Arc Fault Circuit Interrupters

We have these in North Carolina. I had a derailment on Fastrack fed from a ZW . The short was able to wipe out the chip in my Railking PS-1 Allegheny. It did not trip the arc fault breakers feeding the 120 volt supply to which the transformer was connected.

What I did experience when building my layout benchwork was that starting the chop saw would cause the breaker to trip. I had to run an extension cord from the Kitchen on the first floor to the layout room on the second floor. Didn't think about using a bathroom service.

• AFCI devices (and GFCI devices for that matter) that constantly trip or trip soon after resetting indicate a defective AFCI (or GFCI) device or a potentially serious problem in the dwelling's wiring. If replacing the device does not solve to tripping issue, call an electrician as soon as possible to locate and remove the fault source. Left unresolved, fire could eventually result.
• AFCI and GFCI are two similar looking devices with completely different purposes and are not interchangeable. An AFCI detects arcing in circuits. Pinched conductors, broken or loose connections, etc. that can contribute to the type of arcing that can result in fires, have very specific "signatures". The arcing seen in many motor operated devices (such as a drill or vacuum cleaner), or those seen when a fluorescent light starts, should not trip an AFCI device, as this type of arc does not have the signature (duration and amplitude) type that causes fires. A GFCI device on the other hand, is a precision measuring device. In most circuits, the amount of current flowing on the black wire to a device should flow back on the white wire. If there is a difference of as little as .005 (5 thousandths) amps between the hot and neutral wire, this current is "leaking" through the device case, handle, or in the case of a 3 wire cord connected appliance or tool, safety ground. Since it is likely that the user of the device is in contact with this leak current, the GFCI opens the circuit within a fraction of a second from when the leak current is first detected. This helps to prevent serious burns or injury to the user. The AFCI is designed to prevent loss of property and life due to fire, while the GFCI is designed to prevent shock or serious injury to individuals. It should evident why both types of protection are highly desirable.

Given the way the AFCI operates, this is not unexpected.  The short was on the secondary of the transformer, and the arc signature was not sensed on the 110V circuit.  However, the often recommended TVS protection is something you should add to protect the train electronics.

Thanks John

This setup was  temporary a while back for the Holidays. Its now gone , replaced with permanent Gargraves track with the ZW feeding the DCS Tiu with a Radio Shack fused feed and a legacy set. 

With respect to the Arc Fault breaker tripping, the chop saw was the only appliance that seemed to be an issue. It has a 15 amp motor and the breakers are 15 amp. Didn't matter if another circuit was used . I would have thought the starting draw of the saw caused the problem . A hand held Sabre saw works with no issue as well as microwaves, refrigerators and of course the trains. Seems like they are more sensitive.

I guess the motor brushes give it that "arc" signature they're looking for.

Hard to tell how they work.  Externally they are wired the same as a Ground Fault breaker, where both the power conductor and neutral are hooked to the breaker with a neutral lead to the neutral buss bar in the panel.  It may be a GFI on steroids seeing an arc (dissipation of energy) as similar to a GFI leak.  IMO. 

Should be all new residential construction at this point with some remodel work getting excluded, dependent on local inspectors interpretation. Significant cost increase considering an arcfault breaker v.s. standard breaker. 

Not fool proof.  Appears to be a fair amount of service calls related to Arcfault installations. IMO

Interesting to note that I had a PC hooked to an Arcfault circuit tell me im-proper neutral/ground connection, but the PC did work and my polarity tester showed normal/properly grounded.     

Totrainyard,

Thanks for a very nice explanation of the differences and purposes. 

Cheers

Denny

Appreciate all the great info.  One thing I won't have to worry about.  Thanks everybody.