Can you use a run capacitor in place of a start capacitor?

Asked By: Miguela Marze | Last Updated: 25th June, 2020
Category: home and garden indoor environmental quality
4.6/5 (142 Views . 21 Votes)
Run Capacitor:
Yes, the starting characteristics may not up to the mark, motor may take higher starting current with lower torque. The the problem comes when we use start capacitor as run, as start capacitor is short time rated, not designed for long run operation, it will decease slowly.

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Likewise, what is the difference between a start capacitor and a run capacitor?

The start capacitor creates a current to voltage lag in the separate start windings of the motor. The current builds up slowly, and the armature has an opportunity to begin rotating with the field of current. A run capacitor uses the charge in the dielectric to boost the current which provides power to the motor.

Similarly, can a motor run without a capacitor? Capacitor start motors use capacitor only for starting, after which the capacitor is switched out by a centrifugal switch. Motor thereafter runs without capacitor on one winding. Motor thereafter runs without capacitor on one winding.

In respect to this, can you replace a run 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 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.

39 Related Question Answers Found

What happens when a run capacitor goes bad?

If a Run capacitor goes bad then a motor can turn on but the running amperage will be higher than normal causing the motor to run hot and have a short life expectancy. After replacing a bad Condensing Fan Motor a new Start Run Capacitor should always be installed.

Can a capacitor be wired backwards?

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.

Can I bypass a capacitor?

In this case, the bypass capacitor is a first line of defense. It eliminates voltage droops on the power supply by storing electric charge to be released upon the occurrence of a voltage spike. Moreover, it accomplishes this task at a wide range of frequencies by creating a low-impedance path to ground for the supply.

Will a bad capacitor cause a motor to run slow?

Weak or bad capacitors can also cause blower motors to not run or to run slow.

What is the purpose of a run capacitor?


A run capacitor is used to continuously adjust current or phase shift to a motor's windings in an effort to optimise the motor's torque and efficiency performance. Because it is designed for continuous duty, it has a much lower failure rate than a start capacitor.

What is running and starting capacitor?

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. Start capacitors increase motor starting torque and allow a motor to be cycled on and off rapidly.

How do you connect a start and run capacitor?

How to Wire Up a Start Capacitor
  1. Turn off the electricity to the unit the motor operates.
  2. Inspect the start capacitor's wiring diagram.
  3. Push the wire terminal on the start capacitor relay's "Common" wire, usually the black wire, to the common terminal on the load side of the unit's contactor.

Can I replace a capacitor with a higher uF?

You can almost always replace a capacitor with one of a higher voltage. This is the limiting factor of a capacitor due to dielectric breakdown voltages that the manufacturer chose. Varying capacitance gets a little trickier.

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.

Can I use a start capacitor as a run capacitor?


Run Capacitor:
Yes, the starting characteristics may not up to the mark, motor may take higher starting current with lower torque. The the problem comes when we use start capacitor as run, as start capacitor is short time rated, not designed for long run operation, it will decease slowly.

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.

What happens if we increase the capacitor value?

Thus, a capacitor lets more current flow as the frequency of the source voltage is increased. The apparent resistance of a capacitor in an AC circuit is less than its DC resistance. This apparent AC resistance is called capacitive reactance, and its value decreases as the applied frequency increases.

How do you size a run capacitor?

Multiply the full load amps by 2,650. Divide this number by the supply voltage. The full load amps and the supply voltage can be found in the owner's manual. The resulting number is the MicroFarad of the capacitor you need.

Can a charged capacitor kill you?

This can make a large, charged capacitor extremely dangerous -- flash units and TVs have warnings about opening them up for this reason. They contain big capacitors that can, potentially, kill you with the charge they contain. However, any alternating current (AC) signal flows through a capacitor unimpeded.

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 run my AC with a bad capacitor?

A capacitor can go bad after sustaining damage from excess power. As a capacitor connected to the compressor begins to weaken and fail, “hard starting” will occur. This is when your AC struggles to turn on and then shuts off again soon after.

Can a bad capacitor ruin a fan motor?

Using the wrong capacitor rating or a poor quality capacitor can adversely affect the operation of the motor, the compressor or an entire HVAC system. Most HVAC systems use a motor run capacitor to run the blower motor, the condenser fan motor and/or the compressor.