Arc flash breaker failure - let's open it

[@randycarter2001]

The bane of being a repair technician. "It has to be broke while you're looking at it." "If it ain't broke you can't fix it."

[@IustinianP]

Made my day😂

[@uzlonewolf]

Which is why I say, "If it ain't broke, fix it until it is" 😂

[@bigclivedotcom]

Which is also why blanket lock-out-tag-out is actually nonsense for active troubleshooting.

[@bradprimeaux8443]

A maintenance person's worst nightmare: "Intermittent"

[@Murgoh]

Yes, I work as a heavy truck mechanic and there have been countless times when a driver says something is wrong, something does not always work or some fault light comes on intermittently. I check everything and everything works, I read the fault codes, nothing, I test drive the vehicle, everything works as it should and still there obviously is something wrong, it just does not happen when looking for it.

[@argoneum]

At one location a breaker would pop from time to time, and we had to go to the place, turn it on, and it would work for weeks. It is a ground cable, a 40m run. Last week it was already happening daily, so a guy who specializes in finding such faults arrived. I was assisting. He took a meter doing reflectometry thing, and it showed that entire 40m of the cable is solid. No joy. So he took a device his father made, and connected it to one of the broken phase wires (two phases were showing 0.02 and 0.06MΩ to ground, so definitely something was wrong). He made a makeshift grounding with a big screwdriver, connected it to the other pole of the device, and turned it on. While some relay within was clicking he took another part: a galvanometer with amplifier, and two electrodes that looked like ski poles with 15cm long stainless steel spikes at the ends. He started probing, and the meter's needle showed: left, left, right… away from the grounded screwdriver. As he was approaching the place where the fault was the needle would show more signal, so he turned sensitivity down. When he was at the spot he only moved electrodes by centimeters and needle would already change the direction. We started digging, and there was a fault: cable was damaged by people who put a fiber there, we found markings of the excavator bucket (insulation was broken in two places), also the damaged cable was insulated poorly so that water came in, did its thing with electricity, and cable insulation turned into crispy conductive carbon. I asked the guy about the device: apparently there was a capacitor being charged by voltage multiplier, and when its voltage reached certain threshold the relay would connect it to the output. While discharging through the ground it would produce intermittent voltage gradient, probing it would show rough direction where the fault is. It required its own grounding to operate. Apparently his father saw some electricians doing it years ago by hand: charging electrolytic capacitor using a diode from mains and discharging it between local ground and broken wire. Other guy would walk with galvanometer, stick electrodes into ground and find the fault eventually. So he made his own, improved version. No idea if this is patented, simplicity and effectiveness is surprising and satisfying :)

[@bigclivedotcom]

Interesting approach to find a breached outer sheath on a cable. I've had a few instances where underground cables were clipped by contractors and they just buried it afterwards. Very annoying. The utility also uses a device called a thumper to trace underground faults. It charges a capacitor and then dumps it on the cable. It results in an audible thump where the damage is.

[@Gazr965]

They probably knew about damaging the cable but 'ostrich-ed it' probably cowboy contractors avoiding extra cost of repair from the electricity board. Gaz Yorkshire

[@mysock351C]

Rodalco2007 has a demo of a thumper being used on his channel. Seen them, but never in use. I’d imagine they are quite costly, which is why your father opted for rolling his own. Seemed to do the trick.

[@stuart4738]

We had a similar unit for sheath faults. It had a motor driving a contactor to create the signal. It was controlled by a vairac, transformer wtih a bridge rectifier to get about 1000Vdc pulsed (called it a Popie). It used the same duel probes and galvo to sense the current flow. It was all hand built by the old powerboard before I was born. We also had a thumper to locate higher impeadence faults with the headphones. On a good fault you would feel it while walking along. We used to bet a box of pizza for every meter off the final fault location.

[@muh1h1]

@@Gazr965 I used to work for a cable ISP as a field technician and i can tell you this happens all the time. Once I roughly located a fault to a private construction site where they where digging with a mini excavator and asked them if they had seen a cable they might have accidently clipped. Usually when i asked nicely contractors would show me, dig the cable back up, i would fix it and they could move on with their day without even being billed, accidents happen. But these guys.... They where sooooo sure they didn't even come close to any of our cables and that i must be wrong and the fault must be somewhere else, they had me studying plans, locating cables, remeasuring and question my sanity. They also became increasingly unfriendly and hostile, threatened me I would have to pay for any downtime as a result of my fault finding. Eventually i've had enough, called in my own contractors and had them open the exact spot I had been questioning them about hours ago when i came on site, only to find about a cable that was completely destroyed over the length of over a meter. It was also clearly copper with no sign of corrosion so it must have happened probably an hour before i came there. When i showed them they became quiet and then started mumbeling shomething about a treeroot that must have caused this. Not only does tree root damage look completly different, because it is happening over the course of many years, there was not even a tree in sight! That was the first time I billed them, for the materials, for my time, for the contractor and for the downtime to our customers. I was super pissed. This could have been solved within 30 minutes with no cost to them, but they decided to waste hours of my (and their) time because they needed to be absolute dickheads.

[@michaelcherry8952]

The one word that any electrician, mechanic or engineer hates to hear is the word "intermittent". Because you can damn well bet the farm that when you check the circuit/engine/mechanism the fault will be "mittent". The stupid fault runs and hides if it sees someone coming and the whole circuit/engine/mechanism is like "Problem? I don't have a problem. Why are you here?" If this happens often enough, you can see mysterious hammer marks in various areas, caused by professionals repeatedly thumping the offending part and using all of their very best swear words!

[@SeanBZA]

Did trace an intermittent fault to a damaged cable in the conduit. Lucky they would pull through, so ran all the cable in there with new, and found the damaged section where the installer 50 years before had scraped the insulation through, but it had been in air, till the conduit rusted a little and there was some water ingress. then it would trip 5 days after mopping the floor.

[@michaelcherry8952]

@@SeanBZA And THIS is why you have to have trained professionals. To have the knowledge and patience to track down a 50 year old issue that only recently started causing trouble (5 days after mopping a floor, no less!) is (or should be) worth its weight in gold. Clive often talks about the low standards set for electrical apprentices these days and what you describe is precisely why that's a serious problem. A two-week course is not going to make you a competent enough electrician to track down something so hidden and obscure.

[@Mark1024MAK]

Ahh, the lesser spotted intermittent fault. I once had an electronic control system fail while I was on duty. The remote end being twenty miles away. Of course, by the time I arrived, it would be working. Do all the normal checks and tests, no problems found. Leave it on test for a while, all okay. Get back in the van and head back to base. And of course, as soon as I was within touching distance of base, the mobile phone would ring - “it’s done it again! Where are you?”. In the end I found that if I hit my fist against a certain part of the cabinet, I could recreate the fault. But it still took me over an hour to find a dry solder joint on a capacitor that was supposed to be firmly soldered to a terminal post.

[@michaelcherry8952]

@@Mark1024MAK Percussive Maintenance Techniques are valuable skills to have!😁

[@inertnet]

It does give a sense of power though, when you show up and hear someone say: "that's odd, the moment you showed up it started working again". "Yes, my mere presence is often enough for equipment to just start behaving again".

[@chatrkat]

I’m a 60+ yr old semi retired electrician across the big pond. I have worked in service the majority of my career. As a young boy, my father, an electrician his entire life, explained why you don’t keep resetting a tripped breaker. He’s most likely looking down right now enjoying your latest video Clive.

[@zzoinks]

How many times do you think they reset that breaker to blow it up? That sure sounds like sound advice So if you were had to reset it a few times for troubleshooting would that be too much?

[@chatrkat]

@ it is my experience most home circuit breakers will tolerate that for a while no problem. In this case he was working with over 400 volts across the line.

[@mattgayda2840]

​@@zzoinks ONCE... whatever caused the trip can look like the inside of that breaker (or worse). The fault current can be thousands of amps before it trips due to the trip curve so that reset breaker can deliver a surge of 5k to 10k amps instantly which can and will vaporize things.

[@petermichaelgreen]

@@chatrkat 400 volts between adjacent breakers, 230V live to neutral on the individual single phase circuits. Standard setup in most commericial/industrial buildings in the UK.

[@jimwoods9551]

Reset with a stick! I had a domestic RCD drop out very randomly over a year and pretty sure there was no permanent fault in the house, but no way I was going to examine the whole system. Tempted to change the breaker but board was full and messy. Tracked it to the weather - wind and rain raised the frequency - but never more than once a day. Eventually utility supply cable joint blew up 100m down the road. Happy days ever since! It's hard to sit on your hands and do nothing. Great explanation about the carbon track clearing the fault, Clive. Never knew about the reflective injector or thumper test methods, waiting for the bang sufficed!

[@Senior_Mustard]

As an ex-TV engineer and later in industrial electronics, the only certain thing about an intermittent fault is you can be sure you've NOT fixed it when it goes off again.

[@HenryLoenwind]

As a software developer, same here. You won't believe how much code is in a program just to hide and recover from errors that happen intermittently that the devs couldn't find the real reason for.

[@SnakebitSTI]

Yep. Pretty much the reason behind "Have you tried turning it off and back on again?" Something went wrong, but probably maybe hopefully it'll be caught by a safeguard next time.

[@splitprissm9339]

@@SnakebitSTI It was what the customer support of an UPS manufacturer suggested to me with a straight face after a three phase, 8 or 10 kVA (can't remember) rack UPS had failed with a literal g*nshot-loud bang.

[@strehlow]

I could smell that once you opened it.

[@bigclivedotcom]

Strangely it wasn't that bad.

[@mxslick50]

I could smell it before he opened it. Had to deal with this situation many times in my career.

[@lesmaybury793]

​@@bigclivedotcomare you sure you are not suffering from olfactory epithelium deficiency syndrome? I could smell it in Leighton Buzzard!

[@hammerth1421]

I know it's not exactly healthy, but I kinda like the smell of burnt electrical stuff.

[@Sylvan_dB]

@@hammerth1421 For some years I worked in an office environment where the equipment under test and development was a mix of 240v and 120v. The outlets were distinct, but the equipment all had standard IEC connectors and many people who frequently switched out the equipment on their desks had a mix of power cords coming up onto the desk waiting to be connected to equipment needing power. With 80,000 square feet on that open floor, we knew when someone had confused their cords and plugged 240v into 120v equipment. The length of time between the capacitors exploding and the smell arriving gave a pretty good indication where it had happened!

[@gregorythomas333]

I really hate intermittent faults like this...they are so hard to diagnose sometimes

[@Poebbelmann]

Everyone does :-)

[@bobs12andahalf2]

I see what you did there

[@Ariccio123]

The real trick to diagnosing them is having continuous monitoring in place already. REALLY saved my butt several times!

[@mattyb7736]

All faults are either an open circuit, a short circuit, or somewhere in between

[@simonhopkins3867]

​@@mattyb7736 😂

[@JasperJanssen]

For the amount of arcing it's contained that beautifully.

[@gabotron94]

Task failed successfully

[@BTW...]

Not really. The fault was not contained inside the device and it damaged other equipment. Not sure how the CB got the 10kA rating if that happened. A fault higher than 10kA?

[@legominimovieproductions]

@@BTW... We don't know if the distribution panel had proper sized SCC limiting feeder fuses/breakers, also the 10kA rating doesnt mean it can handle a 10kA short and look brand new, it only means that it can still safely cut a 10kA short. Now the problem is that previous reconnections might already have started to char the inner plastics or maybe copper from the contact spread on the mcbs inner walls so that the high current fault then couldnt be properly extinguished because there was a lot of conducting material inside which then led to an unnormal amount of energy being released as plasma and blowing into the next door MCBs.

[@alejandronan607]

I love it when we get some Clive cam alongside the bench cam ❤

[@sparkyprojects]

Unfortunately, when breakers are accessible by the general user (workplace or home), they will repeatedly try to restore the breaker multiple times, even if they manage to clear the fault, the breaker is weakened, carboned up, or splattered with copper. Thise are the breakers that get hot, and especially in a vertical stack, will start making the one above trip prematurely, so you chase your tail trying to find a non existant fault on that circuit

[@djtransnazgrz]

I heard from an industrial maintenance guy something that went like this "If one of the VFDs blows and trips the breaker, we will just slam the breakers until the faulty one is blown clear." This was in response to my surprise at the level of damage inside one of said VFDs.

[@bigclivedotcom]

And the non technical operatives that explain that you just keep switching it on until it holds as if that's the normal way to use the breaker.

[@throttlebottle5906]

@@djtransnazgrz yep, sometimes instead of a branch breaker, it will cause a whole sub panel feeder to go down. reset/reset/reset and look for the smoke emitter or downstream to trip. do it with an extended pole just in case. 🤣

[@ErazerPT]

It's not just in electrical. Anything intermittent is a headache. I'm a soft dev, and the last thing i want to hear is "i was doing stuff and it went pop, but i ran it again and its fine". Some users can give you a pretty good account of what was going on, and logs can help, but for the most part, it's either a very obvious mistake or you'll be looking for needles in haystacks. And sometimes you can't even tell where the haystack is...

[@NoahGooder]

oh my favorite part is the only thing you have to go off of is whatever debug print statements/logging that the developer just decided to enable.

[@spvillano]

Yeah, had some devs that loved to jump to subroutine, never return, so garbage would accumulate and fill the stack. Then, they'd trigger a garbage collect to clean up. Senior programmer had to chase down some issue in that tangle code, finally fixed the problem, called a meeting and went off like a nuke. I took a look and cleaned up a lot of the mess, just to get rid of some aggravation and informed the team, if I ever saw that kind of shit again, I'd solder their fingers together. Given I was mostly a hardware guy, I think that shamed them into better practices. Or maybe they believed that I could solder their fingertips together after they saw me successfully repair to component level a hard to get multilayer board... Of course, I didn't tell them that I'd been a code monkey back in the day. ;)

[@ErazerPT]

@ All code bases i touched became "Logging and monitoring are first class citizens". It's ok to f'up, bugs are part of a devs life, it's NOT ok to waste dev days chasing ghosts just because you didn't bother to log things. I can live with people making mistakes, that's human. Being lazy is also human, but i don't have time for that one ;)

[@Sylvan_dB]

The local electric utility serving my home did the "replace the fuse and it works again" move for many years. The 7.2KV line goes underground at the corner a few hundred yards north of me. That underground line was installed in the 1970s and they replaced the entire run in 2022 (IIRC). Since I moved here in 1998, we had 2 or 3 times per year when the fuse on the pole at the end of the road would blow, leaving the neighborhood to wander the street and socialize with one another. The utility would dispatch a truck, usually with a single lineman who would replace the fuse, close the switch, and we would all retreat inside for another few months. Until one Sunday afternoon when he closed the switch to a resounding KA-BOOM one house down from me and we watched smoke curl up out of the ground. (A large ceramic insulator in the vault had a carbon track the entire length.) It took all afternoon for sufficient crew to arrive on site and replace the connections feeding that transformer and restore power. For another few months. Pattern repeated for several years, and finally after two more incidents where they had to find and replace failed transformer connections, they replaced the entire line. So far we've had years without blowing that fuse. 🤞

[@brianleeper5737]

My parents bought a new house in Virginia in 1988, served by Dominion Virginia Power. For many years, every time it rained, the power would go out for at least an hour. I imagine that they were just replacing the fuse to get it back on. The problem was finally fixed for good when they build another subdivision/neighborhood across the street, and to this day I wondered if they actually intentionally fixed the problem or just accidentally did it when they made the changes to connect the new neighborhood. This sort of crap is par for the course with that power company, from what I've seen. I've seen their primary overhead lines with 5 automatic splices in a row, how does that happen?

[@CollectiveSoftware]

Always love breaker post-mortem teardowns!

[@PeterJ-ij6mm]

This is a classic example of the smoke coming out all at once 🔥.

[@gorak9000]

RUPTURE - Rapid Unscheduled Pop Then Underwear Replacement Everytime

[@PaulG.x]

7:14 It's nice they designed a little 🌙 window in these so that adjacent units can chat to each other and not get lonely as their contacts turn into a plasma 🌩

[@kain0m]

And in all seriousness, these are for external contacts that can detect that a breaker has tripped. It will connect to the external lever as well as the little crescent shape with a small pin.

[@schlabberdog]

The window is for adding additional devices like auxiliary contacts. You'll find the same thing on most (continental) European breakers, but usually there is a plastic cap you have to break off first.

[@antonioadkins5104]

I recently just saw a new video floating around the internet where 2 sub station workers where resetting a large braker inside the controll room of a sub station and when they went to turn it back on they didn't know that the fault didn't clear and the braker exploded causing a large arc flash over inside the braker which sustained itself to the point where it eventually made it's way to from the controll room to the HV lines outside. the whole sub station was a total loss. Thankfully, they both made it out and survived uninjured.

[@BTW...]

One flash and ya ash. Glad they survived. HV is scary enough, let alone flawed operational protocol to ensure fault clearance and sign off before any attempt to close a HV breaker. Tiny sub station? Old? Open form switchgear? ... surely not modern HV breakers and their high arc containment ratings and explosion vents.

[@bigclivedotcom]

There are a few videos like that online. The substations deal with massive current at high voltage.

[@mrDarktrooper]

A classic case of "if it isn't broke don't fix it." well this time it broke.

[@raypilgrim6905]

I know nothing about electronics, circuit boards, but I can sit hours listening to big clive. A very interesting bloke.

[@punktVail]

I used to work at the company that makes these breakers. I worked on some of the machines that make the key components, test the breakers and assemble them. It is exciting to see how outsiders react to the mechanism. it seems to me that the inrush current has exceeded the maximum values by far. That's why there must always be a fuse upstream that can switch off SAFELY at higher currents.

[@steveoddlers9696]

Just wanted to drop a quick rant about how bad youtube's machine translated video titles are, and the lack of an option to turn them off from my end. I'm now testing a firefox addon that's meant to fix that and it seems to do a good job, but some things still slip through.

[@bigclivedotcom]

I had a brief spell of manually auditing the aut-translated commentary, but it is extremely time consuming.

[@GroovThe]

It's interesting how AI is supposedly ready to take everyone's jobs, but in any practical application we still see 2012 era ability.

[@Levo75]

The auto translated titles are absolutely disdainful. Whoever thought it was a good idea at youtube should be relegated to toilet cleaning duties because they like shit so much.

[@DrAHorn]

The machine translated video titles are bad enough. But the machine translated and voiced audio is horrible! I wish we could switch that off, but, alas, we are not Google's customers, the companies running ads are. 🤷‍♂

[@steveoddlers9696]

@@DrAHorn Go into your google account settings and add english to your languages. Then the videos should default to the original english audio track (at least that did it for me).

[@OldGeezerstoolbox]

In my 40 years in business, I've had several electricians sent by the landlord act like I was being really stupid for asking as they insisted that breakers NEVER fail. On at least 3 occasions, breakers had failed--including a 3 phase mains breaker into my machine shop that had never seen a trigger (it dropped only one leg which the machine motors REALLY loved [sarcasm].) Yes, breakers can and do fail. An electrician who tells you it never happens is a greenhorn or goof-ball.

[@Berkeloid0]

Reminds me of those electronics/computer people who handle PCBs with their bare hands and say ESD is a load of rubbish. Invariably they're always having weird faults with their hardware but never seem to cotton on to the fact that they're the ones causing it. They seem to assume that static electricity always kills something completely, and don't realise it can just impair parts of a device and leave the rest seemingly working fine, leading to lots of weird unusual behaviour. But they can assure you it's definitely not static electricity damage!

[@davidg4288]

I lived in a house with a main breaker that wouldn't turn off on one side, even manually. I'd say that's a failure!

[@jeremytoms5163]

Had an intermittent fault on a 11kv dedicated feeder from one substation to another. Cable run was 2 miles, yes 2 miles, long and buried its entire length. Tried resistance measuring to get a rough idea where to dig, repaired the cable, left it pressure testing for 24hrs and re-energised . After finding 3faults, and then blowing a crater in the ground for the fourth time the decision was made to replace the entire cable . £1.5 million ,6 months , to trench, new jointing pits and new cable. Intermittent faults are a real pain 😂

[@cortanajpn]

We had a real inrush issue when I had a load of servers on the same circuit. Their running load was well within the 32A total limit, but the rush when they all started up after a power cut would trip the breaker. I ended up having to adjust the BIOS settings to give each server a different delay after power was restored to stagger the sudden rush of current.

[@cortanajpn]

Also had an intermittent fault with the breakers themselves, and, in the end, the electrician simply replaced them all, which fixed it!

[@bigclivedotcom]

The event industry has sequencers that switch equipment in sequentially. Also good to allow stuff to boot up in a sensible sequence.

[@throttlebottle5906]

you have to factor in the huge peak inrush current and supply enough circuits to cope or use UPS with multiple controlled outputs that an be staged.

[@dogwalker666]

Or cheat and fit a "D" rated breaker, shhhh!

[@nickthompson5025]

A couple notes from the circuit breaker industry. The 10000A figure is a dead short and depending on the claim - the breaker is designed/tested to open on this once or twice- that’s it. Most faults well below that. Arc faults are usually much lower and longer lasting, so what Clive has mentioned with intermittent fault is quite possible. Each trip takes its toll - eventually it gives out. I hope they found the circuit fault!!

[@bigclivedotcom]

After the explosion they got access equipment in and found a melted terminal block in an outdoor junction box.

[@howardsimpson489]

I had circuit breakers in a panel near the ceiling in an old workshop. On really hot days, 40 C, breakers would pop with quite light loads. They could be reset for a few minutes then go again. When the temperature dropped they would stay set. A fan was parked temporarily below the panel and all stayed happy. Because the CBs were not overloaded, they were undamaged. Only two or three days per year.

[@nickthompson5025]

@@howardsimpson489 your description makes it sound like overload rather than short circuit or arc flash. Those circumstances of tripping are far kinder to the contacts. The bimetallic to trip on overload is calibrated for temperature too, so it would not have even been at full load current!

[@BTW...]

@@nickthompson5025 Reads like it's an ambient temp issue, nothing more. Seen the same occur with a Main supply breaker enclosure (3ph - 250A) mounted on a street pole (supply authority property prior to building attachment) that would bake in fully sick hot Western Australian sun. The thing would trip with moderate load... only on those above 40C days. It doesn't help when it's a fully enclosed DB.. or when people cram the pan. eg. 32 CB on a 36P pan. Pays to leave the occasional 'spare pole' space between groups of MCCB's. Same applies to compact contactors mounted on a DIN rail without a gap. TB end clamps space em well... or group no more than 4 in a row. Then with a contactor wide gap between the next group.

[@loganstover5094]

Clive, you are the man. I love the little nuggets I get that would take me 30 years in the trades for these conversations. Keep it up stud.

[@ricknelson947]

I’ve known plant operators that with an intermittent breaker tripping seemingly randomly. To avoid writing up a failure, they would reset a breaker a dozen times until it held long enough to make it to shift change. Then it’s someone else’s problem. I was glad to be a SCADA manager and not an electrician. The SCADA manager just got the call to trend how many times the now smoked breaker was reset before blowing, with time stamps. At least in your case, the Eaton breaker did it’s job well and kept the arc flash mostly contained.

[@bigclivedotcom]

Especially factory workers on piece work being paid per item they make. Machine downtime seriously impacts their wages.

[@mihkus]

Thats a good quality breaker, most 3 phase breakers have overcurrent trip only on 1st phase, the rest are just switches...

[@billdoodson4232]

Had a lot of nuisance tripping on an RCD protecting 10 circuits. Eventually we swapped the RCD for a circuit breaker and turned everything back on again, then waited. A very loud bang from a heating fan that didn't even trip that circuits breaker. New fan fitted and RCD swapped back in again. Sorted.

[@robindeputy]

I enjoy these autopsies. I do something similar with devices damaged by lightning. Catastrophic failures are great teaching tools.

[@HansOvervoorde]

"It went through a phase"

[@jonathansmedley123]

😂

[@dcmoisan]

Or several!

[@zzoinks]

A repair shop (prob. most) troubleshoots shorted computer boards in a clever way. They inject a lower than usual voltage into a malfunctioning board, and use thermal camera to detect heat which indicates there is a short circuit at that area. Then they replaced the malfunctioning components and fix the short circuit. I just think it's cool that they can safely inject voltage into the board to figure out the location of the issue . I'm not sure where else the technique is applicable, certainly probably not a factory floor or high voltage. Because I guess they can't see the entire electrical system under a thermal camera in one go or have it under testing environment. Channel is Dell Parts People

[@bigclivedotcom]

The controlled fault current in electronics is very useful, but does require a decisive short circuit. (Often an MLCC cap on modern PCBs.)

[@paulstubbs7678]

A fairly popular technique, better than it's predecessor (as in pre thermal camera's) where you set the current limit to a bit under what you thing the PCB tracks can handle, then go feel each component looking for a hot one. Sometimes you came away with a manufacturers logo burned into your thumb.

[@Roy_Tellason]

@@paulstubbs7678 That's why I made a temperature probe out of a thermistor and an old pen barrel. Saves my skin looking for hot parts!

[@JoseSilveira-newhandleforYT]

Nothing like an intermittent fault to drive you crazy. You generally only find it, when it goes out with a bang, provided it's not buried somewhere. Interesting talk!

[@mistermeaargee2670]

It looks like a job I had many years ago where an 11kV line came down onto 415V. The contactor in the equipment looked the same and was welded shut, the fuses had vapourised along with many other faults. It was a case of squinting your eyes and using a wooden broom handle to activate the switch and apply power as I repaired it.

[@orion310591RS]

Hahah man, when I saw what Clive has in his hand, I was thinking "OK, from now on, I will activate those with wooden stick"...

[@hattix6713]

I do love these post-mortem investigation videos.

[@WineScrounger]

The instant pull out due to inrush is a huge nuisance but nobody believes me when I tell them they’ll need to unplug some loads, it’s infuriating

[@haroldsmith45302]

This circuit breaker experienced in-fury-ating current.

[@TheExileFox]

In high school and college, teachers told us to not turn the CRT monitors off or on all at the same time. It only took a handful of people doing it in sync to trip the breaker to the computer rooms 😂

[@robboinc1]

Great video clive😊 as an installation spark myself, i found myself nodding along to this video loved the breakdown, great stuff!

[@mcflapper7591]

Yep, done that, seen that. We have some power lines in the ground and some years ago we discovered a "forgotten" outlet rotting. Replaced that, but water seeping into the cable sheath caused the RCD to trip every now and then (RCD still working). This went on for a couple of years and then stopped. After that the breaker started to trip. And again. Resetting it would work except for the last time when it angrily flashed at my finger while pushing the lever up. This was all with very long periods of time in between. November last year the breaker finally had it's moment, it popped and was never to be motivated again. Pushing the lever up to reset it was to no avail. Once replaced I took the unlucky one apart and it was dark and sooty all over in the innards. Just like the one you took apart. Still haven't found what I'm looking for.. (fault). Thank you for this video. Cheers and stay safe, mate!

[@christopherlawler3033]

I've seen this before - when the available short-circuit fault current far exceeds the fault-current rating of a circuit-breaker - it will become permanently damaged as it has suffered damage from excessive fault currents from which it was not designed - or rated for. In North America - 10,000 A.I.C. Amperes Interrupting Current - short-circuit fault current ratings are the most common ratings for small-case circuit breakers that are commonly found or seen in residential/domestic installations as well as light commercial & light or small industrial installations - as electrical services become much larger in size and as the electrical supply utility transformers also become higher in electrical KVA ratings - the available short-circuit fault-currents also become a concern, as fire and explosion hazards do exist when the available fault currents far exceed the short-circuit current ratings of a circuit-breaker over-current protective device as illustrated in your video. Circuit breakers with short-circuit current ratings far greater than 10,000 amperes are also available for situations where the available short-circuit fault currents are available in excess of 10,000 amperes. Other A.I.C. short-circuit ratings could be 22,000 Amperes, 50,000 Amperes*, 100,000 Amperes* or 200,000 Amperes* (*the higher values of these ratings are more common to fuses than to mechanical circuit-breakers, although some certain larger form-factor molded-case circuit-breakers may also be available with A.I.C. short-circuit current ratings up to 100,000 Amperes at a definite up-charge in financial cost.) In North America in particular - with commonplace 120/240V "split-phase" domestic electrical distribution schemes in place - the fault current from only half (120V) of the total transformer secondary (240V) winding will only show half of the total impedance of the total winding coil, where the middle or half of the transformer secondary winding coil is center-tapped to ground - also where the system neutral is then derived from and also tied or bonded to Earth at the utility side of the electrical service drop as well as the system neutral conductor also being tied to or bonded to Earth at the first service-disconnecting means at the premises electrical service as required under Article 250 of the National Electrical Code.(With further digression) the available electrical short-circuit fault current is double at 120V versus 240V due to only half of the short-circuit impedance being seen at the secondary winding of the utility distribution transformer due to only half of the winding as being part of that faulted circuit versus a line-to-line fault across the entirety of the 240V secondary winding - of which is characteristically a low-impedance winding or coil of wire with a grounded tap halfway down the middle where it is bonded to Earth and from which the system neutral point of connection is derived. North America is the only continent where this particular type of electrical system exists along with a 60Hz or 60-cycle operating AC Line Frequency. Although 3-phase systems do exist here also in the "flavors" of 240V (Delta), 208/120V (WYE) as well as 480/277 (WYE) and 480 (DELTA) connected systems commonplace in much larger commercial, industrial and institutional environments where larger equipment is utilized that requires much larger amounts of electricity to be distributed. Canada also uses a 600/347V (WYE) electrical distribution scheme for their larger utility customers.

[@andreasdill4329]

We have this exact problem at our campus. The people installing the outdoor illumination 25 years ago just stuck the lampposts into the dirt. The kabeling runs through a cutout at the side of the metal lampposts. Over the years the lampposts did sink in a bit and now are resting with a sharp metal edge at the kabels. Every time we have a damp windy night that rattles the lampposts one or two phases of the breaker fail (I did change the 3-phase breaker into 3 single phase breakers many years ago). So we check this in the morning and reset the breakers. Luckely at this time the power to this circuit is switched of, so no danger of burned hands. I try to get the renewal of the outdoor lights into the investment plans every year. But as long as it does not burn down itself this is futile. Way to expensive.

[@johnikey38]

Back in the seventies "let the fault develop" was a common saying- if the cause wasn't immediately obvious.😂

[@bigclivedotcom]

Still valid. Some faults have to make themselves more permanent to find them.

[@tncorgi92]

The saying around my place was, "let the next shift deal with it".

[@SeanBZA]

You mean like the council fault tracing, replace the consumer tap off fuse with a bolt and nut off a pole mount, and look for the smoke. as the street wires were open bare copper you could see them shed oxide, and sag down a lot, but those substation fuses are pretty stubborn, and survive that loading long enough to see where the ground either erupted and exposed the damage, or where the steam stopped.

[@muzikman2008]

Love a teardown.. The solenoid plunger is for short circuit protection to quickly disconnect the supply within 0.4s and the bi-metalic strip is to disconnect the supply in the event of overload. Clever design that is reliable on the whole.

[@Atlessa]

One small thing I want to emphasize: "It's designed to break 10000 Amps" yes. But it's designed to do that ONCE. After which it's meant to be replaced.

[@Fantasy179]

Just switch it back on again, it's fine. If it trips again, just try until it remains on. 😅 That's how my father did years ago when the breaker for the stove tripped. Turn it on ten times or more, then it stopped tripping and worked for years without issues. When we moved to another house, we found a charred mouse in the stove, which was probably the reason why the breaker tripped.

[@mfbfreak]

This is untrue. Dive into the datasheet and you can find the actual specified number of cycles at rated short circuit current. It is in the order of 100-500 times depending on the breaker

[@mfbfreak]

If it were a 'once and replace' thing, you're be using fuses and it wouldn't have a resettable lever. Of course the short circuit current specified may never ever be exceeded, and the technician needs to calculate or measure circuit impedance to ensure the available short circuit current will not exceed the breaker's capacity. If it does, you need to buy a different one that can handle larger current.

[@Atlessa]

@ "rated short circuit" is not 10000 (ten thousand) amps though. More on the order of 1000 (one thousand)

[@mrfrenzy.]

​@mfbfreak overload trip can happen hundreds of times as you say (about 20-50A). Short circuit can only happen 2-3 times (10 000A).

[@billygamer3941]

Wow! What a well organised shop. Thank you for the lesson on breakers.

[@ellensburgamplifier]

Us electricitians despise only one thing (besides engineers) and that is intermitent faults. It does take some skill to efficiently and effectively find faults to keep the client costs down.

[@pauldzim]

I was talking to the screen - "Clive, isn't that the other contact connected to the solenoid?" Glad you finally found it :)

[@JendaLinda]

This could be one of the reasons why eletcrtical distribution network is still using fuses.

[@bigclivedotcom]

An HRC fuse has many advantages. Nothing to rust or jam, capable of breaking massive currents and single use, so no unknown history.

[@marcse7en]

I had to ask Alexa, "What's an HRC fuse?" ... She said, "A High Rupturing Capacity fuse, is a type of fuse designed to handle short circuit current for a specified period."

[@BTW...]

So, grid network context... not commercial. Cost and reliability is why they use fuses for streets / customers. Easy to get a good kA rating out of em. Least cost afforded. However, the network distribution industry uses a lot of high fault capacity Circuit Breakers at sub stations. Likewise, a lot of protection/control monitoring that trips those breakers.

[@dav1dbone]

Time domain reflectometery is a fascinating area, amazing to see the accuracy and certainty of digging down to a fault.

[@skygh]

I did one week of training when I got a job at SquareD assembling circuit breakers. I learned so quickly I knew I would go crazy if I returned after training. These are a little more complicated than SqD's but the main components are similar down to the what they termed the arc stack. Interesting how the traces can form

[@WOFFY-qc9te]

The Woofle soot is nicely enhancing the coving detail.

[@GeneCash]

LOL! I had to stop and look, and you're right!

[@bigclivedotcom]

It is odd how it's affected the surface but not gone into the detail.

[@jonathansmedley123]

Thanks just watching your video and thinking logically about my garage always tripping has helped solve our tracking fault. 👍

[@gertbenade3082]

I am not a safety officer BUT do have an opinion: Always install quality, known-brand breakers. As previously tested by Clive, do the ones manufactured from Chinesium have absolutely no overload detection, arc absorbsion or anything of value in them. The are merely ON/OFF switches made by unscrupulous, greedy manufacturers. And yes, I have seen a 3-ph breaker explode inside a TV transmitter when a colleague tried to fire up the old beast. The breaker was splattered all over his hand... Wear the gloves! Great video, thanks Clive!

[@andyreact]

A lesser spotted Clive face on the main channel! 😅

[@andyayres8613]

Still loving your videos big Clive. Keep it up 👍

[@flowerpt]

I had one like these get smoked when lightning struck near one of my solar creations. It saved everything but a 48-12V buck-converter which seems to have saved everything downstream. Very glad I put in a silly amount of breakers. The inside looked very similar to yours. The buck converter was fully potted and I didn't have the drive to dissolve away the epoxy for mere curiosity. These things seem to be well designed to die a meaningful and dignified death.

[@kostasantoniadis5451]

That's why you also install fuses. Circuit breakers are great but you need fuses too.

[@Jbradley612]

I use these Eaton breakers here in Canada, but in the field I'm in I have to use their UL489 type which adds long plastic dividers between the poles. The holes on the side are used for either an auxiliary contact or ganging multiples together.

[@deantiquisetnovis]

When I was young I worked for a plant automation company. Our Machine-Terminals used, at that time fancy, fibre optics for communication with the backend computer. One customer reported that always at a certain time of the morning, but not every day, one of the terminals lost connection and the machine of course would stop. We couldn’t figure out what the problem was, because it never happened when we were there to troubleshoot. So in the end we decided to have one of our technicians to sit in front of that machine, well before the time when the problem usually occured. So, this is what he observed: The sun was rising, the sunlight shone through a window. The bright, sharp sun ray hit the fibre optic cable and basically interrupted the signal flow. The fix was easy, we just shielded that part of the Fibre optic line with a black tube. And why did it not happen everyday? Well when it was a rainy day, there was no sun 😅

[@bigclivedotcom]

Sunshine is a common issue with sensors and imaging systems.

[@vsvnrg3263]

i had one of these intermittent faults on the power supply into my house. only minor interruptions inside but popping or occasionally a bang from outside. as time passed the occasional bang would get louder and when i go outside to see what the cause is there is nothing. then one day it banged just while i looked up. years earlier a pantech truck had reversed into the cable. i like that blade contact idea. round contacts get hot spots in the centre.

[@thpxs0554]

I spent years looking for shorts and disconnects and leakages in BT buried cables, 50v negative battery and 10milli amps, the TDR (. Mole we called it) was good for full dis or short but it would show up joints where cable sizes went from say .5 to .63 as a dis or a short depending which end you’re looking from, ive had them spot on over half a mile and 5 meters out between 2 boxes 20m apart. Some shorts are rectified in that they’re different values depending on which leg you send the test current down, due to a diode affect from mineralisation at the wet short,. Generally I used the “ megger” not a megger in fact but a Wheatstone bridge type tester, which could be great over 3 miles or well out if there was some Ali cable or a bit of higher resistance in a crimp. It got more critical as adsl came in. In soft ground an oscillator 99 and a broom handle with an amplifier set and probe wired to a nail in the bottom would nearly always find a leak, it boomed out as you step on it. At £600 a dig BT wanted them found first dig, otherwise it could’ve cheaper to lay a bit of duct and a plastic box. The oscillator 99 was banned from being put across a pair because if a sub lifted the handset of a dial phone the bleep could damage their ear ( I doubt it but it would make you jump) but as usual, some of the kit from the early days was better than the latest JDSU stuff we had. Anyway, copper going, all the exchanges are going down to maybe 6 nationally and it’ll all be fibre very soon. They’ll pull out the copper E sides often sheathed in lead and brown paper, big scrap money ,and they’re selling off the exchanges..

[@wizrom3046]

A "Megger" is the tradional piece of equipment that is used to find faults in mains wiring. It ramps up to a high (usually DC) voltage, but at a low current. When the insulation fails, the voltage and megaohms of the fault are displayed. We used to use them all the time in industry to test contactors or motor or transformer insulation.

[@bountyhunter4885]

Breakers have some advantages, but I've always liked fuses. Simple and reliable, and often good enough for residential use.

[@malcolmmackenzie9202]

Wow this is the first time i have seen your face in a video. You look different to what i expected. I love your videos thanks for all the awesome information

[@mihaibalint8183]

ohhh, 😮, I see your face for the first time ever! nice to meet you! I think these are made in Romania, My uncle works there and he told me that there are many batches that come back for this kind of problem.😢

[@isettech]

FYI, in some systems in power distribution, the fault creates the pulse on the line and recorders on the line compare arrival times at substations to find the location of the fault. This is not normally in a building due to the expense, but mostly used for HV transmission lines. This is used in place of TDR. For more local utilities, they use a thumper TDR, which puts high current pulses on the line. The short duration pulse can often cause carbon tracking to flash over to be found. Faults in underground buried cable can be heard thumping in the ground. Ariel lines strobe at the fault.

[@MainframeDaydreams]

Definitely a good idea with the gloves. We had servers that would crowbar the supply when the PSU failed. Quite often the underfloor breaker would spark quite badly if someone tried to reset it without replacing the PSU.

[@totherarf]

We have the same kind of problem finding faults on the underground supply network! There is some kit we can use to narrow it down. ..... Rezaps to safely energise 500A supplies with faults. There are sniffers where you sample gasses from underground (hopefully tarmac so they don't go into the air before sampling) and Wezaps for those pesky intermittent faults where they go to a server in Ireland and a possible fault location(s) are given to the engineer to find the fault. We have got to the stage where you can reasonably hope to find underground faults before people are off supply! The lumpy masses of destruction we dig up are a different matter! 1000a is small fry for a fault current! It is interesting to see they think arc suppression works even when the slats are sideways rather than above!

[@SeanBZA]

33kV and higher tend to make the fault location well known though, as they have a crater marking the spot, accompanied by the blown flat remains of the steel joint case as well.

[@totherarf]

@@SeanBZA The HV network is fairly well automated. Most of the HV fuses feeding UK substations are 7a (their rupturing capacity is a lot higher though) Once you get a level up from the 11Kv network the damage does get more noticeable. I have seen subs going up in flame and there is not a cat in hell's chance of getting me near the 4.5m safety zone! I do not care how good the oil is, put enough energy into it and it does get hot .... very hot!

[@jamestompkins8617]

Omg first time ive seen clive's face ...sooo delightfully scottish😊

[@mikebruestle218]

20 year service electrician. Love your intro, so true. It’s a real challenge and ultimate test, using your skills, knowledge and toolset in finding internment faults. It’s the one thing that really pushes me as a technician, and can consume my 2am racing thoughts. Meggers, recording meters, trigger event recording, even installing simple in-line fuses. All which push you to think outside of the box, and use electrical tools in a way that they were not originally designed for, to find an intermittent problem. Troubleshooting, and developing tools and skills at finding problems is a whole other level of technician. Hats off to those who have banged their heads against the walls trying to find a problem. There’s times you give up and just replace the whole dang thing. But you’ve gained an experience. Takes many years to become proficient at fingering smoking guns! There’s no class or textbook that can instantly make you proficient at it.

[@kapioskapiopoylos7338]

Is it weird that I can smell it exactly?

[@bigclivedotcom]

That's a good result. I love videos that I can smell courtesy of synesthesia.

[@peterpkavanagh]

Two stories, one recent one not so much... Had an EICR done on my house wiring last year before renting it out. Turns out both the RCDs were seized - and wouldn't have protected anything. First I'd heard of manually testing them yearly to make sure that didn't happen - scary! Second was my part time job pre university, a little electronics company in West London around 1984/85. Really cold winter, industrial estate building, lots of fan heaters under desks. The main office fuse (porcelain with fuse wire installed) kept blowing. Up until my boss replaced the fuse wire with a 6 inch nail... That worked for about a week, then there was a gout of flame from the manhole outside - he quickly replaced the bodge with a real fuse and expressed complete surprise that such a thing could have happened!

[@TheGreatAtario]

I never noticed before this how strong your lens prescription is, dang

[@hinspect]

People *_need_* to check the often overlooked Buss Bars that the breakers plug into/over for arcs and cleanliness too! I had one instance where that happened and now a breaker cannot be put back in that position. People check the voltage (usually ok) but there will be a *_current_* limitation

[@Legomanfred]

Lots of "carboniferous bits". Great video! 🤔

[@SueBobChicVid]

I've worked in shops with austempering heat treating equipment where molten salt is used as a quench medium. The salt vapors get everywhere and precipitate in the cooler control panels. Have I seen "tracking"!

[@bigclivedotcom]

And seaside electrical equipment too.

[@Mark1024MAK]

Ground mounted equipment or underground near roads or paths where grit and salt is spread in winter can also suffer...

[@Omegajet223]

Yep, here on the marina we see breaker faults similar to this on an almost weekly occurrence as the end users often self reset without reporting it up the chain, and when it fails... spectacular darkness occurs 😂. As always Clive, first class breakdowns and excellent content 🙏🏻

[@ASBO_LUTELY]

The only time I saw a flash at a circuit breaker was in college when a fellow student left live and neutral cables dangling inside the consumer unit and powered it on to prove all the circuits were working correctly. At least it proved the circuit breakers worked...

[@DodgyFPV]

Handle of the insulated screwdriver and looking away from panel are my tips for re-energising a circuit.

[@throttlebottle5906]

long wood broom handle from 6' away to the side(hitting hacked contactor pair for directly reversing a big motor) yeah, did that and had a long sustained arc before at 480v phase to phase, it blew a wire off up behind me and arced for what seemed like an eternity. before the old Federal Pacific 15amp breaker opened. that was at a career center in the mid 1990's, in former welding lab used for "industrial electricity". when it occurred, it browned out half the building and crashed the majority of the computers in the building. nobody got injured, other than some short term arc flashed vision and I did get some copper sputter on my leather jacket(standing 3' away). everyone that year gained high respect of power and arc flashes.

[@dcallan812]

Its Smokey, intermittent faults are the worst especially when its in an inaccessible area, or an area where its going to be expensive to get access. Interesting blow out.

[@alldave]

I feel like the streak on the breaker has a matching streak in the person who flipped it's pants 😂

[@Tombilicus]

at the 5:21 mark, in your video here, that circuit breaker switch is baked, BaKeD, **BAKED!!**

[@tonywebb9909]

Yes, i have done a lot of garden lighting in Ireland, phase to neutral tracking is hard to find, usually damp control ballast or LED circuit, but often a slug has grown up inside the fitting and crawled into the based of an E27 lampholder. Yes one or two resets of the mcb will clear the poor fellow out.

[@fredflintstone1]

Odd years ago, on 3 phase breakers like that insolator sheets would put between them to seperate the phases ??? same if connectors

[@bigclivedotcom]

In this case, the ports were for a mechanical interlink option used for various reasons including ganged breaker groups and external trigger mechanisms.

[@polymath9372]

The circuit breakers suffered a phase worse than death...! 🤣

[@jessebob325]

0:45 Tracking. This perfectly describes what happed to my outside light. It was wired with Mineral-insulated copper-clad cable and buried underground. I had to replace the fuse wire every so often, but it would work for months. Till recently when it blew as soon as I replaced the fuse. I isolated power from the circuit and the fuse wire holds. In two months time the circuit breaker panel is to be replaced with a proper breaker box. 👍🏻

[@KeritechElectronics]

Badly discombobulated, nicely dissected.

[@terrym1065]

KaBoom! Pow! Wham!... Thought for a moment an old episode of "Batman" was coming on. Nope, just a blown circuit breaker autopsied by Big Clive. Excellent!

[@FerralVideo]

Ah, yes... the glorious intermittent. "I'm having a problem." "Sure, let me look at it." *Looks at it... everything's working perfectly. *Walks away... "It's acting up again!" *Runs over, it immediately begins behaving....

[@BobCollins42]

This deserves a teardown, circut diagram, and a functional overview. Please.

[@willgallatin2802]

All the angry pixies came to play in that breaker. BTW Clive, That looks like a normal Eaton breaker. I've opened a couple in the past after a failure.

[@intillex1]

Hey BigClive, I haven't seen you in quite some time. You're looking well man, I hope you're doing great!

[@carlubambi5541]

We have had to put in many manual motor starters and have had to add arc schutes to the manual motor starters .We use ones that have the ability to add low voltage release relay which just clips on to the side of the manual motor starters .Its funny that the manual motor starter is rated for 600v but any VD in the plant while machines are under load cause bad arcs as the machiens shut town to protect 100hp 3p motors

[@johnj4860]

Interesting that the upstream series of protections simultaneously tripped albeit without the destruction of the device(s). It suggests a very high prospective fault current. I'd have been interested to learn a bit more about the distribution network and what devices were upstream. As you mentioned L to E faults differ from L to N faults because it's far more common with L to E protection to encounter time delayed operation disconnecting devices to provide discrimination and contain disconnection to particular sections rather than wide area outages. Good old type S RCDs.👌

[@teardowndan5364]

TDR should work with insulation faults since it doesn't take that much of an impedance discontinuity to cause a signal reflection. Though if the tests are being done under live conditions to avoid disrupting production, those minor reflections could be lost to the noise floor.

[@throttlebottle5906]

the problem there is, old school cabling and splices will show a huge impedance bump and look like the smoking gun, that will often hide the real issues in between them. that does work great for coax/ladder line/twisted pairs without any inaccessible splices mid way. every single splice in a huge bump with TDR, enough so it may show every single splice along the way as bad!

[@teardowndan5364]

@@throttlebottle5906 If you know the distance to the splices, you can ignore those TDR returns. If you don't know where the splices are, your commercial or industrial building probably needs an audit to update wiring plans.

[@chrismayer8990]

Very interesting video. Thank you!

[@TomCee53]

Kind of like putting in a heart monitor to determine I needed a pacemaker. Every few months my heart slowed down. Hard to find on an annual checkup.

[@bigclivedotcom]

My heart misses beats from time to time. But NEVER when I'm being monitored with an ECG.

[@TomCee53]

@ mine was called a loop recorder, which is implanted just to keep track and send reports to my doctor when something was suspicious. My heart went really low, 32bpm I think. The pacemaker is barely noticeable after 3 months.

[@Mark1024MAK]

TDR are fun instruments 😀 They are especially useful if it saves you from walking the whole length multiple times or saves you digging unnecessary... But they can’t always locate every fault.

[@jaylittleton1]

Copper burns such a lovely shade of green.

[@jenkinseric2]

I love your stories, thanks

[@UpLateGeek]

RSVP that circuit breaker. You didn't need to take it apart to tell it had broken its last circuit, the sooty marks were a dead giveaway that it's toast, but it certainly was interesting to see the carnage inside.

[@PiperTube]

Reminds me of reading about Ricky Nelson and his band members. The brief version is the pilots flying his plane kept resetting a circuit breaker for a heater in the rear. Eventually the heater caught on fire. After landing, only the pilot and co-pilot got out. The passengers in the rear all perished.

[@gastube22]

Another great tear-down video, thatnks! Regarding trouble finding the second contact, I agree the copper-only knife-edge contact didn't look like what we would expect. Could the other contact be in the other half of the case, that you weren't looking at? You didn't seem to try following the circuit path through from one connection terminal to the other - and one terminal was in each half.

[@rogercantwell3622]

Intermittent trips at home are often due to failing insulation or moisture in a powerful heating element like that used for a kettle or oven. But it's obvious if that's the cause, as it usually trips when you switch on the appliance. Incandescent light bulbs are the other one, but not so common these days.