"Breakers are for emergencies. The problem is not about routine usage of the appliance, but what happens in case of a short, either in the wiring or inside the appliance. " Umm, not exactly. Breakers prevent overloading of wires, either short term or under a fault condition. There ARE applications that breakers provide ONLY short circuit protection (like motor only circuits, welder circuits, and other equipment that has built in protection that prevents it from overloading the conductors in normal use). The common household breaker is a thermal-magnetic breaker. It allows overloads for seconds to minutes (the thermal trip portion) often up to a few hundred percent of the rating while providing a very fast turn off (the magnetic trip portion) for faults (short circuits). The magnetic portion may not come into play until 500% to 1000% of the breakers rating. This post was edited by brickeyee on Wed, Jun 12, 13 at 10:03

I am not a licensed electrician. Perhaps there is no difference. But from what I understand from conversations with some electricians... than I take my limited understanding, and continue down a logic path - which might not be correct. However: 1. A light bulb is not on a dedicated circuit. It is a general use circuit. (Lighting) 2. Lighting is generally preferred to be 15amp - not the 20. For just the reason you mentioned. The 12 guage is harder to run (than 14guage), more expensive, and overkill for general lighting circuits. 3. A Range is a dedicated circuit. Therefore - we do not wish to have an oversized breaker going to the Range. It is supposed to be able to correctly function within a specified load - when you increase the breaker capacity - you can have more things go wrong with the range - before the breaker kills... 4. Since the Range is a dedicated circuit - we try to balance the breaker with the anticipated load and the wire size. Breakers are not actually installed to protect the appliance or the load. They are installed to protect the wiring. However, I believe it is 'safer' to have a 40amp breaker installed in a Range Circuit with 6 guage wire; when the Range which is installed - calls out for 40 amp service. Now, you are using the breaker to protect the wire, and help protect the appliance and end user. And if the guage of the wire is large enough (like a 6); and you have a 50amp Range, and not a 40amp - than you would install a 50amp breaker. Those are my thoughts on it - coming from conversations I have had, and work which I have done. I'm quite open to being further educated. :)

I know it is wrong to not use AFCI breakers now days, but just putting afci on the 3 new circuits without changing out the whole panel isn't any better than playing Russian Roulette, IMO. Especially, since you would be putting the AFCI on the new wires instead of the potentially old ones that may actually need it. If you have smaller than a 40 circuit panel, no AFCI breakers at present, and may have plans in the future for more electrical such as a hot tub or landscape lighting, then now would be a good time to at least think about the bigger picture, and either change to a larger panel or add a subpanel. BECAUSE, by the time you change all the breakers to AFCI, the time and money spent won't warrant not spending the extra $200 on the new panel. Otherwise, 210.12(B) Branch Circuit Extensions or Modifications -- Dwelling Units. In any of the areas specified in 210.12(A), where branch-circuit wiring is modified, replaced, or extended, the branch circuit shall be protected by one of the following: (1) A listed combination-type AFCI located at the origin of the branch circuit (2) A listed outlet branch-circuit type AFCI located at the first receptacle outlet of the existing branch circuit Exception: AFCI protection shall not be required where the extension of the existing conductors is not more than 1.8 m (6 ft) and does not include any additional outlets or devices. ... 210.12(B)(2) Would be more in line with the actual benefit of an AFCI in this situation, since protecting one cable all the way back to the panel while the other ten old cables that it is run next to are not protected is a bit futile. I would also add a blank face AFCI at the beginning of the lighting, or other circuits that don't start with a receptacle. You could also put the old circuits on the quad breaker, and then put the new circuits on a full-spaced AFCI breaker if you want to please the inspector with a code run-around ;D

How could it be an EQUIPMENT grounding conductor when the receptacle didn't even have a grounding slot? New wiring must meet new codes PERIOD. If there is a direct short from hot to ground, the 16 gauge wire will normally melt. That is why it was only allowed for such a brief time in history. It would be FAR BETTER to use an appropriately sized ground from another circuit. In fact, grounding wires from different circuits are bonded together all the time in multiple gang switch boxes, providing multiple paths to ground. Before 2014, nothing smaller than the Grounding Electrode Conductor was allowed for branch extension grounding. Newly written codes often have unintended consequences where people try to twist the code, and take it out of context with the rest of the codes. It will be rewritten because of people like you who want to take the easy route at the cost of safety. It is not even allowed to upgrade the wiring on a 20 amp circuit to 10 gauge wire within also increasing the size of the EGC to 10 gauge as well. Because, the 10 gauge wire will facilitate a surge of much higher amperage in the event of a direct short than the 12 gauge wire can effectively handle. 250.122 (B) Increased in Size. Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors. . Saying that it is OK to extend from the under sized ground because it was to code once is as absurd and dangerous as saying that it is OK to upgrade a service from 60A to 200A without replacing the Grounding Electrode Conductor with the appropriate size just because it was up to code when the original service was installed. You can not add additional wiring without the properly sized EGC going to a ground of equal or larger size either, or all the way back to the panel. Many states have even amended 250.130 to disallow many of the options because it is not possible to readily know if a ground path has been interrupted during future remodels. For example, If you were to extend a circuit, and bond the ground to a GEC that is in the house, then upgrade the service, and just cut off the old undersized GECs when installing the new ones, you would unknowingly end up with an ungrounded extension. The same thing with water pipes when they change parts of it to PEX in the future. Ground wires smaller than allowed by 250.122 are not allowed anywhere in the code. 250.130 does NOT give permission to ignore the rest of the code for new or extended circuits. Grandfathering only applies to existing wiring, not extensions. The code does not say that you only need to follow the convenient parts of the code. It does say that new work must FULLY meet ALL parts of the code unless there is an explicit exception.