Families living in Arizona face steep summer energy costs to keep their homes cool. Many people believe that they can simply close the vents off in unused rooms to help them save some money. Even though this seems to be a good tactic, it can actually prove to be a costly mistake that leads to HVAC system damage.
Today’s HVAC units work on the principle that there needs to be the right amount of air pressure moving through the whole system. Closing off air ducts creates a situation where there is abnormally high air pressure in certain areas. This causes other parts of the system to compensate for the imbalance.
Regardless of what you have done with the vents, your HVAC unit will try to send the same amount of cool air or warm air, depending upon the time of year, through your house. This will not result in less energy usage.
Not saving money by closing off the vents is only one part of the story. Closing off vents has the potential of creating a worse problem. High air pressure may cause other parts of the system to compensate in ways that cause costly damage.
Most HVAC systems have a PSC blower that moves air. PSC blowers are designed to reduce the air throughput when they detect there is too much air pressure. If you have an air conditioner running in the summer with some vents closed in an unused room, the blower decreasing the output of air through the system can cause your evaporator cooling coil to freeze up. This can cause costly damage to the compressor unit.
In the winter, if you close off too many vents, your heat exchanger can overheat and crack if the PSC blower does not keep it cool enough. Therefore, closing the vents in your air conditioning or heating system will not save money because the units are designed to put out air at a certain rate. Actually, closing too many vents can lead to repair bills that may exceed the cost of running the hot or cool air.