AFCI pulls how much current and when? Current draw mystery

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bekahhren

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So from reading through past posts I know that arc fault breakers generate heat (obviously drawing current) via their microprocessing detection methods.

My question is how much current? I have a whole house consumption meter (which tells me how much current anything in the house draws) and I have a very mysterious event happening only on the one AFCI circuit in the house. At random times (usually early in the morning or in the middle of the night of course) something on that specific circuit (I know for sure it is only the AFCI circuit) starts to draw ~4 amps, for example there might be a fan drawing .5 amps, and the meter reads 4.5 amps when it should read .5, I turn the fan off, it goes to 4 (the fan stops drawing current) and then slowly to 0, where it should be!

At first I thought there might be a short in the circuit somewhere that gets worse as the wires heat up, but it just doesn't seem like it. For one thing the breaker never trips. So it could be a bad AFCI breaker drawing more current than it should, or not tripping when it should? Or it could just be that the AFCI breakers use more power at certain times than I would ever have assumed!

Or it could be something else entirely that I haven't thought of...
This has happened with a fan, the computer, a clock radio, at different receptacles on the circuit (new receptacles I might add) the only common thread is the AFCI. And, by the way, I totally trust the meter, I don't think it is the culprit
 
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1) Are you sure that it is this particular circuit? Have you run the system with every other breaker off and seen this issue?

2) I would suspect the computer. Modern computers are never really off, unless you've unplugged them. The computer may be 'waking up' momentarily, doing something, and then going back to sleep. Do you have a laser printer? These have heaters that are known to draw lots of current.

-Jon
 
I doubt it's the AFCI breaker, at 4 amps, it would need to dissipate 480 watts of heat, which would quickly melt the breaker into a pile of goo. Sounds like you need to isolate the circuit and account for every single thing on it. Also, if you have a current probe and a oscilloscope, you can look at its current profile, which can tell you a lot about the load (resistance, switched power supply, etc.

Also, is your meter true RMS? If the load has a distorted current waveform, it may not actually be 4A at all.

Mike
 
hhmm, pile of goo, I like that. No, I haven't done the obvious and tried a new breaker, but I'm going to buy one today and give you an update tomorrow. If the new breaker trips, then I assume I have an intermittent short somewhere that the old afci wasn't picking up, being a CH piece of junk (sorry to any CH fans out there).

It definitely isn't the computer, I have it on a power switch and it was off when the fan incident occured.
I'm the crazed household electricity monitoring type, so I'm absolutely sure it is this circuit, and I know precisely what was turned on when the incidents occured. The other thing that occured to me was some kind of voltage swing that was causing current to increase. But the strange part is that unplugging the offending device didn't cause the current draw to cease immediately, it was more like a two minute decline to zero amps.
 
For starters, I would either:

1) Attach an amprobe to that circuit, and monitor the outgoing amps from that breaker, or ...
2) Disconnect the load wires from the breaker, and see if your load stays constant, or decreases.
 
Suggestions:

1) Temporarily substitute a standard breaker and repeat tests.

2) Check current on both circuit neutral and breaker pigtail, too.

3) Make sure you don't have something like a waterbed heater.
 
you could go to the first jbox and disconnect it there and see if it still happens. if not, go to the second jbox...
 
ARC Fault Breakers

ARC Fault Breakers

Two years ago we had this problem happening in our panels all over the place. What we found is that if you stack these breakers one on top of each other, A/B/A/B phase they heat up at certain times and trip randomly. We solved the problem by moving them opposite of each other in the panel, just as long as they were not stacked. Solve the problem.
 
bekahhren said:
I have a whole house consumption meter .... starts to draw ~4 amps, for example there might be a fan drawing .5 amps, and the meter reads 4.5 amps when it should read .5, I turn the fan off, it goes to 4 (the fan stops drawing current) and then slowly to 0, where it should be!
Click to expand...
What's the calibration date on the whole-house consumption meter? :confused:
 
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