Why This Doesn't Make You Safe
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Date: 2026-04-12
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Comments and reviews: 20
engineering_mindset
I have known these devices since 1976, working in Cape town as an apprentice electrician on building sites for Murray and Stewart, responsible for the maintenance of the temporary builders electrical system on a variety of 30 story buildings and other sites during construction. All builders used 220Vac/380Vac (unlike UK 110V, 55V-0-55V actually. All sockets 15amp single phase and 16A three phase (for 3ph motor generator welders, etc. All distibution was protected by 250mA RCD's for the wiring and electric tower cranes etc. All sockets single phase and 3phase were protected by 20mA RCD's, CGFI, Earth Leakage Breaker (Manufactured by Fuchs and Heinemann now one combined company. The older variety had a hole through which all the wires where passed through (L and N, 3Lines or 3Lines and Neutral depending on the load and feed etc ) internally it had a magnetic toroid core as described in the video.
THE ACID TEST, one day while repairing the kettle, all builders drink tea, I was adjusting the plug socket, the old type that went into the back of a kettle, common issue! I was holding the earth connector outside of the connector and the screw driver touched the live while I was holding the the betal metal of the screw driver blade, to bend the socket tags closer together. Unfortunately the lead was still plugged in with the power on, result massive shock and the lights went out, the Earth Leakage Breaker, tripped almost instantly but not before shocking we into next week! It saved my life possibly, as it was not the first or the last shock that Ive had in my life, the biggest being getting my electricity bill these days in the UK!
My job consisted of finding earth leakage almost daily at one time, damp weather, damaged extension leads, teas urns with slight leakage to earth, motors the list goes on!
Later I was involved in designing electrinic equipment to comply with EN61010 or EN 60950 etc so the filter Y capacitors in the front end of switch modes became the new form of leakage. 2n2F between Line and Earth being the new source of leakage! USB power supply, eg phone chargers all have this fuzzy leakage current, not so sure about some the far east chargers though.
Great video very clearly explained, Earth Leakage Breaker, RCD, GFCI all terms I know keep up the videos!
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I have known these devices since 1976, working in Cape town as an apprentice electrician on building sites for Murray and Stewart, responsible for the maintenance of the temporary builders electrical system on a variety of 30 story buildings and other sites during construction. All builders used 220Vac/380Vac (unlike UK 110V, 55V-0-55V actually. All sockets 15amp single phase and 16A three phase (for 3ph motor generator welders, etc. All distibution was protected by 250mA RCD's for the wiring and electric tower cranes etc. All sockets single phase and 3phase were protected by 20mA RCD's, CGFI, Earth Leakage Breaker (Manufactured by Fuchs and Heinemann now one combined company. The older variety had a hole through which all the wires where passed through (L and N, 3Lines or 3Lines and Neutral depending on the load and feed etc ) internally it had a magnetic toroid core as described in the video.
THE ACID TEST, one day while repairing the kettle, all builders drink tea, I was adjusting the plug socket, the old type that went into the back of a kettle, common issue! I was holding the earth connector outside of the connector and the screw driver touched the live while I was holding the the betal metal of the screw driver blade, to bend the socket tags closer together. Unfortunately the lead was still plugged in with the power on, result massive shock and the lights went out, the Earth Leakage Breaker, tripped almost instantly but not before shocking we into next week! It saved my life possibly, as it was not the first or the last shock that Ive had in my life, the biggest being getting my electricity bill these days in the UK!
My job consisted of finding earth leakage almost daily at one time, damp weather, damaged extension leads, teas urns with slight leakage to earth, motors the list goes on!
Later I was involved in designing electrinic equipment to comply with EN61010 or EN 60950 etc so the filter Y capacitors in the front end of switch modes became the new form of leakage. 2n2F between Line and Earth being the new source of leakage! USB power supply, eg phone chargers all have this fuzzy leakage current, not so sure about some the far east chargers though.
Great video very clearly explained, Earth Leakage Breaker, RCD, GFCI all terms I know keep up the videos!
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DrewNorthup
Quick note: In the USA they are called _Ground Fault Circuit Interrupters_ for two very important reasons (which don't require meaningful knowledge of electricity. The first has to do with the fact that the _fault_ is actually a Ground Fault (EG: when a hair dryer gets dropped in a bathtub and faults to ground. The second is that the CI part ( _Circuit Interrupter_ ) is mandatory as it describes what function in a circuit the device has. Hence _Arc Fault Circuit Interrupter_ uses a very similar name (again, describing both the device and the problem it helps solve. Alas, this has also spawned DFCI ( _Dual Fault Circuit Interrupter_ ) which is branding for a breaker ( Circuit Interrupter ) which has both Arc Fault and Ground Fault safety features.
Second Note: In the USA there are several classes of GFCI. Basically, is it meant to protect humans, is it meant to protect equipment, or is it meant to protect the electrical system itself
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Quick note: In the USA they are called _Ground Fault Circuit Interrupters_ for two very important reasons (which don't require meaningful knowledge of electricity. The first has to do with the fact that the _fault_ is actually a Ground Fault (EG: when a hair dryer gets dropped in a bathtub and faults to ground. The second is that the CI part ( _Circuit Interrupter_ ) is mandatory as it describes what function in a circuit the device has. Hence _Arc Fault Circuit Interrupter_ uses a very similar name (again, describing both the device and the problem it helps solve. Alas, this has also spawned DFCI ( _Dual Fault Circuit Interrupter_ ) which is branding for a breaker ( Circuit Interrupter ) which has both Arc Fault and Ground Fault safety features.
Second Note: In the USA there are several classes of GFCI. Basically, is it meant to protect humans, is it meant to protect equipment, or is it meant to protect the electrical system itself
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smitajky
There is a completely different type of ground fault interrupter which measures the current flow back from ground to Neutral. This was once more common. It is not the same as a core balance relay. There are circumstances in which that device could be FOOLED by other earth return paths. Which is why I was required to replace those with the more modern designs. But it is why the NAME is used even though the FUNCTION is not the same. For example in the event of badly wired circuits power could go out on one active but return via the WRONG neutral. The core balance relays detect that and shut down. Even though earth is not involved. A failure of the earth wire does not prevent a core balance relay from working. A broken neutral wire can become live but the lack of return current also trips the RCD. Again there is not an earth fault. It isn't earth leakage detection.
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There is a completely different type of ground fault interrupter which measures the current flow back from ground to Neutral. This was once more common. It is not the same as a core balance relay. There are circumstances in which that device could be FOOLED by other earth return paths. Which is why I was required to replace those with the more modern designs. But it is why the NAME is used even though the FUNCTION is not the same. For example in the event of badly wired circuits power could go out on one active but return via the WRONG neutral. The core balance relays detect that and shut down. Even though earth is not involved. A failure of the earth wire does not prevent a core balance relay from working. A broken neutral wire can become live but the lack of return current also trips the RCD. Again there is not an earth fault. It isn't earth leakage detection.
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yosefmacgruber1920
It is a GFCI. Ground Fault Circuit Interrupter. The U. K. does not know how to speak proper English. They think that a car has a bonnet and a boot, when it actually has a hood and a trunk. And they think that a bathroom can be called a loo, but hardly anybody calls it that in the USA. And whatever-the-crap does residual current mean Something to do with how a circuit board operates What causes a glowing light switch to grow, current leakage through the light bulb That almost sounds like the name of a video game, the mod for _Half-Life_ of _Residual Life Half-Life. _ Is it against their religion to make anything simple, and to call it what we Americans call it And whoever heard of a RCD That must be hmm, Radio Computer Device Oh, like maybe wifi or Bluetooth
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It is a GFCI. Ground Fault Circuit Interrupter. The U. K. does not know how to speak proper English. They think that a car has a bonnet and a boot, when it actually has a hood and a trunk. And they think that a bathroom can be called a loo, but hardly anybody calls it that in the USA. And whatever-the-crap does residual current mean Something to do with how a circuit board operates What causes a glowing light switch to grow, current leakage through the light bulb That almost sounds like the name of a video game, the mod for _Half-Life_ of _Residual Life Half-Life. _ Is it against their religion to make anything simple, and to call it what we Americans call it And whoever heard of a RCD That must be hmm, Radio Computer Device Oh, like maybe wifi or Bluetooth
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SouravTechLabs
16: 15 - I think putting the current probe on the live wire after the GFCI (the output) shouldn't really show the fault current. The test current is injected internally and mainly creates an imbalance through the sensing transformer, not through the downstream load conductor.
So the spike you saw was most likely just noise or a transient when you pressed the test button. If the probe were placed on the live wire before the GFCI, the 30 mA test current would be superimposed on the lamp current waveform. In that case you should see a slightly larger current lasting until the breaker trips (tens of milliseconds, not just a brief nanosecond spike. So what appeared on the scope was probably just a coincidence.
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16: 15 - I think putting the current probe on the live wire after the GFCI (the output) shouldn't really show the fault current. The test current is injected internally and mainly creates an imbalance through the sensing transformer, not through the downstream load conductor.
So the spike you saw was most likely just noise or a transient when you pressed the test button. If the probe were placed on the live wire before the GFCI, the 30 mA test current would be superimposed on the lamp current waveform. In that case you should see a slightly larger current lasting until the breaker trips (tens of milliseconds, not just a brief nanosecond spike. So what appeared on the scope was probably just a coincidence.
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StefanoBorini
There is another scenario where the RCD will not trip, but it's so unlikely that is barely worth mentioning. If you have a transformer between you and the RCD, and you touch the cable after the transformer, the RCD can't see the leakage because from its perspective, it only sees the current going through the primary. Most scenarios having a transformer tend to reduce current e. g. from 240 to 5, 9 or 12 volts, so it's never going to generate enough current through your body to harm you. However, if you are mister electroboom and you make a step up transformer from an old microwave to generate thousands of volts, then the problem is very real.
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There is another scenario where the RCD will not trip, but it's so unlikely that is barely worth mentioning. If you have a transformer between you and the RCD, and you touch the cable after the transformer, the RCD can't see the leakage because from its perspective, it only sees the current going through the primary. Most scenarios having a transformer tend to reduce current e. g. from 240 to 5, 9 or 12 volts, so it's never going to generate enough current through your body to harm you. However, if you are mister electroboom and you make a step up transformer from an old microwave to generate thousands of volts, then the problem is very real.
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FntX-Video
RCDs are fun little devices. When I modernized my house I put one on each individual circuit group because I had to rewire the whole cabinet anyways and I thought better safe than sorry. I found out that previous owners and I paid for electricity that, through some strange wiring arrangement in the wall, crept into the void without doing anything useful. The lights that were connected to that circuit never showed any issues and to this date I haven't found the erroneous bit of cable in the wall but the RCD sure didn't like that and tripped immediately. I had to run a new pair of wires to fix it.
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RCDs are fun little devices. When I modernized my house I put one on each individual circuit group because I had to rewire the whole cabinet anyways and I thought better safe than sorry. I found out that previous owners and I paid for electricity that, through some strange wiring arrangement in the wall, crept into the void without doing anything useful. The lights that were connected to that circuit never showed any issues and to this date I haven't found the erroneous bit of cable in the wall but the RCD sure didn't like that and tripped immediately. I had to run a new pair of wires to fix it.
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QC1-T7
Whatever this device is called from whatever location in the world it's simply can't save life's at all in various situation if we deep dive in the subject from another perspective taking multiples safety measures, however must of electrical code around the world except Japan this device whatever type X should be installed by an certified sparky who believe in the commercial electrical code to pass the inspection then after 2 or 3 years the electrical code change so it should be replaced by another device type Z because type X is not safe anymore and so on
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Whatever this device is called from whatever location in the world it's simply can't save life's at all in various situation if we deep dive in the subject from another perspective taking multiples safety measures, however must of electrical code around the world except Japan this device whatever type X should be installed by an certified sparky who believe in the commercial electrical code to pass the inspection then after 2 or 3 years the electrical code change so it should be replaced by another device type Z because type X is not safe anymore and so on
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JC-jv5xw
SAFETY WARNING ON USING OSCILLOSCOPES! In the demonstration at the end where an oscilloscope is used, this is connected to measure current using an isolated current transformer clamp. Do NOT under any circumstances attempt to directly connect any mains electrical circuit to the input of an oscilloscope. An isolation transformer must be used. The BNC shield side of a 'scope input is almost always connected to ground for safety. (And do not ever override this by lifting the earth connection in the oscilloscope plug)
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SAFETY WARNING ON USING OSCILLOSCOPES! In the demonstration at the end where an oscilloscope is used, this is connected to measure current using an isolated current transformer clamp. Do NOT under any circumstances attempt to directly connect any mains electrical circuit to the input of an oscilloscope. An isolation transformer must be used. The BNC shield side of a 'scope input is almost always connected to ground for safety. (And do not ever override this by lifting the earth connection in the oscilloscope plug)
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phasm42
When I wired my house, I did the mandatory GFCI circuits in the kitchen, but didn't know that fridges have a tendency to trip GFCI breakers as they get older. Nearly two decades later, sure enough, had a few instances of coming home to an unpowered fridge/freezer. Since it was on a second circuit opposite the side with the sink, I just rewired the GFCI receptacle so that the downstream outlets were in parallel instead of series on that circuit, so the fridge can continue to ground-fault in peace
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When I wired my house, I did the mandatory GFCI circuits in the kitchen, but didn't know that fridges have a tendency to trip GFCI breakers as they get older. Nearly two decades later, sure enough, had a few instances of coming home to an unpowered fridge/freezer. Since it was on a second circuit opposite the side with the sink, I just rewired the GFCI receptacle so that the downstream outlets were in parallel instead of series on that circuit, so the fridge can continue to ground-fault in peace
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kyleweiland6876
Just curious, how can a regular breaker supply hundreds or thousands of amps with out tripping. From what I read the surge capacity of a regular 15 amp breaker might be 20 amps and I was unable to find any other info suggesting that it might be more than that. Also stating that the breaker provides no protection would make it seem that touching a service drop coming off of a transformer is the same as touching a power cord coming off of a house hold outlet which is not true at all.
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Just curious, how can a regular breaker supply hundreds or thousands of amps with out tripping. From what I read the surge capacity of a regular 15 amp breaker might be 20 amps and I was unable to find any other info suggesting that it might be more than that. Also stating that the breaker provides no protection would make it seem that touching a service drop coming off of a transformer is the same as touching a power cord coming off of a house hold outlet which is not true at all.
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50cts
Please keep in mind that it won't limit the current flowing until it tripped. Therefore electric shocks should still be considered as serious accident even if an RCD is installed and you should see a doctor/hospital for check up to be safe afterwards as nobody know how high the fault current was until the RCD tripped. Yes it reduces the risk because at least it will cut the power after a few milliseconds but it still can cause damage to your body.
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Please keep in mind that it won't limit the current flowing until it tripped. Therefore electric shocks should still be considered as serious accident even if an RCD is installed and you should see a doctor/hospital for check up to be safe afterwards as nobody know how high the fault current was until the RCD tripped. Yes it reduces the risk because at least it will cut the power after a few milliseconds but it still can cause damage to your body.
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imark7777777
What do you mean the standard breaker wasn’t designed to save you. It sure does do a lot and preventing you from burning your house down and that would in effect to save you right. prior to that we had people running around putting higher value fuses in where they shouldn’t or putting their trust in Lincoln with pennies underneath their fuses. wait we still have people doing that, the number of HVAC disconnects with copper pipe.
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What do you mean the standard breaker wasn’t designed to save you. It sure does do a lot and preventing you from burning your house down and that would in effect to save you right. prior to that we had people running around putting higher value fuses in where they shouldn’t or putting their trust in Lincoln with pennies underneath their fuses. wait we still have people doing that, the number of HVAC disconnects with copper pipe.
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MikeHarris1984
In North America we also have AFCI, arc fault circuit interrupters. Those are required for all living areas inside of a house. Where if they detect a spark or an arc, they trip so don't plug your old vacuum cleaner in there that's from the 1960s otherwise it's going to keep tripping on you. But those are designed to save your house from bad wiring or if a rodent shoot through your wires or something like that and it cause an arc
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In North America we also have AFCI, arc fault circuit interrupters. Those are required for all living areas inside of a house. Where if they detect a spark or an arc, they trip so don't plug your old vacuum cleaner in there that's from the 1960s otherwise it's going to keep tripping on you. But those are designed to save your house from bad wiring or if a rodent shoot through your wires or something like that and it cause an arc
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volgzagdiev5966
Fun fact - a czech norm basically says, that all new electroinstallations have to be protected by rcds (lights, sockets, everything in bathroom. But there is also a norm that says that in a place, where only people with electrical education and proven accountability are allowed, there don't have to be rcds installed: D Which works for me because I don't really want to upgrade my installation from TNC to TNS
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Fun fact - a czech norm basically says, that all new electroinstallations have to be protected by rcds (lights, sockets, everything in bathroom. But there is also a norm that says that in a place, where only people with electrical education and proven accountability are allowed, there don't have to be rcds installed: D Which works for me because I don't really want to upgrade my installation from TNC to TNS
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GeoffCostanza
I saw AFCI outlets at the hardware store next to the GFCI outlets some time ago. I did a brief internet search to see what the difference was, but I didn't find a sufficiently satisfying description in the minute or so I spent looking it up. I forgot to research it again after getting home, but this video explained it very well. Thanks for making these videos.
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I saw AFCI outlets at the hardware store next to the GFCI outlets some time ago. I did a brief internet search to see what the difference was, but I didn't find a sufficiently satisfying description in the minute or so I spent looking it up. I forgot to research it again after getting home, but this video explained it very well. Thanks for making these videos.
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DezsikeDevil1
RCD also trips when the neutral and earth wires are touched together. This can cause issues in some switching power supplies where the neutral and earth are connected together via a capacitor. When that capacitor blows up it can create a short circuit between neutral and earth, tripping the RCD without letting enough current flow to blow the internal fuse.
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RCD also trips when the neutral and earth wires are touched together. This can cause issues in some switching power supplies where the neutral and earth are connected together via a capacitor. When that capacitor blows up it can create a short circuit between neutral and earth, tripping the RCD without letting enough current flow to blow the internal fuse.
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TinLizzieAnime-d4e
GFCI for me. Ground Fault Circuit Interrupter feels more intuitive (I did not know the term residual current so a residual current device would just leave a big in my brain.
I love the videos! You make the best explainers I think I've ever found for concepts that I've needed to wrap my head around as I attempt repairs. Thank you: )
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GFCI for me. Ground Fault Circuit Interrupter feels more intuitive (I did not know the term residual current so a residual current device would just leave a big in my brain.
I love the videos! You make the best explainers I think I've ever found for concepts that I've needed to wrap my head around as I attempt repairs. Thank you: )
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davewright3088
Must say that the graphics are very well rendered. However, what is missing is the depiction of the 'body current' / fault return path via the ground circuit (copper and/or 'earth') to the neutral-ground bond at the breaker 'panel'. The current doesn't disappear off the screen, it returns by a different path, which would be helpful to see.
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Must say that the graphics are very well rendered. However, what is missing is the depiction of the 'body current' / fault return path via the ground circuit (copper and/or 'earth') to the neutral-ground bond at the breaker 'panel'. The current doesn't disappear off the screen, it returns by a different path, which would be helpful to see.
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HappyLittleDeco
In Australia, we use RCBOs. Residual Current Breaker w/ Over-current. They’re compact, so can be used in place of CBs for every circuit. For example, in my house, we have L1 (Lighting 1, L2, L3, P1 (Power 1, P2, P3, P4, AC1 (Aircon 1, AC2, Oven and Shed. All are RCBOs. There’s also the master non-resettable fuse on the utility side.
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In Australia, we use RCBOs. Residual Current Breaker w/ Over-current. They’re compact, so can be used in place of CBs for every circuit. For example, in my house, we have L1 (Lighting 1, L2, L3, P1 (Power 1, P2, P3, P4, AC1 (Aircon 1, AC2, Oven and Shed. All are RCBOs. There’s also the master non-resettable fuse on the utility side.
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