When our up-to-date furnace was installed we were amazed at how quiet it was.
My associate and I were used to hearing the drone of the aged on each time it kicked on plus now we hear nothing.
It is a superb feature but sometimes I wonder if it is one or not. There is one funny indicator that I cherish telling people about. My Cat! Animals have a much more sensitive hearing ability plus she can still hear the furnace kick on. She instantly runs to the floor vent to wait for the rush of air to come out. She almost seems impatient as she waits. There is always a delay between when the furnace turns on plus when the air comes out. This is due to the high-limit switch. In easy terms this is part of the furnace plus makes sure the air is heated before sending it through the ductwork. If your system did not have this it would blow cold air until it was able to heat it up each time. This would be like blasting the heat in the car while the engine is still cold. You would be miserable while in that time plus it would make you colder than you were plus it would take longer to heat the space or your car. If you ever notice that your furnace is blowing easily cold air prior to hot air you may want to have this part ran tests on to make sure it is still working properly. Because this part gets a lot of use it can wear out over time plus should be part of your proper tune up routine too.