One method we have used to find a short on the old plug style fuseholders is to replace the fuse with a standard lightbulb. If there is a load or short on the circuit, the bulb will light. Start by removing all loads from the circuits. If the bulb is still on, half-split the circuit (pick an easy spot to work on). Keep using this method until the bulb goes out. For breakers you can install a pigtail socket w/bulb in series.
Closing a breaker or switch on a "bolted" fault can be risky business. You could damage the breaker, or cause further damage at the site of the fault. It is always wise, when closing a switch or breaker on a circuit that you are not familiar with, to stand to the side and avert your eyes in case the circuit is faulted and the equipment can't handle the fault current.
Like Ed mentioned, bolted fault situations can result in breakers exploding when reset if the fault remains.
My common testing would be to leave the breaker off, then look for the fault [or isolate it in J-Boxes or such]. To verify if the fault has been cleared, make sure all loads are disconnected, then shunt the breaker with your wiggy. With the breaker still off, "Jump" the breaker with the wiggy's probes by placing one lead on the bus where the breaker taps in and the other lead on the Load Terminal of the breaker with the affected fault. If there's a voltage reading the fault still remains [or there is some load still connected]. When no voltage is shown across the breaker, then the fault has been located.
Only after the wiggy shows no voltage do I reset the breaker.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
I work in an industrial setting so we are under the gun to get the power restored quickly, but I also usually know what caused the trip( forklift ran over a cord). I try to determine the cause but after reading this I sure will be more hesistant about just throwing the breaker back on, and I do always stand to the side and look away before resetting any breaker, has gotten some strange looks and comments from people though.
I am always very careful about turning on breakers because I did once where a dead ground fault was present in the circuit--the breaker didn't trip, sparks started flying and then the bus melted before my eyes(after I jumped back about 15 feet)
OSHA 1910.334(b)(2) requires: “Reclosing circuits after protective device operation. After a circuit is deenergized by a circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized. The repetitive manual reclosing of circuit breakers or reenergizing circuit through replaced fuses is prohibited. Note: When it can be determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, no examination of the circuit or connected equipment is needed before the circuit is reenergized.”
Thus, the only time you can resett a circuit breaker without inspecting the cause is if it is a known overload. Also, when resetting a circuit breaker, I agree with Ed's comments as a typical practice.
I know what mean about those strange looks spkjpr. LEFT HAND RULE ALWAYS!!! i use it on machines breakers buss box everything. one of the younger guys said what are you doing are you scared you wired it wrong. i said no you have never seen one of these blow have ya, my face aint the greatest but i love it just the way it is. LOL.