Blocked air vents can create a variety of problems. Air conditioners are not creating air, they are merely recycling it by drawing it through the return vents to cool it and then sending it back out. By blocking the vents, the efficiency of the air conditioner is diminished.
When the vents become blocked, the air conditioner uses more energy to perform its job. This creates a strain on the components, which in turn increases the energy bill in a home or business. The strain might also lead to a need for more repairs to the system.
Another problem that can occur due to blocked vents is a frozen coil. If the vents are blocked so severely that the air conditioner cannot pull an adequate amount of air through the return vents, the lowered amount of warm air flowing across the cold evaporator coil will not be able to increase the temperature of the refrigerant inside the coil. The refrigerant will then freeze the condensation along the coil, blocking heat absorption and creating more ice. This will prevent the air conditioner from being able to cool the home or business.
To prevent either of these problems from occurring, make sure nothing is blocking the return air vents. This can include long drapes, rugs or pieces of furniture. Even one blocked vent can drastically throw the entire system off balance and increase the energy bill.