We bought our house over a year ago and have had problems with our furnace since day 1. It's a 3000 square foot old farm house and 7 years ago 2 furnaces were installed. This was done while no one was living in the house because the previous owner died 10 years ago. The problem is that the upstairs never gets warm. We've had 3 companies out, and they all say that they were installed improperly and we will not work until they are taken down and reinstalled. NOt enought cool air return. I called the original company and of course they say that nothing is wrong with it. My question is, do they legally have to come out and fix the problem? I can't afford to do it myself.
Simply take the blower door off the unit and manually depress the door switch --then operate the system for about 20 minutes, this will give the blower motor more return air. IF the house seems to warm up fine simply have more additional return air installed. But note that if the blower is taking air from te attic it will be drawing in unfiltered air.
We have already tried it and it runs for a little while and shuts off. We have had more air return installed but we're still having problems. WE've been told that the problem is the two furnaces were installed to run as one instead of independent of each other. Something happens where one over heats and shuts down and then when it starts back up, the blower runs backwards. We've also been told that our basement is too small for the way they were set up.