What is the Difference Between a Short Circuit and a Ground Fault?

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Troubleshooting can be one of the most daunting tasks an electrician can face. There are usually just so many variables to consider when trying to figure out what went wrong or when something isn’t working. In todays episode of Electrician U, Dustin answers a follower’s question regarding the difference between Short Circuits & Ground Faults and the values you should see on your multimeter when testing for them.

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While the terms Short Circuit and Ground Fault seem to be used frequently and interchangeably, they are in fact quite different from one another. Think of a Short Circuit as a Short Cut, removing the load from the equation, and providing a path for the circuit to make its completed loop to the source of power. By doing this, it generates more amperage than the breaker is rated for, and the breaker trips. A ground fault is simply where a hot conductor has come into contact with something that is specifically grounded (maybe the grounding conductor itself or the case of a piece of equipment that is grounded, or a box/conduit that are grounded) and providing a return pathway to source. Either way, both of these scenarios happen BEFORE the load and in doing so, result in much higher amperage than the breaker is designed to withstand so it trips.
A great way to diagnose your power issues is to use your multimeter. There are two functions of said multimeter that would be helpful in this situation. You could use the OHM setting to check for resistance in the circuit. However, if you did not know the EXACT wiring of the circuitry, this would not be the most helpful of the functions. If you were to check between a hot and a neutral, you would most likely get the same values as checking from hot to ground. This happens as the grounding conductor AND the neutral conductor are run in the same conduit and have roughly the same length. A better choice would be to use the continuity function of the multimeter. If you are measuring before the load, you should not have continuity between the hot and either ground, neutral, or another hot. Once you figure out which two wires are completing the circuit, then you have found your problem!
Another great journeyman’s tip when troubleshooting is to gather as much information as you can about the situation and find out as many KNOWNS as you can. How much amperage is it supposed to draw? Has it done anything like this before? What exactly happened when it faulted (was there a shower of sparks, or a loud boom, etc.). A great one to ask is “did anyone perform any work on it recently? And if they did, are those folks available to speak? If something used to function, someone performed some type of work on the system, and now it doesn’t work, usually means the malfunction is either located within the work they did or is a direct result of the work they did. So, be a detective of sorts and gather as much information as possible. Use those KNOWNS to mark off the UNKNOWNS and it will narrow down the areas you will be looking in. It is also helpful to pull back and get a higher altitude look at the situation, then dive down into the details. Doing this in multiple areas of the whole system will help you eliminate possibilities, so you aren’t chasing demons throughout the entire system!
Also, remember that breakers don’t just randomly trip, and fuses don’t just randomly pop! There is a reason that they do. So, it isn’t prudent to just attempt to continue cycling the breaker until the equipment stays on or replace the fuse with a higher rating (or bypass the circuits protection entirely!). Something has happened and the breaker/fuse is just doing what it was intended to do! The appropriate action would be to diagnose the problem and then correct it!
We hope this has been helpful in understanding the difference between a Ground Fault and a Short Circuit and given you some useful information for troubleshooting an electrical problem. Please continue to follow Dustin and Electrician U as we are constantly updating our content to assist our followers in becoming the best electricians that they can be.

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