AFCI Breakers Keep Tripping
My house is brand new. I've only been here for 3 weeks. But I've noticed that the only 2 AFCI breakers keep tripping. What causes this? Is it caused by something I'm doing?
If this is not caused by me, at least it is covered under warranty.
Sometimes they trip at the same time, sometimes a single one will trip. They are the only AFCIs in the box. They are 15 amp breakers and control the bedroom receptacles and lights.
Is there any more info that you need?
Do they hold for awhile, then trip? Is it random tripping or can you trace it back to when something is turned on or plugged in? What brand breaker?
I've been experimenting to see if it only happens when certain devices are plugged in. I'll let you know what I find out.
Both AFCI breakers are Square D brand. At first I thought they may be bad. But what are the odds that the only two AFCIs in the box are both bad?
Thanks for your help.
Reversed hot and neutral wires
Shared neutral wiring on single pole circuit breaker circuits: this is already an existing problem with GFCI's on multiwire branch circuits.
Incorrect or accidental connections between the ground and neutral wire:
A common source of accidental ground-neutral connections occurs when an electrician over-tightens the clamp connector on BX (armored cable) where it connects to a steel junction box.
We saw that his over-tightening the connector pinched inwards the edges of the BX cable. If the BX cable edge cuts into the hot wire the electrician discovers this fault immediately when power is restored to the circuit. But if the cable edge cuts into the neutral wire, the electrician does not discover this fault until a GFCI or an AFCI is installed on the circuit, or until someone touches a supposedly safe armored cable wire exterior and gets a shock.
Normal arcing in appliances: Nuisance tripping that could occur from the normal arcing that occurs in some appliances (such as a vacuum cleaner motor) has been considered in the design of the AFCI circuit. The AFCI is designed to tell the difference between this ordinary arcing and the type of arcing in a circuit that may cause a fire.
I guess there could also be a ground fault.
And one OP lived near a radio station and had to get filters from the AFCI manuf. for the thing to work properly.
Three types of arc faults common to household wiring are parallel, ground, and series.
A parallel fault occurs when there is an arc resulting from direct contact of two wires of opposite polarity.
A ground fault results when there is an arc between a wire and ground, and
a series fault occurs when there is an arc across a break in a single conductor.
voltage and current waveforms
will exhibit some unique characteristics including the following:
ï Flat "shoulders" in the current around current zero
ï Arcing current lower than ideal current
ï Voltage across the arc approaching a square wave
ï Voltage spikes each half cycle as the arc ignites and extinguishes
ï High frequency "noise"
As might be expected, arc current and voltage waveshapes are
generally not simple sinusoids.
An arc looks much
like a resistor element in a circuit and will frequently have a
constant voltage drop of between 20 and 30 volts across it. Also,
notice that "shoulders" appear on the current traces around the
current zero locations. The arc ignites only after sufficient
voltage across the gap returns following a current zero. It
extinguishes when voltage drops below that needed to sustain the
arc. Arc voltage is almost a square wave except for the transient
near current zero. The choppiness of the voltage wave indicates
another distinct characteristic of the arc, which is that of a high
frequency voltage source.
With a series arc present, the rms value of current and I2t sensed
by an overcurrent protective device in the circuit is less than it
would sense without the arc. In other words, an overcurrent
protective device would be less likely to operate effectively with a
series arc in the circuit than without.
The arc is not continuous. Once it starts, it is interspersed with
segments of normal load current. Again, the rms value of current and
I2t delivered is considerably less than that of a solid fault,
especially when viewed over several cycles.
Switching-mode Power Supplies
four computers all energized at
the same time and then reaching steady-state current. Shoulders
similar to those for arcing current are present in both start-up and
steady state traces due to the high harmonic content of the load.
Start-up current has characteristics similar to those of an arcing
short circuit. Such loads as this must be allowed to start and run
without activating an AFCI.
This load waveform also has trace shoulders and high peaks
with similarities to a sputtering arc.
Traces of arc current and voltage illustrate that:
1. Current with an arc in series has a lower rms value than
current without the arc due to extinction and re-ignition around
2. When a sputtering arc exists in a line-to-line fault, the rms
value or I2t delivered over several cycles is considerably less
than that of a solid fault.
3. Voltage across the arc has characteristics of a square wave
with some high frequency noise.
-George D. Gregory and
Gary W. Scott, "The Arc-Fault Circuit Interrupter, An Emerging
Product," IEEE Transactions on Industry Applications,
September/October 1998, pp. 928-933.
George Gregory is manager of Industry Standards, Square D Company, Cedar
Interesting read, but that is waaaayy over my head.
What I can tell is that there could be a ton of reason for a AFCI breaker to trip inconsistently.
Time to do some experiments.
The next generation AFCIs won't do this, we promise!
Seeing as how I had the EXACT same problem, I figured I'd post here as well with my solution.
That's my story, but I'll give you the short version - only on of our three TVs did it, but sure enough, as soon as the power button was pressed, the afci circuit tripped. I found out later that even if that TV wasn't plugged into a switch on an AFCI circuit, it would trip one that was only marginally connected. Here's what happened...
I plugged the LCD into a non-AFCI 15amp switch on my back porch. No a/v cables were hooked up, just power. However, also on that circuit was another TV, which was connected via HDMI cable through a wall to an HDMI switch in my entertainment center that WAS ON AN ANFC circuit. Guess what??? It tripped that AFCI circuit - two sattelite boxes, a receiver, a separate video switcher, XBox 360, BluRay player, computer...all on surge protection, just died right then and there.
Weird stuff, right??? As a last resort, I decided I'd try a different brand/newer AFCI breaker. Lo and behold, when I replaced the original Seimens breaker with a GE breaker (both AFCI 15amp), the problem went away!!!
Don't ask me why or how, but I would try another brand or breaker, or at least one from a newer batch. As I understand it, the breaker industry is a very fluid one, and subtle changes in technologies and construction/behavior of these devices happen all the time.
I guess I should give an update. The electrician came and replaced both AFI breakers a couple weeks ago. That seemed to fix one of them. But the master bedroom still trips on an extremely inconsistant basis. So today, they came back and swapped both circuits, to figure out if it was a problem with one of the phases.
It turns out that which ever circuit is on the A phase trips. So, according to the electrician, it seems like it's a voltage spike problem on the A phase. He just plugged that breaker into one of the B phases and everything seems to work fine.
So are they going to troubleshoot the A phase?
If you can't put an AFCI on 1/2 your panel that sort of limits your options
......and on a new house
Do you have a surge protection power strip plugged in somewhere? Those things can be notorious in nuisance tripping AFI and GFI circuits. :furious:
Apparently, I have to call the utility company to have them check for voltage spikes and have them fix what ever is wrong from their end.
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