A capacitor provides the initial jolt of electricity to start the motors and compressor in a PTAC unit and is needed to run successfully. It stores electricity and sends it in powerful bursts that get your unit revved up as it starts the cooling cycle. Each motor (indoor and outdoor) and the compressor will have its own capacitor.

HVAC capacitors are measured in voltage and microfarads. Voltage shows how much electrical current is moving through the capacitor. The more voltage in your capacitor, the faster the electrical current moves throughout it. Microfarads, meanwhile, describe how much electrical current the capacitor can store. Microfarads are typically referenced by an uF symbol on the capacitor. Most motor capacitors will range from 1.5 MFD (microfarads) to 5 MFD. For compressors, they will range from 20 to 40 MFD. The majority of the PTAC units we sell use 450 VAC. Some PTACs use 470 VAC. A capacitor MUST match both values or it will not work with the motor or compressor.

Below is an example of a compressor capacitor. They typically have a tall cylinder shape and a metal silver material. The MFD would be the 35 uF number. The voltage would be the 450 VAC number.

Below is an example of a motor capacitor. Typically the lower MFD are for the indoor motors as the indoor motors are smaller and run at less RPMs (requiring less power). This example is an indoor motor. The MFD is 1.5uF and the voltage is 450 VAC.

Below is an example of a motor. Sometimes (not always) a motor or compressor will state the MFD and voltage required. This motor requires an MFD of 1.5uF and a voltage of 450VAC.

In the case of a fan not running or the compressor not running, the capacitors should be tested first as they are easy to test and a cheap part to replace.