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Great video!Make another video if you could talking about the benefits of a multi wire branch circuit, like voltage drop reduction and wire saving in long runs.

Also tried with an extension cord on a small container of water and it didn't trip the GFCI, I'm wondering if extension cords are designed to keep a small buble of air to prevent water from entering each terminal perhaps? I'm confused as to why it didn't work with the outdoor extension cord.

Cool video. I know there is a way to ringout a cable where the ends are very, very far from each other using two multimeters. Do you know any tricks to that? Do both meters need to be connecting to the SAME ground?

Some errors in this video! The voltage to ground in 120/240 and 208/120 systems is 120 volts. Putting a handle tie across two single poles does not meet the requirement for 2 pole circuit breaker. Handle tie is for means of disconnection. 2 pole breaker also does overcurrent protection for both poles. Handles do not comply. Amps on the neutral does not cause more danger. Think about this, your service is exactly the same as a multiwire branch circuit. A feeder to a sub-panel is the exact same thing. So, losing a neutral is bad, correct, but where are you going to assign it to be lost in tests? Multi wire branch circuits are still legal and have been for over 100 years. Are they more dangerous? NO. Can they cause damage to electronics? Yes to some, but not all. Many electronic equipments run from 100 to 300 volts. There are hundreds of millions of multi-wire branch circuits in dwellings, and commercial and industrial buildings!

Work in a school built in 1962 3phase 120 208 one neutral for 3 every circuits ABC

You should stress in the example by using two light bulbs of equal wattage, with an open neutral the lights would be of equal brightness. Since the resistance is equal between the hot legs (Series circuit).

Considering the USA has had electricity longer than most, their electrical system is so backwards...

Thanks big bro much love for the free game

why i hope this guy isnt an electrician.....but i am sure he probably is

So if I do something stupid I might hurt stuff who would have thought! What a freaking genius! Lol idiots

Excellent demonstration, thank you very much.

Thank you for the excellent instruction!

Mega dittoes brother! I’ve replaced many switches and receptacles burned to a crisp from backstabbed connections. None of them tripped AFCI breakers. But I’ve seen the breakers nuisance trip from a radio being plugged in. Faulty technology shoved down our throats by overzealous authorities and greedy manufacturers.

Saving lives a year later

could you also do it if you put it in continuity mode ????

@Eric Stark, Was there a reply from the manufacturer

You are so right, I accidentally opened the neutral in a small 4 breaker panel in my garage and everything electronic burn up thier high voltage to low voltage transformers such as my raideo, alarm panel, and all LED lights !

You are a brave man by having the lead on the power source and the other waving in the air ready for a possible arc or shock

is an arc the same as a spark?

VERY, VERY EXCELLENT VIDEO! For well over two decades at this point… Multi-Wire circuits have been a myriad of both mystery and curiosity… However, like you say at the end of your video: just grab a couple of 14/2 or 12/2, and call it a day! I definitely smashed that subscribe button. I’m really looking forward to the next in this series! Great work :-) No. B

Don’t Trip!

Very informative. Thank you for sharing your knowledge. Much appreciated.

Great explanation and demonstration. Thank you for sharing your knowledge. Much appreciated.

Touch it to the metal box it will trip

Fantastic explanation sir,, please keep up the great work

How is the best way to figure out a nuisance trip on a afci siemens breaker.

great example thank you for the diagrams , your explanation added clarity

Gee, an open neutral on a multi-wire circuit is scary. Does something similar happen if the neutral should open on a 120/240 volt, single phase service? Maybe it’s important that trained and qualified people install and service such systems.

That is insane the moment is started arching it should have tripped that's what it's for it says to prevent arcing for homes Etc don't catch on fire I'm electrician residential and Commercial as of lately that's all we've been doing is putting those in I already didn't like them putting them on a GFI makes no sense to me but they are making us do it thank you I appreciate the video

Good demonstration. A very small, pedantic comment. At around 2:00, you state that "both circuits are running." Keep in mind that a multiwire circuit is considered a single circuit in the NEC, not two circuits. It's right there in your video title :). In addition to saving 25% in the amount of wire needed, one huge, often overlooked advantage of multiwire circuits is with counting conductors for the purposes of derating in a raceway. In a multiwire circuit, only the phase conductors are counted, not the neutral, since the neutral only carries the circuit's imbalance and doesn't contribute any additional current to the raceway. In essence, you can push more current in a raceway before derating because the potential between the two phase wires is 240v. P=VI. For example, you can put three multiwire circuits in a raceway and only derate to 80% because it only counts as six conductors instead of nine, which would require a 70% adjustment. With the three multiwire circuits, you'd have the same current delivery as six linear circuits. I don't know why people find multiwire circuits so mysterious. You essentially run one every time you connect a clothe's dryer or range, albeit one with a single outlet configuration.

Can someone please explain the problem of working on circuit A while circuit B is still on? How does the shared neutral make a difference? ALL of the neutrals are shared in the entire house since they are ALL joined together to the same neutral bar. The need for opposite poles and the open neutral make perfect sense, but this part about the need for simultaneous disconnect makes no sense at all.

Ordinary circuit breaker only overload short circuit protection function, but does not have arc protection function, when the arc occurs, the ambient temperature rises rapidly to about 200 degrees ro the surunding materials will cause electrical fire, only 2 minutes will catch fire this is very terrible, especially wooden material houses or warehouse recycling station and other places are more likely to catch fire

I tried this before seeing this video with tap water and a extension cord it didn't trip... im sure the line and load wires are correct.. something im missing???

If u take that light bulb of the bottom will the top blow

Why do I need to do an experiment when I can just do the math? I didn't study electrical engineering in order to put experiments before physics/mathematics. What I would say about the multiwire branch circuit is that they probably do not belong in any residential applications because its too complex for most ppl. I wouldn't even put it in my own house b/c I would be concerned for the next home owner after I move out.

If you search, you should find documentation stating something to the effect that it takes 70amps (or more) of load to detect arcing with these devices. Ironically, as I’m sure you’re privy to… regular 15-20amp breakers do a really good job of tripping at this current level too 🤨. However, I think it would be interesting for you to do a comparison with a high inrush- like a motor load from standard breaker vs afci…

Great introduction and explanation. I know multi-wire (12/3) used to be run into kitchen receptacles before GFCI was required and is no longer permitted for kitchen outlets. One remaining use that I have seen, is to run a multi-wire 12/3 120V 20A 2-pole breaker to a dedicated workshop duplex 5-20R to supply two devices (like a 120V table saw and another 120V shop tool) that will be upgraded down the road to a 240V 20A 6-20R simplex receptacle (for the table saw only, when its motor is upgraded or a new higher power saw is placed into service). Saves having to re-enter the panel and switch out the breaker... you just update the receptacle (duplex 5-20R to simplex 6-20R). I assume the (white) neutral is just left disconnected (capped) at the receptacle end, since it is no longer needed. Have you seen that use?

Great demo! Been looking at my 1960's panel with a mix original wiring from 1925 and some added around 1960 . I just became aware of how multiwire circuits work and see that I have a couple with the newer cable. Now I see the danger if not done properly. Just wondering - if one of the bulbs were disconnected , wouldn't the other one go out too? (the series connection is no longer complete)

this practical demonstration explains it well because I was most confused about that; I thought that with the neutral disconnected that it would spark and be dangerous because the voltage is then 240v instead of 120 on each circuit. Electricity has to be demonstrated, numbers and diagrams on a chalk board still leaves me confused. I would like to learn about a 30amp circuit that is NOT DEDICATED ; can it have multiple receptacles like say a 20A circt with multiple 15A recepts?

To prove your point why did you not compare other brand arc breakers to sell your findings?

Mr. Startk , good video/info but you my not know of other power companies around that have the 120/240 volt supply different than the Edison method ! In case you dont know the Transformer secondary outer phase is grounded and then you have 120 volts to ground and the other outer leg is 240 volts to ground ! This so you still have (2) 120volt feeds and need only (1) wire to get 240 to grd or neutral ! ! Kinda crazy but it is used here in In.

I don't like those shared neutral circuits, and avoid them at all costs.

Dude you just made my day on this video I'm just a general contractor no electrician an inspector here in Connecticut had me put handle Ties on all my circuits due to the fact he thought they were shared I understood about the share neutral but not the fact about the voltage drop and possibility of sensitive equipment at Jeopardy because of it. Thank you for your video

Great job explaining this. I have always been intrigued by multi-wire circuits because of the way they eliminate the need for an entire wire.

I was in deep discussion about this a week ago, excellent demonstration.

Great video this clearly should not be labeled as a arc fault breaker

Secondly again this is sensationalism without performance of what you’re doing. If you plug in an AFCI tester I’m sure your device will trip. But what you are not showing is what kind of an arc in milliamps are you actually drawing so if you don’t own one go rent a couple thousand dollar tester the contract the continuous number of arcs you are producing and what their actual peaks are on a chart

But is this a true test based on the devices specifications. You’re not talking about what are the specifications that the device is built and listed under what you are the time/arc loads that actually tripped the device and what are you doing in reference to that are the arcs that you are creating within the realm of what was designed and listed. What is the UL listing and testing for these devices Unfortunately I feel what you are doing here is sensationalism to a degree

Excellent. Thank you

You people are idiots.