ME: Residential, 2000 sq ft. New England, 18 year old York system - air handler and ducts in the attic. I'm getting contractors to come and bid to replace it.
No one can give me a good explanation of what a variable speed fan does for me, except to suggest that with a high-end control system (with a humidistat), it allows for more gradual cooling in cooler (~70-80Deg) humid weather to better facilitate dehumidification. Some people say it facilitates better cooling in hot weather by cranking up the fan, but these new systems have fans that peak (for 4 ton) at only 1600 cfm and my current system pushes 1800cfm all-the-time.
Can someone explain why a variable-speed fan is really there - is it simply for the dehumidification I explained above, or is there some energy-saving effect that escapes me.
PS - I assume I should take with a grain of salt the Trane dealer who said that the quality of carrier systems had gone way down (offshore parts, etc).