What Does Available Fault Current Mean?

[@andreismirnov7200]

Good video, thanks! How do you calculate this Fault Available Current?

[@IceBergGeo]

That's a whole video in and of itself. It has to do with %Z of the transformer, the size and length and number of conductors. Some specific loads can also affect it. (Think anything can store a charge/energy - motors, capacitors, etc.)

[@brian21m33]

Exactly what I was wanting to know. The term "available fault current" is pretty self explanatory. An example calculation would have been nice.

[@jeffwooton7138]

You killed me with Johnny 5 showing up everywhere. Just want to thank you for what you do. I've dealt with construction for a long time. I've always respected electricity, but never wanted to learn about it. My thirst for electrical knowledge has grown, and you are my number one go-to YT channel for gaining knowledge. Keep up the awesome work.

[@jamesr.dubose6469]

Totally agree!

[@tiggeroush]

This is so that someone like me can come along later and calculate arc flash/arc blast, and know what cal rated safety equipment I need to have on before doing none service work on the equipment. Not service as in Service Equipment, but service the equipment. Power the equipment down, or back up when finished. Not working on live equipment ether... All of that to say; so I can put on safety clothing, turn off the power, and test to see if the power is off. Take off safety clothes to work on what I need to work on. When finished, put safety cloths back on and turn the power back on.

[@soccerstylez8705]

Yes sir... I was gonna comment saying he should of stated the purpose for it, but hopefully those who were wondering that scroll down to your comment.

[@MCP647]

Been enjoying your content for a while now but really got a kick out of the Johny-5 cameos in this one.

[@paulblissenbach8641]

Johny 5 popped out I spit my coffee out. Thanks for that

[@mrnade333]

Johnny Five is (still) ALIVE!!!

[@ThegrinchsaysLEAVE]

Assuming it's Drake or the new-ish guy helping him, but awesome placement of Johnny 5! love it

[@PatrickTorsell]

Number 5 is alive!

[@cliffgrexton3760]

Love your videos they are getting so much better and 2 thumbs up to the video person

[@stevenscott6337]

I'm a second year electrical instructor for ABC of Iowa's apprenticeship school and absolutely love using your videos to incorporate into my lessons. I really felt my age on this one when I had to explain the "robot" that kept popping up when saying "Short Circuit." Not one of my fifty students between two classes had heard of the movie. I'm going to have to go back and watch it again. ("Hey laser lips! Your momma was a snowblower!")

[@bjkofron]

Number Five is alive!

[@jamesr.dubose6469]

You are”The Man!” Thank you so much for the through and detail information.

[@MrBanzoid]

I'm in the UK and our codes (we call them regulations) are different but I still enjoy your informative videos. Thanks very much.

[@Sal_needs_Salt]

Hey Dustin, amazing content! I was wondering if you could explain more on floating neutrals, harmonics, etc. I don’t know what these are, I’ve just heard them in practice exams. Thanks!

[@jacewhite8540]

Harmonics have always confused me

[@electricianron_New_Jersey]

Just know that harmonic currents are developed when several small motor loads are used in a 3-phase system. Appliances such as commercial computers and printers will cause chaos to the grounded neutral conductor on that particular circuit. Fluorescent lights on a circuit like that can cause the lights to flicker and flash to the point where one cannot stay in that room for long without getting a headache. Dedicated circuits fixes this problem.

[@Mac19124]

Floating neutrals are , assuming I'm not confusing it with something else LOL. Say you have a 2 Gang Box with two separate circuits. When you tie the box together you may or may not tie all the neutrals together. In your electrical panel out of those two circuits if you were to disconnect a neutral from just one of the circuits you would still have a neutral going back to your panel because you tied them all together in the 2 gang

[@Mac19124]

@@electricianron_New_Jersey great explanation. To add to it, this is why a lot of office areas with lots of computers actually are spec'd to have isolated ground circuits for the computers

[@DonaldEMinor]

I suggest being very cautious working on commercial panels and anything connected to them. Always use your own locks to lock out panels too. Here's why a long time ago I was sent out to the city of Delaware to remove Corkscrew pump motors for sludge along with another employee. We got there and the panel was lockout by the Administration there. Most would think that OK. No, it's not when you're working in a commercial environment. You need to be able to open that panel so you know what's connected to it. That panel may be running many things you never know unless you open it. I suggest you always use your meter in that panel to see if there is any voltage present in the panel after the hammer on the disconnect has been thrown. I've worked around place up to 23,000 Volts. You don't make mistakes with it and live to tell about it too often. Here's the reason to be checking the panel and always practicing good safety habits. On this job, we went to disconnect the wiring from the motors. The guy that was with me laid down on the concrete floor and started to remove the wires as did I but I did lay on the floor because I did trust the locked-out panel fulling because could not confirm the panel is dead. As he started I heard him yell. I looked over and saw he had just been shocked. He bitching now because the neutral was hot and it bite him Good. He looked at me and ask why I had been shocked. I told him I never trust panels lockout by someone else that I can't confirm are dead. That's why I did lay on the floor and become the ground... I had rubber sole shoes on that saved me from that shock. Something was back feeding the panel of something that was holding a charge just wait for him to reach in and grab it. He was lucky we were working with 460 at the time or it could have been worse. Not all things are predictable with electricity also I have seen things happen in the field that can't be explained. Condition change, things are change, and are not always marked even though they are supposed to be. Motor and machine can build static electricity and they can pack a punch also nd could kill you. Motors with the rotors taken out can build static electricity just sitting there and must be grounded when working around them. A motor that you can walk through build lots of especially without the rotors in them, enough they could kill you. I saw 10ph motors sitting on the bench being cleaned out after being rewound them do it. These are good reasons to always practice all safeties, they could save you a lot of pain and maybe your life...

[@hikarushindo9131]

Love the Johnny 5 pop ups

[@AJA48]

Aloha Dustin from Hawaii, I’ve been watching your videos for four years. Keep it up. I’m kind of a DIY electrician at home. Thanks

[@Forest0922]

I know with PV systems when we have 400a or higher services we are required to go from the breaker on one split to a 200a fused disco and then to a 200a main breaker in whatever panel before we tie-in our breakers for batteries/inverters due to fault currents. Your explanation here now makes sense as why. Also depending on AHJ and how far the transformer is from the service entrance sometimes it's required with even normal 200a services. Thanks for the explanation.

[@garbo8962]

Just one thing in large buildings you must be extra careful on all of the fault ratings on large circuit breakers. At the large hospital that I retired from boss had us remove a dozen 600 to 1200 amp spare circuit breakers from one switch gear room to another and rack them in to make it easier for company performing yearly PM. the ones we moved only had a fault current of 65 KIA while the other location had breakers all rated for over 100 KIA. Entire equipment is only good for lowest related IAC breaker.

[@rx7addict]

This only matters if the available fault current is actually above the 65ka rating

[@mr.c3928]

Once again Dustin, thank you!

[@blackzexe]

Bro, I wanna thank you for these educational vids. I recently got my Journeyman ticket in Canada and I still don't quite understand how a lot of stuff these stuff works. haha Your videos makes it way more easier to understand!

[@yacovbil9711]

Love your content man !

[@allenshepard7992]

I like the term Impedance because impedance is more prevalent during inrush currents. Resistance is always there, even when the voltage is off. So how do you do the calculation ? Transformer impedance, voltage, length of cable and raceway vs. conduit. One guy put a 3/4 wrench on the back of the buss bar and then went around to the front to re-torque the bar in a motor controller. Yep two things happened. 1) we did not ohm out the system. 2) They left the wrench in the unit. Panel where not put on because we needed to take voltage and current measurements live. I will never forget the deep thud felt in my chest from outside the room when the break was turned on. No injuries. No fires. Very little damage as the plasma liquefied the metal and blew it away.

[@firsttimeforeverything941]

🤣 Johnny 5 is alive! I couldn't stop laughing. Good info too!

[@brianosgood618]

So, how do you calculate the available fault current and why is it important that commercial entrances be so marked? Thanks for the great content.

[@tiggeroush]

it is used to calculate arc flash and arc blast so that someone can know what safety clothing they will need to put on. see my other post here for more details.

[@electricianron_New_Jersey]

The short-circuit current rating (SCCR) is needed to to clear a fault and trip the main disconnect. Take a look at a main breaker next time for a 22K or a 10k SCCR number on a panel. If you install the wrong SCCR main disconnect the disconnect (Main Breaker) could explode from excessive fault current flowing through it.

[@carultch]

@@tiggeroush Ark = a boat built by a man named Noah, according to the Bible. Arc = the electrical problem created by ionizing the air and turning it from an insulator in the normal gaseous state to a conductor in the plasma state.

[@tiggeroush]

@@carultch yes, but; ark of the covenant was not a boat... and geometry arcs are not normally used in electrical.

[@carultch]

@@tiggeroush I'm aware of both of those. I don't know what ark means in general, maybe it was a term that was transliterated from two unrelated terms that both sound similar. Noah's ark is the most common one that comes to mind, in my opinion.

[@carloslocsin1532]

thanks sir dustin..your videos were a great help in my teaching..🙏

[@brittanylyn7042]

Dustin! Been following you for awhile and learn so much from you. I'm learning motors now and went to your channel first and foremost. Nothing! Can you do an "overcurrent vs. Overload"???

[@edwardbyrd7667]

I hadn’t thought of that movie in years. Thanks

[@JSailor1964]

the editor did a great gob

[@333tubed]

Just watch this video and the breaker interrupting rating video and I really appreciate the explanations! The only thing missing is a calculation. How does one figure out where to use a higher aic breaker? Do we have to measure primaries, secondaries to find the available fault current?

[@ryanstubbs3211]

No disassemble #9!

[@mcroccaro]

I dont know if this was a coincidence or not. But I asked for this video and here it is! Thank you for doing this.

[@KevinCoop1]

Dustin, You answered the question about what “available fault current” is but said not one word on why it is important nor what happens if the equipment installed is not rated for the available fault current when there is a “short circuit”. Hopefully someone taught you the WHY we need to know how much is available. Respectfully, Kevin

[@ssaraccoii]

Have had to have disconnect switch fuses replaced with specific current-limiting fuses because the motor controller is labeled for 10kA max, but the circuit can deliver significantly more. Check the load labels, and your supply labels because sometimes the electrical engineers get surprised.

[@Qazxswer68]

No disassemble!

[@mdawg8770]

The name is pretty self explanatory, I'm sure explaining why it's used is more beneficial

[@wasimedoo7994]

Very good information bro keep it up

[@mattdiehl83]

Do you plan on going through the calculations for the AFC ?

[@KevinBenecke]

I have a question about the arc fault circuit breakers. Maybe you can do a video on this. How does the arc fault circuit breaker know the difference between a device that is designed to create an arc such as a gas stove that has electronic ignition that creates an arc to light the burner and an arc between a wire and a metal box for example?

[@rupe53]

you forgot to mention carbon arc lamps and arc welders. OTOH, I doubt these items will be used in a bedroom where AFCI breakers are required.

[@danjacob755]

thanks would be happy if you could kinda lead through electrician license exam questions and stuff. ppl like me would watch u all day

[@kevinarmstrong1650]

Ok in this video you Mentioned that the highest fault current would be Line to line, but in my on the job calculations on the city engineer give me a much bigger fault current for line to neutral than line to line. Thus I use the larger of the two for my placard, line to neutral. But I just can't see how there isn't more available between lines like you said.

[@MontyRL]

Dustin, could you make a video on how Electrical flow actually works? Been seeing a lot of videos that haven't really explained it well for me. They speak of unconventional things that are entirely different from what I've encountered. I ask you because you explain everything so well. Thank you, and hope you see this comment

[@markwadsworth1254]

Most split phase household services have the neutral and ground circuits connected directly so there is no difference between a fault current and a direct short fault as I understand for households. A distinction can be made for 3 phase power since a ground fault would not be the same as a direct short between phases. 280v to ground vs 480v ptp difference in the USA if memory serves.

[@ericwalden8979]

Thanks for doing this video!

[@Eddy63]

Good explanation and some good ole code book review ... Thx ...

[@robertball3578]

If the fault is in a branch circuit, won't the fault current be limited by the main and branch circuit breaker? I had a disagreement with a guy at the utility, same guy said my site plan was wrong, the house faced north, not south as shown on plans. The plans showed ground mounted solar, the PV panels face south, not north so that should have been a clue.

[@MrAbz92]

Hi, I have a problem understanding this concept at my work, thank God i found your channel. I ran into a situation where I'm asked to design industrial air compressor protection. The compressor is 150hp recommends using a time delay for class J fuse to be used in a circuit not more than 65KA symmetrical rms. The compressor is fed from an MCC with 350A CB, however my question is why I can't just use this CB as the only protection even though the recommended is a time delay fuse by the compressor manufacturer. Can I just stick to a CB at the MCC feeding the compressor with a general disconnect switch?

[@talbertadams6586]

I guess you explained Available Fault Current's meaning, but how do you determine the amount?

[@itskerbs]

There's a bit of math involved but if you're in the field and need to figure it out, the easiest way would be to use the Eaton Bussmann Fault Current Calculator app. Dumbs everything down to where you just need to input certain values to get your available fault current

[@carultch]

The short answer, given no complications, is that you can determine an upper limit to this by looking at a transformer's KVA and impedance. Calculate the amps associated with the KVA rating, and then divide by the impedance as a decimal. So for a 300 kVA 3-phase transformer at 120/208V, the "amps associated with KVA" is 833A. If the %Z impedance is 4%, convert this to a decimal as 0.04. 833A/0.04 = 20.8kA. When you know information about the feeder length/size/material/conduit, you can reduce it from this, accounting for the impedance of the feeder wire. You can also calculate it across a transformer, by considering more information on the primary side to reduce what it will become on the secondary. The above short answer, assumes "infinite bus", meaning that primary voltage * primary fault current is infinity. If you graph secondary fault current vs primary fault current, you'll see that the graph eventually approaches a "cruising altitude", and we call that "cruising altitude" the infinite bus fault current. There is a complication when you have motor loads that contribute their own fault current.

[@electroduval831]

I’ve gotten the numbers from the utility the few times I needed it.

[@M82Predator]

What do you do if you have to work on energized equipment that is above 40 cal/cm2. Wear your CAT4 gear and be extra careful? Or are there other measures in place. I dont remember there being much in osha 30 on energized work above 40 cal. Thanks.

[@chuckhickman8093]

@Dustin would you be able to do a series on PLCs? Hopefully Allen Bradley Micrologix plcs

[@joeSHMO8347]

No disassemble!!

[@vicenteasaro1823]

I consider fault meaning as to an unplanned change in the system or environment that influences the operation of the system and environment from then on as something that now needs to be accounted for. Thus enter the wording for fault in electrical systems, it needs to be accounted for when an unplanned short circuit happens.

[@jarrydee2799]

hahaha Love Johnny 5

[@pierrebelarge892]

You mention several times that a "ground-fault" is not a short-circuit. It is a type of short-circuit. Available fault current is a misunderstood topic for many electricians, part of the reason for that is the misinformation that is presented on a daily basis, especially on the internet. The 3 main types of short-circuits are: 1. phase to neutral, 2. phase to phase, 3. phase to ground (ground-fault) - which does not fault to ground/earth.

[@rupe53]

I just had a brain flash: The service entrance cable and anything else before the main disconnect seems to have the biggest variable. Just because you only have a 200 or 4000 amp service, it doesn't stop there. The pole transformer(s) are rated higher and those can run several hours at 140% of their rated capacity. It's very likely they can even run 200% of the stated rating for many minutes. Something tells me this type of fault might only be limited by the fuses on the high voltage distribution system. IOW, a shit load more that you can imagine!

[@aliosman3543]

Thanks dear

[@commenter5469]

To be totally truthful - ground fault is a short circuit fault, but the intentional protective function at that.

[@kgt9535]

Thanks for this video, for your channel and for the invitation to suggest topics, Dustin. With that said, "Typically, how are generators sized per code with calculations, please?"

[@jasonparkinson7621]

It would be good to know how to do fault current calculation.

[@NickFrom1228]

OK, show of hands. How many people don't get the little robot popping down when he says "short circuit"? For those that don't know, it's a reference to a movie that has nice software.

[@musicianu]

It's from the movie called SHORT CIRCUIT! His name is Jonny 5!

[@NickFrom1228]

@@musicianu Yes indeed.

[@martinlally4050]

Can you try to explain why sometimes my lights with led bulbs in them flicker sometimes for no reason. Switches were changed and breakers were changed but problem comes back. Most of the time it does not happen. I can not make it happen and it is so random. Does not happen with non led bulbs.

[@uhighsmith]

Is there a formula to find out what the AFC would be?

[@petercampbell4220]

The biggest effect is the transformer impedenance, the conductor size is a smaller effect.

[@Jgawalters72]

If the two hots from the transformer connect, will that cause the transformer to blow or trip? Basically, is it possible for a house or business to create such a current draw from the transformer that is trips or "blows".

[@wirenut9062]

I have a town inspector that wants the AIC rating for a residential 1 family 200 amp service upgrade

[@nathanburt8139]

What is the problem with bonding your neutrals and grounds in a sub panel IF you use a ground rod and ground each sub panel? Might be a dumb question but I was just curious.

[@agnusviolan1808]

Johnny 5

[@nlee2492]

JOHNNY FIVE, IS ALIVE!!

[@MP57719]

Do lineman follow nec or is their a different code they follow?

[@trelljiles]

10+ year Electrician here...any suggestions on what to study to pass a test to become a Electrician for a city?

[@ryantschaper]

Can you talk about SSCR or Short Circuit Current Rating for Main Breakers? What is it, how do you calculate it, and why does it matter.

[@AOZMONSTER]

Typically, SCCR of the equipment or panel is going to be the lowest SCCR of all the devices in a circuit. You can check out the Annexes of NFPA 79 or UL 508a for more detailed descriptions and calculation methods as well.

[@traditionaltools5080]

At 1:47 you say it's not a short circuit. Then at 3:02 the actual code definition is a short circuit. What a word salad without actually saying anything. Available fault current is very simple to explain and calculate.

[@vaulmoremack3072]

What would the process be like for someone to migrate to the states get enrolled and educated in electrical and start a career ?

[@Femur15]

Dustin, is that Robot looking for Stephanie??😂

[@tommays56]

My company got really intense on labeling everything to this standard WITHOUT educating the maintenance staff on ARC FAULT SAFETY and limits of there job

[@Jay-fp8iy]

In tennis a fault is when you stuff up a serve. You get 2 serves per point if needed.

[@superman_pnutpnut8098]

Hey Dustin my moms hallway light doesn’t seem to be getting enough power to it how do I check to see and how to check to see what could be the issue with it. Like I turn the switch on and it doesn’t come on but when I put my hot checker on it it says there’s power but the light won’t come on?!

[@affluentj4992]

Please explain floating nuetral

[@balexan530]

So how do you calculate Available Fault Current?

[@goodnightmr5892]

Johnny Five is Still Alive…

[@thomasschneeloch6054]

Dustin love the channel love the content I have a question about a three phase service for generator which I'm sure you covered in previous videos but I need to ask it anyway because I might have not completely understood it. I have a scenario that involves a generator producing a three-phase supply not sure if it's Delta or y but I am reading 208 across to phases. So my 2 million dollar questions are what video do I need to watch again to understand it? And how bad of an issue is it if I connect a single phase service to a three phase line? Thank you

[@ivandiaz5791]

You have a wye-connected 120V/208V three-phase generator. 120 volts from line to neutral, 208 volts line to line. No, you cannot feed a single phase service from this generator, you have no way to provide line to line 240 volts. You can feed power for a three phase panel and use only 120 volt circuits if that suits your needs.

[@johnwalker890]

Not to sound stupid or anything like that, I went to trade school 1993 for electrical maintenance technology, and I keep running across air conditioner condenser units that have the white and black wires in cable that is sometimes romex and sometimes outdoor cable or exterior cable and they use the white and black as both line hots and ground is grounding and is usually 10-2 w/ ground and think that is a waste of money and time to use 10-3 w/ ground because there is no need for a neutral. So my question is, is that code today, because my instructors of school all said as long as you mark or identify the white wire with black or red tape or shrink tube it would be code back then.I looked in my 2017 code handbook and could not for the life of me find it, maybe my eyes are going bad ,but could not find it. But do you or one of your friends know about this? Would appreciate a response, thank you Dustin.

[@marcovaldez9059]

Hello, i want to learn electricity i don't nothing which online course can you recommend me

[@ElectricianU]

We have courses on our website: electricianu.com

[@farmertony4504]

Johnny 5 dropped in.... LOL!

[@charletonzimmerman4205]

How about Power Factor ?

[@carultch]

You asking for an explanation of the definition of power factor, or are you asking for how power factor affects available fault current?

[@jamest.5001]

So it's not , if it's over current, it's not the electricians fault!

[@terrykerger8670]

Are your robots out for hire? Need experienced electricians.

[@seniorcomputer3292]

Trying to say “Closest to the transformer.”

[@michaelmolter8828]

The number of electricians I’ve heard explain this and SCCR incorrectly is uncomfortable.

[@charliehustle544]

Now that I know what it is, my question then would be, Why is it important to know the amount of 'Available Fault Current'?

[@charliehustle544]

@@jb9072 Thank you. Now this topic makes perfect sense!

[@The_Boiyo]

Ha ha get it cause johnny 5

[@affluentj4992]

PLEASE EXPLAIN FLOATING NUETRAL.

[@latexroach]

Yo

[@DesmondLagal-ti2ww]

Is the line fault, earth fault?

[@AOZMONSTER]

You made a video on AFC and didn't even mention SCCR... My man, you did me wrong.

[@michellet_thatsme]

Fault = Mistake or Error lol 🙃

[@DamonJohnCollins]

This is probably part of your master plan, but this will bea good lead into the arc flash requirements of NFPA 70E. I'm no engineer, but we have had to calculate this for all commercial panels (not just the SE). Good luck, this is a tough subject.

[@scottsparky1]

So in English this is the PFC

[@gltovar]

Here is a question, when I look at residential power lines there can often be all kinds of "doodads" installed on or adjacent to the power lines. Would be interested in a video that goes over what all that stuff can be.

[@jeremynguyen2346]

What is the video about

[@nhzxboi]

It's your fault, not mine. You being the utility. Give to me and I'l calculate the downstream fault currents. Gotta know the power at the front to determine the fault downstream. River rules the stream.