What needs to match when replacing a capacitor?

Author: Janessa Kuhn  |  Last update: Sunday, July 20, 2025

Must have matches – capacitance and size. Probably important matches – voltage rating, tolerance and temperature coefficient.

How do I know which capacitor to replace?

You mainly need to look at 2 values: the voltage and the capacity -both are written on most capacitors-. For example, if you are going to charge a capacitor with 24V, you need to make sure your capacitor will support that voltage; so you'll need a capacitor for at least 25V (plus error margin).

What specifications must be followed to replace a capacitor?

When selecting a new capacitor to replace a broken one, ensure the following specifications match:
  • Capacitance: Measured in microfarads, (µF or MFD) the capacitance refers to how much charge the capacitor can hold.
  • Voltage: Capacitors are usually rated for both 370 volts and 440 volts.

Can I replace a capacitor with a higher uF?

Yes. You can replace the capacitor with the same or greater voltage rating. But always keep the same capacitance rating and capacitor type.

Is it better to oversize or undersize a capacitor?

This is not to imply bigger is better, because a capacitor that is too large can cause energy consumption to rise. In both instances, be it too large or too small, the life of the motor will be shortened due to overheated motor windings.

How to Choose a Replacement Capacitor

What are the rules for replacing capacitors?

Rules for Replacing Electrolytic Capacitors
  • Replace with exact type if available.
  • Replace with capacitor that has the same capacitance (uF – microfarad) as the original.
  • Replace with capacitor that has the same voltage rating or higher.
  • Use higher temperature capacitors when possible (105c).

How do I choose the right capacitor?

Take into account the capacitance, voltage rating, ripple current rating, and temperature when selecting a capacitor. The physical size of a capacitor depends on the capacitance value. As the capacitance increases, the size becomes larger. The capacitance variation is temperature-dependent.

Can I replace a capacitor with a higher voltage capacitor?

The voltage rating is just an upper limit, which must never be exceeded in a functional circuit. Replacing a capacitor with something that has a higher voltage rating is always safe. The only problem there is that a capacitor rated for a higher voltage is often physically larger, everything else being equal.

What is the microfarad tolerance when replacing a run capacitor?

There is always a tolerance level on the microfarad (µF) rating. A typical tolerance on the capacitance of a motor run capacitor for HVAC applications is +/-6%. With this being said, that means that a 40 µF capacitor can rate from 37.6 to 42.4 µF and still be considered a passing capacitor.

What is the rule of thumb for capacitors?

The rule of thumb for derating is to select a ceramic capacitor with a voltage rating greater than or equal to two times the voltage to be applied across it in the application. That means, for example, if the actual capacitor voltage is 50V, select a capacitor rated for at least 100 V.

Can I use a 1.5 uf capacitor instead of 1.2 uf?

Any issue if I replace a 1.2uf 550Vac capacitor to a 1.5uf 450Vac on my ceiling fan? yes, you will change the circuit characteristic.

Can I replace a 35 3 capacitor with a 35 5?

A: I believe you are looking at replacing a 35/3 with a 35/5 MFD capacitor and this will in all probability be OK. I would not hesitate to use the 35/5 if I could not find the 35/3.

What are the 2 typical signs that a capacitor is bad or has failed?

The short answer is you may have a failing AC capacitor if you are experiencing any of the following symptoms:
  • Your AC system isn't blowing cold air.
  • You hear a humming noise coming from the outdoor unit.
  • Your monthly energy bills are rising unexpectedly.
  • Your air conditioner will shut off unexpectedly.

Can I replace an AC capacitor myself?

Since AC capacitors are high-voltage components that might cause significant injury to you even if the power is out, it is strongly recommended against changing them yourself. Follow any instructions provided with your new unit purchase if you're thinking about replacing your own AC capacitor filter.

What happens if you use a bigger capacitor than the recommended one?

A motor will not have an even magnetic field if an incorrect-sized capacitor is installed. This will cause the rotor to hesitate in uneven regions. This hesitation causes the motor to become noisy, increase energy consumption, decrease performance, and overheat.

Can I use a 440v capacitor instead of a 370v?

The voltage rating displays the “not to exceed” rating, which means you can replace a 370v with a 440v but you cannot replace a 440v with a 370v. This misconception is so common that many capacitor manufactures began stamping 440v capacitors with 370/440v just to eliminate confusion.

Why does my motor keep blowing capacitors?

Overheating is a primary cause of a failed start capacitor. Start capacitors are not designed to dissipate the heat associated with continuous operation; they are designed to stay in the circuit only momentarily while the motor is starting. If a start capacitor stays in the circuit too long, it will overheat and fail.

Can I replace a 40 5 capacitor with a 45 5?

However, If the original was 40/5uf and you replace it with 45/5uf, then the compressor motor will start even at a somewhat lower AC voltage (which often happens in rural areas too far away from power plants); but at the same time the compressor motor will use slightly more energy it will run a little more hot, which ...

Do capacitors have to match?

For an alternate capacitor: Must have matches – capacitance and size. Probably important matches – voltage rating, tolerance and temperature coefficient.

Can I use a 2.0 uF capacitor to replace a 1.5 uF capacitor?

Therefore, if the capacitor capacity is changed from 1.5UF to 2UF, the circuit performance will also be changed. There are changes. According to the empirical formula, the output load of a 1uF capacitor is generally about 50mA, while the current of 1.5uF is almost 75mA, which is still relatively large.

What happens if you hook up a capacitor wrong?

If a polarized capacitor is installed incorrectly, the capacitor whistles then explodes. On the other hand, non-polarized capacitors are primarily used for filtering out harmonic noise in almost every circuit, are more friendly to handle. "Some large, electrolytic capacitors can store a charge for a long time.

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