| firstname.lastname@example.org wrote:
|> | I am assuming these are likew the GFCI breaker and the GFCI part is in
|> | addition to the normal OCPD hardware with the addition of a trip coil.
|> | Even when the AFCI is totally dead it is still a breaker.
|> | SqD has this in their recalled AFCIs. They say the breaker part is
|> | still normal.
|> Basically, if the little chip based circuit goes dead, the OCPD parts
|> (thermal and magnetic) should still operate. But that could be false
|> confidence ... "the power is on, the breaker must be OK" or "I reset
|> the breaker and it comes on, so it must be working".
|> One simple test can verify if a GFCI breaker really is working as it
|> should, and that's by putting 20,000 ohm 3/4 watt resistor between
|> the hot wire and ground to pull 6 milliamps across. It better trip,
|> and fast. The test button the breaker can do that, though connected
|> to the neutral on the source side of the current sensor.
|> Testing an AFCI will be harder. It has more aspects to the protection
|> it provides. If it is a combination AFCI+GFCI, what will the test
|> switch on the breaker actually be testing? The GFCI function? The
|> AFCI function? I think one hazard is that the AFCI protection, which
|> is much more involved than GFCI protection, could go dead while the
|> GFCI protection remains working. If the test button tests that GFCI
|> part by being the previously mentioned 6 milliamp crossover test, you
|> end up with false positive confidence.
| If a breaker has both AFCI and 6mA GFCI protection it needs a test
| button for each.
I would argue that AFCI functionality itself needs 2 test buttons, and
thus an AFCI+GFCI (regardless if it is 6ma or 30ma) needs 3 test buttons.
|> The AFCI protection also has more than one aspect to what it protects
|> for. It tests for current levels that represent a L-N or L-G arc at
|> a level I've read is around 70 amps or so. This is below the magnetic
|> trip point, and the thermal trip would be a few seconds away (enough
|> time for the arc to ignite other material). And it also tests for
|> current waveforms that represent a series arc such as from a loose
|> connection, or contacts to the hot wire that have substantial impedance
|> and would not otherwise trip either thermal or magnetic and maybe not
|> even leakage.
| Series arc protection is not required until 2008 and I don't think AFCIs
| are available yet with that protection. AFCIs now (parallel arc) look at
| the waveform in addition to current magnitude.
Series arc has been described in some brochures I've read. Whether it is
required or not, if they describe it with the product, the product better
| I was surprised when I read parallel arc detection looked at high
| current, 70A pulses, but at least that is relatively non-normal. Series
| arc has the current generally lower than the load current. Would think
| it would be really hard to differentiate "arc" from "normal".
The pattern may be telling. Lighting would have a variety of waveform
patterns, depending on if it is incandescent, fluorescent, discharge,
etc. That can be modified with dimmers. But the pattern is relatively
Computer switching power supplies that are not specifically corrected
for it (cheap ones are not), would have sharp current pulses. But even
these would be steady.
Motors would have some more random arcing. But their current phase
shift could reveal more about it being a motor.
Who knows what induced RF fields could do to AFCI. It can definitely
fool some GFCI.
|> So how does one test an AFCI properly? And how can we equip all home
|> owners to have this kind of test available to them to do on, say, a
|> yearly basis. How can one test button a breaker really do it?
|> |>Does this combination protection require 6 ma level leakage protection
|> |>or is the 30 ma level sufficient where the 6 ma level is not otherwise
|> | It can be either. Most are 30ma. The "combination" part refers to
|> | protecting the branch circuit plus the outlet connected load.
| Series arc detection is also added in the new AFCIs.
|> So does the code require the GFCI protection be part of the combination?
| New AFCIs, like the old ones, have 30mA GFCI as part of arc protection.
| A breaker could have both AFCI and GFCI combined, but that is not the
Some have 6mA GFCI protection.
The code says "combination type" but doesn't define it. A liberal
interpretation could say "if it combines AFCI with _any_
of protection, it is thus a combination type, and therefore meets
Since 210.12(B) Exception 1(b) refers to the arc-fault circuit interrupter
as separate from the overcurrent protection device, but does not exclude
it from being a "combination type", that would suggest that the intent of
210.12 is that "combination type" must be including some kind of protection
other than overcurrent.
OTOH, I really think separate devices for each type of protection is better,
although usually not practical to install. Imagine and visualize a breaker
panel. Now imagine for the break slots on the left hand side, each has two
more slots to the left. For the ones on the right, each has two more slots
to the right. The bus runs down the middle divide 6 columns of slots into
3 on the left and 3 on the right. It would be a rather wide panel. For
each "triplet of slots", separate OCPD, GFCI, and AFCI would be installed.
Then when you have an interruption event, you can determine the cause of
the event based on which device tripped. Additionally, you would not have
as much of a heat issue between different functions that you might otherwise
They're packing a LOT more functionality in a 3/4 inch wide little plastic
box, now. And that functionality is going to be expected to be reliable
of use without maintenance or testing.
| What is the progress on the new AFCIs?
| Are any in production? Near production?
Square-D, Cutler-Hammer, and GE have them. I haven't been able to find a
Siemens catalog to download from their horrible web site. I will limit
my own selection to Square-D or Cutler-Hammer, anyway, and I am leaning
towards Cutler-Hammer CH series. Cutler-Hammer has AFCI with 30mA GFCI,
AFCI with 6mA GFCI, and in both one pole and two pole versions.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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