Can I use a higher MFD start capacitor?

Asked By: Belal Nukala | Last Updated: 25th January, 2020
Category: home and garden indoor environmental quality
5/5 (2,320 Views . 40 Votes)
Watch out: as a general rule of thumb, electric motor start capacitors can be replaced with a micro-farad or µF or mfd rating equal to or up to 20% higher µF than the original capacitor serving the motor. On the replacement capacitor the voltage rating must be equal to or greater than the original.

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Furthermore, can you use a higher rated capacitor?

Generally speaking there is no problem using capacitors of a higher voltage rating. If you use capacitors rated for higher voltage, these are often in bigger can sizes, which means lower ESR, so in some situations the ESR may drop below some safe threshold and then the linear regulator may become unstable.

One may also ask, what happens if you use the wrong size capacitor? If the wrong capacitor rating or a poor quality capacitor is used, then the motor will not have the correct phase angle between the current and the voltage, and consequently the motor torque or rotational force will be affected. Depending on the motor load, this may result in a reduction in the motor's overall speed.

Keeping this in view, can you replace a capacitor with a higher uF HVAC?

In any HVAC unit, the capacitor must match the motor. The voltage can go higher if necessary but never lower while the MFD (uf) should always be the same.

What is the difference between uF and MFD capacitors?

In short, the answer is yes — mFd is the same as uF- which is also the same as the symbol 'µ' as seen in 'µF'. Technically 'mfd' represents 'milliFarad' while 'uF' stands for 'microFarad' which is an order of magnitude smaller. Some older capacitor manufacturers used 'mF' in place of uF on their capacitors.

27 Related Question Answers Found

Can I use a 50v capacitor instead of a 25v?

2 Answers. Probably yes: Ideally you should replace the capacitor with one of the same nominal capacitance and an equal or greater maximum voltage rating. You can always substitute a capacitor with a higher voltage rating into a circuit designed to use a capacitor with a lower rating.

Can I replace capacitor with lower UF?

2 Answers. Yes, it's possible given the necessary skills and tools. Yes, it's safe. The only rating that matters for safety is the rated voltage: if you put a higher voltage than the maximum you might see your cap explode.

How do you know what voltage capacitor to use?

It is normally recommended to give a good amount of room when choosing the voltage rating of a capacitor. Meaning, if you want a capacitor to hold 25 volts, don't choose exactly a 25 volt-rated capacitor. Leave some room for a safety margin just in case the power supply voltage ever increased due to any reasons.

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.

Can I use 25v capacitor instead of 16v?


Yes, with no problems, the voltage rating is just the maximum voltage you can deal with that capacitor. Make sure what voltages you are dealing with. Never exceed 25V if you are using 25v rated cap. Similarly never exceed 16v for a 16v rated cap.

Can I use lower voltage capacitor?

NEVER use a lower voltage than required because it lowers the life of the capacitor exponentially. Using a lower voltage rated capacitor will not damage the system, but it will accelerate the capacitor's end of life. The voltage rating is the working voltage for the capacitor to reach 60,000 applied hours.

How do you size a capacitor?

Multiply 0.5 times the square of the voltage. Call this result "x.". Continuing the example, you have 0.5 times 11.5 volts times 11.5 volts, or 66.1 square volts for "x". Divide the start-up energy requirement, in joules, of the motor by "x" to arrive at the capacitor size needed in farads.

What are the symptoms of a bad run capacitor?

Signs of Capacitor Problems
  • Cracks or bulging of the capacitor.
  • A burning odor coming from the capacitor.
  • Smoke coming from the capacitor.
  • Oozing fluid around the capacitor and circuit board.
  • Insufficient charge when checked with a multimeter.

Does it matter which way you wire a capacitor?

In an AC circuit it does not matter if a capacitor (intended for that circuit) is wired backwards. In a DC circuit, some capacitors can be wired backwards, others cannot.

Will a motor run with a bad capacitor?


A motor connected to a run and start capacitor may still attempt to start if one or both of the capacitors has failed, and this will result in a motor that hums and will not remain running for long. In most cases of capacitor problems, such as damage or a loss of charge, the capacitor will need to be replaced.

How often should you replace AC capacitor?

To make sure your A/C unit is always running at its peak performance and to make sure you get the full lifespan out of that capacitor, be sure to routinely schedule preventative maintenance every six months, look out for the signs of a bad capacitor, and if all else fails, give us a call.

Can I replace a start capacitor with a higher uF?

Watch out: as a general rule of thumb, electric motor start capacitors can be replaced with a micro-farad or µF or mfd rating equal to or up to 20% higher µF than the original capacitor serving the motor. On the replacement capacitor the voltage rating must be equal to or greater than the original.

What does 40 uF mean on a capacitor?

The symbol uF that you see on capacitors is actually a representation of microfarad (μF) and it equals 10E-6 of a farad, i. e., a millionth of a farad. Your capacitor is rated at 2.2 μF which means it could hold a charge of 2.2 microcoulomb for every volt applied across its terminals.

What does 50 uF mean on a capacitor?

It's a symbol that means micro so 50 μF means 50 microfarads. or . 000050 Farads. The farad is such a large unit that the microfarad is the practical unit for capacitance.

What is a MFD capacitor?


Capacitors with ratings above 70 microfarad (mfd) are starting capacitors. Run capacitors are designed for continuous duty, and are energized the entire time the motor is running. Single phase electric motors need a capacitor to energize a second phase winding.

Does UF matter capacitor?

The base unit of capacitance is the farad (F). This value is much too large for ordinary circuits, so household capacitors are labeled with one of the following units: 1 µF, uF, or mF = 1 microfarad = 10-6 farads. (Careful — in other contexts, mF is the official abbreviation for millifarads, or 10-3 farads.)

What is a 10uF capacitor?

Capacitors used in electronics are usually in the micro-Farad, nano-Farad or pico-Farad ranges. Examples: A ten micro-Farad capacitor is written as 10µF or 10uF. A one-hundred nano-Farad capacitor is written as 100nF or just 100n. It may be marked as 0.1 (meaning 0.1uF which is 100nF).