How Many Duct Registers Can I Close Without Damaging the Air Conditioner?

Duct Registers

• Air conditioners are designed to supply cold air to the calculated square footage of the home and the flow needs of each room. While closing ducts in unused rooms seems like a good way to save money, when the vents are closed, an imbalance of pressure may result and the air conditioner will be less effective.

Air Conditioner Damage

• If several vents are closed when the air conditioner is running and there is a large buildup of pressure or the vents are closed on a regular basis, the pressure can damage the motor on the air conditioner. There may also be leaks from the duct system because of the increased pressure. If you choose to close any vents, close only one or two at most, but note that professionals recommend that all vents remain open when the air conditioner is in use.

Closing Doors

• Closing interior doors has the same effect as closing the registers because the air conditioner is meant to move a calculated amount of air through each room. The air pressure increases in the room when the vents or doors are closed, which causes the air to leak through any other opening in the room, such as the window or ceiling fixture.

Reducing Energy Costs

• If the purpose of closing the vents is to save money on the air conditioner costs, use other methods to increase the energy efficiency of the air conditioner instead. Set the thermostat to a warmer temperature and adjust the air conditioner to run continuously. This allows the air conditioner to reach the set temperature and run at maximum efficiency. Turning the air conditioner on and off continuously forces the unit to turn on and run for around 10 minutes before peak efficiency is reached each time. If possible, use a programmable thermostat that turns the thermostat up and down at set times during the day and night. In addition, keep the air filter clean and the vents clear of any obstruction for the best air flow to and from the unit.