Why Humidity Goes up When AC Is On?

The entire purpose of an HVAC system is to keep your home comfortable all year long. During the winter, the heater warms up your home and keeps you snug. During the summer, the AC kicks in and cools it off from the outside temperature.

However, you may find yourself asking the following, “Why humidity goes up in the home when the AC is on?”

Your home remains humid, or the humidity increases when the AC is on, there may be a problem with the AC system. Older AC units are often to blame for the humidity increase, but also a system that is too large can make the humidity go up, too. Running the AC with the fan on can also increase the humidity.

The last thing you want is to have to rush to fix your air conditioning system in the heat of the day.

However, before you run to dial the first HVAC contractor you can find, there is a little bit of sleuthing you can do first to identify the possible causes for your AC system not dehumidifying as well as it should. 

Causes for Humidity Increase When Ac Is On

As with any home appliance, doing a little bit of detective work can help you identify if the issue is something you can solve on your own or if it’s time to call the professionals.

While getting a contractor is always the right choice, sometimes there are little things you can do to correct an issue or at least buy you some time before a service call becomes necessary. 

Thankfully, these three options are fairly easy to check out and determine if they’re the culprit for increasing the humidity:

  • Check the thermostat, is the fan setting turned on?
  • Do you have an older or aging system that might be on it’s last leg?
  • Is your system made for a larger home?

Take your time and get a good look at your system, including your thermostat, documentation on the system, and even the installation process if you were present for it.

Looking over this information can highlight potential issues that you were unaware of, allowing for a simple fix. 

Is Your Thermostat Set to Have the FAN ON?

It seems simple. Turning “Fan On” is there to move air around the home, and if it’s moving, it’s cooler, right? Not necessarily.

Part of your air conditioner’s purpose to use refrigerant to cool the air and then pass it along to the inside of your home. This means it draws in air from the exterior.

Typically the system then passes that air through the evaporator coils, which cool the air and condense water molecules, removing them before passing the air.

The condensed water then passes through the system to drip off into the condensate pan, giving you cool, fresh air and less moisture. 

The fan of an air conditioner works independently of the cooling effect. When you have a fan on, but the AC is off, the fan will kick on and not cool your air.

This means it draws in air from the outside and just passes it along to the home, moving it through the ducts and into your space. 

In essence, while great for getting the air around your home, FAN ON will bring in the humidity from the outside and can even draw more humidity in if the system’s condensate hasn’t fully condensed out.

This is a quick switch of the thermostat to correct, preventing you from needing to contact service immediately. 

Is Your System Getting Close to The End of Its Life?

No one wants to think about having to replace their old HVAC unit. It can be a costly venture that you are unprepared for and take a significant amount of time for a scheduled service. 

That is why it is so important to plan. Keep note of the age of your AC so that when the time comes, you are ready to have the procedure done.

Most air conditioners can last from ten to fifteen years, according to Carrier, before requiring replacement and possibly even longer if proper maintenance is completed. 

As the system nears the end of its life, it may work harder and harder just to perform its normal functions. Wear and tear can damage your system from years of service, making it less than efficient.

Unfortunately, this also means that it can fail in its duties to dehumidify air in the home. Without maintenance, the coils can work less and less reliably, allowing more warm air to pass without cooling. 

This will be evident by increased humidity in the home and less cold air, causing your system to run more frequently to correct its mistake. 

Repair may be available depending on how advanced the wear is. Only a professional will tell you whether it can be done or if it is time for a replacement.

Contact an HVAC contractor to inspect your system and determine which is your best bet. 

Is Your System Too Big?

There is such a thing as too big when it comes to an air conditioner. Most people assume the bigger the system, the better the efficiency.

Bigger specifically refers to more cooling power in the instance of air conditioner units.

After all, if your system is more powerful, that means it will cool air quicker, right?

This is not necessarily true, as, with a bigger system, it is set to cool a bigger space. When you have a larger system, it is working overtime to determine if it has done its job. 

This is evident by the compressor kicking on and then suddenly kicking off to decide to turn on once more. As it turns on and off, it starts to cool, then stops very frequently.

For one, this means less energy efficiency for your home since all those times the system turns on, it draws power.

Higher bills will occur from all of this. Worst of all, it means the system is so busy trying to figure out if it’s done its job that it doesn’t cool or dehumidify your home correctly. 

Making sure the system is sized just right can be complicated at first, but knowing your square footage and conversing with a professional can help.

They can direct you to the correct size and even help install systems to ensure you get the best cooling and dehumidifying for your home. 

This way, you lower your energy cost and get the system your home was meant to have.

How to Solve Your Humidity Crisis

Now that you have investigated the cause of your AC’s failure to dehumidify, what can you do?

Finding the solution to a long term problem can help you prevent this issue in the future, keeping your house comfortable and removing the mugginess. 

  • Installing a supplemental dehumidifier
  • Replacing your AC all together with a new system
  • Preventative maintenance

Supplemental Dehumidifier

Installing a dehumidifier in the home can help you and your system. These units are designed specifically to do the evaporator coil’s job removing the water from the air. 

This solution may be best if your AC unit just isn’t cutting it or having a larger system that cools but doesn’t seem to get all of the humidity out.

If your system works great but the humidity factor is an issue, then this might be the best solution. 

If you’re home is smaller, or if there’s just one area that seems to be more humid, you may be able to get away with a portable humidifier.

Replacing the AC System

For many, the worst-case scenario, a brand new installation, does not have to be the worst case.

If your system was not sized correctly or is just too old to cope, getting a new system can more than just remove water; it can increase your energy efficiency! 

More modern systems are designed to use less power to do the same job, so you may recoup your cost quicker than expected.

Stay on Top of the Maintenance

Finally, it cannot be stressed enough that preventative maintenance can keep your system running at its best.

While many defer the requirement for maintenance, it ensures any parts that may be failing quietly get the treatment they need before it becomes an emergency.

It can also work with your warranty to ensure things are replaced at little to no cost. 

Final Thoughts

If your AC allows for more humidity in your home, you may have an underlying issue to contend with.

Review all past documentation and history of your system to see if there is an easily solvable issue or if a professional is required.

Whether it’s a simple setting or just due to age, you may find the solution quickly if you just look.  

With quality service, you can make sure your system is running smoothly year-round.

Consider supplementing older systems with a dehumidifier and getting preventative maintenance to keep all parts in working order.

Time and use can catch up to a system and allow the evaporator coils to lose efficiency. If you follow these steps, you can stay cool and dry!

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