AC Capacitor

Buy Capacitor Replacments from TEMCo

If your motor stops working, or just doesn't seem to be working the way it should, visit TEMCo to find out how to fix it. We have everything you need for you to buy capacitor replacements for any motor.

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What types of motor capacitors are there?

Before you buy new capacitors, you should first know the difference between the two types of capacitors you might need.

If your motor 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. A start capacitor brings the motor to 3/4 of full speed in a few seconds and then disconnects from the motor right after it starts. Starter capacitors are designed to give off a large burst of energy for only a few seconds. If used for longer, they would be damaged.

The other common type of motor capacitor is the run capacitor, which maintains a constant voltage supply to the motor and increases its torque at startup. If your motor doesn't seem to run as well as it used to, then the run capacitor is most likely your problem. All run capacitors are designed for continuous duty, and have a much lower failure rate than start capacitors.

The main difference between a start and a run capacitor is that the run capacitor can store less charge, also known as its capacitance rating, for its size than the start 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.

Start Buy Capacitor Run Buy Capacitor

On the left is a start capacitor. On the right, a run capacitor.

How do I know if I need to buy capacitor replacements?

If you need to buy capacitor replacements, knowing when your capacitor needs to be changed out is extremely important.

For the start capacitor, it can be fairly obvious. If your motor is either not turning on at all, or is slow to start, your start capacitor may be worn down and old. It is also possible that you may have other issues with your motor unrelated to the capacitor, but replacing a start capacitor is relatively cheap, so it is a good way to see if there is an easy fix to your problem.

In most cases, the start capacitor will fail completely, so you will likely know when need to buy capacitor replacements. The motor's starting circuit may get stuck, causing the start capacitor to overhead and potentially rupture. The top of the starting capacitor may become dislodged, and the insides may be partially or fully ejected. If any of these occur and damage the capacitor, simply replace it.

On the left is a working start capacitor. On the right is a start capacitor that has failed.

Start Buy Capacitor Buy Capacitor Failure

When it comes to knowing when you need to buy capacitor replacements for your run capacitor, it can be trickier since it will be far less obvious that the part has failed.

For information on how to test capacitor condition, click here. »

If the performance of the run capacitor does begin to decline, it can be attributed to a number of things. First, the capacitor might just be old and worn down. It might also have overheated from lack of ventilation, or the run capacitor just might not have been designed for the amount of voltage that the motor produces. All of these can significantly reduce the lifespan of the run capacitor. A high quality aftermarket run capacitor can run for 30,000 to 60,000 hours, while factory installed motor run capacitors might run for as little as 1000 hours.

What to Know When Choosing to Buy Capacitor Replacements

The majority of run capacitors will have a voltage rating of 370 or 440 VAC, a frequency of 50 or 60 Hz and a capacitance range of 2.5-100 uf.

If you are in the market to buy capacitor replacements, you should be aware that 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.

When you buy capacitor replacements, you should make sure the new capacitor has the same capacitance and frequency as the original. You can choose a new capacitor with a voltage that is in the range of the operational voltage of the motor; a capacitor will have a marked voltage indicating peak voltage acceptable. Starter capacitors will have either a black plastic or phenolic case, though this will not have any bearing on how well the capacitor will work.

Nearly all start capacitors will be round, but they may be oval shaped as well. An oval 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.

Starting Capacitor Help