AC Capacitor Wiring Colors: A Complete Guide

AC Capacitor Wiring Colors
Images /

AC Capacitor Wiring Colors: A Complete Guide

When it comes to troubleshooting an AC electric motor, one common solution is to replace the starting capacitor.

This simple and cost-effective fix can often resolve issues with motor starting.

However, it’s crucial to understand the wiring colors associated with AC capacitors to ensure a proper replacement.

In this comprehensive guide, we will delve into the world of AC capacitor wiring colors, explore how capacitors function, and learn about their typical wiring in AC electric circuits.

Understanding the Basics of Capacitors

Before we dive into AC capacitor wiring colors, let’s first understand what a capacitor is and how it functions.

In the realm of electrical electronics, a capacitor is a passive device that stores electrical energy in an electric field.

It consists of two terminals and is commonly used in AC electric circuits that power electric motors.

Capacitance, on the other hand, refers to the effect that capacitors produce in an electrical circuit.

Types of Capacitors in HVAC Systems

In the context of HVAC systems, dual-run capacitors are commonly used. These capacitors have three terminals, making them ideal for space-saving installations.

They function similarly to standard capacitors but with an additional terminal.

The terminals are typically labeled as “C” for common, “HERM” or “H” for the hermetic compressor, and “FAN” or “F” for the fan utilized in HVAC equipment.

Decoding AC Capacitor Wiring Colors

Properly connecting the wires of an AC capacitor is crucial for ensuring the efficient operation of electric motors in HVAC systems.

Although there are standard capacitor wire colors, it’s important to note that variations can exist depending on factors such as the motor’s brand, application, and age.

However, electricians typically follow a set of steps to determine the correct wiring connections, even in the absence of clear markings on the wires.

1. Identifying Capacitor Wires

In some instances, electricians may encounter disconnected wires with no markings. In such cases, it can be challenging to determine which wire goes where.

While different opinions may exist within the HVAC community regarding capacitor color wiring codes, one widely recommended practice is to use an insulated screwdriver to short the F and H terminals connected to the COM terminal.

This step discharges the capacitor’s stored power, ensuring safety while working with the wires.

2. Best Practices for Wire Tagging

To avoid confusion and ensure accurate reconnections, it’s best practice to tag and label every wire before disconnecting it from its electrical connections.

Assigning each wire an ID and noting its original connection point will simplify the reconnection process.

Additionally, consulting the equipment’s wiring diagram, which is often found inside the HVAC equipment’s air handler cabinet or blower compartment door, can provide valuable guidance.

3. Utilizing Volt-Ohm-Milliammeter (VOM) Tests

For a more systematic approach, electricians can follow the marked terminals on the start or run capacitor or perform simple Volt-Ohm-Milliammeter (VOM) tests.

These tests involve measuring the resistance between the speed and common wires of the motor using a multimeter.

By tracing the wires from their loose ends back to the source, electricians can match the connections specified in the diagram or identify the different terminals through motor testing.

4. Connecting Start-Run Capacitors

Start-run capacitors, which come with color-coded insulations, are commonly used in electric motors.

To wire a start-run capacitor correctly, follow these steps:

  1. Turn off the motor by unplugging it or switching off the circuit breaker.
  2. Refer to the wiring diagram provided with the start-run capacitor to identify the capacitor’s specific terminals and wire colors.
  3. Connect the common wire (usually black) to the common terminal on the load side of the contactor.
  4. Connect the run wire terminal to the “HERM” terminal on the run capacitor.
  5. Connect one wire terminal from the start capacitor kit to the start capacitor’s terminal.
  6. Connect the second wire terminal from the start capacitor kit to the common terminal on the start-run capacitor.
  7. Ensure the hot terminal on the load side of the relay or contactor is connected to the appropriate wire.

Dual Run Capacitors: Simplifying HVAC Systems

Dual run capacitors have become increasingly popular in modern HVAC systems as they provide a space-saving alternative to using separate capacitors for the fan and compressor.

These capacitors also have three terminals, simplifying the wiring process.

By understanding the wiring connections and terminal designations, HVAC technicians can easily connect dual run capacitors to the different components of an air conditioner.

Wiring Connections and Terminal Designations

The wiring connections on dual run capacitors are typically labeled as follows:

  • “C” for common, which connects to the running terminal of the compressor and the fan.
  • “HERM” or “H” for the hermetic compressor, which connects to the starting terminal of the compressor.
  • “FAN” or “F” for the fan, which connects to the fan’s starting terminal.

These capacitors usually have voltage ratings ranging from 370 to 440 volts and operate at frequencies of 50 Hz or 60 Hz.

Evolution from Separate Capacitors

In the past, outdoor air conditioners utilized two separate capacitors, one for the fan and another for the compressor.

However, modern air conditioners now employ dual-run capacitors, streamlining the system by using a single capacitor for both the fan and compressor.

With advancements in technology, manufacturers have embraced the space-saving benefits and simplified wiring connections provided by dual run capacitors.

Frequently Asked Questions

To wrap up our comprehensive guide on AC capacitor wiring colors, let’s address some commonly asked questions:

  1. What are the wire colors of a capacitor?
    • In general, capacitor wires are designated by three colors: red for the power source’s positive side, yellow for controlling the fan motor’s speed, and white for the neutral side of the power source, which connects to the ground.
  2. How do you connect wires to a capacitor?
    • To connect wires to a capacitor correctly, follow these steps: turn off the motor, consult the wiring diagram, push the common wire terminal, push the run wire terminal, push the wires from the start capacitor kit onto their respective terminals, and ensure proper connections.
  3. What happens if a capacitor is incorrectly wired?
    • Incorrectly wiring the wires going to and from a capacitor in an HVAC system can have catastrophic consequences, including explosions or fires. It is crucial to follow proper wiring procedures to avoid such hazards.


In conclusion, understanding AC capacitor wiring colors is essential for any electrician or HVAC technician. By following the recommended practices and consulting wiring diagrams, professionals can confidently and safely wire capacitors in AC electric circuits.

Whether it’s replacing a starting capacitor or connecting a dual run capacitor, attention to detail and knowledge of wiring color codes are paramount for ensuring the efficient operation of electric motors in HVAC systems.

Related reading:

Leave a Reply

Your email address will not be published. Required fields are marked *

You May Also Like