What Size Dual Run Capacitor Do I Need

Divide the start up energy requirement in joules of the motor by x to arrive at the capacitor size needed in farads.

What size dual run capacitor do i need.

Locate the stat run capacitor if it is a dual run capacitor there will be only one. We use cookies to give you the best possible experience on our website. A properly sized run capacitor will increase the efficiency of the motor operation by providing the proper phase angle between voltage and current to create the rotational electrical field needed by the motor. This is the size the new capacitor must be.

The first two numbers are the capacitance 35 µf for the compressor and 5 µf for the fan motor. If you have a faulty run capacitor. The term ac capacitor usually refers to your air conditioners run capacitor simply because run capacitors are more commonly found in air conditioning systems. You can round up or down 10 percent to match the number to a capacitor size that is available.

Use the equation below to verify the size of the capacitor. A dual run capacitor supports two electric motors such as in large air conditioner or heat pump units with both a fan motor and a compressor motor. Verify the mfd and voltages then connect the new connections from the old capacitor to the new capacitor one leg at a time to be sure the connections are correct. A typical run capacitor rating ranges from 2 µf to 80 µf and is either rated at 370 vac or 440 vac.

For a start or run capacitor can be linked into one capacitor known as dual capacitor designed with three leads though can be fragmented between two separate capacitors. Assuming a start up energy of 0 00033 joules you obtain 0 33 divided by 66 1 which equals 5 0 times 10 6 farads. The start capacitor provides a fan motor with the torque it needs to start spinning then halts. With the condensing unit operating under a load you will need to measure the total volts between the herm and common terminals on the run capacitor i e.

A lot of torque is necessary to start up an ac system so a start capacitor will have greater capacitance than a run capacitor. While the run capacitor proceeds to provide the motor with the extra torque needed. If there is two then only the fan motor capacitor will need to be replaced. The resulting number is the microfarad of the capacitor you need.

Next measure the amperage on the wire leading from herm to start on the compressor i e. The full load amps and the supply voltage can be found in the owner s manual. Answered by a verified hvac technician. If the label is faded you must size the capacitor by the model of the unit.

The capacitor you are describing marked 35 5 440 is probably a dual run capacitor. This information will usually be on a label on the outside casing. The start up energy of the motor is found either in its documentation or written on the motor itself. Step 4 identify the make and model number of the air condenser or heat pump.

An mfd is a unit of electrical capacitance and will be written on the capacitor or its packaging.