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AC Unit Size

AC Unit Size

September has arrived, Austin. Air conditioning remains as important to our daily lives as it ever was despite the oncoming fall. Temperatures may be slowly dropping but not far enough, and the humidity sure isn’t going away anytime soon. AC repair in Austin is never something you want to have to think about, but when you do, make sure you find yourself in the hands of a reputable company. It makes all the difference in the world.

Another thing that makes all the difference in the world is the size of your air conditioner. Such is a topic not often talked or thought about, but one that nevertheless has a large impact on the quality of air conditioning you’re getting and the amount you’re paying for it. In this tip of the day I’ll go over some of the factors that AC unit size affects, how to know what size your own air conditioner is and how to know what size is perfect for your house.

Explaining BTUs

BTU is a measurement of energy. Specifically, it is a unit that is a measurement of work, which is a physics term that basically just means applied force. BTUs measure heat transfer, as can be gathered from the acronym’s meaning, British Thermal Unit. A single BTU is equal to 1055 joules. Why 1055 joules? How was the BTU derived and why do we use it? 1055 joules is how much energy it takes to raise the temperature of one pound of water by one degree. So BTUs are helpful for determining how much something can heat its surroundings.

BTUs are used to describe the power of an air conditioner, which is usually directly related to its size. BTU/h is a useful unit because it represents the amount of heating or cooling an air conditioner or heater provides per hour. BTUs are used for both heating and cooling, as cooling is described simply by how much heat an air conditioner can remove from a room.

So, what does BTU have to do with the size of your air conditioning unit? Well, as mentioned, we use BTUs to describe the amount of cooling an air conditioner supplies. And the bigger the air conditioner, generally, the more BTUs it can displace. For example, your typical small window air conditioning unit can remove around 5000 BTU per hour from a single room. Typically, when we talk about the size of an air conditioner, we don’t talk about its physical dimensions, but its cooling power.

So, when you hear someone talk about sizing an AC unit to your house and they mention tons, they aren’t talking about how much the air conditioning unit weighs. A ton of cooling is a convenient and often used unit that translates to 12000 BTUs per hour. So a 2.5 ton air conditioner can remove 30000 BTUs per hour. This is what is being talked about in the discussion of AC unit sizing, the tons of cooling it provides, which is a measurement of BTUs per hour, which is a measurement of the amount of heat transfer that is going on.

Why the Size of your AC Unit is Important

When you start thinking about whether it’s time to upgrade your air conditioner you should take into consideration a number of factors. The biggest one is likely to be the age of your current air conditioning unit. Recommendations vary, but generally it is considered wise to replace your air conditioner once it reaches ten years old, or, if you’ve purchased an old house and the air conditioner is even older. Air conditioners lose their efficiency over time, they start to break down and need repairs more often, and technology has progressed enough that new air conditioners bring considerable advancements in comfort and energy efficiency.

But what size your current air conditioning unit is should also be of concern. Because, if your current situation includes an air conditioner that’s too big for your house, you’re getting a less than ideal air conditioning experience in a number ways. First of all, you’ll be paying too much. Of course, when you’re looking to buy a new air conditioner, if you get a unit bigger than you need, you’ll be paying more than necessary right then and there. But what you might not know is that having a bigger air conditioner also will raise your utility bills. This is because an inappropriately sized AC unit is going to go through this procedure: first, it will switch on; it will quickly cool the house to the set temperature; then it will switch off; repeat ad infinitum. This quick shuffling through cycles of on and off uses more energy, as air conditioners typically use the most energy in their startup phase.

Also, your comfort is at risk with an inappropriately sized air conditioner. That is because they often give you overly hot air in the winter, and they cause uneven temperatures throughout the house because they don't run as long. The cycles are too quick, and the air isn't circulated as much as it would be with a properly sized system.

Your Current AC and What Size you Need

So, how do you know if your current air conditioning unit is oversized? Well, you start by figuring out what size your AC unit is then you determine how much cooling power your house needs. Let’s start with determining how much cooling capacity your current air conditioner has. In most cases, this can be done simply by looking for specific number on the label of your air conditioner. Go outside and find the outdoor unit of your air conditioner. It will be a large metal box somewhere near the outside wall of your house. On it, you’ll find a label. This label describes a number of characteristics of the air conditioner. At the top there should be a model number and a serial number, denoted by something like M/N and S/N. What you’re going to be looking at is the model number.

The first few characters in the model number tell you what level of energy efficiency your air conditioner has, its SEER rating. The number after that though, separated by a dash, gives you the amount of cooling power the air conditioner has, in thousands of BTUs. So, if the model number reads 13HPX-048. It has a SEER rating of 13 and can output 48,000 BTUs. Then, it’s a simple conversion to turn this number into tons of cooling, just divide by 12,000. So, in this example, the air conditioner is a 4-ton system, removing 48,000 BTUs from the house per hour.

Now, unfortunately, the question of how to size a new air conditioner to your house isn’t an easy one to answer. There are multiple methods of determining how big of an AC unit you should get and their accuracy varies. Square footage alone isn’t a good measure of how much cooling power you need. Unfortunately, this is the metric that many less capable contractors use as their sole method for finding the right sized AC unit for you. The problem with this measurement is that it doesn’t take into consideration the climate you’re in, the amount of insulation, or a number of other factors. A better way is to use a square footage and climate chart. These charts give recommened tons of cooling for different square footages in different areas of the US. For us in and around Austin, from Round Rock and Buda to Cedar Park and Taylor, this means that for a 2000 to 2400 square foot home, a 4 ton AC unit is recommended.

In addition, there are some online calculators that can be sought out which will take a number of factors in consideration including how cool you want to keep your home, what the insulation is like, and how many floors the house has.

Austin AC Repair and Sizing with AC Express

Getting the right sized air conditioning unit for your house is important. It will affect everything from the amount of humidity and the circulation of air in your home to the amount of money you spend both upfront and over time. Luckily, you don’t have to do all the work of determining whether your air conditioner is too big or what size you need alone. An Austin AC repair company of high standing like AC Express can happily help you with this task.

AC Express specializes in air conditioning repair in Austin. Whether you live in Round Rock or Kyle, or anywhere between and around, we can give you excellent same day AC repair that will exceed expectations. Call today! 512-452-COLD


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