All: If you check my previous posts, you'll see that I've been having ongoing problems with my forced air furnace, primarily related to the limit switch. I believe that the problem with the limit switch may have been resolved, but another problem has cropped up. Here's a brief description of the problem: the fan continues running even after the limit temperature has been met for either zone. The thermostats are set on "auto". Sometimes the fan will run all day even though neither zone is calling for heat, and the fan will not shut down until the next heating cycle when the fan stops and then starts again. This time I checked the indicator light on the control board, and it indicated that the pressure switch was open.
Here are my questions: 1. What is a pressure switch? 2. Does the "pressure switch open" indicate that there's a problem? Will replacing the pressure switch resolve the problem or is there something else that the tech should be checking?
In prior posts I indicated that the problem was with the limit switch, but this time the indicator light didn't show that the problem was related to an open limit switch. To deal with the limit switch problem we had the supply and return ducts enlarged, added another return duct, and added a by-pass damper to dump the excess air into the basement. So far, the house is uniformly warmer, and I can't tell if the furnace is short cycling...it appears to be cycling normally except as noted above.
Thanks for the information.