AFCI question

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Ronald, don't you steal my title. I never thought of dumbest. You are stealing the wind under my wings. You are not playing fair:wink:
 
I think that I see a bit of what is causing the confusion here, and this is something that I know from published literature.

The 'signal' that the AFCI is seeing is not some sort of radiated high frequency noise, such as you might get on an AM radio from a spark gap transmitter. The signal that the AFCI is looking at and analyzing is the current that actually flows through the breaker to the branch circuit.

Okay, back to surmising rather than knowning :)

A fault on another branch circuit in the same panelboard won't change the current flowing through the AFCI, and so should not have an effect on it.

If there is no current flow through the AFCI, say because there is no connected load, then nothing upstream of the AFCI should trip it.

But if there is sufficient current flowing through a load, and something upstream of the AFCI causes the load current to have an 'arc signature', then how could the AFCI tell where the arc is? The AFCI sees current flowing through it, and that current flow is distorted in the fashion caused by an arc, and it doesn't matter where that arc is. The key is that the arc current flows _through_ the AFCI.

Now I suppose that it is possible that any given AFCI will be subject to interference, and could in an _untended_ fashion detect signals from other circuits. Key a transmitter near many devices, and they will likely malfunction. I don't doubt that AFCIs are similarly sensitive to outside interference. But this would not be correct function.

-Jon
 
Do you see it now Ron? An OCPD, no matter of what type, will only open load side. It takes the internal circuitry of the breaker itself to clear the fault. It HAS to pass through the device so it can clear itself.
 
Ok then Certified Dumb:D



Winnie that make more sense to me than any thing I have heard tonight.
You think we are talking about a signal in the milliamps or possibily amps.
I need to go back over the literature.
 
ronaldrc said:
Ok then Certified Dumb:D



Winnie that make more sense to me than any thing I have heard tonight.
You think we are talking about a signal in the milliamps or possibily amps.
I need to go back over the literature.
Click to expand...

I might allow you to hold a title of the sort, but you don't come anywhere close enough to hold such a title:wink:

Now back to winnie, are you saying you have heard of breaking from line side problems???
 
http://forums.mikeholt.com/showthread.php?t=104963&page=5

76nemo said:
Now back to winnie, are you saying you have heard of breaking from line side problems???
Click to expand...

No, I have not seen this happen, and I have not heard of it happening.

I am saying that it is plausible that line side problems could cause a properly functioning AFCI to open, but only if the line side problems cause the appropriate load side current flow. I entirely agree with you that the AFCI is looking at the current flow through the load; but I can draw out a circuit where something on the line side affects the current flow on the load side.

-Jon
 
Nemo

Yes and Yes for right now I have a different perspective on it now.

It was a dumb question or the first post would have said the usual thing,No there is no such thing as a dumb question.I quess I broke the mold.:D

Thanks all its been fun anyway:good night :)
 
winnie said:
I think that I see a bit of what is causing the confusion here, and this is something that I know from published literature.

The 'signal' that the AFCI is seeing is not some sort of radiated high frequency noise, such as you might get on an AM radio from a spark gap transmitter. The signal that the AFCI is looking at and analyzing is the current that actually flows through the breaker to the branch circuit.

Okay, back to surmising rather than knowning :)

A fault on another branch circuit in the same panelboard won't change the current flowing through the AFCI, and so should not have an effect on it.

If there is no current flow through the AFCI, say because there is no connected load, then nothing upstream of the AFCI should trip it.

But if there is sufficient current flowing through a load, and something upstream of the AFCI causes the load current to have an 'arc signature', then how could the AFCI tell where the arc is? The AFCI sees current flowing through it, and that current flow is distorted in the fashion caused by an arc, and it doesn't matter where that arc is. The key is that the arc current flows _through_ the AFCI.

Now I suppose that it is possible that any given AFCI will be subject to interference, and could in an _untended_ fashion detect signals from other circuits. Key a transmitter near many devices, and they will likely malfunction. I don't doubt that AFCIs are similarly sensitive to outside interference. But this would not be correct function.

-Jon
Click to expand...


I completely agree with all the above, as far as my question it is answered :Thanks Winnie :)
 
Does anyone know how long it takes for an arc fault to trip with a series arc. I did a very crude experiment by cutting the hot conductor to make a series arc. I plugged in the shop vac and although it was arcing it did not trip. Yes I was using the new combo unit. Is it not possible to create this fault as I tried?
 
Dennis,
What was the load current? The AFCI does not look for the arc signature unless the current exceeds 5 amps for the combination device or 75 amps for the original device.
 
Dennis Alwon said:
Does anyone know how long it takes for an arc fault to trip with a series arc. I did a very crude experiment by cutting the hot conductor to make a series arc. I plugged in the shop vac and although it was arcing it did not trip. Yes I was using the new combo unit. Is it not possible to create this fault as I tried?
Click to expand...
Seems like I saw a test video not too long ago (Eaton, maybe), where they simulated this series arc with carbon rods in the circuit being drawn apart. I can usually put my hands on neat links like that, but I can't for the life of me remember where I saw it at. I want to say arcfault.org, but I can't find it there.
 
don_resqcapt19 said:
Dennis,
What was the load current? The AFCI does not look for the arc signature unless the current exceeds 5 amps for the combination device or 75 amps for the original device.
Click to expand...

Thanks Don-- not sure what the shop vac draws. I will try a larger load.

So what good is AFCI it if the arc is there but less than 5 amps. Does that mean that a 5amp arc is not a safety issue?
 
Dennis Alwon said:
Thanks Don-- not sure what the shop vac draws. I will try a larger load.

So what good is AFCI it if the arc is there but less than 5 amps. Does that mean that a 5amp arc is not a safety issue?
Click to expand...
No, I don't think that means that an arc with less than 5 amps is safe....I think it means that they can tell the difference between a normal arc and a "bad" arc when the current level is below 5 amps.
 
081008-2032 EST

Dennis:

I think the problem with AFCIs is how to define a current signature that is an arc, but not some normal load.

The reference I previously listed is related to older AFCIs but seemed to indicate a lack of effectiveness.
http://www.mikeholt.com/mojonewsarc...I_-_Why_I_Have_a_Problem_With_It~20020801.htm

Suppose that AFCIs catch some arcs that would cause fires or damage, but not others. If the probability of true positives is moderately high, then AFCIs may be worth while.

It is certainly difficult to design an arc detector that will detect virtually all arc faults and produce few false trips.

What is a good universal signature? There seems to be little or no useful information on this.

There may be more effective ways to solve the problem --- such as ---
Better quality devices, require screw compressive connections, good contact material with good fatigue life.
Use copper wire.
Require impedance testing.
Require double checking by an independent person from the installer.
Require higher quality devices that plug into receptacles.

All of these are extra cost, but so are AFCIs. If AFCIs do not work well, then there is a cost of non-function.

If you mandate something that does not work correctly, then ultimately it will be eliminated.

On the other hand GFCIs are easily defined and tested. Probably quite effective. But maybe tighter control is needed on their quality.

.
 
gar said:
081008-2032 EST

There may be more effective ways to solve the problem --- such as ---
Better quality devices, require screw compressive connections, good contact material with good fatigue life.
Use copper wire.
Require impedance testing.
Require double checking by an independent person from the installer.
Require higher quality devices that plug into receptacles.
.
Click to expand...
gar:

How much of the above is required by NEC? I mentioned in another AFCI thread how in the UK, loop testing is required by law but some made a joke of it!:rolleyes:
 
081009-1020 EST

bill:

I do not know.

I have not heard further on the preload adjust repair yet. However, at one point they were considering moving a machine from line 1 to line 2 since line 1 is apparently being scraped in a year. I think cost, downtime of line 2, and possible problems changed their minds.

.
 
gar said:
081008-2032 EST

http://www.mikeholt.com/mojonewsarc...I_-_Why_I_Have_a_Problem_With_It~20020801.htm


.
Click to expand...

That was old but interesting Gar, Thanks.
I was intending to do exactly that test myself on a new combo AFCI. I was interested in seeing the new ones trip on a >5 amps series arc. I decided against dealing with having to adjust spewing carbon rods and with arc shields. So it was neat to see someone who had done just that test.

If I get inspired and find the time I would still like to build my own electronic series arc "Tester" But don't tell anyone because no such thing exists:D only indicators do
 
I just got on line and noticed that this thread was backup.

So I thought I would explain why I ask the question.

Well, like Winnie said I didn't and have not read enough literature on the AFCI like I should have before asking the question.

I had read enough to know that it monitored the arc voltage and compared it to an electronic wave form of sum sort and if it looked like a fault it would trip. Like Winnie said I thought this was in the micro volts or micro amps. I had no idea it had to be a substantial current in the amperes.So that being the case the line side should not come into play.

Bob or Iwire and most all of you tried to tell me but Winnie explained it a whole lot better.


I do appreciate all the input.

Thanks:Ronald :)
 
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