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Message: <blockquote data-quote="Ryan Lantzy" data-source="post: 27603" data-attributes="member: 7">Re: Electrical safety question (xposted from PSW) Honestly, a breaker is really only there to protect the wire from overheating, and protect everything else from a short circuit condition. The instantaneous current from a short is in the tens of thousands of amps... the rating of the branch circuit over-current device is largely irrelevant. You'll often see breakers with a 10 kA or 20 kA rating. This is what they can withstand in a short circuit condition. If you do the math on the resistance of a 50 ft piece of 12 gauge at 120VAC you'll see why they have those ratings. Pretty much all standard branch circuit over-current devices designed for 120V use, no matter their nameplate rating, will have a 10kA rating. Main breakers will have a 20 kA rating. Think about a standard floor lamp. It might have a 3-way 50/100/150W bulb in it. That's about 1/2, 3/4 and 1 amp (roughly). It will have a zip cord wire on it (SVT jacket) and probably is 16 or 18 gauge wire, good for about 5 amps of current. In a short circuit condition, it doesn't matter what the branch circuit is rated at. In the case of most cord an plug connected equipment in your average home, the device in question typically uses well less than half of the current the circuit is rated for. I.e. a TV uses about 1-2 amps but is usually plugged into a 15 or 20A circuit. There is nothing inherently dangerous about connecting a device that uses less current that a given circuit is rated for. Most amplifiers have internal current protection (weather through a fuse or breaker).   It also allows for the connection of 15A receptacles to a 20A circuit breaker in a home so long as the wiring is 12 gauge. The concern over matching amperage to amperage is a little strange IMO. Voltage keying on connectors makes sense because it can damage equipment not able to handle higher values. A better solution for current ratings would be that every piece of cord and plug connected equipment have it's own current protection based on it's typical current draw and wire sizing. Then all connectors (outlet and plug) should be rated in "classes." Low, medium and High. Something like 5-50, 50-100, and 100 and above or something. The outlets could be designed to have very wide slots, that could deliver up to the maximum current of the breaker, but allow smaller blades to fit (for smaller devices). These are mostly my musings on the strange and sometimes contradictory regulations regarding current protection and plug/outlet ratings for cord and plug connected equipment. They should not be used to justify violating any current electrical codes or considered advice on how to properly supply or distribute electrical current in a home or to portable equipment.</blockquote>

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