Understanding Your Air Conditioning System: It Doesn’t Have to be Scary!

understanding your hvac system picture 1

Have you ever looked at your system and wondered what all of the numbers and letters mean? If you have, you’re not alone! Unless you’re a trained professional, you will likely not understand a lot of the labeling on your system. We will go over a few common items on your heating and air conditioning system’s nameplate so that you can better understand what you’re seeing when you read it.

To begin, we have the model number. This is usually printed on a label on the system, which is often located on the inside of the access panel or it will be on the inside or outside wall of the unit. Frequently, this will also be where the serial number will be located. The model number usually indicates the heating or cooling capacity, but on newer systems the cooling capacity can also be stated separately.

The model number will indicate the tonnage of the air conditioning or heat pump system. Tonnage is a unit of measure that is used to describe the cooling or heating capacity of a system. A ton of cooling is based upon how much heat is needed to melt one ton (which is 2000 lbs.) of ice in 24 hours. A ton of cooling equals 12,000 BTU/hour. BTU is short for British Thermal Unit. For example, if a system is 30,000 BTU/hour, it is said to be a 2.5 ton system. Within the model number, there will be a number that is divisible by 12. That number will determine allow you to determine the tonnage of the system. If you see the number 30 in the model number, that will tell you that your system is 2.5 tons.

If you have a newer system, the cooling capacity will generally be indicated directly on the nameplate. Usually, the nameplate will be located on a sticker on the outside or inside of the unit.

Also frequently listed on the nameplate is the voltage. The voltage indicates how much electricity the system uses. The voltage of a system will remain constant regardless of the load that is placed on it. However, as more of a load is placed on the system, the current will increase. As a result, the amount of watts used will increase. Additionally, you may also see how many phases your system is. For most residential applications, it will be single phase.

Another important piece of information on the nameplate will be the Rated Load Amperage, often times labeled as RLA. This is a calculation that is used to get approval by the Underwriters Laboratories for a compressor motor. You will also see the Full Load Amperage, often labeled as FLA. With an increase in load on a motor, the total amperage needed to power the motor increases. When the full load of the motor is reached, the total amperage that the motor is drawing at this point is the full load amperage, or FLA. This is a value that is used in order to size field wires and fuses.

understanding your hvac system picture 2

Next, the serial number, which is usually located on the nameplate, can tell you some important information as well. While this may look like a long string of numbers and letters that do not mean anything, they sometimes can tell you the age of your system. The serial number of a unit means different things on different systems. In general, the serial number will tell you the age of your system.

understanding your hvac system picture 3

Another common and important piece of information on your system is its Energy Efficiency Ratio. This information tells you how much electricity you use to obtain a certain amount of cooling. The unit of measure for this is KW per hour of electricity used/1,000 BTU’s. You will usually be able to find this information on an Energy Guide sticker that is bright yellow and often located on the side of the system. This sticker will tell you your estimated yearly operating cost as well.

As you can see, there are many common items on that will be labeled on your system. While it may seem overwhelming, a simple understanding will help you make the best choice in the long-term maintenance of your system.