I recently moved my office to the second floor of our home and I haven't been able to get the temperature below about 78 even though the thermostat is on 72. My son's bedroom had been the same way until the other day when I removed his vent cover (diffuser) to paint the ceiling. Today I noticed his room was like a freezer, so I removed the vent cover in my office and now it is cool in here. Is this normal?
My vent cover is round and looks like this:
with the exception that mine only has two openings rather than three.
Here's my theory…when the diffuser is on, the cold air is mostly pushed out along the ceiling where the air is the hottest. This warms it up as soon as it comes out, before it has a chance to "fall" down to where I am. By removing the cover, the air is being pushed straight down, essentially cooling the air lower in the room rather than near the ceiling.
My cover is about 30 years old, so perhaps it is poorly designed?
Best Answer
It's possible.
And may make sense if you think about how the system is working...
First the temperature near the thermostat goes above the set temperature, which causes the thermostat to call for cool air. The A/C unit kicks on, and starts blowing cool air. Once the temperature near the thermostat reaches the set value, the thermostat tells the A/C unit to shut off. The A/C unit shuts down, and stops blowing cool air.
While the A/C unit was blowing, the 30 year old vent covers were restricting the air flow from the ducts. So while the proper temperature was reached at the thermostat, not enough cool air was supplied to the other areas of the house. So the area near the thermostat may actually reach the proper temperature sooner, because that area had unrestricted air flow and received a bulk of the cool air.
When you removed the vent covers, you allowed more of the cool air to enter the other areas (away from the thermostat). So it took longer for the area near the thermostat to reach the desired temperature. Now, because the majority of the cool air was supplied to the other areas (away from the thermostat), those areas were cooled more than the area near the thermostat.
In a perfectly balanced system, all areas would reach the same temperature at the same time. Alas, we don't live in a perfect world. So you end up with a hot office and a comfortable temperature in the rest of the house, or a frozen office and a comfortable temperature in the rest of the house.
To fix the problem you could try to balance the system yourself, or you could call in an HVAC company to balance it for you (which will likely include installing dampers and new vent covers).