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.

#electrician #electrical #electricity

[atmacm]

I’m glad you made this video. You’d be surprised how many electricians don’t realize the difference between ground faults and short circuits.

[Sparky-wwre]

If your having trouble finding if you have a ground fault or short circuit, and tried removing appliances, turning wall switches off with no success, then you know the problem is within the building. Because grounds and neutrals ultimately end up at the same place in the main panel, what you might consider doing is removing the neutral of the problem circuit from it's bus bar, then check if you have continuity between the hot coming off the breaker and the neutral. If you don't, but you have continuity between the hot and ground bus, you narrowed it down to a ground fault. In either case, ask yourself, what circumstances changed? Ex. an electric heater was being used for an extended period, and you smell burned plastic near a receptacle, see wisps of smoke, and now the breaker won't hold. Perhaps you heard a pop or crackle, or seen a flash, before the breaker tripped. You narrowed it down to a ground fault in the building wiring. Upon pulling devices upstream of the space heater location, you find a wirenut had burned off the hot wire and is touching the metal box. Not all troubleshooting is going to be so simple and logical, but you get the idea.

[dmeemd]

This is good stuff, you don't have to be in the electrical trade to need to learn the stuff I understand it, which is what I appreciate about this channel. People have trained in HVAC, I have sent them your way to do some homework. Videos like this being a perfect example, because I tell everyone, if you're not putting in time off the clock as well you're never going to succeed or learn what you need to learn or need to know

[JCWren]

This should be obvious, but never test continuity on a live circuit, e.g., using the meter in continuity mode across hot and neutral, hot and ground, or hot to hot (for 220V). A Harbor Freight quality meter will be destroyed, a good meter will blow the fuse. While electricians don't typically use this, but there's a device called a Time Domain Reflectometer. It fires pulses down the line, and measures the return times. It can find shorts, changes in resistance, and open circuits. You can also measure the length of the wire if you know it's velocity factor. They're not crazy expensive, but they're not cheap either.

[igintell]

I'm a green maintenance tech and this video helped me out a lot.

[Stones_Throw]

An excellent explanation. I would have only added the step of unplugging/disconnecting the load from supply wiring to isolate and narrow down possible causes.

[pdk]

Prior to continuity check, It seems a very important step is to disconnect the device from the supply neutral (and hots) otherwise the bonding at service panel will not allow you to differentiate between neutral and ground.

[MakeNoise]

Remember when testing resistance or continuity remove power or turn off power. Thanks for the info, helpful.

[colinstu]

"Finding the knowns" … yeah, that's an amazing troubleshooting step - and applies to all kinds of stuff including outside electrical. I can't tell you how many times someone asks for help only to find out they skipped all the easy stuff to check, didn't "look for the knowns" and is struggling off in some completely unrelated area because of it. I always step ALL the way. back, start from the beginning/scratch, and yeah, go thru all the knowns and go from there.

[Sparkeycarp]

We had a job subbing for a company that had a contract to move all the service meters from the panels on the sides of mobile homes to pedestals in the front corner of the houses. They ran all the new supply lines under the houses to the main panels. Our job was to solve all the ground to neutral faults in the whole park. As well as replace some very old or under rated panels and any other problems. I did all the troubleshooting with my apprentice helping. We had to open and disconnect a lot of wire nuts. First thing we always did was pull the electric dryer cord. A lot of those are neutral bonded to ground. Keep up the great videos. Still learning and finding better ways to explain things to apprentices and customers. Even though I have my own company now.

[JohnThomas-lqqp]

I'm a retired sparky with over 50 years in this great trade. Several times I have came out and found that a circuit breaker trips as soon as you turn it on. Unplugged everything & turned every switch on that circuit off and problem did not go away. Could not pick up and grounds on either of my VOM'S. Used my expensive Fluke combination VOM/ Megger. Did not pick up a ground at 50 volts but got a low resistance reading using 100 volts. One of these was caused by water that halve filled an outdoor receptacle box. Another time old rubber insulated wire had broken pieces of insulation allowing two wires maybe seperste by a hair. If I had 10 devices on a circuit would try to guess middle point and disconnect wired then flip the breaker.

[FRERUNNR]

Needed this today. Came across someone’s shoddy work and just immediately stressed out when I opened the j-boxes. Hopefully when I go back on Monday I can solve my problems.

[trentthompson]

I'm in hvac but we do some of our own electrical. Making me a better tradesman. Thank you

[keltonfoster]

Man the way you explain it makes me understand it much better, thank you. That mentor you had is the man. Knowns is what will help you pin point the issue.

[williamcash]

i am a master electrician and hvac tech over 30 years .I am disabled now .Everything you said is correct .the first thing l was taught about electricity is it all ways looking for the ground and you don`t want to be the best way to it! all ways turn the load off before turning on power!Because a loose connection under a load is the same a welder. it heats up and makes a bigger gap and bigger arc every time load comes on! and a breacker matches the size wire to protect the wire from heating up and burning!The nuetral is the designated path to ground and it just as hot as the power wire under a load!

[berthongo]

We would get sent out to work on a customer's turbine with a "known" issue. That is, until we got on site and found that the customer's "known" issue didn't make sense. I finally figured out that the best thing to do was to start shooting the breeze with one of the operators and find out what they were trying to do when the "known" issue popped up. It usually had nothing to do with what the office people said it was. It usually also pointed out that they did something stupid or that something else on site caused the issue to begin with and the turbine was collateral damage. Really cut down on the troubleshooting. Know your knowns. I like that.

[firdausravindar]

Thank you for uploading this precious educational video on YouTube.😊😊😊

[ryanhoffman]

Dustin, could you please do a video with tips and tricks to troubleshooting with both a multimeter and a clamp meter? I’m an industrial electrician that’s been with my company for a year, and I’d like to get into service calls and learning how to use my meters to help with troubleshooting. Love your videos, and I would appreciate it a lot. Thanks in advance if you do this.

[Sembazuru]

There may not be "continuity" as defined by your DMM when a device is turned on. This is because the continuity feature of DMMs beeps below 1-2 ohms. But the actual load may be hundreds to hundreds of thousands of ohms. That said... __NEVER__ use the ohms/continuity reading of a DMM on a live circuit. You'll either blow a fuse in your DMM, damage your DMM, or explode your DMM (depending on the voltage across your DMM leads when you take the reading and the safety features inside your DMM).

[arthurburke]

Fantastic job on explaining how to troubleshoot a circuit issue! Many times the first thing people think is that it must be a wiring problem without considering the possibility that it could be something running off the circuit.