Tips for optimizing air ducts

July 28, 2015

Adjusting the air ducts can do a lot to balance your indoor climate during the switch between seasons. Here's how to do it.

Tips for optimizing air ducts

Seasonal settings

  • If your forced-air system includes air-conditioning, you may need to do some between-seasons tweaking. Heated air and cooled air mix and move differently but are carried through ductwork that treats them pretty much the same.
  • Tweaking your system's duct dampers gets air moving in the right direction and balances the indoor climate. This exercise takes a little time on the first go-round (usually a day or so), but once you've selected and marked the optimum damper settings for the season, you'll be good to go at the start of winter and summer every year afterward.
  • To start, Set up a temperature-monitoring scheme by assembling a set of identical tabletop thermometers. Place one in each room of your house.
  • Open all the duct dampers and registers in your forced-air system, then set the thermostat to 68 degrees and fire up the furnace.
  • After half an hour, check your thermometer readings and partially close the dampers in the warmest rooms in the house. Readjust those dampers and the dampers in all other rooms until you've achieved the desired temperature throughout the house.
  • Use a permanent marker to mark the final handle position you've set on each damper, noting "W" or "winter" next to the mark you've made. When you do a pre-summer balancing run, note an "S" or "summer" next to that season's marks. You're set now, no matter what the season.

Making the switch

  • Though you'll want to bring in a pro for your annual inspection, this simple tune-up is something that any homeowner can handle. Taking care of this "fall cleaning" a month or so before heating season kicks off will ensure a warm winter indoors.
  • Turn off the gas to the furnace and cut power to it by turning off both the switch at the side of the furnace and the appropriate circuit breaker or fuse at your service panel.
  • vacuum the base and burners of the furnace, extending the vacuum hose with a drain tube to reach the farthest nooks and crannies.
  • Clean dusty blower blades by removing the bolts that hold the blower in place and lifting away blade debris with the vacuum or a small brush. Be careful not to touch fan blade counterweights or the delicate wiring.
  • Check the filter, and replace or clean it if it's dirty.
  • Inspect the drive belt on the motor and blower, and replace it if it's cracked or frayed. Adjust the belt tension so that it deflects by about the thickness of your index finger.
  • To adjust the tension, loosen the motor mounting bolts and move the motor away from or toward the blower. (Check your service manual for instructions on setting the tension or replacing the belt on your particular model.)
  • If you have an older furnace, its two motor and two blower shaft bearings require an annual oiling. To do this, first clean the area around the oil caps, then take them off and apply no more than three drops of 20-weight machine oil to each bearing.
  • While your heating system is on your mind, take the opportunity to adjust damper settings for the new season; those settings should be marked on the duct surface from the prior year's balancing.
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