Co-Authored By:

##### Asked by: Alexandria Sorron-Urquia

home and garden indoor environmental quality# How do I know what size capacitor I need?

**capacitor**you

**need**.

Regarding this, how do you size a capacitor for a motor?

Multiply 0.5 times the square of the voltage. Call thisresult "x.". Continuing the example, you have 0.5 times 11.5 voltstimes 11.5 volts, or 66.1 square volts for "x". Divide the start-upenergy requirement, in joules, of the **motor** by "x" to arriveat the **capacitor size** needed in farads.

**motor will**not

**run**properly with a weak

**capacitor**. This is not to imply

**bigger**is better, because a

**capacitor**that is too

**large can**cause energy consumption to rise. There is amaximum of +10% tolerance in microfarad rating on replacement

**start capacitors**, but exact

**run capacitors**must bereplaced.

In this way, what AC capacitor do I need?

The most common **need** for replacement of an **AirConditioner Capacitor** is the starting **capacitor** used insingle phase compressors or fans. Starting **Capacitors** createa phase shift during start up of the electric motor to help produceenough torque to bring the motor to full speed.

**Capacitance Equations** The definition of **capacitance** is given by this**equation**: **capacitance** C, measured in farads, equalscharge Q, measured in coulombs, divided by voltage V, measured involts. If the **capacitor** had a higher **capacitance**, itwould store more charge when connected to the samebattery.