What Is AIC? A Simple Guide to Circuit Breaker Interrupting Ratings
Introduction
If you’ve ever looked at a circuit breaker and seen ratings like 10kA, 22kA, 35kA, or 65kA, you may have wondered what those numbers actually mean.
The good news is that AIC is much simpler than it sounds.
Understanding AIC can help you choose the correct replacement breaker, avoid costly mistakes, and keep your electrical system protected.
In this guide, we’ll explain AIC in plain English—without the engineering jargon.
What Does AIC Mean?
AIC stands for Ampere Interrupting Capacity.
You’ll also see it referred to as:
- Interrupting Rating (IR)
- Short-Circuit Interrupting Rating
- Fault Current Rating
All of these describe the same basic concept:
The maximum amount of fault current a circuit breaker can safely stop without failing.
Think of It Like a Seatbelt
Imagine driving a car.
A seatbelt isn’t designed for everyday driving.
It’s designed for the worst-case accident.
A circuit breaker works the same way.
Most of the time, your breaker carries normal electrical current.
But if something catastrophic happens—like a short circuit—the current can instantly increase to tens of thousands of amps.
The breaker has one job:
Stop that enormous surge safely.
That’s exactly what the AIC rating tells you.
A Simple Example
Imagine two breakers:
Breaker A
- 18 amps flowing normally
- 10,000 AIC
Breaker B
- 18 amps flowing normally
- 35,000 AIC
Both breakers will operate exactly the same during normal use.
The difference only matters during a major fault.
If a short circuit produces:
- 8,000 amps of fault current → both breakers can safely interrupt it.
- 22,000 amps of fault current → the 35kA breaker can safely interrupt it, but the 10kA breaker is not rated for that level of fault current.
Why AIC Matters
When a short circuit occurs, the electrical current can rise almost instantly to levels far above the circuit’s normal operating current.
If the breaker’s interrupting rating is too low, it may not be able to safely clear the fault.
That can result in:
- Equipment damage
- Arc flash hazards
- Fire risk
- Personal injury
- Major downtime
This is why electrical engineers calculate the available fault current before specifying a breaker.
Can You Use a Higher AIC Breaker?
Yes—in most cases.
One of the most common questions we receive is:
“Can I replace a 10kA breaker with a 22kA or 35kA breaker?”
The answer is generally yes, provided the replacement breaker is otherwise the correct breaker for the application.
For example:
Original breaker:
- 100A
- 3-pole
- Same breaker family/frame
- 10kA
Replacement:
- 100A
- 3-pole
- Same breaker family/frame
- 22kA
This is typically acceptable because the higher AIC breaker simply has the ability to safely interrupt a larger fault current than the original.
Think of it like buying a stronger safety helmet.
It still performs the same everyday job—it just offers protection in more demanding situations.
Important: Always verify that the replacement is approved by the manufacturer for your equipment and application. Matching amperage, poles, voltage rating, trip characteristics, frame, and mounting style remains essential.
Can You Replace a Higher AIC Breaker with a Lower AIC Model?
No.
This is one mistake you should never make.
For example:
Original breaker:
- 65kA
Replacement:
- 10kA
If the available fault current exceeds the lower breaker’s interrupting rating, the breaker may not safely interrupt the fault.
That’s why replacing a higher-AIC breaker with a lower-AIC model is not acceptable unless an engineering review confirms the available fault current is within the lower breaker’s rating and the installation complies with applicable codes and the manufacturer’s requirements.
Common AIC Ratings
Some common interrupting ratings you’ll encounter include:
|
AIC Rating |
Typical Applications |
|---|---|
|
10kA |
Residential and light commercial |
|
14kA |
Commercial buildings |
|
18kA |
Commercial and industrial |
|
22kA |
Industrial facilities |
|
35kA |
Manufacturing and critical infrastructure |
|
42kA |
Heavy industrial |
|
65kA |
Data centers, hospitals, utilities, industrial plants |
|
100kA+ |
Utility and specialized industrial applications |
The required AIC depends on the available fault current at the installation point—not on how much current the equipment normally draws.
Frequently Asked Questions
Is a higher AIC breaker more powerful?
No. A higher AIC rating doesn’t change the breaker’s normal operation. It simply means the breaker is capable of safely interrupting a larger fault current if one occurs.
Does AIC affect the breaker’s amperage?
No. Amperage and AIC are two different specifications. A 100-amp breaker can be available with several different interrupting ratings.
Is AIC the same as amperage?
No. The amperage rating indicates the continuous current the breaker is designed to carry. The AIC rating indicates the maximum fault current it can safely interrupt.
Need Help Finding the Correct Replacement?
Whether you’re replacing an obsolete breaker, upgrading to a higher interrupting rating, or simply confirming compatibility, the team at Essential Electric can help.
We stock more than 70,000 electrical products from leading manufacturers, including Eaton, Siemens, Schneider Electric, ABB, GE, Bussmann, Littelfuse, and more. Our experts can help you identify the correct replacement and answer questions about AIC ratings, frame sizes, voltage, poles, and compatibility to keep your project moving.
