Very educational video on the operation of GFCI devices! Nice to know they're fast enough to save a life.

@ElectromagneticVideos

8 күн бұрын

Thanks! Yes - I was particularity interested in how old devices would behave - had they slowed or become less sensitive over time. Like you said - nice to know that even the old ones I tested seem to work well and should save lives.

Very interesting. Especially the graph at the end with the danger zones was eye opening. I wonder what type of load the human body resembles to. Guess it's not just a resistive load but has a more complex frequency and time dependence.

@ElectromagneticVideos

14 күн бұрын

I think that an unfortunate thing is the human body as a load is quite variable. If skin is dry, the resistance can be in the 10s or 100s of k Ohm range. Much less if damp or wet. If the skin gets broken, resistance drops dramatically - after all inside we are mostly salt water. Old time electricians used to test for power by touching wires. One told of of a friend who wasnt thinking and did that with a 600V circuit and blew the end of his finger off- higher than a few hundred volts the field is strong enough to puncture dry skin and make good connection with the salty flesh. Your point about complex frequency and time dependence is a really good one - in a crude sense we probably look like salt water from a skin depth perspective - so higher frequency electricity - even a lighting spike which has a lot of higher harmonics will tend to stay close to the surface - which I suspect is why you often see surface burns from things like that but the person survives. Being wet from rain also probably helps lighting victims. Same thing with Tesla coil currents - they tend to stay on the surface. One thing I edited out of the video due to it getting too long - harm can also depend on where current flows. If its in one toe and out another toe on the same foot, you could probably get get a massive shock without it being lethal. However, in one finger and out the feet, while passing though the heart/lungs and its life threatening. I'm guessing the accuracy of the chart isnt as well verified as we would hope, other than 5mA or less is probably ok for mot people in most situations.

@Potti314

14 күн бұрын

@@ElectromagneticVideos Thank you for the extensive reply. Yes, as always, things can become really complicated once you dig deeper.

@ElectromagneticVideos

14 күн бұрын

@@Potti314 Your welcome! The added complication is what always makes this stuff so interesting - at least to me :)

@johnrumm4786

12 күн бұрын

@@ElectromagneticVideos Quite often we see 10mA trip limit RCD being specified for use on farms where there might be underground cables run near livestock. Animals can be far more susceptible to fatal shocks from any voltage gradient on the ground - the wider foot spacing exposes them to greater potential difference, and any most electrical paths will be past the heart.

@ElectromagneticVideos

11 күн бұрын

@@johnrumm4786 I have also heard even it it doesn't injure them, it can do thing like reduce milk production, presumably because they arnt as comfortable (some farmers around here have installed blow up mattresses for the cows and have had milk production go up from happier cows!). I going to have to ask one of my electrician friends if they do anything special for cow barns etc in terms of keeping ground currents low.

I'm a big believer in using GFCI protection in wet or potentially wet areas because my life was saved by a GFCI type receptacle on new years eve 2021 in the house I was renting with a roommate at the time. I was washing dishes in the sink when my roommate opened the cupboard above to grab some more hot sauce, when the bag of flour fell out and knocked the blender into the sink. I felt a jolt for a tiny fraction of a second as the GFCI tripped. GFCI protection also works well in situations where the house has the old style wiring with no grounds and the two prong receptacles need to be changed out to three prong. Two pole GFCI breakers are also available for 240V circuits. Speaking of which, earlier this year I helped on a renovation of a home built in 1947, that had one of those old two prong double T slot outlets that I think you demonstrated a couple years ago on one of your previous videos. Anyway this particular two prong was in the living room, with a 240 volt window air conditioner plugged into it, had a NEMA 6-20 plug with the ground prong removed, wiring behind it was the then modern cloth braided romex, with two wires black and white, with no ground, 14 guage protected by two 20 amp edison base fuses. Some of the wiring had already been replaced over the years. That was the first time I've ever seen a two prong double T slot used for 240 volts. For those that don't know, the reasoning behind the double T slot two prong outlets common in many home built before the 1950s, had nothing to do with 120 or 240V, 15 or 20A. Up until around WWII or so, when the industry came to an agreement about what we should be using for various voltage and current ratings, there were two versions of plugs used interchangeably, the parallel, now known as NEMA 1-15P, rated 125V/15A, and the tandem, two horizontal prongs, now known as NEMA 2-15P, rated 250V/15A, still in the NEMA configuration charts to this day even though this plug has not been manufactured since the 1960s; if such a plug were found today on an antique appliance or lamp, it will fit into a modern 6-15/6-20 outlet but you best be absolutely sure it's a 240 volt appliance.

@ElectromagneticVideos

13 күн бұрын

As always your comments are so interesting! The first hand GFCI experience is something - interesting that you felt a jolt but not much more - so glad the device worked! I never thought about it before, but many small appliances like blenders a double insulated without a ground. Find for normal use but in your scenario, not much protection. At least with a ground to (internal) metal parts there would be some chance of it intercepting the current before it get to the sink full of water. Great example why kitchens and bathrooms should all have GFCIs. My kitchen doesn't - has 15A split phase non-GFCI - should replace the outlets near the sink with GFCi ones even if one looses the split phase advantage. Your history of the two 120V plugs before standards - there must have been some confusion in the early post war years as two horizontal prongs were phased out. I guess the one good thing is that 240V 2-15 outlets were probably rare so little chance of 240V getting into a 240V device. Probably the biggest issue might have been having to change plugs when moving into a house with modern receptacle. Reminds me when I was a kid and we lived in various countries that had inherited the British power plug standards and often different houses - or rooms in a house - needed different plugs (rectangular or round prongs,and big or small). It seems to have taken them longer to standardize.

@Sparky-ww5re

13 күн бұрын

@@ElectromagneticVideos well, the good news for your kitchen circuit dilemma is that the 240V GFCI circuit breakers, are made in 15 amps and have 3 load terminals, L1, L2 & neutral, designed for split outlet, technically known as a multiwire branch circuit in the National Electrical Code, in the US anyway, other countries may have different names for this circuit, which has the advantage of using 3 wires (plus your safety ground of course) to run 2 circuits, thereby saving money in labor and material, this is why you typically see this in homes built in the 1990s and older. Since two pole GFCI breakers run between $120-$160 per breaker, and dual function AFCI/GFCI breakers are not yet manufactured and would be SUPER expensive if and when they are, we don't use split outlets in kitchens today, we run two separate 20 amp circuits for the kitchen small appliance circuits instead. For a 240V circuit that doesn't use a neutral and needs GFCI protection, such as for a 240V 20A outlet in the garage for a 4000 watt portable electric heater for example, you would hook up the black and white to L1 & L2 terminals on the breaker, the neutral terminal would be unused. The white wire in this case should be marked with black or red tape or similar method since it is being used as a hot.

@ElectromagneticVideos

13 күн бұрын

​@@Sparky-ww5re Unfortunately, I think both the outlets near the sink are on the pony panel that can bring in power from the generator, and its all tandem breakers. But on loads on those are the radio and can opener, so loosing the extra power isnt that bad.

Thanks for sharing your research!

@ElectromagneticVideos

14 күн бұрын

Your welcome! Finding out how good (or bad) GFCIs actually are, particularly older ones that have aged, is something I have wanted to for a while! I feel much more reassured about the 24 year old ones that were installed in my house when it was built. Tested some of them too - all seems to be operating similar to the ones in the video.

@jeremiahbullfrog9288

14 күн бұрын

@@ElectromagneticVideos I have a couple that nuisance-trip, either that or I have a genuine hazard ... I might test the devices with this technique.

@ElectromagneticVideos

14 күн бұрын

@@jeremiahbullfrog9288 The variable resistors I used were Digikey CT2160-ND. But a simple 30K to ground would create a 4mA current (hopefully no trip) and a 20K one, 6mA (hopefully trip) which would be a good simple way to do it (even wire the resistor right into a 3 prong plug.

Nice video. Good to know they all fell into a safe zone for use. I am moving along on garage/lab and will have to have one of those at entrance through the man door. Not using anywhere else inside. There is no plumbing, sink, ect. Spent last week putting in fiberglass insulation. That was a job for me. I am 69 and sore joints so stapling a ton for the 12x24 building was hard on my hands. I am about to put walls in in next few days then electrical will be on the outside of the walls with pvc conduit wire covering to breaker box that also needs to be installed plus all the outlets. I fiqure I may get done about Fall or early winter. I have never done any of these things in the past and pretty much working 100% alone.

@ElectromagneticVideos

14 күн бұрын

I remember you mentioning the garage project a while ago - glad its progressing! That fiberglass insulation is horrible stuff! One bit of advice - make sure there are no gaps that mice could get into it and be cure to cover the vapour barrier with plywood, osb or drwall - I have had cases where they chew though the plastic vapour barrier and make a mess inside the insulation. Anti-rodent spray foam is a good way to seal any entry points. A GFCI protecting all outlets is great protection - did the same for my basement workshop. But keep any ceiling lights on a different circuit so your arnt in the dark when the GFCI trips. By the way - I got a bunch of florescent lights free from a local business that was upgrading. Have the a large number of them all over the ceiling like in an office building. The extra light is fantastic - particularly as our eyes get older! How big a cable do you have providing power for the garage? Big enough to put in an outlet for a construction heater (240V 30A). Would make it much more comfortable on cold days.

@55Ramius

14 күн бұрын

@@ElectromagneticVideos I am required to have a light switch at entrance, running through a GFCI . Guess it could just turn on one light and rest run off other circuits. There is zero electrical in there yet but I bought a 200 amp breaker box. My son offered to let me have an house trailer heater he has. Said it worked fine when removed. Is fairly small but should be plenty and it is electric so 240 volt circuit would be needed. You spoke of the extra light. Yes, that is what I wanted. A lot of light, like in an office. My 69 year old eyes would be more relaxed I think. led shop lights is what I was going to put in. But, I want lights that dont buzz when a photocell or photresistor sees it. Slow motion video would also suffer with the wrong lights. But that is a later problem to deal with. BTW , thanks for the advice about mice. First time ever messing with fiberglass and I bought $50 worth of googles, gloves and mask plus wore a long sleeve in a hot garage. Really sucked but it is done. Ok, I said enough. Will let you get back to makeing more great videos/// 😃

@ElectromagneticVideos

14 күн бұрын

@@55Ramius Maybe one gfci to the light circuit, and another to the workshop outlets? By the way - outlets above where the workbench will be are so helpful. 200A panel and 240V - excellent! Use 12-2 for the outlets if you can! Lights the electronic ballasts in standard T8 fixtures with either old fluorescent bulbs or LED-replacement bulbs are flickerless. I use both in my workshop and for "movie lights" aimed at me in front of my electronics bench where I do the intro to the videos. Way cheaper than new LED fixtures if you get them used/free. I really like 4100K color temp - half way between sunlight and incandescent. I have about 20 two bulb fixtures in workshop - area about twice yours so if you can do 10, it will be wonderfully bright. "googles, gloves and mask plus wore a long sleeve in a hot garage" - been there - done that - not fun!!!!!!!

Here in the UK RCD/GFCI protection is mandated for most circuits now - especially any with sockets/outlets. However there are almost always installed in the distribution board/consumer unit and protect the whole circuit rather than individual outlets. That keeps the power wasted by the RCDs to more manageable levels since most properties will typically only have two or three socket circuits (often one per floor, and and an additional one for a kitchen / utility where there is likely to be a high concentration of higher current loads). One of the advantages of our use of plugs with built in fusing means the protective device at the origin of the circuit does *not* need to provide fault protection for the appliance power cords, only the hard-wired house wring. So we can run a 32A / 240V circuit that can support many sockets. As a result two or three socket circuits is often enough.

@ElectromagneticVideos

13 күн бұрын

Interesting! Great way to save power! Is there any issue with nuisance tripping with a so many devices on a single RCD? I gather the trip fault current is 10 to 30 mA for most home RCDs in Europe which probably alleviate the problem. Regarding the the 32A 240V circuits - I'm always amazed to see how small your circuit breakers panels are compared to ours. I;m sure you find ours to be gigantic! The crazy thing over here is there is enough space to put a fuse in our Canadian/US power plugs - some Christmas light string do that. We should have that at least on extension cord plugs.

@johnrumm4786

13 күн бұрын

@@ElectromagneticVideos When RCDs were first introduced they were often implemented as a "whole house" RCDs - with the RCD placed inline before the distribution board. That certainly did have nuisance tripping issues. One of the main problems that brought was the total lack of discrimination - any fault caused a loss of power to the whole installation. It made electrocution less likely, but breaking your neck falling down the stairs in the dark more likely! So that quickly evolved to "split load" consumer units, with only the more risky socket circuits on the RCD side of it. More recently multiple RCDs with circuits split between them has become normal, and the trend is towards "all RCBO" installations (a RCBO is a "Residual current Circuit Breaker with Overcurrent protection" - basically combined miniature circuit breakers and RCDs, so every circuit gets its own RCD). For shock protection, 30mA trip threshold devices are normal, and sometimes 10mA devices are used in particularly risky situations. 30mA keeps you out of the danger zones in the time vs shock current curves. Most domestic installs don't have nuisance tripping issues unless there is actually a latent fault somewhere, but some loads can me more problematic. Lots of IT / electronic kit on a circuit can cause problems with the combined effects of multiple mains input filters, each with a small leakage current adding up. Kitchens / utility rooms can also be another with lots of mineral insulated heating elements that can become leaky if they get any moisture in them.

@ElectromagneticVideos

13 күн бұрын

@@johnrumm4786 Interesting - I can see the unintended consequences of a whole house RCD plunging the place in to darkness. The combination of many RF filters causing nuisance tripping - I actually had videoed the leakage current from some power input connector filters and was going to point out how multiple ones can be an nuisance trip issue but didn't include it due to the video getting too long. Thanks for mentioning it! I didn't know heating elements get leaky due to moisture. Over here we dont have things like that on GFCIs - just ground for protection. I suspect its because we feed them with 240V from our split phase system (two opposing phase 120V wires = 240V) which requires essentially two GFCI breakers connectd together ($$$).

@johnrumm4786

12 күн бұрын

@@ElectromagneticVideos The mineral insulated elements found in ovens are a common culprit. With age and repeated heating and cooling, the metal case can develop cracks. That can allow moisture into the element where it combines with the magnesium oxide insulation, creating magnesium hydroxide which is electrically more conductive. In regular use it does not matter - the heating will drive out enough moisture to stop the situation getting worse. Infrequently used elements though can get to the point they cause a nuisance trip. Historically we did not have things like cooker circuits RCD protected, but the current wiring regulations require RCD protection for any cable that is not buried more than 50mm deep, or not fully enclosed in an earthed metal sheath - so that has lead most new installs to have RCD protected everything. The basic install would be two RCDs with circuits distributed between them (mixing lighting and sockets on each storey so that you don't lose both together in one location). However the price of RCBOs has fallen quite a bit (~ £15 each), so having one for each circuit is not unreasonable. That means the effects of a RCD trip are limited just to the circuit in question.

@ElectromagneticVideos

11 күн бұрын

@@johnrumm4786 Your RCBOs are cheap compared to ours - often i the $50 to $100 range! So with RCDs on everything, do you have arc-fault or combined arc-fault rcd breakers as well? AFCI breakers are being required almost everywhere over here these days - may not be an issue for UK/Europe since you houses are usually brick and concrete and dont go up in flames like our wood framed houses. (correct me if I'm wrong!)

Great video. Any thoughts on diving into AFCI? Maybe analyze the how the device detects real world arc fault? The circuit characteristics of a series vrs parallel arc? Talk about a device that's created nuisance tripping issues...

@ElectromagneticVideos

13 күн бұрын

Actually I have an AFCI receptacle to do a video like that - assuming I can get it to trip. I think all I can hope for is series arc since would be hard to make parallel one without tripping a breaker via simple over-current. Funny you mention nuisance tripping - I replaced my 20 year old table saw for that very reason. The basement has AFCI breakers, and they began to trip when the saw was turned on - I think the brushes are getting old and sparking a lot. The new saw solved the probolem, and the old saw in is the garage which was wired before AFCI was a thing. I gather the newer ones are better at reducing nuisance trips. You wonder how many AFCI breakers have been replaced by for situation like that?

Great video, very informative! I was surprised that the GFCI breakers were so fast. Yes, there's a large spring, but large springs have more mass, so it's a battle between spring force and mass - apparently spring force wins in the design of those things. I'm curious if a GFCI device, and a GFCI breaker in particular, is "bidirectional". By this I mean I wonder if the direction of power flow was reversed, would the GFCI breaker still function normally? The reason I ask is that I once did a bad thing: I powered an outbuilding from a generator, by opening the main breaker that fed the outbuilding's power panel, and fed the generator output to the panel through an existing 50A 240V outlet circuit. The 50A outlet circuit was protected by a 50A GFCI breaker, which immediately fried (sparks and a puff of smoke). I replaced the 50A breaker with a non-GFCI breaker (and double-checked my wiring), and everything then worked as expected. I did an autopsy on the 50A GFCI breaker, and it was well and truly fried inside - not a subtle failure. (I should add that this was a one-time thing I did as a convenience to do some testing on the generator, since the outbuilding already had a variety of existing 120V and 240V loads, ranging from light to heavy, real and reactive, power draws.) Anyway, I'm still a bit mystified why the reverse power fried the (very expensive) breaker. My understanding is that the ground fault current is detected by a supermalloy differential current transformer that essentially subtracts line and neutral current, and these transformers need to have immunity from huge overloads for safety reasons (i.e., a line-to-earth fault that trips the breaker should not quietly cripple the GFCI functionality of the breaker).

@ElectromagneticVideos

12 күн бұрын

Your comment made me look a a broken GFCI receptacle I had disassembled to confirm it was the spring that was used to open it when tripped and it was - a solenoid is used to release the spring. Some regular breakers use the AC through a coil to help speed up the opening sequence. I'm so intrigued I will have to open some GFCI breakers and see how they trip. The spring powered trip - as you point out, there is speed limit based on the spring force and its own mass, but add to the the mass of the contacts being moved. I guess the conclusion is springs do hold enough energy in proportion to their mass to be able to accelerate and move really fast. You expensive GFCI experience. I probably would have made the same mistake. You right about how gfci's sense the current so that cant be the issue.My guess is it is the tripping electronics and solenoid used trip it. The trip solenoid would be powered from the normal line side of the breaker. With the generator attached, its now on the load side. If a ground fault was detected, it would try and trip, possibly begin to open the breaker, and loose power to the solenoid and sense electronics before the it can finish opening. It would close again, let more power in and essentially become a high power buzzer circuit, probably generating all sorts of spikes and passing current through a solenoid that was only intend to be activated for a few ms. So with spikes and solenoid heat, destroy the breaker. Thinking a bit about generators, many have ground and neutral tied together, and so would the power service to you outbuilding (if not directly, via you house's main panel). So not surprising that there would be ground currents tripping the GFCI under normal operation of the generator. Fascinating! Thanks for sharing that - good thing to know!

@miltonthecat2240

11 күн бұрын

@@ElectromagneticVideos Reading your analysis, I flashed back to the event (pun intended), and I do recall the breaker destruction was accompanied by a brief loud scary buzzing noise. So I think you nailed it. Thanks for that, I consider that one less unsolved mystery in my life. I recall pondering long and hard about whether to disconnect neutral and earth at the generator, but I don't remember what I decided. In hindsight, they should definitely be disconnected, or the return current would split in some proportion between earth and neutral according to their relative impedances, and you never want current purposely flowing through protective earth (green wire) except in a fault situation. The feed cable from the generator was pretty long, and the large metal frame of the generator is connected to the green wire, so I suspect there was enough stray capacitance to cause enough earth current to trip the GFCI breaker even if not connected to neutral at the generator.

@ElectromagneticVideos

11 күн бұрын

@@miltonthecat2240 To add to that, being outside, there could easily also be in various things also leading to leakage. I do have a few of those GFCI breakers I used in the video - I may try and re-create what happened to you. Of course a different brand of breaker ma behave differently. Do you recall what type of breaker that was?

@miltonthecat2240

10 күн бұрын

@@ElectromagneticVideos It was a Square D HOM250GFICP (4884006004)

Realizing I forgot to email you in response to your last message. I'll send soon...

@ElectromagneticVideos

14 күн бұрын

No worries - I will keep my eye open for it so it doesnt get lost in the junk folder!

You could say you did a more scientific version of what Electroboom did!

@ElectromagneticVideos

14 күн бұрын

Did he try to zap himself though a GFCI? I sure wouldn't try that - no matter how many views it might get :)

@emilalmberg1096

14 күн бұрын

@@ElectromagneticVideos Electroboom has two sides, which he himself complains about. When he pretends to be naughty and hurts himself, his video gets millions of views. When he is serious and tells correct things he gets thousands of views….

@ElectromagneticVideos

14 күн бұрын

@@emilalmberg1096 Doesn't surprise me! My most popular video is when I test to see how much current can go though some standard house wiring and the wiring burns up in the end. I get that he playing up to the KZread audience - and is certainly good at it!

my house rcd is rated at 30 mA in the UK .

@ElectromagneticVideos

14 күн бұрын

That is interesting - I had read in 230V places its usually between 10 and 30mA. Sounds like you have a whole or half house one - also explains why such a "large" trip current - would be easy to get nuisance trips from all the electronics we that have RF filtering with capacitors to ground creating trickle ground currents. I'm guessing they are designed to trip very fast if the current is exceeded to stay within the green safe zone. I was actually going to mention the higher tip currents in to 230V places - unfortunately the video as getting too long :(

@retrozmachine1189

14 күн бұрын

@@ElectromagneticVideos It's certainly a deep and broad subject. Even with the limited amount I know about the things I could write pages about it. In places that implement TT earthing you will often find a 100mA to 300mA master RCD (RCCB) that can cut off power to the entire installation to protect the wiring against earth faults, but there will also be 30mA devices to provide personal protection on all the final circuits too. In Australia where most installations have a neutral/earth link RCDs are almost exclusively 30mA, even ones built into sockets but they aren't all that common. Different ratings are available such as 10mA but you'll only find them in specific circumstances such as medical etc. The IEC standards that a lot of countries use as some sort of basis for their electrical standard says RCDs may act between 50% and 100% of the rating (30mA would be 15 to 30mA) but must act at 100% or higher. Time to act can be up to 300ms but typically far far less. With electronic (EC) types (has circuitry in the device) trip time is fairly divorced from the level of imbalance directly but can have a response time change built in while magnetic (EM) types are directly influenced by the level since the trip is run directly off and solely by the CT. There are standalone RCD testers used by electricians to see if a device is performing acceptably, as well as multi-function testers that are a magic box of tricks that does anything and everything - voltage, low ohms resistance, insulation resistance including PI and DAR, fault currents and of course RCD testing. EC is cheaper to make but vulnerable to loss of neutral and due to the difficulty of manufacture 10mA devices are 99.9% likely to be EC rather than EM. Where the risk of loss of neutral (not a PEN fault) is considered to be a problem a functional earth wire to the RCD provides a backup 0 volt reference for EC. EM devices don't need neutral and phase intact to operate, put sufficient current through either L or N of the device and it will trip without the other wire being attached. These are different from the magnetic latching type of GFCI you have over there, those types exist in 'IEC' countries too for circumstances where you don't want equipment springing to life randomly after a power failure. GFCIs at 6mA would be classed as electronic (EC) type RCDs. The spec sheets for GFCIs, including 240V ones, that I've read talk about requiring a neutral for the device to produce it's internal power supply. No neutral = no function. A magnetically latched device will release but not because of an earth fault, just that the device's supply went away. Whoops, almost started writing pages ...

@johnrumm4786

11 күн бұрын

@@ElectromagneticVideos 40ms max at the nominal trip current. (In my experience, most manage 20ms or better (2 cycles at 50Hz))

@ElectromagneticVideos

11 күн бұрын

@@johnrumm4786 So really like the "fast" ones I tested.

@retrozmachine1189

8 сағат бұрын

@@ElectromagneticVideos The standards in the UK used to require all sorts of tests be done on RCDs to verify their operation but recently they relaxed it quite a bit and now follow the IEC standard more closely. RCDs are now considered to be working correctly so long as they trip at no worse than 300ms at the rated trip current for a non-time delayed device. As current rises above the rated value the trip time decreases, same as with GFCIs over there. BTW I made a fairly long comment to this thread 2 weeks ago and only just noticed that youtube shadow banned it. It can only be seen by sorting by Newest First. Nice.

lots of math and a oscilloscope , awesome

@ElectromagneticVideos

14 күн бұрын

Ha - most people hate the math :(