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AC Capacitor

AC Capacitor Specifications


Is your air conditioner not working like it used to? Is it not turning on at all? Suspect it needs a new capacitor? Then you've come to the right place. Here at TEMCo we have all the capacitors you need to get your air conditioner back to the way it should be.


See what specifications you need to know to replace your AC capacitor.


Replacing an AC Capacitor


View the video below on how to diagnose problems in your air conditioning unit and to replace an AC capacitor.



What do I need to make my air conditioner run at full capacity again?


If your air conditioner is not turning on, taking a long time to warm up or not running at full capacity, what you may need is a new ac capacitor. There are two kinds of air conditioning capacitors, and the first thing to know is which kind you need depending on what problem you are having.


1. Start Capacitors


Start capacitors are used during startup to help produce enough torque to bring the motor to full speed. Designed for momentary use, the start capacitor disconnects from the motor after it starts to prevent damage. If your air conditioner is not turning on, or is taking a lot longer to get up to full speed, then a new start capacitor is probably what you need.


In hot environments, this capacitor may be over worked and fail prematurely. At this point, a replacement will need to be obtained to bring the system back online. Fortunately, these are very simple to select. Start with the voltage, then capacitance, and finally, you'll need to verify that the capacitor selected will fit within the space available by checking the measurements.

Start AC Capacitor

2. Run Capacitors


The other common type of capacitor is the run capacitor, which maintains a constant voltage supply to the motor and increases their torque at startup and efficiency once the motor is running. All run capacitors are designed for continuous duty, and have a much lower failure rate than start capacitors. There are two types of run capacitors: single unit and dual-run. If your air conditioner is starting up without a problem but then doesn't seem to run as well as it used to, then the run capacitor is most likely your problem.


The main difference between a start and a run capacitor is that the start capacitor has a much higher ability to store charge, also known as its capacitance rating, for its size than that of the run capacitor. While the start capacitor gives the motor a boost of energy in order to get it up and running, and then cuts off, the run capacitor keeps the motor going for rest of the time it is turned on.

For this reason a run capacitor can, in some circumstances, be used as a start capacitor, as long as the capacitance and voltage ratings of the original start capacitor are the same as the replacement. A start capacitor can never be used as a run capacitor, though, simply because it could not handle the continuous current and would burn out.



Run AC Capacitor

How do I know if I need a single unit or dual unit run capacitor?


AC Capacitor Selection

A single unit run capacitor is generally used in smaller air conditioner units. A single unit run capacitor will have two connections and will be hooked up to a single motor.


A dual run capacitor is essentially just two run capacitors in one. They have nothing else that makes them electrically special. A dual run capacitor supports two electric motors, such as in large air conditioner or heat pump units, with both a fan motor and a compressor motor.


A dual run capacitor will generally have three connections:


  • "H" or "Herm" for "Hermetic Compressor"
  • "F" for "Fan"
  • "C" for "common"

They will also have two different ratings for the two different run capacitors. For example, you might see 40/5 MFD, meaning that one side is 40 microfarads (measurement of capacitance), and the other side is 5 microfarads. The smaller value will always be connected to the fan, while the larger connection will always be connected to the compressor.


If necessary, you can use two separate run capacitors in place of your original dual run motor capacitor, as long as there is enough space for both.


You should be able to tell which type of run capacitor you need by how many connections your old one has.


Selecting the correct AC Capacitor

Replacing the correct starting or run capacitor should be fairly easy. Match the voltage and capacitance of the failed capacitor with the replacement, and check the measurements of the selected capacitor to verify that it will fit within the space available.


A capacitor will commonly be round, but they may be oval shaped as well. An oval dual run capacitor could be used instead of a round capacitor, as there is no electrical difference between the two. As long as the replacement will fit within the space provided, the case shape makes no difference. If it does not fit, the mounting strap can be changed to better fit the oval shape.


Capacitor for Motor Help