Your electrician just left.
You’ve had some issues—maybe a new OLED TV is acting strange—so the landlord sent him out. He grumbled, swapped a întrerupător, and left. You look at the panel. The old, matching row of NHP breakers all say “C20” și “6kA”.
The new one, a brand you don’t recognize called “Fusion,” says “C20”… but “3kA”.
Wait. Did you just get “downgraded?”
You’re not an electrician, but 3 is definitely less than 6. When you challenged the electrician, he waved you off. “It’s all the same. I install 6kA, 10kA, 20kA… no difference.”
And now you’re really confused. He’s talking about 20kO (20,000 Amps?), but the breaker says C20 (20 Amps?), and the number you’re actually worried about is the 3kA (3,000 Amps).
What is going on?
You’ve just uncovered one of the biggest “insider” knowledge gaps in our industry. You’re not just looking at a cheap breaker; you’re looking at a massive “red flag” about your electrician.
As an engineer, this is the story I love. You’ve pulled the right thread. Let’s unravel it.
1. The “User’s Number” vs. The “Doomsday Number”
First, let’s clear the confusion. You and your electrician were talking about two completely different things.
Your breaker has two primary jobs, and each has its own number.
The “User’s Number” (C20)
This is the Overcurrent Rating. It’s the number you, the user, actually interact with.
- What it is: C20 means this is a 20-Amp circuit. (The “C” is the “trip curve,” a detail for another day).
- Its Job: To protect the wires in your wall from overloads—what I call the “Slow Burn.”
- How it works: If you plug in a 10A microwave, a 6A kettle, and a 6A toaster (Total: 22A), this breaker will “see” that 22A is more than its 20A limit. After a few minutes, it will heat up and TRIP.
- The Verdict: Your electrician got this part right. He swapped a C20 for a C20. Your circuit’s capacity hasn’t changed.
The “Doomsday Number” (6kA / 3kA)
This is the Capacitatea de întrerupere (or “Breaking Capacity” / “AIC”). This number is not for you. It’s for the grid.
- What it is: kA stands for “kiloAmps,” sau “THOUSAND AMPS.” So, 6kA = 6,000 Amps. 3kA = 3,000 Amps.
- Its Job: To protect… well… itself (and your house) from exploding during a catastrophic scurtcircuit.
- How it works: This isn’t a “too many toasters” problem. This is a “power drill just went through the main line” or “a mouse just chewed a hot and neutral wire together” problem. In a dead short, the current from the street transformer doesn’t just go to 22A. It can instantaneously spike to 2,000A, 4,000A, or more.
- The “Doomsday Number” is a promise: “I, this breaker, do solemnly swear I can safely extinguish a fault current of up to 6,000 Amps without catching fire, welding shut, or exploding in your face.”
Pro-Sfat #1: The electrician’s dismissive “6kA, 10kA, 20kA” comment was him actually talking about the C20 rating, just using “k” as slang for “Amps” (20k… 20A… get it?). It’s lazy, confusing “sparky” slang. He was ignoring your very valid question about the kA rating because he was either lazy or, worse, didn’t know the answer.
2. The Great kA Debate: Is 3kA a “Downgrade”?
So, the big question: Does that 6kA vs. 3kA “downgrade” actually matter?
Welcome to the fiercest “insider” debate among electricians. The answer is… complicated. You’ve got two camps, and both are technically correct.
Camp A: “The Pragmatists” (3kA is Fine)
This camp, full of seasoned field electricians, says: “In a residential house, 3kA is almost always enough.”
Why? That “Doomsday” number of 4,000A or more? That’s the potential current at the street transformer.
But from that transformer to your house, there are hundreds of feet of cable. That cable has resistance.
This resistance acts like a giant “choke” on the fault current. By the time that “Doomsday” surge reaches your breaker panel, it’s often been choked down to only 800A, or maybe 1,500A.
In this (very common) scenario, a 3kA breaker is plenty of headroom. It can handle the 1,500A fault with its eyes closed. The electrician who says “3kA and 6kA make no difference here” is, pragmatically, probably right.
Camp B: “The Professionals” (3kA is a Red Flag)
This camp, which includes me and anyone who follows the rules, says: “This is a ‘Red Flag’ violation and a sign of a hack.”
Why? Because an electrician isn’t supposed to guess.
Electrical codes (like AS/NZS 3000 in Australia, where this story likely happened) are written in blood. The rule is simple:
You MUST install a breaker with a kA rating high enough for the “Prospective Fault Current” (PFI) at that panel.
How do you know the PFI? You measure it with a special meter, or you calculate it based on the cable run.
But what if you’re lazy? The code gives a “deemed to comply” shortcut: If you don’t measure, you MUST assume the fault current is 6kA.
Pro-Sfat #2: Your electrician did not measure the PFI. I promise you that. He just slapped in a cheaper breaker. He violated the default 6kA rule to save his boss (or himself) about $5.
This is what I call “The $5 Red Flag.”
If an electrician is willing to cut a corner, violate a safety code, and use a “junk” brand to save $5, what other corners did he cut? The ones you can’t see?
3. The Final Twist: Your TV Doesn’t Care About 3kA
So, we’ve established your electrician is a “cowboy” who installed a non-compliant, cheap breaker. This is a “Red Flag.”
But… here’s the final “Aha!” moment.
That 3kA “downgrade” has absolutely, positively, 100% nothing to do with your OLED TV acting strange.
Zero.
Remember, the “kA” rating numai comes into play for a fraction of a second during a catastrophic short circuit. It is not “in-circuit” during normal operation. It doesn’t “clean” your power. It doesn’t filter, regulate, or stabilize voltage. It’s just a big, dumb, heavy-duty switch waiting for “Doomsday.”
Your TV problem (flickering, lines, weird behavior) is a Power Quality issue.
That “Red Flag” electrician, the one who just saved $5? He was supposed to diagnose this.
- He should have checked for a floating neutral (a very dangerous fault that makes your 120V/230V outlets swing wildly, frying electronics).
- He should have checked for voltage sags when the A/C kicks on.
- He should have checked the MEN (Main Earthed Neutral) connection, the heart of your entire electrical system.
But he didn’t. He saw a symptom, threw a $5 breaker at it, and left.
Pro-Sfat #3: The 3kA breaker isn’t your problem. It’s the evidence. The problem is that your landlord is using a “Red Flag” electrician who is unqualified, lazy, or too cheap to find the real fault that is likely still lurking in your system.
What to Do Now
- Stop Worrying (About 3kA): Pragmatically, that 3kA breaker is probably not an immediate fire hazard. Camp A is right that it’s likely sufficient for your home’s fault level.
- Start Worrying (About the Electrician): This is the “Red Flag.” You have proof that the electrician is unprofessional and non-compliant.
- Refocus on the Real Problem: Your OLED TV is a “canary in the coal mine.” It’s telling you the power quality in your home is bad. This could be due to a dangerous neutral fault.
Tell your landlord, in writing: “The electrician you sent installed a non-compliant 3kA breaker (a ‘downgrade’ from the 6kA specified by default) and failed to diagnose the underlying electrical issue that is still damaging my electronics. The kA rating is a code violation, and the original problem is unresolved. Please send a different, licensed electrician to perform a full panel-and-neutral-fault inspection.”
You’ve got them. You now know more than the “sparky” they sent. That’s the power of engineering.
Technical Accuracy Note
Standards & Sources Referenced: This article is based on the coordination principles in AS/NZS 3000 (Australian/New Zealand Wiring Rules), specifically the “deemed to comply” requirement for a 6kA default interrupting capacity.
Disclaimer: This is a common scenario in AU/NZ. In North America, the default residential AIC is typically 10kA (marked 10,000A). The principle remains identical: the kA/AIC rating must be equal to or greater than the available fault current.
Timeliness Statement: All protection principles are accurate as of November 2025.
