If you are trying to get better air flow of your central heating and a/c I have a little tip that really worked for me, and it may toil for you as well, but what I did was close the air vents to my central heating and a/c that were not in use in spare rooms, etc, and by doing this it pushed the air harder through the other air vents in the house that were opened. And this in turn created a much better air flow in my home. My central heating and a/c can heat and cool my house a lot faster and a lot better by doing this method of closing off air vents in the rooms in my house that are not being used. When you have a immense house like I do, you will most likely have these kind of rooms unless you have a super pressing family… Even in smaller homes this method should toil the same, if not better because there are less spaces to heat and cool in a smaller house of course. I have been doing this method now for a few years and it works real great. I have even been able to save cash on my weekly weekly bills because my central heating and a/c equipment does not have to run as long and as often as it did before I started closing the air vents in the unused rooms of my home. This is a great energy saving tip as well. I know most people should take notice to what I am saying.