They may or may not be required for all living spaces where you live when upgrading the panel. Call your local inspector to find out. In my area they are not required on an upgrade but I always install them in bedrooms, closets, living rooms, den, sun room, breakfast room, dining room, libraries, any place people gather may require them. AFCIs will not be required in bathrooms, kitchens, laundry rooms, unfinished basements, garages, attics or outdoors. I personally install them when I upgrade a service panel. They are a great safety device that will protect the people living in that home. I also recommend and install GFCI outlets where needed if the homeowner agrees.
the high fault currents in the event of a short can weld the breaker contacts closed
Fuses never have this problem and are much safer.
Its up to your local codes. My local inspector requires them in bedrooms
Not required
Short circuit fault.
If the main breaker has ground fault detection, and the fault is a ground fault, then only the main may trip. Also if the fault is a direct short, the fault current may be several thousand amps, much greater than the trip point of both breakers. Breakers have an I^2T curve (current squared-time), which is an indication of how fast the breaker will trip at a given overload. When both breakers are overloaded, the breaker with the faster I^2T rating at that current level will trip first. This would be an indication that the breakers are improperly specified or adjusted.
You don't specify whether you mean low-voltage circuit breakers, such as MCBs (miniature circuit breakers) or high-voltage circuit breakers. In either case, repeated tripping under fault conditions causes arcing which damages the main contacts of the circuit breakers. For this reason, high-voltage circuit breakers are taken out of service after a specified number of tripping operations, so that the contacts can be maintained or, if necessary, replaced. MCB contacts are inaccessible, and the MCB may eventually require replacing.
2
There is a heated bimetallic strip that provides a time delay small overload protection. When its contact makes, it energizes a coil to trip the breaker. Some breakers are mechanical, though. There is a coil that trips the breaker instantly on large overload.
Yes, if you are replacing the service panel.
An electrical fault is where the electrical current goes where it is not intended to go. Usually this is the quickest and shortest return path to the electrical supply service. An electrical fault will trip breakers and blow fuses in the circuit as protection to stop the short circuit.
An electrical fault is where the electrical current goes where it is not intended to go. Usually this is the quickest and shortest return path to the electrical supply service. An electrical fault will trip breakers and blow fuses in the circuit as protection to stop the short circuit.
If your jurisdiction is using a version of the NEC that requires arc fault breakers, then yes. Call your local building and planning department to see what revision of the code they are using. The exception to this is that you cannot use arc fault breakers if the circuits in question are wired as multiwire circuits (two or more individual circuits sharing a common neutral) because the arc fault breaker won't work in that arrangement. You're not required to replace the entire electrical system just to change a load center, so in this circumstance you wouldn't need them. If you're using the 2005 NEC, you only need arc fault breakers in the bedrooms. If you're using the 2008 NEC, you'll need them just about everywhere that isn't covered by ground fault breakers.
You can't change the one breaker, but you can't use two separate arc fault breakers unless you separate the neutrals. However double pole arc fault breakers are made for this purpose and the common neutral would be O.K.
There are isolation devices (Circuit breakers) meant to cut off or OPEN automatically when a fault occurs. The breaker has "opened" on fault.
The City of Tyler, TX approved ordinance 0-2008-141 on 11/11/2008. This ordinance requires arc-fault breakers in bedrooms.
Short circuit fault.
yes it is a service fault
If the main breaker has ground fault detection, and the fault is a ground fault, then only the main may trip. Also if the fault is a direct short, the fault current may be several thousand amps, much greater than the trip point of both breakers. Breakers have an I^2T curve (current squared-time), which is an indication of how fast the breaker will trip at a given overload. When both breakers are overloaded, the breaker with the faster I^2T rating at that current level will trip first. This would be an indication that the breakers are improperly specified or adjusted.
No, bedroom lights fixtures do not have to be on arc fault breakers. In fact it is better if they are not. The neutral should return straight back to the distribution panel, for the arc fault circuit that the neutral is in. In some jurisdictions an electrical code amendment requires that the cable fed from arc fault breakers be identified with a blue outer sheath.
You don't specify whether you mean low-voltage circuit breakers, such as MCBs (miniature circuit breakers) or high-voltage circuit breakers. In either case, repeated tripping under fault conditions causes arcing which damages the main contacts of the circuit breakers. For this reason, high-voltage circuit breakers are taken out of service after a specified number of tripping operations, so that the contacts can be maintained or, if necessary, replaced. MCB contacts are inaccessible, and the MCB may eventually require replacing.