hello,
i am trying to install ARC fault circuite breaker but it keeps tripping
because the neutral wire that's supposed to connect to the ARC fault
breaker is not dedicated but is shared with another non arc-fault
circuite breaker.

Some one told me that both circuit breakers that share the same neutral
wire need to be ARC Fault breaker. Even if this is true, arc fault
breakers are expensive so I hope that there's another way to fix this
problem.

PS I have tried running a neutral wire from the Arc Fault breaker to
the neutral bus and of course the breaker still trips.


Thank you in advance for your help.

"An appliance plug damaged by impact repeatedly caused tripping of the
AFCI until the problem was discovered. When the appliance cord was
replaced, no further tripping of the AFCI occurred.

n A room air conditioner that had developed a defect tripped the AFCI.
The performance of the AFCI was questioned until the offending
appliance was discovered and disconnected. The AFCI continues in
service with no further tripping.

n An AFCI installed in a new building tripped repeatedly until damage
caused by a nail through insulation was discovered and corrected.

n An AFCI installed as a retrofit in an older building tripped as soon
as it was turned on. The installing electrician found the problem with
extensive evidence of arcing in an old lighting fixture.

n Another damaged lamp with line-to-ground arcing was found when an
AFCI was installed in an existing circuit. The AFCI tripped when the
circuit was first energized after the installation.

n An AFCI tripped when retrofitted into an existing circuit.
Examination of the circuit disclosed that wire insulation had burnt
back exposing bare conductors near their connection to a receptacle.
The exposed wires had been arcing through the charred insulation. It
appeared that heat from a loose connection at the receptacle had caused
the wires to burn back.

As you might guess from that list, the greatest number of fires from
electrical causes is in homes ten years old and older where changes
have been made to electrical circuits by various owners and where
insulation is deteriorating with age, use and misuse. However, fires
from electrical arcs are recorded for residences of all ages. Besides,
all homes become older homes. If the protection is not present before
they age, they will remain unprotected as they age."
full story at:
http://www.iaei.org/magazine/03_a/ma...gregmanche.htm

) said...

hello,
i am trying to install ARC fault circuite breaker but it keeps tripping
because the neutral wire that's supposed to connect to the ARC fault
breaker is not dedicated but is shared with another non arc-fault
circuite breaker.

If it is a shared neutral, then I sure hope the other breaker is on the
other line, otherwise that shared neutral is going to be overloaded. On
opposite lines, the neutral carries the DIFFERENCE in current between the
two lines. On the same line, it carries the SUM of the currents!

AFCI breakers do provide a level of ground fault protection (though, often
AFCI breakers trip on ground faults greater than 30 mA, which is about six
times too high for GFCI protection when needed!).

If it is properly on another line, then you could get a double pole AFCI
breaker. Each circuit's hot would connect to one of the poles and the
shared neutral would attach to the neutral coming from the breaker.

Trouble is, I don't know what the availability of double pole AFCI breakers
is, and if you can find one, it will likely be quite expensive.

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
NOTE: if replying by email, remove "remove." and ".invalid"

How does the AFCI detect arcing if the current is so small (smaller than
the instant trip level of a regular breaker)?

mcha wrote:

i am trying to install ARC fault circuite breaker but it keeps tripping
because the neutral wire that's supposed to connect to the ARC fault
breaker is not dedicated but is shared with another non arc-fault
circuite breaker.


Some one told me that both circuit breakers that share the same neutral
wire need to be ARC Fault breaker. Even if this is true, arc fault
breakers are expensive so I hope that there's another way to fix this
problem.

Short of discontinuing use of one of the circuits, or running a new
circuit, you need a double pole AFCI breaker.

Steve Kraus ) said...

How does the AFCI detect arcing if the current is so small (smaller than
the instant trip level of a regular breaker)?

Arcing can occur between the hot and the neutral or between the hot and
ground. Arcs involve short bursts of high current, and it is this that is
detected for hot to neutral arcs. This would be very difficult to detect
for small levels of current, but true arcs are not small.

HOWEVER, the design of arc fault breakers take the approach that instead
of actually detecting arc current between hot and ground, ANY current
between hot and ground is BAD. By definition, current in the hot that
does not return through the neutral is a ground fault, so by using ground
fault detection, the breaker can trip if current between the hot and
neutral exceeds the GFCI rating.

"Standard" GFCI protection that is required around sinks for instance must
be capable of tripping when this current reaches about 5-6 mA. Many AFCI
breakers detect and trip on ground faults once they exceed 30 mA. Any
imbalance in the current in the hot and the neutral that is greater than
30 mA will cause it to trip because of this ground fault.


So, getting back to the original poster's issue: if the neutral were shared
between two circits on opposite hot legs, then anytime there is some load
on the other circuit, the current in the neutral and the hot on the AFCI
breaker will NOT be equal (or, at least not within 30 mA) and the breaker
will trip.


--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
NOTE: if replying by email, remove "remove." and ".invalid"

If it's TRIPPING, it's on drugs. Take it to a hospital for rehab....

On a serious note, the common neutral may be the cause. Shut off the
other circuit that shares that neutral and see if it still trips. If
this stops the tripping, run separate neutrals.

On 13 Jan 2006 15:12:20 -0800, wrote:

hello,
i am trying to install ARC fault circuite breaker but it keeps tripping
because the neutral wire that's supposed to connect to the ARC fault
breaker is not dedicated but is shared with another non arc-fault
circuite breaker.

Some one told me that both circuit breakers that share the same neutral
wire need to be ARC Fault breaker. Even if this is true, arc fault
breakers are expensive so I hope that there's another way to fix this
problem.

PS I have tried running a neutral wire from the Arc Fault breaker to
the neutral bus and of course the breaker still trips.


Thank you in advance for your help.