AFCI safety or just trouble?

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  #1  
Old 01-10-08, 12:14 AM
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AFCI safety or just trouble?

Hi

Here in Norway, the AFCI is an unknown phenomen, and I just wonder:

Does it really protect you, or is it only a false feeling of safety.

Does the AFCI act when you are using a drill or vacumcleaner with an good old brush motor?

What about a welder?

dsk
 
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Old 01-10-08, 02:08 AM
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Originally Posted by d_s_k View Post
Hi

Here in Norway, the AFCI is an unknown phenomen, and I just wonder:

Does it really protect you, or is it only a false feeling of safety.

Does the AFCI act when you are using a drill or vacumcleaner with an good old brush motor?

What about a welder?

dsk
1A. yes it do protect by detecting a either series and parallel arc falut[s] but the techolgy is getting better each time they come out with new product
the early generation did have setting at 75 amp threshold on AFCI detection but now it much lower due better electronic senseing devices i heard low as 30 MA but i dont have the fact with me right now.

2A the early generations of AFCI did have alot of issue with this but seems most are taken care by now but once awhile it will show up.

most AFCI manufacters is working very hard with the applaince manufacters to come up a soluation.

some of ceiling fan can kick the AFCI and some dimmer as well.

3A. Welder ? nope here most wirefeed welder some small one do run on 120 volt useally on 20 amp circuit and useally found in some basement but majorty it will be found in garage and they ran pretty good with the GFCI [ not the AFCI that is diffrent ]
[ otherhand larger wirefeed welder and stick arc welder useally strictally a 240 volt device and will take more than 30 amp circuit for this ]


DSK i am sure you have RCD on the main panelboard.
i know some circuits dont even have any RCD on it.

{ I allready know French electrical code but not much on Norway regulations yet.]

depending on the RCD setting it can be pretty close to our AFCI setting

Merci, Marc
 
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Old 01-10-08, 06:24 AM
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Thanks for the quick answer, If RCD = GFCI its quit common here, and this summer the NEK400 (quite simular to your NEC) was canged to have an GFCI (30mAmp) on each circuit of 20 amps or less (230V) having an outlet. (Quit expensive) Usually almoast all circuits are at 20Amps or less in a normal home.

I have been talking to several electricans and supplyers, but they have not heard about somthing sensitve to arc failures.

But i just got an invitation to say what my idea is about putting in recuirements regarding AFCI's in next NEK400.

Regarding the regulations here, and in France, they are based on the same EU documents, but we have differnt outlets, and Norway still uses a lot of 230V 3-phase with no grounded conductor, eighter in the house, or at the transformer. An other difference is a possibility to use thinner cables burried in ground with high heat conductivity.

dsk
 
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Old 01-10-08, 02:40 PM
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You will find quite a few discussions of the good and the bad of AFCI devices over at http://forums.mikeholt.com I am quite certain that Marc participates there as well

As I understand the current 'state of the art':

AFCIs can reliably detect arcing current that is well in excess of the normal trip rating of the breaker. I believe that a 20A AFCI breaker is designed to trip instantly if it detects a 75A or greater arc. This is a benefit, because normal breakers are designed to permit a significant overload for short periods of time; and so would permit a 75A arcing fault for quite a while before tripping.

AFCIs incorporate ground fault detection, operating at a trip level higher than normal GFCI protection (I believe 30mA or 50mA). This ground fault detection provides additional protection in the event of a fault, tripping even on a high impedance ground fault.

As of January 1, 2008, AFCIs are required to be 'combination' devices, capable of detecting arcing down at the 5A level. The jury is still out on how reliably these devices work, and how well they distinguish arcing faults from arcing operation.

Many electricians believe that the benefits provided by AFCIs are not worth the costs, both dollars at installation, and reliability caused by false tripping. I do not have much experience using AFCIs, and so have no opinion as to how well they 'really' work.

-Jon
 
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Old 01-10-08, 05:32 PM
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Originally Posted by winnie View Post
You will find quite a few discussions of the good and the bad of AFCI devices over at http://forums.mikeholt.com I am quite certain that Marc participates there as well

As I understand the current 'state of the art':

AFCIs can reliably detect arcing current that is well in excess of the normal trip rating of the breaker. I believe that a 20A AFCI breaker is designed to trip instantly if it detects a 75A or greater arc. This is a benefit, because normal breakers are designed to permit a significant overload for short periods of time; and so would permit a 75A arcing fault for quite a while before tripping.

AFCIs incorporate ground fault detection, operating at a trip level higher than normal GFCI protection (I believe 30mA or 50mA). This ground fault detection provides additional protection in the event of a fault, tripping even on a high impedance ground fault.

As of January 1, 2008, AFCIs are required to be 'combination' devices, capable of detecting arcing down at the 5A level. The jury is still out on how reliably these devices work, and how well they distinguish arcing faults from arcing operation.

Many electricians believe that the benefits provided by AFCIs are not worth the costs, both dollars at installation, and reliability caused by false tripping. I do not have much experience using AFCIs, and so have no opinion as to how well they 'really' work.

-Jon
Jon,
AFCI's have nothing to do with GFCI's. A completely different type of protection. The reason for AFCI's is that normal breakers do not pick up the Arcing condition that happens very quickly. They rely on the wiring heating up and then tripping. The Arc can happen very fast and the circuit board inside this breaker identifies it as either a good or bad Arc. A good arc (not dangerous) happens everytime you switch on and off a light switch or unplug say an iron while it is still on. A bad arc is when it is dangerous like cutting the wiring inside the walls by doing some work or something. GFCI's work on a leakage of electrons. What goes out on the hot must come back on the nuetral in other words. It is to protect against shock. The ole hair dryer dropped in the bathtub situation. Wet locations are where you need these. The new "combo" code for AFCI's has to do with the kind of Arc's detected. The current product only protects parallel arcs or hot to nuetral. The combo protects parallel or series arcs or hot to hot or nuetral to nuetral. The code also changes the applications to all living areas not just the bedrooms circuits as the 2001 code states. They are expensive but you can't put a dollar amount on protecting lives that are being saved unnoticed since AFCI's have been used in new and existing homes. Something like 80% of homes fires are b/c of arcing conditions. Ask some of those folks if a 30$ breaker would have been worth their losses. The nuisance tripping has been brought up but is not as common as it is talked about. Here's a link with some good info. Take care.

click the small "on your side" in the videos section for more.

http://www.myfoxaustin.com/myfox/pag...d=1.1.1&sflg=1
 

Last edited by tjtexas; 01-10-08 at 05:35 PM. Reason: directions to see video
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Old 01-10-08, 06:20 PM
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Please read what I write before you correct me

While I agree that Arc fault detection is different than ground fault detection, ground fault detection is one of the features built in to all AFCIs. The ground fault trip level is much higher than that of a proper GFCI, but it is still ground fault detection.

The difference between a series arc and a parallel arc is the current level. A series arc has its current limited by the load, and is thus a lower current situation than a parallel arc. The detection threshold of the older AFCIs is 75A (meaning that a current greater than 75A combined with the arcing signature causes a trip), the detection threshold of the combination AFCIs is 5A. (Current levels from memory, look them up for precise values.)

The job of differentiating between a 'good arc' and a 'bad arc' (what I called arcing operation versus arc fault) is quite difficult. The lower your detection threshold, the more computationally difficult the job is. It is pretty easy to say 'oh, it looks like an arc and it is > 75A, so trip now', but much harder to say 'looks like an arc and it is only 5A, what sort of arc is it'? I don't believe that there is enough field experience to know if the 'combination' AFCIs are sufficiently accurate to differentiate between arc faults and normal arcs.

Finally, while you cannot put a price on a human life, you can certainly analyze any tool used to improve safety and do a cost benefit analysis. At the very minimum a code change that increases safety (and I agree that AFCIs will increase safety) should be compared against other possible that might give a better safety improvement for the money spent.

-Jon
 
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Old 01-11-08, 12:37 AM
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Thank you, I've got a lot of knew wisdom here.
But still, I dont understand. If I have a circuit with an AFCI, and I get a bad connectiont to a lamp making an arc in series with the lamp, the amps in the circuit may be 1/20 of the amp rating of the breaker, or even in paralell wit som other well working loads, will it trip before I get a fire?

Or do I just relax and sleap well thrusting my new safety device (causing me be less careful and burn to death in my own home)?

dsk
 
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Old 01-11-08, 05:59 AM
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Originally Posted by d_s_k View Post
If I have a circuit with an AFCI, and I get a bad connectiont to a lamp making an arc in series with the lamp, the amps in the circuit may be 1/20 of the amp rating of the breaker, or even in paralell wit som other well working loads, will it trip before I get a fire?
dsk
It appears the new AFCI would require at least a 5 amp load to trip in the "series" mode. Not likely a home lamp would cause this, although the inrush current on a cold tunsten filament is many times its steady state draw. It should trip if a portable space heater causes the backstab connection to go south, however. At the end of the day, some engineer has to decide what current waveforms are dangerous, and which are safe, and make a cheap circuit to follow that logic.
 
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Old 01-12-08, 10:59 AM
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Thank you again, for the moment i will say AFCI is not good enough to put inour code, The grat arcs will be detected by visual observations, smell or smoke-alarms. (witch is required by code)

dsk
 
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