ECN Forum Forums General Topics of the Trade General Discussion Area AFCI breakers

I've been reading some of your older messages about provision of AFCIs. This is quite fascinating as we don't have anything like these breakers over here (not yet anyway!).

Does anyone know exactly how these devices work?

http://www.zlan.com/arc.htm

Paul;
they sense an arc of (i believe) 75W or more

.......have you ever heard the expression 'tail waggin' the dog'???


[This message has been edited by sparky (edited 09-09-2001).]

Thanks for the link. I figured they'd obviously have to be more complex than the standard thermal/magnetic or even amplified GFI types.

The only way I can see for them to work is for the circuitry to look for short pulses of increased current but not trip on longer pulses. I can see how such a circuit could be developed with simple op-amps etc. in integrated form, though I wouldn't be surprised if they actually use a micro-controller to analyze the current pulses.

I just wondered if any more technical details on the actual arrangement were available.

Does the AFI rely on the control circuitry to trip on normal overcurrent, or does it incorporate a normal thermal/magnetic trip as a backup?


Most definitely!

http://www.zlan.com/afci_c4.htm

Paul,
i could'nt really answer any of your Q's , this (check pix in link) is definitly not my forte' .

i'd like to know how to detect a bad AFCI

Steve,

No "test button" as per GFCI?

I've yet to get a close look at one of these buggers...

Guess the "pair of wires and a really steady hand" won't do it...

Great Q... Just how do we test them?



I suppose one could run a spot (read arc) light on an AFCI circuit (If you could find one that runs on 120V 20A) and provide a known safe long-lasting arc...

[This message has been edited by sparky66wv (edited 09-10-2001).]

Virgil;
yes there's a test button on the breaker itself, just like a GFI. I just haven't found a tester to plug in thoughout the circuit like the one's used for receptacles with the GFI tester.
where would i get a calculated arc of say, 76watts's

Don't worry since this will be a problem sure the mahufacturers who got the code comitte to cram them down our throuts will soon have a expensive tester for us to buy.

Now there's another word that has a somewhat different meaning on this side of the Atlantic!

Thanks for that. The diagrams & notes on that site are very helpful. Looks as though as I was right about the microprocessor analyzing the current.

Did you follow the links there to the pages about testing an AFCI?

They seem to be using another micro-driven test unit which stores typical arc waveforms and then re-generates them to test the breaker, except it's done via the non-shunted neutral line only in order to keep the current down.

http://www.zlan.com/testing/testing3.htm

well it certainly looks $$$$