone?