D Yuniskis wrote:
Jamie wrote:

D Yuniskis wrote:

Also, note that there is no way a (typical) GFCI can "test
itself" to determine that it is (likely) operational. So, a
failure in the sense electronics can cripple the protection
feature in a way that is not obvious to the user (i.e., the
circuit still supplies "unprotected power").


Btw. there are Self testing GFCI's..


Really? I stand corrected (I will have to chase down the link
to see how they work). Presumably, they test the sense
electronics *while* disabling the "trip" function? (I
can't see how else they could operate as you surely wouldn't
want the circuit to open each time it tested itself : )
In which case, I guess they hope that the circuitry that
inhibits the trip never fails! :

http://www.hubbell-wiring.com/Press/PDFS/H5185.pdf

We use these extensively. Coast more, but what the hell.


What sort of cost premium? Are they required for use in
certain applications (medical, etc.)? Or, is it just
"a nice feature to have"?

Just a nice feature, its not code to have one like this and
also, code makes previsions for life saving equipment where is,
you don't install one of these devices and the receptacle is
suppose to be a coded color, if every one follows these rules ?
I don't know. As far as cost ? I'm not the one that buys them
how ever, been told they are not cheap compared to run of the mill
versions.
You must remember that anything from HUBBELL is going to have a
premium on it. For example, the guys at work tell me it's cheaper
to buy a cheap extension cord because just one HUBBELL device cost
more than the whole cord!. So I guess if you factor in the other end
, and wire, you have yourself an expensive extension cord.

And those that get a little confused with the AGFCI units
which are mostly in the modern GCFI receptacle, just not
stated. Most don't know the difference.

Those that don't have U-ground corded devices get confused when they
still see their GFCI trip just from sliding in the
plug. This only happens with the newer GFCI's that include the arc fault
detection along with the ground fault current sense.


Ah, OK. So, I assume most modern electronic loads (i.e.,
things with line switchers in them like PC's) trip these
often?

Most devices that involve switchers, which of course generates
noise, have their own common mode chokes that blocks out sufficient
noise to prevent this. Some very older switch mode supplies may cause
the AGFCI to fault how ever, at one time, and maybe you still can, you
used to be able to purchase inline filters, which were nothing but
common mode chokes.

I just love it when high powered R.F. disturbances trip those lovely
AGFCI and AFB units


RF as in *radiated* (not *conducted*)? Like someone keying
a transceiver nearby? How close do they have to be (i.e. does
this cause grief in actual *practice*)?
Oh they have to be like driving by your home and it depends on the
installation in the home it self. Service vehicles like police and
fire that do not have a clean tail drop on their transmission can cause
wide band interference and cause these arc breakers to trip.

I also like it when the installer removes what looks like excess
neutral wire that's in a coil. by by RF choke. I haven't looked in a
code book lately how ever, Since it's not designed to teach those about
electricity, but just follow some guide lines for safety, I don't think
there is an assert about the coil being present. This is done via the
manufacturer for noise amuity. Not all may suggest to do this how ever,
if you see it packaged in a coil, bets are, you should keep it that
way or as much as possible. We have some Square-D line that will false
trigger if you remove that coil form, in the plant.


Is it an air core or ferrite? In either case, it is fairly obvious (?)
that this is something that is *meant* to be part of the assembly?
(contrast that with a pigtail that just "happens" to be coiled
up nicely for packaging)
The original Arc fault breaker never had a neutral wire supplied, you
had to bond the N with the bar yourself. This didn't last long because
installers were taking short cuts and not bonding them at all. Then,
a neutral wire was supplied with each device but was just folded or
big hand coiled for boxing. It was not to long afterwards they found out
that RF was tripping these so, for quick fix, they started to ship them
with the neutral wire coiled in a tight manner so that it could be
install with most of the coil still in it's form. They had a small slip
of paper in there suggesting the installation. The last time we saw a
new box, they no longer ship any revision notes like that. SO, I guess
it's assumed that most should know to keep the wire coiled and only undo
what you need to reach the bar.
To resolve issues where these coils have been cut out and you think
there is an RFI issue. Electricians have installed large gauge chokes
inline with the neutral that belongs to the AFB device.

The last time I talked to my friend that is on the NEC code board,
that gets together annually, he stated that these devices are still
being battled out among the committee and electrical Engineers etc.. no
2 sides can come to an agreement. go figure.

I know that we had big issues using them at work on HI-POT devices
that are mounted near a water source. The very nature of the device
itself is design to hit ground when a fault occurs, which takes out the
GFCI circuit. We had to install isolation transformer service for each
one of these devices to prevent a ground current loop to develop between
the neutral and ground.