What Setting Should Your Air Conditioning's Fan Be Set To?

Posted on: 10 September 2014

Even a very simple, old style thermostat can be difficult to use if you are unsure of what settings to use. Temperature and hot or cold air are relatively straightforward, since they do exactly what you think they do. While the fan settings either have the fan run only when you need it or all the time, it is far less obvious which setting will work best for your home.

What Happens When You Leave the Fan On

Setting the fan to "On" will force it to run 24/7. As you can imagine, this is going to cause a significant increase in your energy bills. However, in some homes this is necessary to insure that the cold air properly circulates throughout your home. It can also help to reduce pollutants by continually circulating air through your filter system.

In addition to increasing your energy bills, leaving the fan running is going to circulate additional moisture in from your A/C into your home. Unless you have a dehumidifier installed in your main HVAC system, this is going to increase your discomfort as well as the risk of mold growth in your walls and ducts. If your HVAC system is installed properly, it will be able to circulate air properly at the outset, eliminating the need to continually run the fan.

What Happens When You Set the Fan to Auto

Setting the fan to "Auto" tells it to run only when your A/C unit is producing cold air. An efficient HVAC system will work just fine with these settings,and it will certainly cost less when the bill comes. Some professionals will advise against it because stopping and starting the fan will cause it to wear out more quickly.

Problems with setting the fan to auto really stem from poorly designed HVAC systems. The air distribution problem has already been discussed, but the sizing of your air conditioner can also cause problems here. If the unit is too big, the temperature inside your home will drop rapidly whenever it is on, causing the system to shut down before a full cycle is done. Yes, it is bad for your fan to keep stopping and starting, but it is even worse for the main A/C unit. If you need to run the fan all the time for these reasons, it is time to consider having your HVAC system replaced completely.

What to Do If You Have Other Options

A few thermostats include a "Circulate" option that bridges the difference between "On" and "Auto." It is exactly the same as auto, but it also makes sure the fan runs for at least a portion of every hour. It allows you to equalize the temperature and keep the air running through your filters without increasing your energy bill nearly as far.

A programmable thermostat might even have the option to set the minimum amount of time the fans will be running each hour, and smart thermostats can go even further than that. They may have options to let you run the air during certain times of the day, or start the fan now and keep it running for a certain amount of time. This lets you mitigate issues caused by things like cooking dinner every night without having to manually make change the settings every day.

Setting your thermostat incorrectly can cost you hundreds of dollars each year. While most guides focus on temperature, there are plenty of other settings you need to get right. Unfortunately, if your HVAC system is having problems.you will need to resolve them before you can use the most efficient settings on your thermostat, so don't hesitate to call for air conditioner repair