ECN Forum Forums Safety Discussion and News Safety News and Product Recalls Resetting a Breaker

I always use the "Left-hand Rule"- Stand to the right side of the disconnect (or breaker) and use your left hand to throw the switch. Keeps your body "out of the line of fire"

Andy
The incident that tripped the breaker could have caused damage to the lineside conductors that feed the panel, or any other conductor(s) in the panel. When reenergizing the said breaker, it may cause this situation to escalate into a catastrophic situation, which is a fault condition that can lead to an arcblast condition. The arcblast can develop very quickly into multiphase arcblast that has tremendous potential to cause property and bodily harm.
Try a www.google.com search on this subject, and you will find plenty of info on it. www.bussmann.com also has very good information on this subject.

Pierre

I personally have never heard of low amperage (household light and outlet breakers causing arc flash.
however when resetting a large amperage (industrial) breaker into a dead short a big arc results. the breaker could weld shut untill a meltdown occurs, but normally it will just pop open again. when it pops, there is a giant arc. in arc flash, the arc ionizes the air and makes it conductive. even though the breaker is open, the ionized air is arcing and carrying current accross the opened points of the breaker. this arcing makes even more ionized air. eventually the ionized air fills the breaker panel. arc flash then starts to occur accross the bus bars in the panel. the air is heated so quickly that the only way for it to escape the panel is to blow the front off. I have also heard that the massive amount of heat and the arcing will even dissosiate (split) the hydrogen and oxygen from moisture in the air and any condensation in the panel. if that is true, your panel basically turns into a hydrogen bomb

The standard for industrial power breakers with several hundred amperes is, that they hve to be able to safely shut off even in case of a total short circuit. So exactly what you mentioned, at the given voltage the breaker will not meltdown. to kill the arc, these breakers (also the samll household ones) have "loeschkammern" (i dont know the word), small metal plates in a row to weaken the arcs power and finally extinguish it.

If the poco's transformer short circuit power is bigger that the short switching capacity of your breaker, you have to install another breaker or (mostly here) big melting fuses with enough switchoff capacity.

with these precautions, and assuming the power transformer works correctly, you wont run into a meltdown nowhere.

just different if you've got an overvoltage on the line due to a transformer coil failure ect.
thats why most (all?) high amperage panels are equipped with surge detectors, also capable of at least the switchoff capacity
of the fuse they are connected to.
they short the line out in case of overvoltage, causing the fuse to blow. These are one-time surpressors, after one strike they're dead.

i've seen boxes for them with a clear front that spring mounted. The tripping detectors would break the cover if it wouldnt lift up


to come back to the breaker at home: i've never heard f dangers in resetting a shorted breaker. never heard of anyone that heard of anyone who dreamed of someone that heard of this.
the standard after a breaker tripped here is to assure no one is in danger and switch it back on. if it bangs and the breaker tripped again, go for a search.

[This message has been edited by :andy: (edited 02-28-2004).]