Blocked air vents prevent air from entering or exiting the AC unit, breaking the circulation. If a return vent is unintentionally covered, it may reduce airflow coming from supply vents. Your system will also require more energy to maintain temperature settings, increasing your monthly bills.
Blocking the return air supply to the air handler or blower compartment reduces the amount of air that flows easily into the system. The fan's speed won't slow any more when you close off the returns, and it creates positive air pressure.
If there's not enough return air, your living room can be 10℉+ warmer or cooler than, for example, the bedrooms. Not enough return air in summer can cause rooms close to the central unit to be cooler and those farther from it to be warmer. In winter, rooms farther from the furnace can be too cool.
What Happens When Return Vents Are Blocked? The system will have to work harder to take in air, ultimately pulling it in through minute cracks in the home's exterior. The HVAC system's parts may wear out sooner than they should, and ultimately, malfunction and fail.
Their purpose is to allow air to return to the furnace to be heated or cooled. It is an air inlet. If your home has returns in most rooms this is the best setup, allowing for the best circulation and air flow. But sometimes we see that people cover/close them up because they don't realize their importance.
You should never block your air return vents. Period. However, if you're looking to keep your home cooler in the summer, you can try closing lower supply vents and keeping upper ones open, allowing cooler air temperatures to come in from above and sink throughout your house.
Along with the air your HVAC system pushes through the ducts and vents, the air inside your home can lead to a dusty buildup — especially if your air conditioner recirculates dirt, pet fur, or other debris. This means the exterior cause of your vent's dirty situation may actually come from an interior problem.
AC is Producing Warm Air
One of the surefire signs of a clogged refrigerant line is if you notice the AC producing warm air when you expect cold air. The warm air is caused by a problem with the proper circulation of the refrigerant fluid, which is instrumental in cooling the air.
The engine's combustion relies heavily on air, which mixes with fuel to generate energy. In the absence of a sufficient quantity of oxygen, an engine will not be able to generate power, and it may not even start. Whenever the air filter in your car's engine becomes too clogged, it may start to misfire.
Return vents are usually larger than supply vents and are in large rooms in the home. The return vents in your home help equalize the pressure that changes as your HVAC system heats or cools your home. These vents should never be fully closed because closing them off restricts airflow and strains the system.
Blocked or insufficient return air can lead to reduced airflow from your vents. Symptoms include weak airflow and uneven cooling or heating throughout your home, with some rooms feeling much cooler or warmer than others. Homeowners should regularly check vents for consistent airflow.
Down Low: if you have your air return lower on your wall it will function better as a cold air return. This will allow your air return to draw in cold air as it sinks to the bottom of the room. Making it more efficient at recirculating this cold air through your furnace to repeat the heating cycle.
Limited Return Air
You will want to check and ensure that the return vents throughout your vent are not blocked. If these vents are blocked, it can lead to a lack of air being pulled back into your system.
Not only does it force your HVAC system to work harder—shortening its lifespan—but it also results in frozen air conditioning coils, overheated furnaces, cracked heat exchangers, and leaks in duct systems. Those issues come with both danger to your home AND big price tags for repairs.
Restricted Airflow: Filters in return vents can impede airflow, causing your HVAC system to work harder, reducing efficiency, and increasing energy costs.
If the return duct is too small or there are an inadequate number of return grilles, your HVAC system won't be able to return enough air to recirculate into the system. Again, it's like if you were breathing in through a straw while jogging.
Decreased Acceleration and Power
One of the first signs of a clogged intake air filter is a noticeable decrease in acceleration and power. If your car feels sluggish or struggles to pick up speed, it could be due to restricted airflow caused by a dirty filter.
A dirty engine air filter will often lead to a decrease in power and effectiveness of the equipment. If the machinery is having issues accelerating or is operating slowly, this likely means that the air filter is limiting the equipment's air intake, diminishing its overall performance.
To unclog an AC drain line, turn off the power to the unit. Locate the drain line and use a wet/dry vacuum to suck out the clog. Flush the line with water using a garden hose or cup of water. Check and clean the drain pan under the indoor unit.
Clogs in the condensate drain line cause moisture to back up in the air conditioner, which can be damaging. The repair cost to have the drain line flushed runs between $75 to $250. If replacement is needed because the condensate drain line is damaged, a new condensate drain line is usually only around $20.
Symptoms of a Faulty Orifice Tube
You might notice a significant drop in cooling performance, unusual hissing noises, or even frost on the evaporator. These symptoms indicate that the refrigerant is not being properly regulated, which can lead to inefficient cooling and potential damage to other components.
Cold air returns are crucial to the overall process, effectiveness, and goal of reaching the desired temperature. If a return air vent is blocked, whether intentionally or by accident, it can also impact your indoor air quality. It can also cause undue stress and possible damage to your HVAC system itself.
Common Issues with Return Ducts: Clogs and Leaks
You can generally identify a blocked air duct by a distinct drop in heating and cooling efficiency, increased energy costs, and occasionally a musty, dusty smell throughout the home.