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Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
Its probably a cheap panel, mine is the same, all the round and neutral bars are at the top so its damn near impossible to get any more wires in without disconnecting an existing circuit :S
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Backyard Skunkworks wrote ...
I'll bet the contacts in that breaker welded themselves as soon as the flat short happened, after all you can get at least a couple hundred amps from a flat short in a wall socket.
Hmm, I once shorted the hot and neutral together (230V) and I didn't hear even a pop! The breakers in our house are darned fast. I once used a 4A fast fuse for my mains powered project and the 15A breaker tripped before the fast fuse. So I guess the breakers are built to withstand "dead-shorts" without any damage.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Actually those breakers are designed to handle a dead short, I believe they are designed to gracefully dissconnect a 10kA surge
In any case, it sounds like your problems is an open nuetral. I would take the voltmeter from something known to be ground (say, the ground, or a piece of wire to the nuetral buss in the panel) and see which wires are floating or not.
You should find that the ground it actually at 0v, but both the hot and nuetral are at 120v. This means that somewhere along the line your nuetral is not connected ot the nuetral bus in the panel, probably just a loose/burned contact.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Circuit breakers are usually chosen to safely interrupt the prospective fault current at the location where they are installed. (This is basically the short circuit current predicted by dividing the line voltage by the supply impedance. Typically in the tens of kA in residential UK.)
The fun starts when the utility companies up-grade the supply transformer to one with a lower impedance than when the test was originally carried out!
When I worked at Seaward they used to make a Prospective Fault Current and Earth Loop Impedance tester. This hand held instrument would measure the live/neutral impedance and the earth loop impedance. It would also tell you how many kiloamps would burn off your hand if you managed to short them all together.
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Fuse box failure
