AC Running but Not Cooling House

Name: Magic Touch Mechanical
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September 7, 2020

Help, My AC is Running But Not Cooling My House Down!

We’re dealing with a lot of strange things in 2020… to put it mildly! Adding fuel to the fire, it’s been one of the hottest summers on record in many parts of the country. Here in the Phoenix, AZ area, we’ve had over 50-days above 110° so far this summer. In fact, it’s already officially the hottest recorded summer ever in Phoenix according to the National Weather Service. With more people housebound than ever, it’s been a busy season for air conditioning companies like Magic Touch. A lot of first-time customers tell us their AC is running but not cooling their house well. In this article we look at some of the things that cause these types of home air conditioner problems.

Air Conditioner Running but Not Cooling the House Well

Let’s start with a common problem. Complaint: The air conditioner is running but not cooling the house well.

Guess what? Sometimes the air conditioner itself is not the problem at all!

Ambient Temperatures Exceed Design Temperatures

Every good HVAC System installation should start with a Manual-J Load Calculation. A load calculation is a formula that determines the capacity (often referred to in “tons”) needed to cool the space. It takes into account the cubic size of the home, insulation, windows, building construction, ductwork, etc. This data is then entered into a software to determine how many BTUH (British Thermal Units per Hour) are needed. 12,000 BTUH = 1-Ton

Depending where you live in the country, there is a universally accepted “design temperature” applied to the load calculation. For example, in Mesa, AZ the summer design temperature is 75° at 108°, meaning the system is designed to maintain 75° indoors when the temperature is 108° outdoors.

Last month we hit 120° on the hottest day of the year. It was 12° hotter than the design temperature of 108°. That doesn’t necessarily mean the inside temperature will also be 12° higher than 75°, however it does mean the unit will be working it’s hardest to keep up. Even the best units on the market will be taxed by 120° temperatures. I should know, I own two of the best air conditioners money can buy and they were working hard that day.

Why Not Use 120° as a Design Temperature?

I’m purposely oversimplifying load calculations and design temperatures in this article. There’s a lot of math and science involved in a load calculation. Most of which was figured out by people a heck of a lot smarter than me! However, the short answer to the question why not use 120° as the design temperature is – your AC would be too big for the majority of summer days.

120° is the extreme and it only happens for a couple of hours a day, every few years. If you designed your AC for these ‘extremes’, it would be too large for the house the majority of the year. Believe it or not, you’d be more uncomfortable most of the summer with an oversized air conditioner. I’ve written many other articles on this subject if you’re interested in understanding why.

Bottom line: If your AC is running but not cooling your house well and it’s 120°, it may not even be the AC. Other home issues like insufficient insulation, duct leakage, undersized ducts or even too much heat gain through windows may be the culprit. You might not need an air conditioning company – you might need a home energy audit.

Refrigerant Issues – My AC is Low on Freon

“My AC is running but not cooling the house well, I think it’s low on Freon.” If I earned a nickel every time, I heard this from a customer, I’d be loaded!

It’s true a low refrigerant charge could keep your AC running but not cooling the house well. However, refrigerant leaks are not as common as most people think. Air conditioners are sealed systems. They do not run out of refrigerant unless they have a leak.

That said, other refrigerant-based issues can cause an AC to run but not cool well. Metering devices that control the flow of refrigerant can fail or get stuck and cause cooling issues. Contaminants in the refrigerant lines, while rarer than a metering device failure will diminish the machines performance as well.

WASH ME. If You Want a Cool House, Clean Your A/C Coils!

We’ve all seen the dirty car in the parking lot with “WASH ME” written in a child-sized finger on the back window. Dirt on your car’s exterior won’t impede its performance, but it will wreak havoc on an air conditioner. In fact, heat and dirt are the two main reasons an air conditioner component fails.

A dirty condenser coil prevents your air conditioner from removing heat. Keep in mind, the heat that it’s removing is the heat inside your home. This in and of itself could be the reason your AC is running but not cooling your house.

Likewise, a dirty evaporator coil will impede airflow and not only significantly decrease your AC’s performance, it can’t remove humidity. In Arizona, the humidity inside your home is higher than the outdoor humidity. When the relative humidity inside your house starts creeping above 50%, your home will feel less comfortable. Even dirt build-up on the indoor fan motor’s blade will significantly decrease the performance of your air conditioning system.

Last, but not least: A dirty or partially plugged condensate drain system can cause your AC to run but not cool your house well. If the air conditioner can’t remove condensation, that moisture stays in the blower compartment – and your home! In that scenario your home can feel ‘swampy’ and a lack of maintenance is to blame.

Failing Capacitor, Motor or Compressor

Of course, the most common reason your AC is running but not cooling your house… your air conditioner is broken!

Like a car, an air conditioner can have a single broken component and still run. Your air conditioner may be running but struggling due to a failing part or intermittent issue. One common issue (especially in Phoenix, one of the hottest areas in the country) is a failed or failing capacitor. Capacitors assist motors and compressors in running by ‘helping carry the load’ so to speak. When they start to fail, the motor or compressor has to work harder to continue running. This situation can rapidly damage the motor or compressor and lead to expensive failures of multiple components. In extreme cases, what started as a fairly inexpensive repair can lead to irreparable damage to your entire AC unit.

Likewise, a failing motor or compressor can cause your AC to intermittently run but not keep your house cool. In any of these cases, you need to address the situation right away. Nobody gets excited to spend their hard-earned money replacing air conditioner components. However, delaying simple repairs can quickly lead to much greater expenses and longer periods of living in an uncomfortable home.

The AC is Running but Not Cooling the House Well

What can you do if your AC is running but not cooling your house well? First, you need to diagnose what the problem is and determine if it’s persistent or intermittent. If you can find a company that knows both air conditioners and building science (building performance), it’s for the best.

Just like describing your symptoms to your doctor, tell your service technician what you’ve been experiencing. For example; does the A/C unit seem to work better at night than in the heat of the day. Have you noticed the machine making any unusual noises? Does it seem to miraculously just star working fine every few hours? Keep in mind, just as your doctor might prescribe further testing, so may your service technician. Your service tech. may even determine further testing is needed on the home, not the air conditioning unit. Home testing can include duct leakage testing, thermal imaging of the insulation in the walls and ceiling, and others.

Magic Touch Can Help Phoenix Area Homeowners

Magic Touch Mechanical has remained one of the top-rated HVAC & Energy Audit Companies in Arizona since 1997. We don’t do plumbing; we don’t do alarm systems or exterminating – we only make homes and their occupants comfortable & efficient. Whether the issues stem from AC problems, insulation issues, too much heat gain through windows or all of the above: Magic Touch Mechanical can fix it once and for all! Speak to someone at Magic Touch today!