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Can I run just the indoor fan?

This is a question that has a few different answers to it. So to get started lets talk a little about the indoor fan.

On most thermostats the indoor fan can be set to the position “on” or “auto”. In the “on” mode the indoor fan will run non stop unit you switch the settings. On the “auto” mode the fan will run only if there is a call for heating or cooling. So why does all of this matter you ask. Here in Phoenix Arizona we can get away with running the fan in the “on” position for most of the year to circulate the air. Some people just like the idea of air moving in their home. Others may have dust issues and want to run the fan so the filter in the system can better filter the air. After all if the fan is not on the filter is just sitting there doing nothing. And then there are people who have health issues and have installed an electronic air cleaner or maybe a UV light. We will get into all of those in a later article on air quality.

Fan “ON”
The question was can I run just the indoor fan…..well….yes and no. Lets take a deeper look into this. For Phoenix you can run the fan in the “ON” position in the late fall, winter, and early spring. It is recommended to only do this after the outdoor temperatures have dropped to around 80. Here is why….lets just say for argument sake that you keep the temperature in your home at 80 degrees during the summer. Normally you should have the fan in the “auto” position during this time of year. This will allow your fan to come on as need when the AC unit comes on to cool your home. It will run until your home is brought down to temperature then cycle off. But if you have your fan in the “ON” position in the summer you will encounter a few issues. First, we said the temperature in your home is set for 80 degrees. And lets just say its a average summer day in Phoenix and the outdoor temperature is 110 degrees. But the temperature in your attic is around 130 degrees. Why do we care what the attic temperature is? Good questions! The ductwork is located in the hot attic air. If the fan is “on” and you are taking 80 degree air from your home into the hot ductwork located in the attic it will act as a heater and heat your air. So now the home temperature will start to warmer making the air conditioner come on. In short it costs you more money in electricity because the air conditioner will be running a lot more that it normally would. And who wants to just give there money away to the utility companies. Another issue is during the humid month of monsoon season if the fan is left in the “on” position you ac unit will run and cool off the house as it should and remove humidity from the air. But if the fan is “on” the moisture that has just been removed from the air collects in the drain pan in the air conditioner will be evaporated and brought back into the home. This will leave your home feeling very humid and sticky. As a result the only way to get rid of the humid air is the run the AC unit. The only way to fix this issue is to put the fan in “auto” and allow the AC unit to run and remove the humidity. Now when the unit turns off so does the fan. This allows the moisture in the drain pan to drain out of the unit and not be evaporated and put back into the home.

Having an understanding of when you can run the fan will help you save money on your utility bills, feel more comfortable in the home and have cleaner air.

Still have questions or concerns?
Feel free to contact us!
623-295-1911

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We have over 20 + years experience in the heating, ventilation and air conditioning industry (HVAC). We believe in quality workmanship and customer service.