When technicians and hobbyists search for an AC capacitor color code, they are usually looking for one of two distinct identification systems. In heavy electrical and HVAC work, the "color code" refers to the physical case color of motor run and start capacitors, which indicates internal chemistry and sealing type (not the microfarad rating). In electronics and AC line filtering, it refers to the EIA color band system printed on small ceramic and film capacitors. This reference guide breaks down both systems, maps regional wiring standards, and explains how to safely identify unmarked components.
AC Capacitor Case Colors and EIA Band Reference Tables
Unlike resistors, large AC motor capacitors do not use painted bands to denote their capacitance or voltage ratings. Relying on case color to determine microfarads (µF) or voltage (VAC) is a critical error. Instead, case color identifies the capacitor's dielectric type, construction standard, and typical application. For smaller AC-rated suppression capacitors (X/Y safety caps), the legacy EIA color band system applies.
| Case Color / Material | Type Code | Internal Chemistry | Primary Application | Key Characteristics |
|---|---|---|---|---|
| Black (Plastic/Epoxy) | CBB60 | Metallized Polypropylene (Dry) | Motor Run (HVAC, Pumps, Fans) | Self-healing, flame retardant, continuous duty. Most common modern run cap. |
| Silver / Aluminum (Metal Can) | CBB65 | Metallized Polypropylene (Oil/Gel Filled) | Motor Run (Heavy Compressors) | Hermetically sealed, superior heat dissipation, higher surge current tolerance. |
| Red, Brown, or Black (Bakelite/Plastic) | CD60 | Aluminum Electrolytic | Motor Start (Hard-start kits) | High capacitance, intermittent duty only. Will overheat and vent if left in circuit. |
For small AC line filtering, snubber, and crossover capacitors, manufacturers use the Electronic Industries Alliance (EIA) color code. Values are read in picofarads (pF).
| Color | Digit 1 & 2 (Band 1 & 2) | Multiplier (Band 3) | Tolerance (Band 4) |
|---|---|---|---|
| Black | 0 | x1 (10^0) | — |
| Brown | 1 | x10 (10^1) | ±1% |
| Red | 2 | x100 (10^2) | ±2% |
| Orange | 3 | x1,000 (10^3) | — |
| Yellow | 4 | x10,000 (10^4) | — |
| Green | 5 | x100,000 (10^5) | ±0.5% |
| Blue | 6 | — | — |
| Violet | 7 | — | — |
| Gray | 8 | — | — |
| White | 9 | x0.1 (10^-1) | — |
Worked Example: A small AC-rated film capacitor has Yellow, Violet, and Orange bands, followed by a Black tolerance band. The first two digits are 4 and 7. The multiplier is x1,000. The value is 47,000 pF, which converts to 47 nF or 0.047 µF. The black tolerance band indicates a standard ±20% tolerance.
Regional Wiring Color Codes for AC Capacitor Circuits
While the capacitor itself relies on case colors and printed text, the wiring connecting the AC mains to the capacitor circuit is strictly governed by regional electrical codes. Miswiring a dual run capacitor in an HVAC system or a single-phase motor circuit due to regional color confusion is a leading cause of blown control boards and compressor damage.
The following table outlines the mains supply and motor winding wire colors you will encounter when wiring AC capacitor circuits across different global standards. Note that these apply to the branch circuit and motor leads, not the short jumper wires directly on the capacitor spades (which are typically all brown, yellow, or blue depending on the OEM).
| Function / Terminal | US / Canada (NEC / CEC) | EU / Global (IEC 60446) | Old UK (Pre-2004 Harmonization) |
|---|---|---|---|
| Line 1 (L1) / Common (C) | Black (or Red for 240V) | Brown | Red |
| Line 2 (L2) / Run Winding | White (or Black for 240V) | Blue | Black |
| Start Winding (to Cap) | Yellow or Orange | Yellow or Orange | Yellow or White |
| Equipment Ground | Bare Copper or Green | Green / Yellow Stripe | Green |
Source Note: US wiring practices are guided by NFPA 70 (National Electrical Code), while international harmonized colors follow IEC 60446 standards. Always defer to your local Authority Having Jurisdiction (AHJ) for final compliance.
Rows and Markings People Get Wrong
When reading capacitor specifications, experienced bench techs and electricians know where the traps are. Here are the most common misinterpretations of AC capacitor markings:
- Assuming Case Color Dictates Voltage: A black CBB60 case does not mean it is rated for 250VAC. Black cases are manufactured for 250VAC, 370VAC, and 450VAC applications. You must read the printed VAC rating. Installing a 250VAC cap on a 240V nominal line (which can spike to 260V+) will result in rapid dielectric breakdown and a vented capacitor.
- Confusing the EIA Multiplier Band: On small film capacitors, technicians often read the third band as a digit rather than a multiplier. A Red-Red-Red capacitor is not 222 pF; it is 22 x 100 = 2,200 pF (2.2 nF). For deeper component theory, resources like Electronics Tutorials provide excellent breakdowns of dielectric behaviors.
- Ignoring the 50/60Hz Rating: AC capacitors are frequency-dependent. The capacitive reactance ($X_c = \frac{1}{2\pi f C}$) changes with frequency. A capacitor rated strictly for 50Hz will exhibit different impedance and heat dissipation characteristics on a 60Hz North American grid, potentially leading to thermal runaway in continuous-duty run applications.
- Misidentifying Start vs. Run by Shape Alone: While start capacitors (CD60) are often larger in physical volume and use red/brown bakelite cases, some high-microfarad run capacitors share similar cylindrical dimensions. If the label is missing, a start cap will typically measure much higher ESR (Equivalent Series Resistance) and will fail a continuous-duty leakage test.
Frequently Asked Questions
What does a black vs silver AC capacitor case color mean in practice?
In modern HVAC and appliance repair, a black case almost always signifies a CBB60 dry-type metallized polypropylene run capacitor. These are encapsulated in flame-retardant epoxy or plastic, making them lighter and cheaper to produce. A silver or bare aluminum metal can signifies a CBB65 capacitor, which is hermetically sealed and filled with dielectric oil or gel. The silver CBB65 is used in high-heat, high-vibration environments (like inside a compressor shell) because the metal can and oil fill dissipate heat far better than a plastic shell. Neither color tells you the µF or VAC rating; you must read the label.
How do I read an AC capacitor when the printed text is faded or missing?
If the label is baked off by years of attic heat, do not guess based on physical size or case color. First, safely remove and discharge the capacitor. Use a digital multimeter with a dedicated capacitance setting (and ideally a discharge/bleeder function) to measure the µF. If it reads within ±5% of your suspected circuit requirement, it is likely a run capacitor. To determine the voltage rating of an unmarked capacitor, you must look at the physical dimensions, terminal spacing, and cross-reference the OEM part number for the specific motor or compressor it was pulled from. Never install an unmarked capacitor in a 240V or 480V circuit without verifying its voltage rating via the equipment schematic, as an under-voltage capacitor will explode.
Are AC capacitor wire color codes universal across all HVAC brands?
No. While the mains supply wiring follows strict NEC or IEC color codes (as detailed in Table 3), the short jumper wires connecting the contactor to the capacitor, and the capacitor to the compressor/fan motor, are entirely at the discretion of the Original Equipment Manufacturer (OEM). For example, on a standard US dual run capacitor, the 'C' (Common) terminal might receive a yellow wire from the contactor and a brown wire from the compressor, while the 'HERM' (Hermetic compressor start) terminal receives a brown wire with a white stripe. Always trace the wires using the schematic glued to the inside of the service panel rather than relying on wire color memory. Terminal markings on the capacitor top (C, FAN, HERM) are your only reliable guide.
