120/240 signal split phase explained

[@KevinCoop1]

Straight forward and to the point. Great Job!

[@cassidar]

Great video!

[@ademanster]

Thanks for the explanation, so you saying I can just use the 2 hot leg to get 240v single phase ?

[@matthendrickson5538]

your drawing also explains that the two legs of 120v are not 180 out of phase as is commonly believed. they are in phase.

[@Stevenj120volts]

@@matthendrickson5538 that is one of my pet peeves

[@iceman9678]

I don't know why this continues to be controversial. It comes down to your reference.

[@roddiesmith2167]

Very informative. Great job explaining. I have a question. In Europe they use 240. Is this a single phase without a neutral?

[@marcop8273]

No, we have 400V 3P+N, so we have 230 L+N in our houses (240V/415V in UK) or 400 3P+N without much effort. Until '60, in my country (Italy), we had 220V 3P+N and 127V L+N, then it was standardized to 220/380 and then, 230/400V in 2012.

[@MrSummitville]

You shorted out the secondary winding. Captain, she's gonna blow! 😊

[@Stevenj120volts]

Non conductive safety marker.

[@scotty3114]

Not saying you're wrong about your power pole, but most have the neutral/ ground on top for added lightning protection. The hot wire is on the bottom. Look at the plethoria of power poles, whether 1 or 3 phase, the gound is usually on top. This is intentional so that lightning will hit it first, according some protection to the hot wires.

[@scotty3114]

@Joe-by8jh Huh! In the US, except for some older systems, it's usually the way. I grew up in a rural setting, and we had REA systems. They were always single phase, ground on top. But then again, you could guarantee a few hits every time a thundercloud pops up within 10 miles! And an outage if it took a good hit.

[@Calico5string1962]

Here in Texas, on single-phase HV distribution (7200v to ground), the hot leg is always on top, with the neutral below... I've never seen the neutral above the hot. Also, since all pole-mounted transformers have their H1 bushing (or bushings) on top, it makes the jumper short & safe (through a drop-out fuse). And we get A LOT of lightning here. Very rarely are ourages (here) caused by strikes.

[@GH-oi2jf]

It is just as shown here, with the neutral at the bottom of the transformer, in my area (Pacific NW), as far as I have observed. In an area prone to lightning, perhaps they add a separate grounded counductor for lightning protection.

[@JohnThomas-lq5qp]

@@scotty3114 Worse part in my area lazy cheap PECO/Exelon only connects one high voltage wire to all single phase transformers. They connect the other side of primary ( 7,300 volt ) to the center tap of the 130/240 volt secondary and to transformer case and ground rid at bottom of pole. This makes it an autotransformer and every copper water service, steel gas service & even cast iron underground soil pipe have current flowing thru the ground feeding the transformer. Even when I had the utility meter pulled and every circuit breaker off could measure at least 1/4 amp flowing out the copper water service.

[@scotty3114]

@@JohnThomas-lq5qp wow! I have never seen this. Doesn't sound safe or efficent. Where are you located, roughly?

[@Joee1257]

Thank you

[@garymiller3194]

so what's the available fault current on that 25 kW transformer electo man

[@Calico5string1962]

That "25" is not the "kW" of the transformer (kW = kilowatts). That 25 would refer to the "kVA" - the "kilovolt-amp" rating - of the xfmr. Thus, if you know the secondary voltages of the xfmr, you can then calculate the available full-load current rating - at a given voltage - for that xfmr. You could also calculate the input current (at full load) if you know the input voltage. Since that is a single-bushing primary xfmr (and tied to neutral), here in west Texas, the primary voltage would typically be 7200v, being derived from one phase of a 12450v, 3-phase primary distribution.

[@MrSummitville]

@garymiller - Fault Current can be, as high as, 8,000 Amps between the two 240 volt wires.

[@MrSummitville]

​@@Calico5string1962 For the *average* residential consumer ... 25 kilowatts is the correct answer. Your convoluted and esoteric answer of ... 25 kva provided no useful information, to the average person. You did not even answer the question, that was asked.

[@Calico5string1962]

@@MrSummitville Sorry sir, but a "kilowatt" is not an measure of fault current [either]. A kilowatt (kW) is a unit of power... while amperes (amps) is the unit of current measurement. The question asked was flawed initially (as is your answer) , and so my "answer" was attempting to correct/clarify the terminology used in the original question. That said, the available fault current in a 25kVA transformer would be in the thousands to tens-of-thousands of amps range, and would be dependent upon the nature & type of fault, and ultimate duration (i.e., clearing time). This is why "service-rated" equipment typically has a minimum interupt rating of 10,000 to 20,000 amps - or more, depending on the system operating voltage. Lastly, most "average residential customers" would have no idea what fault currents even are, much less what the utility's transformer ratings would be. Thus, the esoteric nature of my answer....

[@MrSummitville]

@@Calico5string1962 I know what fault current is! And I replied 8,000 amps. You did *not* .

[@Calico5string1962]

Your description of the 240/120 volt system is essentially correct, although a little muddled. These systems are actually, specifically called "split-phase" systems, because they are (as you said) splitting the single phase 240 in two. BTW, great idea to show an actual pole-mounted transformer for reference! (Although, I've NEVER seen a utility use a guy-wire as a ground bond!) Here are two great YT videos from another channel, which describe VERY WELL how split phase systems work, and what happens when a neutral opens on a 240/120 split phase system: kzbin.info/www/bejne/pIC2inuLra2rfZo kzbin.info/www/bejne/gnvZqpWVjNqdkMk

[@Stevenj120volts]

I have seen all of Dave stuff. I have built he battery stack and wired to a 120/240 panel. I have also done videos with losing a neutral but I did it with line voltage form a panel

[@Stevenj120volts]

kzbin.info/www/bejne/j2O8XomwrtN7oNUsi=qcwzyeIAnRrOy2Cm

[@Stevenj120volts]

Split phase is a type of single phase

[@Stevenj120volts]

This video I explain how it actually works and why the neutral carries only the imbalance kzbin.info/www/bejne/gna5XoJpZbx3ibssi=kQwJ5vS7EHCtK8Gv

[@JohnThomas-lq5qp]

Wrong it's all single phase. Can never get split phase from a conventional plain Jane transformer.

[@JohnThomas-lq5qp]

Was taught split phase is only certain single phase motors that usually use a capacitor to produce an out of phase power to a start einding to produce starting torque. What uou have us 100% single phase 3 wire secondsi 120/240 volt system with the center tap grounded to profuce a GROUNDED CONDUCTOR on and not a nuetral !

[@Stevenj120volts]

You were taught wrong....and its a neutral . Do you own NEC? Look of the definition of neutral conductor and neutral point.

[@Stevenj120volts]

I will pay pal your $100 if that does not middle connection does not match the definition in the NEC for neutral conductor and neutral point

[@matthendrickson5538]

all single phase motors, both 120v and 240v, need a capacitor to produce starting torque because a single phase alone cannot produce a phase displacement between voltage and current the way there is with 3 phase. the capacitor is not splitting the phase. it is shifting the phase relationship between voltage and current. remember ELI the ICEman. you can think of split phase neutral in the same way you would think of a transformer tap. (full voltage/total turns) x number of turns at tap. bring that tap out from the center point of the phase coil and you have a conductor that is common to all tap connected loads and carries the unbalanced portion of current. this specific tap is a neutral tap, ground it and you have a grounded neutral.

[@JohnThomas-lq5qp]

@@Stevenj120volts We were told over 5 years ago at several continuing education classes that to stop using the term neutral because it was changed to grounded conductor. I have NEC books dating all the way back to the 1970'S but do not have the latest two because I retired and gave up my license and no longer do any work outside my house.

[@JohnThomas-lq5qp]

@@matthendrickson5538 Wrong. Look at erector sets motor it's a shaded pole ( ya made before you were born ). No capacitors, Some split phase motors that run off single phase do not have a capacitor. They use the start winding to produce a lower starting torque then split phase motors that have one of two capacitors. A 120 wall clock motor never have a capacitor. I still have my doubled sided spiral bound probably 500 page motor book from the 1960's that has a full page listing single phase motors along with starting torque and other pros & cons. Think a genius named Rosenberg wrote it along with hundreds of illustrations. Vacuum cleaner and old drills have universal motors that have a winding wired in series to a commutator brush holder thru the commutator then out the other brush holder to other winding. They never did & never will have capacitors. Only motor that I can think of that if running off of 60 HERTZ instead of running the nominal 3540 to 3600 RPM can reach speeds over 10,000 RPM. My dad had a 3/8" hand drill that label stated it could run off of 120 volts AC or DC. I connected it thru a variable transformer & a full wave rectifier to see if it did run on DC. ( YES it did ).