So the AC is running, but you’re still feeling hot. What’s going on? Why is the air conditioner running but not lowering temperature in your house?

There are actually several reasons this might happen. Some have to do with how the air conditioning system was installed or commissioned. Others have to do with the AC equipment itself, and other possibilities include the extent to which your home is sealed and insulated.

If your AC is blowing cold air but not cooling the house, here are the most common reasons why.

1. The system is oversized for the home

When your AC is too large for your home, all kinds of things go wrong.

For starters, an oversized AC will cool your home much faster than one that’s the right size for your home. That might not sound like a big deal, but it is! When the AC satisfies the thermostat very quickly, that means it probably isn’t evenly distributing cool air throughout your home. You will probably have cooler areas and warmer areas. In addition, the system probably isn’t running long enough to dehumidify your living space.

A home with high humidity is a home that feels too warm in the summer. End of story. There are a couple of solutions for an oversized AC:

  1. Replace it with one that’s the right size. If that AC is relatively new, you might not want to do this, and that’s understandable!
  2. Install a whole-house dehumidifier. The dehumidifier will deal with the humidity that your oversized AC can’t remove on its own. It runs even when the AC isn’t on, keeping your home cool and dry.

Of course, you might notice your air conditioner running but not lowering temperature on the thermostat itself. When that’s the case, you may have a different issue.

2. Your AC wasn’t designed to make your home as cool as you want it

Most residential air conditioning systems installed in the Atlanta area are designed to cool your home to 75 degrees on a 92-degree day. That’s a standard specification, although it varies according to how well the system was installed and whether your system is the right size.

That being said, let’s assume that we installed your air conditioning system (so you got a great installation!) and that it’s the perfect size for your house. If the manufacturer only designed the system to cool to 75 degrees during peak summer, you might be disappointed when you set the thermostat to 70 on the fourth of July.

You might wonder why the AC is not cooling the house and why it’s not lowering the temperature. The answer is that it wasn’t designed to do what you’re asking it to do.

3. Thermal barriers, air barriers, and ductwork

Your home has a thermal barrier and an air barrier. The first is the layer that blocks heat from entering or escaping. A home with the proper amounts of insulation in the ceiling, crawlspace, and walls will stop more heat from entering the home during the summer.

The air barrier is the layer that prevents hot air from moving from the outdoors into your home. Every time you open a door or a window, you compromise your home’s air barrier. Other “holes” in this barrier consist of gaps and cracks between your living space and your attic or crawlspace, not to mention air gaps around windows, doors, and electrical penetrations.

So, if your AC is blowing cold air but not cooling the house, it could be because lots of heat and warm air are entering the home through your less-than-optimal thermal or air barrier.

And we’re going to say it right here: Most homes in Metro Atlanta have insufficient thermal and air barriers! It’s a super common problem.

The fix? Beef up your insulation and seal the air leaks!

The best way to do this is via a home assessment and energy audit, which includes a blower door test and thermal imaging. Basically, a home performance pro pressurizes your home and explores it with an infrared camera, noting all areas that lack insulation or allow air to enter or escape. Afterward, you can prioritize what areas of your home to address.

Chances are, your AC will perform a whole lot better after you have better insulation and fewer air gaps letting in hot, humid air!

4. The refrigerant wasn’t charged properly

Here’s something we see often when someone complains about an air conditioner running but not lowering temperature. The proper refrigerant charge is often the difference between the AC working well on a really hot day and, well… not working well when it’s hot outside!

Most HVAC contractors charge refrigerant based on the reading from a pressure gauge, but that doesn’t always result in the right charge. What these contractors should be doing (and what we always do at PV) is check a variety of different metrics, such as superheat and subcool, to get a precise reading on whether the system had the appropriate charge. We actually use some pretty advanced tools to do this – not just a pressure gauge – because we know it’s important to get the refrigerant charge right.
If your AC isn’t lowering the temperature, have your HVAC technician check the refrigerant charge. There’s a good chance it’s off.

5. The outdoor unit wasn’t installed up to code

Unfortunately, there are a lot of ACs out there that were not installed in compliance with building codes. If the unit wasn’t installed with enough clearance on all sides, you could end up with a situation where the home traps heat around the indoor unit, preventing it from cooling properly.

Example: An outdoor AC unit that’s located under a covered patio or deck.

Maybe it made sense to the installer to locate the outdoor unit here. Maybe it would have been difficult to locate it somewhere more ideal. But the reality is that the patio being above the unit could prevent the dispersion of heat away from the unit. As a result, it might not cool your home properly.

The installer should have complied with codes and followed the manufacturer’s clearance specifications. But if that didn’t happen and you find yourself with a poorly located AC, the best fix is to hire a new contractor to reinstall and/or relocate the system.

When you notice your air conditioner running but not lowering temperature, please don’t wait to see if it will start working again, because it probably won’t.

Unless it’s just a very hot day and you’ve set the system to a really low temperature, there’s a good chance you have an issue with your air conditioning system. Or, if you don’t, something about your home (poor insulation or air leaks) might be causing the problem.
If you live in Metro Atlanta and are concerned about a misbehaving air conditioner, get in touch with PV Heating, Cooling & Plumbing today! Our team is ready to examine your air conditioning system and identify the problem.

Give us a call at (404) 798-9672 today or complete the form below!

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