Closing the ducts

I had several ducts closed off that led to unused rooms in my house because I was trying to increase the air flow to other vents. Then my AC went out and the guy who fixed it noticed all the vents that were closed. He told me point blank that I am ruining my AC unit by closing off the vents, and that I should only turn the flapper a little bit if needed. But he made it sound like even that shouldn't really be done. Is he right? I've always thought that closing off the vents to unused rooms can save on energy costs.

Creating too much backpressure in the system puts more wear and tear on the fan and can shorten the life of it plus affect the overall performance. There is a range of acceptable values and if you stay within them, you should be okay.

He's right. closing off the vents causes high head pressure in the system and can lead to compressor failure.

Thanks for the help. Now I know.

Just a thought...

If you have some room/ rooms that are not getting enough air supply, (depending on how your duct work is set up, and if the duct work is accessible) you may conceder adding another vent/ vents to those rooms. This would allow you to close off unused rooms, without creating back pressure, and increasing the poor delivery to rooms you do use. Then when company comes over, you close off the new vents and open up the vents to the extra rooms.
All depends on how much money you want to put into this problem.

Mike