Overcurrent Tests FAQ 

Exactly!!!

And might as well add an insulator is only an insulator until it fails. Then it becomes a conductor!

@@unknown-zc8be How true! Charring of plastic is an example. A gas before an after an arc has formed is another. One of the most interesting things I saw in Florida in near the beach was an insulator on power pole that would gradually become contaminated with salt. Every few days there be would be a very loud bang with a momentary spark that must have blown away, dried out, or vaporized all the accumulated moist salt and the the insulator would be an insulator again.

It really was an eye opener for me! But also left me a bit concerned about cables in thick insulation where worst case, the safety margin is slim.

Exactly! And thanks - I will!

I wonder why there is a difference the size of wire required for a certain current between the two continents? The only thing I can think of is maybe we require a bit larger wire, not because of the heat, but to reduce the voltage drop which, since our line voltage is lower, would have a more significant percentage effect on the voltage seen by the load than it would for you with 230V?

@@ElectromagneticVideos Voltage drop may well be it. The Australian standard sets the nominal voltage at 230, +10%/-6%, from the grid. We are then allowed a max of 5% drop from that grid voltage to the load across the building's internal wiring. Pushing that to the limit means about 203V at the load, which is also unacceptable so the wiring would have to be upsized to cope. Seeing 216V from the grid would be a pretty abnormal situation anyway. More jiggliness.

@@retrozmachine1189 So you made me look up what the standards are here. Two interesting links: www.hydroone.com/business-services/commercial-industrial-generators-and-ldcs/power-quality/power-quality-definitions and www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf . Hydro One handles power in Ontario where I am, Pacific Gas and Electric Company is in California. Both indicate at the service entrance (where the power enters the home or building presumably at the meter ) the normal allowable range of voltages is from 110V to 125V for the now standardized nominal 120V system with occasional extremes from 105V to 127V allowed. So for the 110-125 range, we are promised +4%/-8% . And we seem to allow the same 5% additional drop after meter. I typically measure 115V on hot summer air-conditioner days to 125V at low consumption periods at my house. So our input range is slightly tighter than yours. As you point out, both system s allow for a surprisingly large range of voltage that devices have to cope with. Your larger +10% range going up makes more sense to me that our larger -8% going down when you add in the additional 5% allowable wireing drop. At least in the end you are more centered around the nominal system voltage.

In Sweden we fuse our 2,5 sq mm cable with max 16 A. It is even ok then to have single wires in a plastic pipe (conduit) inside a wall that has insulation. That is how we install electrics in buildings, loose wires in plastic pipes or hoses. Then it it easy to change broken wires or even add more wires if needed. Usually we have in houses 16 mm outside diameter plastic pipe or hose with 1,5 sq mm wires in them.

@@Jonas_Aa So it sounds like your a bit m,ore conservative in terms of current than the Australians since they put 20A though the same size cable.Our #14 is 2.08 sq mm rated at 15A so a bit closer to you than Australia. Over here (Canada and also the US) in homes with walls made with 2x4 lumber vertical studs 16 inches or 24 inches apart, we usually use 14/2 cable - two insulated #14 wires and on insulated ground wire in a plastic covering. Conduit for businesses or where the wire would be exposed to damage. Are your houses built like ours or are they brick and cement like in central Europe to the south of you? I'm guessing with a similar climate, you have lots of forests with wood like we do?

Well thank you! I hope it will help some people other understand!

Thanks! Your guess is close - I'm a Electrical Engineer/Computer Engineer and I did teach a number of courses at some local universities after finishing grad school. I have always enjoyed teaching, but doing hi-tech startups really is the thing for me rather than being a full time Prof. Doing this channel has been great fun - a wonderful excuse to do a bunch experiments and a great challenge to get the theory across without the underlying math. For a catastrophic short condition as you describe with a failed breaker or the penny "trick", yeah, my welder does not have the ability to mimic that. I would think 120V across an arc, then dead short, without a breaker or fuse saving the day would result in 1000s of Amps a lot of vaporized copper with perhaps the #14 wire becoming the fuse shortly before the house catches fire? Have you ever seen something like that? Would be fascinating to hear an account of what happens in a real example. You know, the arc experiment you suggest really has me intrigued. I have an old 3KW generator that I could slow down to make 25Hz, and with a proportional drop in voltage I do have transformers that should be able to boost the voltage to make a nice Jacobs Ladder arc, and by showing how far up the ladder the arc climbs, one might be able to see how easily the arc is extinguished. But the real test would be using a bunch of identical switches - probably plain light switches - and see what happens. I'll bet the 25Hz extinguishes better due to the longer off or low voltage time, but maybe the longer cycle time does more damage to the electrodes because of the potentially increased time before off happens. The same experiment with smooth DC (not pulsating DC) should be much more spectacular. I'll have to figure out how to easily create smooth somewhat regulated DC 120V DC with a few amps of current to really try that.

@@ElectromagneticVideos yes, if you get the chance, please do an arc experiment with Jacob's ladder and regular switches with with various frequencies starting with pure DC, then 60hz, 50, and finally 25Hz is worth an honorable mention because many decades ago 25 Hz was apparently common in factories and for trolley motors in electric railways, for ancient motors designed for low speed/high torque applications providing an ideal blend of the advantages AC and DC offers. In the late 1800s and early 1900s many other frequencies were used as well depending on the power provider and applications in mind before the industry settled on 50 & 60 hz. 133Hz was used supposedly to reduce flicker rate for carbon arc lamps, and for a brief period General Electric used 40Hz as a comprises between 25 and 60 hz. Wonder how a Jacob's ladder would act if some of these early frequencies could be duplicated somehow, maybe a VFD would work?

@@Sparky-ww5re Believe it or not, 25Hz was still being generated in Niagara Falls, Ontario till 2009 for the last few steel mills that used it. Apparently in some areas of Ontario and Quebec, residential customers still had 25Hz in the late 40s or even early 50s. My dad told me about the flickering lights at 25Hz when he was a kid, and I later heard the same story from my supervisor when I was grad student, so amazing it did exist even that recently in homes. I hadnt heard about the 133Hz for arc lamps - makes sense. It must have been wild with all those frequencies back then, and I gather quite a variability in 110, 113,115,117,118, 120 etc voltages depending on where you were. I wonder how well a VFD would react to the non-linear nature of the arc, even with the arc being fed though a transformer? I dont have VFD but if I come across a used one I'll grab it and try it. After you said it I'm now really intrigued at the reaction of a Jacobs ladder at 25Hz.I'm also guessing at higher frequencies like 133Hz there may not be time for the plasma to cool so the arc may be more like DC. Such interesting stuff!

I have see long spools of LED cable or strips. Never thought of the limitation in terms of length but you provide a great example of how resistive losses are so much more apparent at lower line voltages. Those strips should have max length specified ...

Ha! Having a lot of of trolls is apparently no uncommon for technical videos. The really interesting thing is the video " How many Amps to burn up 14/2 electrical wiring?" seemed to get promoted by the RU-vid algorithm over the last week. I was also had that happen to it about a year ago. This time more trolls. My guess is whatever their AI system identified as an audience somehow this time was more on the troll side. What they don't realize is every comment - positive or negative - indicates interest to to the algorithm and actually helps promote my channel. So the the last laugh is one the trolls! There are a number of commenters who legitimately asked things like "is low voltage really realistic" and when I responded with answer we ended up with a really good discussion and that's always great!

Well thank you!

Yes! You could very quickly use up all your supply voltage as simply voltage crop on the wire.

@@ElectromagneticVideos - I'm amused to see the various comments on Quora. Some people say we should use 12V or 24V for everything because it's so much "safer" than 120V or 240V. There there are the people who think we should convert everything to 240V to be compatible with Europe. And there are others who think all electricity should be distributed as DC, since DC is used for electronics. Of course if you understand all the considerations, none of these changes should be pursued.

@@8546Ken You should see some of the comments under my "how many amps to burn 14-2 wire" video! I think a lot of people have a cursory understanding and unfortunately end up with a bunch of misconceptions. And some are just looking to argue :)

Thanks! I believe the way the protection relays work is they have a thermal switch that heats up based on the current and time it is flowing. Under normal operation, the current is low enough to not trip the thermal switch, but during the starting sequence, not only is the starter winding activated but also the main running winding draws way more current - I have seen up to 6x the running current. For a normal start the high current isn't on long enough to trip the thermal protection cutout. But for repeated starts - or a stuck rotor the heat build up and hopefully the power is cut before the windings burn. The stuck rotor is typical for fridge compressor that was running, then turned off, and then restarted while everything is still pressurized. The real expert on that sort of thing is David at www.youtube.com/@davida1hiwaaynet. Well worth looking at his channel if you haven't seen it!

I suspect the issue is most circuits (even the ones you mention) are on such a small proportion of the time it may not pay - but would be an interesting calculation. From some comments it appears in some areas #12 is used for all house wiring these days (in 120V regions). Had an interesting discussion with an electrician a while back,. The additional cost for wiring a house with #12 as opposed to #14 is a relatively small increase compared to the rest of the electrical cost. If I were having a house built today I would go for #12 and for that matter, better quality receptacles than the usual cheapest ones.

That's not a bad idea for a future video - possibly also with the conduit embedded in insulation.

Yes! It really makes it hard to predict what will happen if the line voltage goes up or down a bit since you would really need to know the exact characteristics of the load which could be anything these days. Or think of a whole house with a complete mish-mash of different load times. I'm sure it makes it harder for power companies who used to drop the voltage a bit to reduce the loads if they were close to capacity. Today doing that could make the situation worse.

Well if she does complain, you can oversize the cable and put in the wall :) In the end, if you are putting something like a 50A cable its so stiff it would probably be hard to get in a finished wall anyway without messing up a significant of drywall.

I calculated it with V=IR and then P=VI because I wanted to show people the size of a typical voltage drop - more than a few commenters on the " How many Amps to burn up 14/2 electrical wiring?" confuse voltage drop along the cable with voltage delivered to the load and them misapply P=VI. Also wasn't sure how many people with more limited electrical background would know I squared R. Yeah - your 240V is most noticeably different from our 120 with the wire to heaters and kettles not getting warm and devices like that delivering more heat! Also read about your ring (?) circuits to use even less wire for house outlets.

We also use 240V in the states by the way. We simply reserve the 240V for large appliances such as Stoves, A/C units, Dryers, Welders, Water heaters, Well pumps etc. We use the lower (120) voltage on convenience outlets around and throughout the house for everything from refrigerators, TVs, hair dryers, coffee makers and many other small appliances. We can wire 240V to wherever it's needed and I usually put several 240V outlets in the Garage area of course as convenience for welders, car charger etc.

@@ThriftyToolShed Thanks for pointing that out. I think outside of North America I don't think its widely know that homes here generally have 240V available if needed.

@@ElectromagneticVideos you have split phase for 240 v which is much safer than UK 240 v

@@leetucker9938 You know, I have wondered in the end how your safer big plugs and receptacles + higher voltage compares to our smaller plugs that are easier for fingers to get zapped + lower voltage. Are there more electrical injuries in one region or the other? When I was kid we lived in a number of 240V countries and I got an almost lethal shock from a live wire where a pump had been removed in the garden and no-one had sealed off the wire ends. I have never had a shock like that here, but I also have neber been as well grounded as I was with the 240V shock. I have a hunch that the widespread use of GFIs (aka RCDs) have made 240V much safer than the old days. I had read that in construction sites in the UK 110V tools were used with a split phase 55V to ground on each leg which seems brilliant.

Actually I'm in Canada but we use the US wire gauge number. Half our stuff is metric, and the rest like wires uses US measurements. I just looked at your Knob and Tube cottage wiring video again - so cool!

@@ElectromagneticVideos Sure yes, careless of me. I should make another video, now that everything is green and lush here!

@@emilalmberg1096 Same here - I think your climate is quite similar! I so nice to have summer!!!!!

@@ElectromagneticVideos I hope your summer is going well too. Everything comes to life here, even the ants who suddenly want to invade the house! I'm forced to resort to heavy artillery to avoid them starting to chew on the walls!

@@emilalmberg1096 That's so funny because I just discovered an invasion of tiny ants and have to do something about it. The one thing thats different this summer is all the smoke from forest fires. Really lucky that so far no fires near me but for the last few days the smoke has been like thin fog.

Thanks! Well - bear in mind that any answer I give to that question will result in people disagreeing. So to put things in perspective, I am very experienced electrical engineer who often deals with very weak signals and noise. I'm not a high end audio person, although I'm amiliar with high end audio and also look at probably the same RU-vid channels you watch. So with that said: With a well designed power supply in the audio amp it should not matter unless you are a really long way away from the breaker At somewhere around 50' the electrical code says you need bigger (10/3) anyway. The reason the code limits the length is to limit the full load voltage drop along the cable to 3% or less. Now consider this: you can easily get way more voltage drop/swings during the day to day voltage fluctuation from the power company. So I am very doubtful that a shorter cable run 10/3 would help much if the system isn't bothered by those even larger voltage fluctuations. But - since your already going to the expense of running a new dedicated circuit, the additional expense of upping the cable gauge will not be that great in relative terms, so I would suggest you do it rather that potentially regretting not having done it afterwards. Whats $100 more (if that) given the total cost of your system. The isolated ground outlets is a good idea and I would have suggested it it if you hadn't mentioned it. It will minimize noise from other electrical devices. Sound and TV studios often do that. I trust all the connected equipment will also be plugged into the two dedicated wall outlets on that 20A isolated ground circuit? If not, they will bring noise into the system. By the way - with expensive audio gear like that, might also be worth considering a whole house surge protector if you don't already have one. Would be a good way to protect your investment. Hope this somewhat pragmatic discussion is of help!

Thanks very much for detail information , after doing all work myself the 2 mono blocks amps on own circuit . With volt meter to check voltage before it ranges from 118 to 124 volts now is steady at around 123-124 volts here in Canada.Consider I already have 10/3 cables from exsisting electric hot water tank now natural gas. My final cost is just $C60.00 I noticed right away there more low in bass less muddy sound before and less harsh sightly higher volume sound. Before I was using a loaner inline conditoner value just under $C15,000.00 now sounds very close without conditioner. Again thanks very much for advice

@@hexen0076 Thats interesting - and amazing to me - that the difference is noticeable! At $60 its a no-brainier! I'm in Canada too - just outside of Ottawa. I find my power varies from just below 115V to a bit over 125V. Lowest typically during the day in the summer when people run their ACs. Highest at night during times of low power use.

ESS - sorry - what does that stand for - I`m guessing somthing to do with off grid power....