Heating and cooling adjustments on a forced air furnace - Winter and Summer Settings
Warm air rises; cooler air sinks. Keep this principle in mind, and you’ll realize why opening the correct air returns in winter and summer will provide better air distribution-which, in turn, allows more even temperatures in your home.
When you use a forced air furnace for summer cooling, you should open the high returns. This allows the furnace to take warmer air from the top of the room back to the air conditioning cooling coil in the furnace. In the winter, open the low returns to collect cold air at the floor.
For a two-story home, you may also need to adjust the supply air for winter and summer. In the winter, warm air rises to the second floor, so less heating is required there.
In the summer, warm air still rises, and a hot attic adds even more heat, so you need greater cooling (air flow) to the second floor than to the first floor.
The best way to control air flow is to adjust the small dampers in the heating/cooling duct system in the basement at the furnace itself. Often, these dampers are found where round supply duct runs connect to the main (rectangular) ducts. Look for small (¼-inch) threaded rods and wing nuts. You can adjust the damper by turning the screwdriver slot on the small rod. When the slot is parallel (going the same way) to the duct, the damper is fully open. You don’t need to adjust the wing nut, which simply locks the rod into place.
Heating ducts vary. Some systems have levers indicating the direction of the damper. Some rectangular ducts have dampers and levers.
To adjust air flow for summer cooling, start by fully opening all second floor dampers. Next, partially close dampers to first floor rooms that are getting lots of cold air. You will find that closing the damper to 50% or turning the shaft to 45 degrees will only partially slow the air flow. Often, even if you fully close the damper, there will still be air flow because the dampers fit very loosely in the ducts.
Closing first floor dampers will direct air to the second floor. Mark your damper settings for summer and winter once you have found the correct balance.
Remember to clean the furnace filter, too, because a plugged filter can also restrict air flow.
Older homes were not built for cooling - the supply and return ducts to the second floor may not be adequate so adjustments may not solve the problem. A quick fix may be to run the fan furnace continuously.
I just moved into a new home recently and I had a 'mini melt down' on the 2nd floor. It was just too hot all the time! Went on the internet to find these settings which used to be marked right on my old furnace! Guess what - no marks, no nothing on the new furnace, so my guess work began. It actually took me quite a bit of work and research to find these directions so hope you can make use of them in your home.
Happy heating AND cooling!