
Originally Posted by
Chili Palmer
No, no, no, no, no!
Do not shut off the registers going to a room you don't use; it does nothing to help the system's efficiency, and in fact, will make it run harder to cool your home.
Let's say your system is designed to deliver 1,000 units of cool air throughout your home, split up evenly between all the rooms. If you close off a register, that air is still being delivering down that duct run, except that now it has no place to go and the system is forced to find those missing units of air elsewhere: attics, basements, outside via doors and windows and any other unconditioned space available. Additionally, the air that is forced into that run starts to back up, and will eventually make your indoor coil ice up, and possibly even damage your compressor (the heart of your system).
The proper way to redirect air away from rooms you don't need/use is with dampers located inside the duct system. These can either be manual dampers or (more expensive, but ideally) a zoned system that automatically raises and lowers the dampers and cools just the rooms you want, to the temperatures you desire.
Most duct systems are very, very poorly designed. Whenever I travel the country doing my training, every contractor tells me the ducts in their area are the worst. A study done a few years ago by Florida Power & Light shows that, on average, the typical duct system loses at 30% of its airflow into the attics and crawlspaces. Having a well sealed duct system, combined with a regular maintenance program, will make your system run a lot longer, and deliver the efficiency you are actually paying for but not receiving now.
We could talk about the advantages of variable air flow and 2-stage cooling, and how that would solve most of your problems, but that is whole other class.
CP
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