What Does KAIC Mean on a Circuit Breaker?

Published: 2026-07-01 | 6 min read | Category: Technical Guide

KAIC — Kilo Ampere Interrupting Capacity — is the single most critical safety specification on a circuit breaker that most people never think about. While everyone knows their breaker's amperage (20A, 100A, etc.), the KAIC rating determines whether the breaker can actually do its job during a dangerous short circuit. Get this wrong and the breaker doesn't just fail to trip — it can explode.

KAIC in Plain English

Your breaker's ampere rating (say, 20A) is the normal operating current it allows. KAIC is completely different — it's the maximum FAULT current the breaker can safely interrupt.

During a short circuit, current doesn't flow at 20 amps. It can spike to 10,000, 22,000, or even 200,000 amps depending on how close you are to the transformer. The breaker must open its contacts and extinguish the resulting arc under this extreme current. KAIC tells you the maximum fault current the breaker is tested and certified to handle.

| Specification | What It Measures | Typical Values | |--------------|-----------------|----------------| | Ampere Rating | Normal operating current | 15A - 2,000A | | KAIC Rating | Maximum fault current the breaker can interrupt | 10 - 200 KAIC | | Voltage Rating | Maximum system voltage | 120V - 600V |

Why KAIC Matters

NEC 110.9 Requirement

The National Electrical Code Section 110.9 states:

> "Equipment intended to interrupt current at fault levels shall have an interrupting rating not less than the nominal circuit voltage and the current that is available at the line terminals of the equipment."

This means every breaker in your panel MUST have a KAIC rating equal to or greater than the available fault current at that point in the system. This isn't optional — it's code.

What Happens When KAIC is Exceeded

If a fault occurs that exceeds the breaker's rating:

1. **The contacts try to open** but the arc energy is too great 2. **The arc burns through the arc chutes** designed to extinguish it 3. **Internal components melt** from the extreme heat 4. **The breaker housing can rupture** — sending molten metal and plasma outward 5. **The fault continues uncleared** — potentially causing a fire or upstream damage

This is called a "catastrophic failure" and it's the reason KAIC exists as a specification.

Common KAIC Ratings

| KAIC Rating | Typical Application | Example Breakers | |------------|--------------------|-----------------| | 10 KAIC | Residential panels | Square D QO, Eaton BR, Siemens QP | | 14 KAIC | Small commercial | Square D QOB, Eaton BAB | | 22 KAIC | Commercial buildings | Standard FA, FD, ED frames | | 25 KAIC | Medium commercial | Enhanced standard frames | | 35 KAIC | Large commercial | High-IC versions | | 42 KAIC | Light industrial | Siemens HED, Eaton HFD | | 65 KAIC | Industrial facilities | Square D HJA, HKA, HLA | | 100 KAIC | Heavy industrial | Current-limiting breakers | | 200 KAIC | Utility/switchgear | Power circuit breakers |

How to Determine Required KAIC

For New Installations

A licensed electrical engineer performs a short-circuit study that considers:

• Utility transformer kVA and impedance
• Conductor size and length from transformer to panel
• Motor contribution (motors feed fault current back into the system)
• System configuration (radial vs. loop)

Rules of Thumb (Not a Substitute for Engineering)

| Distance from Transformer | Approximate Available Fault Current | |--------------------------|------------------------------------| | At transformer secondary | 10,000 - 65,000+ amps | | 50 feet from transformer | 8,000 - 40,000 amps | | 100 feet from transformer | 5,000 - 25,000 amps | | 200+ feet from transformer | 3,000 - 15,000 amps |

Note: These are rough estimates. Actual values depend on transformer size, conductor size, and system voltage. Always get an engineering study for commercial/industrial installations.

KAIC vs. AIC vs. AIR

You'll see these terms used interchangeably:

• **KAIC** = Kilo Ampere Interrupting Capacity (thousands of amps)
• **AIC** = Ampere Interrupting Capacity (same thing, just in amps instead of kilo-amps)
• **AIR** = Ampere Interrupting Rating (older term, same meaning)

So 22 KAIC = 22,000 AIC = 22,000 AIR. They all mean the same thing.

Series-Rated Systems

In some installations, a downstream breaker with lower KAIC is protected by an upstream breaker with higher KAIC. This is called a "series-rated" or "fully-rated" system:

• **Fully rated** — every breaker individually meets the available fault current (safest, most expensive)
• **Series rated** — upstream breaker limits fault current before downstream breaker sees it (requires engineering verification and UL testing of the specific combination)

Series ratings must be listed by UL for the specific breaker combination. You cannot assume any two breakers are series-rated.

Bottom Line

Shop These Breakers

Popular models available for immediate shipping:

• Square D HJA36020 (65kAIC)
• Siemens FXD63B200 (35kAIC)

Call **(877) 611-0034** for pricing on any circuit breaker in our inventory.

KAIC is not a "nice to have" specification — it's a life-safety requirement. Every breaker must be rated for the available fault current at its location. When ordering replacement breakers, always match or exceed the original KAIC rating. AllBreakerSales.com stocks breakers from 10 KAIC residential to 200 KAIC industrial. Call (877) 611-0034 and we'll help you match the correct interrupting rating for your application.

Frequently Asked Questions

What does KAIC stand for?

KAIC stands for Kilo Ampere Interrupting Capacity. It measures the maximum fault current (in thousands of amps) that a circuit breaker can safely interrupt without damage. A 22 KAIC breaker can handle up to 22,000 amps of fault current. This is different from the breaker's trip rating — a 20-amp breaker might have a 22 KAIC or 65 KAIC interrupting rating.

How do I know what KAIC rating I need?

You need a short-circuit study (also called a fault current analysis) performed by a licensed engineer. This calculates the maximum available fault current at each panel in your facility based on transformer size, conductor length, and utility capacity. The breaker's KAIC must equal or exceed this calculated value. For most residential panels, 10 KAIC is sufficient. Commercial buildings typically need 14-65 KAIC.

What happens if my breaker's KAIC is too low?

If a fault occurs that exceeds the breaker's interrupting capacity, the breaker may fail catastrophically — it can arc internally, melt, explode, or fail to clear the fault. This can cause an arc flash, fire, or electrocution. NEC 110.9 requires all overcurrent devices to have an interrupting rating sufficient for the available fault current. Using an under-rated breaker is a code violation.