special circuit breaker question

[mcf57]

I had a basement finished about 2yrs ago. Everything went good and is still functioning with no major problems, but I have a question regarding one of the room's circuit breakers. I'm not sure what its really called, but a special breaker had to be put in the panel for the two bedrooms down there. It basically looks like a regular breaker switch in the panel, but just below it is a special little button that is associated with it.

At the time, it was required for code for bedrooms & is some sort of safety feature. I think I understood it as being needed cause it will help prevent an overload (or something like that) for high current items that might get plugged in to a bedroom (like a space heater). I think you are suppose to plug the item in first and THEN turn it on. If you plug it in with the switch on, it will trip the circuit. Again, I'm not totally sure how this type of breaker works so I might not have the correct info here (& sort of why I'm posting here)

For the most part, we don't have any problems, but occasionally, the circuit will get tripped when I plug in simple items. Most recently when I tried to plug in a satellite radio in one of the bedrooms that has a universal AC adapter. The breaker switch would not reset until I totally unplugged this universal AC adapter from the outlet. Once unplugged, the breaker would reset properly.

What is maybe going on here with this simple electronic item that I can't seem to believe is the sole reason it is tripping the breaker EVERY time. Or how does this kind of circuit breaker really operate in general and the correct way to go about using items in these bedrooms with this type of breaker system?

Any help understanding this would be great. Thanks

 

[bychon]

As far as I can tell, you have a "Ground Fault Circuit Interrupter". Much loved by construction inspectors. Much hated by microwave ovens.

These devices are supposed to save you from death if the electricity escapes from the wires and goes through you. The problem is that several electronic devices trip them. They are not over-current circuit breakers. They are leak detectors.

 

[crutschow]

Yes, it's a Ground Fault Interrupter. It trips the breaker if it detects any small (≈ 15mA) current in-balance in the two power lines since that indicates that current is escaping from the normal circuit and going to ground through some other path. Since that path may be a person touching the line, the breaker protects you from the shock. Those breakers are often required for bathrooms and outdoor outlets, where the danger from a shock to ground is greater.

Unfortunately if any appliance has a small leakage to ground, then that will also trip the breaker.

 

[Birdman Adam]

All the GFCI's in my house are built into the outlet. Is there a difference between that and at the breaker?

 

[RCinFLA]

New code requires Arc Fault interruptor (AFI). Bedrooms and living rooms require them now. They are not GFI's. Their purpose is to trip open when current flow becomes sporatic which is what happens when there is a power cord arcing. They are to prevent fires.

GFI's are required for bathroom's and outdoor outlets. They trip when the slightest amount of current (uA's) leaks to ground. They do this by insuring the same current is flowing from hot line to neutral line (wider prong of plug). If not, it trips open. They are to prevent electrocution.

 

[crutschow]

All the GFCI's in my house are built into the outlet. Is there a difference between that and at the breaker?

No. They operate the same. The advantage of being in the breaker box is that it's easy to protect several outlets with one breaker.

 

[Birdman Adam]

Ah - good to know!

So AFCI's are the next best thing from GFCI?

 

[Reloadron]

New code requires Arc Fault interruptor (AFI). Bedrooms and living rooms require them now. They are not GFI's. Their purpose is to trip open when current flow becomes sporatic which is what happens when there is a power cord arcing. They are to prevent fires.

GFI's are required for bathroom's and outdoor outlets. They trip when the slightest amount of current (uA's) leaks to ground. They do this by insuring the same current is flowing from hot line to neutral line (wider prong of plug). If not, it trips open. They are to prevent electrocution.

RCinFLA has it correct to my way of thinking. The circuit breakers in question are Arc-Fault Circuit-Interrupt Protection. Here in the US they were required in bedrooms but as of the NEC (National Electric Code) 2008 they are required in all new construction dwellings. NEC Article 210.12 reads as follows:

(A) Definition: Are-Fault Circuit Interrupter (AFCI). A device intended to provide protection from the effects of are faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.

(B) Dwelling Units. All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun rooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.

I am sure you get the drift of what the current NEC rules say. Keep in mind that this is for new construction. Additionally the NEC is a National code. Individual States, Counties and Towns may adopt some or all of the code.

Here in the State of Ohio the state without reading or understanding the code (they are politicians not engineering types) chose to adopt the entire code as written. They later overturned that decision after outcry from contractors in new home construction. I can buy a 15 or 20 amp GFIC for about $3.95 USD while that same AFCI cost about $39.95. Consider a new service panel with 200 Amp service and 40 breaker slots. If I install 40 GFIC breakers the cost is about $158 to load the panel. However if I install 40 AFCI breakers the cost is now $1,598 just for breakers.

Anyway the original requirement prior to NEC 2008 was for bedrooms so any new work done powering a bedroom required a AFCI to be installed. Additionally an AFCI will function as a GFCI but with the added feature of detecting arcs and are aimed at fire prevention.

Birdman:

Ah - good to know!

So AFCI's are the next best thing from GFCI?

Actually a better animal with a higher cost.

Ron

 

[crutschow]

Well, I learned something new. Hadn't heard of AFCIs before.

 

[mcf57]

OK, it sounds like these bedrooms are on AFIs (as described by RCinFLA) & not GFCIs. I remeber the electrician saying something about them years ago & how they were suppose to help prevent fires so this seems like more along the lines of what it is. I am aware of GFCIs and have them in several other locations throughout my home (all bathrooms & kitchen area). I even tried this simple electronic device (universal AC adapter with satellite radio) by plugging it into a bathroom GFCI outlet and it worked fine. No reset (on the outlet or breaker panel) was required.

Now, I did some more experimenting with these AFI bedrooms. I notice that if I plugged JUST the universal AC adapter in by itself (no connected device), it still tripped the AFI in the bedroom & I had to reset it at the breaker box. If I plugged in a surge protected strip outlet (6 outlets) and then plugged in the Universal AC adapter, all was perfectly fine and NOTHING had to be reset. Odd & I guess if I want this satellite radio device in this room, will have to use a strip outlet between it and the wall outlet.

Anybody know what is going on here too & explain why the strip outlet made it all work perfectly fine, but plugging it in directly would trip it? Its not necessarily a big problem, but rather I'm just really more curious than anything & want to understand how it all works a little better.

 

[Birdman Adam]

Does the strip outlet have all three connectors, hot, neutral, ground? If there is no ground connection, then no current will be flowing to ground in the device, and of course the GFCI won't see any faults.

 

[mcf57]

Yea, the strip outlet (Belkin brand "surge strip with powerline protection") has all three prongs for connecting to a wall outlet. Its doing something cause the breaker doesn't trip if I use this strip outlet. If I direct connect the AC adapter (even with nothing connected to the AC adapter)....bam!!! trips right away

 

[Reloadron]

Actually neither a GFIC or AFIC need a ground to function. Even though in GFIC (Ground Fault Interrupter Circuit) the "G" would lead you to believe a ground is needed. A GFIC looks at current in and current out between the line (Hot) and neutral lines. If I measure the current on the hot line to a load and then measure the current from a hot line on a load according to Kirchoff's law the current should be the same. (To and From aren't the best terms to use but you get the idea). The GFIC works on that principal. When there is a Δ factor exceeding a limit between the two currents the circuit is tripped out. The assumption is the missing current on the one side is going somewhere it should not be going like through a person making a path to ground. Don't quote me but I think off hand in the US for 120 VAC mains the current trip is about 5 to 6 mA to trip a GFIC. This is all done with a few torrid coils and a comparator. Anyway a third wire ground is not necessary for a GFIC to function.

Now an AFIC does everything a GFIC does with the added feature of detecting erratic perturbations between hot and neutral like arcing that could generate heat and lead to a fire. A good example would be a wall outlet with a loose mains connection feeding an appliance drawing considerable current. The loose connection could begin to arc and the junction resistance increases but the circuit will continue to try and deliver rated current to the load, Even though the current is erratic with perturbations a GFIC will not react as the goes in and goes out current is the same. This is where the AFIC does its thing and disconnects the circuit.

Now, I did some more experimenting with these AFI bedrooms. I notice that if I plugged JUST the universal AC adapter in by itself (no connected device), it still tripped the AFI in the bedroom & I had to reset it at the breaker box. If I plugged in a surge protected strip outlet (6 outlets) and then plugged in the Universal AC adapter, all was perfectly fine and NOTHING had to be reset. Odd & I guess if I want this satellite radio device in this room, will have to use a strip outlet between it and the wall outlet.

This is interesting as a basic surge protector is little more than a few MOVs (Metal Oxide Varistors) between line to neutral, line to ground and neutral to ground depending on the quality of it. A device where is a spike (sharp line transient) happens it is shunted when the MOV breaks down. Beyond that it should have no effect on the circuit. Unless possibly it is masking a problem in the line. When the device is plugged in it does produce a small load generally not there. It trips. But when connected through a surge suppressor it doesn't trip. Strange unless it is suppressing transients so the line seems normal? I don't know but something here is strange in the symptoms.

How about plugging n a variety of other things?

Ron

 

[RCinFLA]

You may have some EMI chokes in the surge suppressor extension cord. Some AFI are too sensitive and plugging in some devices cause initial current surge to charge up filter caps that the AFI thinks is an arc. Ferrite inductor interference chokes in the surge suppressor may be enough to filter out the initial, plug in surge current so the AFI does not see enough of the surge to cause it to trip.
Siemen's seems to be working on getting better standards set up for specifying and testing AFCI's. This would include noise bandwidth and trip time integration specifications. Presently UL uses a crude contact arc test relay to evaluate performance.

I have heard of the neon 'candle flame simulating' candalabra bulbs causing an AFI to trip. Also some triac based dimmers and fan speed controllers cause problem trips. Triac dimmers/speed controllers should have EMI chokes to filter out their abrupt switching. Some cheap ones don't have enough filtering on the input AC lines. It is also possible that the AC adaptor is a switching power supply that does not have good line filtering so it is injecting switching noise back into AC line.

Some electrician's try to save on wire cost by running a four wire Romex normally used for 240 vac outlets to supply two different remote 120vac branch outlets from L1 and L2 sides of breaker panel. The common white neutral line between the two 120vac branches can cause problems with false AFCI trips.

AFI's detect high frequency noise, which is what is created by a connection arcing. Unfortunately, a lot of other devices can inject high frequency noise that fakes out the AFI.

AFI's do not generally contain GFI function. I looked at G.E. site and see nothing in the specs implying they have GFI functionality.

In fact they call it Combination AFCI, just to confuse (intentionally?), but none of the '5 kinds' of protection listed are GFI related.

From their web page:

"Combination AFCI

GE's Combination AFCI delivers 5 kinds of protection:

Parallel protection – Just like its Branch/Feeder counterpart, Combination AFCI can detect and neutralize parallel arc faults
Series Protection – A series arc fault is the unintended flow of electricity over a gap within a single wire. These arc faults were not detectable until advanced technology allowed the development of the Combination AFCI breaker.
Ground protection – Arcing between a single conductor and a ground line
Overload protection
Short circuit protection "

From 'Square D' site, they specifically say their AFI's don't provide full GFI protection.

"Ground Fault Interrupters (GFIs) can be found in a kitchen, bathroom, utility
room, or outdoors. GFIs have the sensitivity (4–6 mA) needed to provide
protection for people who might contact the circuit in some way. Square D
AFCIs do not provide people protection, but do detect residual current levels
starting at approximately 50 mA."

IMHO, a GFI that does not provide people protection is NOT a GFI.

From 'Siemens' web site:

"Does the term “Combination” mean that GFCI protection is included?
No, it only means that the device protects against all three types of arcing. Any device that would include GFCI protection would be referred to as a dual function device."

A UL Class A GFCI is meant to trip between 3 mA and 7 mA of ground path leakage.

I tested my bathroom GFI by putting a 1 meg resistor from hot to ground while running a 1200 watt hair drier and it tripped the GFI when I contacted the 1 meg resistor. That's 120 uA's of ground leakage while main load was over 10 amps. Very impressive but way too sensitive for any outdoor outlet.