When using just the fan mode of an air conditioning system, it depends on the type of system and the specific settings:
Window or Portable Air Conditioners: In most window or portable air conditioners, the fan mode circulates the indoor air only. The unit pulls indoor air through the air filter and then recirculates it back into the room. The fan does not bring in fresh outside air, and the cooling function is not activated in this mode.
Split or Central Air Conditioning Systems: For split or central air conditioning systems, the fan mode can work in different ways, depending on the settings:
a. Indoor Air Recirculation: Similar to window or portable units, when the fan mode is on, it typically circulates and recirculates indoor air without bringing in outside air. The cooling function is not activated, and the air passes through the system's air filters, providing some ventilation and air movement.
b. Fresh Air Intake: Some split or central air conditioning systems have a fresh air intake option. When this mode is activated, the fan will draw in outside air and circulate it indoors. This is especially useful when you want to bring in fresh air from outside without activating the cooling function.
It's important to note that using the fan mode of an air conditioning system without the cooling function can help improve indoor air circulation and provide ventilation, but it won't provide any cooling effect. The cooling function (compressor) needs to be turned on to achieve cooling. Using the fan mode alone is often useful when you want to ventilate the space, circulate air, or save energy on cooler days when full cooling is not required.