120/240 and 120/208 Volt Transformer Secondaries

Explanation of how we derive 120/240 V and 120/208 V from various Transformer Secondaries.
Additional video of interest: "120/240 V In-Phase or Out-of-Phase" • 120/240 V In-Phase or...
PLEASE NOTE: The arrows above the left schematic show that this is one winding that has simply been tapped in the center. The waveforms below it in the lower left can give the wrong impression that the "halves" of the winding are out-of-phase with each other. This is because I'm using the neutral as a reference and as I mention in the video, from the perspective of the neutral you look "up-arrow" to one end and "down-arrow" to the other end of the winding. BUT, from either end (i.e: black wire to red wire, or vice-versa) you will be looking "up-arrow" or "down-arrow" for the entire length of the winding (i.e: in-phase).
You can dig through the comments for further discussion on this. I have made a video addressing the phase relationship within 120/240 V systems, and I hope to create other videos focusing on current flow in each of the scenarios that will further our understanding of these transformer configurations.
Thank you,
Dave

[@ronmurphy2069]

This man is a master at teaching... so clear. his body movements, his eye movements , hands all work in coordination with each other. his voice, easy on the ears... His brain the conductor of the whole operation. A pleasure to learn from...Thank you Dave.

[@TheCompton1963]

Yes sir!! 🧑🏻‍🏫

[@Impedancenetwork]

Rolling my eyes

[@matthanaford4614]

Dave taught at my JATC for a couple years. He’s literally the only reason about 40 of us made it past our second year.

[@danielalexander8402]

I get the same vibe. This man knows how to teach well.

[@Professor-taboo]

Sheesh .....get a room 😆

[@rty1955]

As a EE, I have to commend you on a well diagrammed and spoken lesson. Good job!

[@DRay62889]

30, 60, 90 degrees and you get 208. Wow, I never realized that trigonometry and electricity were connected!

[@nassimzouaoui469]

Truly a master in explaining, makes it easier to understand the concepts

[@abrahamjaime9417]

I was so lucky to be in his classes. Dave, you rock, man.

[@608_rich]

Nice work Dave. This is one of the most thorough and understandable descriptions on 120/240 and 120/208....excellent.

[@pterafirma]

13:47 "They ended up blowin' up a bunch of stuff because they were Russian"? In other words, they connected to the wrong Pole?

[@pterafirma]

@@ivanzapata396 😑 ::whooshh::

[@tlhIngan]

The 120/240V thing was actually a late 19th century thing - all derived from the Great Fire of Chicago. Edison lamps were made out of carbon, and used 110V, however, other companies figured out how to make lamps using tungsten, a much more resilient metal and could work at 240V (carbon lamps burn up at 240V). Since adoption of electricity was much slower in Europe, the European utilities went with 240V as it saved money on copper and is more efficient. Our 110V system was derived as a split-phase system, because Edison noticed that some people's lights were brighter than others. So he designed the system as two 110V generators (this was DC, mind you) and connected them together to form a third neutral line. He realized by monitoring the current flowing on the neutral line, he could determine how bad the imbalance was and rebalance the grid so the same number of lamps were on each half so everyone's lights were the same brightness. In addition, if you needed more power, you had 240V (DC) available. Now, electrification was huge in the US - especially after the Great Fire of Chicago which meant everyone started from scratch, and skyscrapers were a thing. Gas lamps couldn't be lit more than a few stories up, and everyone wanted electric lighting. So much so that demand for light builbs was so big even though carbon lamps were obsolete, Edison was still making millions of them as the tungsten lamp makers couldn't keep up (in the late 19th century, they made around 10 million tungsten lamps, and Edison made nearly 60M carbon lamps. This changed about 20 years later in the early 20th century when carbon lamps were finally obsolete and replaced with tungsten lamps. However, by now the die has been cast - 110V had been around for so long, there was no appetite to change over to 240V.. In Europe, electric lamps were seen as a novelty, and very few people had it. The rich folks refused to install it in their castles, so when it came time, it was trivial to switch over. Oh, and the first war of the currents was between Edison and Westinghouse, not Tesla. The second war of the currents was between GE and Westinghouse which dictated if we'd use two-phase (Westinghouse, via Tesla's patents) or three-phase (GE, Edison had been kicked out) AC. Tesla is confused in these because Westinghouse bought Tesla's AC motor patent (and later all of Tesla's patents). That patent showed how a motor would work at 60Hz two-phase. You have to remember though, that just because of this, power was still not quite standardized as you could get DC, 60Hz, or 133Hz AC power (133Hz because Westinghouse managed to find a design for an electric meter but that required 133Hz to run properly).

[@Sparky-ww5re]

133Hz from my understanding, was more commonly used with carbon arc lamps common for streetlights and in factories and large retail stores from the early 1880s until the early 1900s, because it flickered less than 60Hz. You also had very oddball frequencies such as 25, 33.3 & 40Hz, to name a few. The early days of electrification must have been a very intriguing time to live through. And all this was in major US cities, many farms and homes in rural areas didn't have electricity until after WWII, my grandmother recalled not having electricity until merely a few months before she married in 1947, born in a farmhouse in 1925 and lived to be 96.

[@jolyonwelsh9834]

Give me a 240/120 volt delta system anytime. Forget the wimpy Wye.

[@weavercattlecompany]

Other than you kept referring to the peak voltages as 120V which would be confusing to a beginner when actually Vp ≈ 170Vac or Vp-p ≈ 340Vac hence the need for capacitors with 370V or 440V ratings. Root Mean Square is just the DC equivalent hence there would be a straight line drawn through the sine wave to represent that average. Vrms = Vpeak/√(2). RMS is the only way to average a sine wave in case your wondering. It's also used to take an average in statistics to minimum the effects of outliers 😉 - 1st drawing - Single Phase - 2nd drawing - Three Phase (Wye) - 3rd drawing - Three Phase (Delta) I suggest adding "Ugly's Electrical References" book to your toolbox because it covers all this and much more in case you forget. Great video 😊

[@eduardoconde9247]

I am electromechanical engineer, your explanation is very very clear. THANKS a lot teacher.

[@equiteemfg]

Stupid question time. Are the line 280 wires Brown, Orange Yellow and the black, red and blue the outputs? Would you be running the Neutral for 120v in white? You probably have a wire color code video, I'll look. You do amazing videos. Some airhead talks about stringing beads and gets 100K subscribers, but real , well presented videos don't. Life isn't fair. Thank you for taking the time, the videos are great.

[@AT2Productions]

My favorite term for the high leg of a delta transformer for 120/240 is the "bastard leg."

[@hackingnut4164]

Fantastic video. However, the one thing I disagree with is at 13:47 and people blowing up a bunch of stuff because they were Russian. I think any electrician in the industry long enough has blown up a few things and they aren't all Russian... Yes I had to

[@zacharybob4336]

Dave your videos are so immensely understated. You're an absolute hidden gem and I can't thank you enough for making this material available. I'm an IBEW electrician apprentice in my 3rd year and I constantly supplement my school work with your videos.

[@TheGermanElectrician2000]

High-leg delta is a bad system. Symmetrical load is almost impossible and it´s complicated to use. Here in Europe, every household gets 230/400V three-phase power. 230V 1p for normal appliances and 400V 3p for every device above 4kW.

[@apostle100]

At 13:47 it sounded like he said people were blowing up a bunch of stuff cause they were Russian 🤣

[@DormantIdeasNIQ]

wronnnnnnnnnnnnng.... this is just wronnnnnnnnnnnng!

[@BobbaFett312]

i feel lucky that people like dave are on youtube and shares their knowledge, great info!

[@xandriasmall6668]

i recently installed 3 phase in my building, they would not give me 240 delta so i had to go with 208. do you know why they won't install 240 delta anymore? is it just because people don't know how a dmm works?

[@Sparky-ww5re]

You'd probably have to argue that with your utility provider. Although here are the reasons I can tell. In a delta configuration with a center grounded transformer, maintaining a balanced system is nearly impossible, since all the 120 volt loads come off one transformer. 240 volt, single phase loads strategically placed in the panel can help, but there is a catch. The two pole breaker must be rated 240V, not 120/240V if placed on the high leg, and 240V double pole breakers are not as common and more costly than the 120/240V and will likely need to be special ordered. And most, but not all 240V equipment will run fine on 208V, for instance many larger window AC units and outdoor condensers mention 208V and 240V on the nameplate. So to sum it up the 240/120V three phase system although still useful in very specific applications, is something a lot of utilities no longer install, although other's will install one upon request, and electricians therefore must be aware of this system because you will run into it at some point in your career.

[@mindingownbusiness555]

Best explanation ever. I finally understand!!!!!!!!!! Thank you.

[@litocroy7147]

You have simplified months of frustration in trying to understand these concepts. I cannot wait to check out the rest of your videos. I so appreciate the clarity you deliver. THANK YOU!

[@khalidfouda3278]

Amazing explanation, very good job 👏

[@mauriciogonzalez618]

Wow I wish I had a teacher like you when I was in trade school, nice job explaining and simplify something so complicated, please continue uploading videos!!!

[@robertochavez8196]

Great people share their knowledge!!! God bless you!

[@hamskidoo]

This is one of the best videos I have watched out of a lot out there that explains with this much clarity and expertise. Thanks for passing your knowledge how it should be with all.

[@douglieberman6406]

I like the idea of the radius of a circle in terms of a generator, starting from west or zero axis , like a radar from west , north , east , south and to west. ! Radar or radius is from center point to the inner circumference of the circle ⭕️ . Diameter is from west to east or north to south, that is why a radius really is interesting like radar !

[@tmengistu1778]

Dave, I was looking for the definition of a great teacher, and now I got it on this KZbin video. You are beyond excellent and keep up doing this amazing teaching style.

[@KinGIIRomE]

Wow you are amazing! Thank you so much for making this video. I will share this to all my friends.

[@TXRoeJogan]

Thank you for helping me understand the wye out of phase 208 and the delta ! My teacher could use some lessons from you on explaining things better!

[@DerekJohnson-zx3co]

Thanks for explaining a different method to calculate the HIGH LEG to ground. I did not know using Pythagorean theorem gives you 208AVC. I've always use Vector addition.

[@adrianellis5779]

I did the HW chum rms = root means square center neutral opposing and pushing relativity of product Bus wiring Voltage = Points if differential potential of to points (Check out angle theta!!) as well as from which 120 degrees of the exact moment of the circuit became energized comparing the constant peaks per delegated cycle (Alternating Current and it's Value) while subbing out impedance with greater use of Volts and VA (Volt Ampere) to mediate or use the Load (What the conductors are connected two and their rating) for treatment of the new simulated resistance from use of Center Tapped Neutral Connecting within the center if the Wye Connect will split...not only the windings but the voltage. Equaling=B phase To High leg is 208V Make Sure You label!

[@fldave612]

Question: Where would a wye transformer like this one be used? It seems like the only place it would be good for would be structures requiring only 120V services. Are there any instances where straight hot leg to hot leg 208V would be needed? Aren't most devices 120V or straight 240V? I understand 3 phase where you have a high 208V leg, but I've never seen that high leg used on a single pole by itself, it's always used in conjunction with the other 2 phases to produce +240V at 3 points during the cycle.

[@justdoit4518]

I understand everything perfectly the only issue im having is the right triangle reference where he says c2 - b2 = a2 , so in normal its A2 + B2 = C2 , so 120^2 + B2 = 240^2 , divide by both sides to isolate the unknown B^2=57600/14400 B^2=4 , root both sides B=2 is my math wrong , i havent taken algebra in years so i might be missing something

[@lxbanos]

Thank you, as a mechanical engineer I’ve always struggled with electrical concepts and this helped me understand much more about how the different windings affect voltage.

[@MrUlises56]

Thank you so much for the video 🙌😂🙌🙏🏻🙏🏻🙏🏻🙏🏻 it helps me to understand many dots 🫡🙌🙌🙌🤜

[@achalbhoir1359]

@dev Gordon 1 question.... I din't got that why center tap is grounded instead they (who made this ckt firstly) can keed either side of it can be connected to ground.... Idea is when we running 240 volt appliance.... If ground fault occurs then PROBABILITY will be 50% that wire will be live and 50% will be neutral wire So that during neutral connects to ground... Damage will be almost equal to zero and in other hand if live touches ground fault current will more and immediately clears out fuses in path , i know someone will say potential with respect to ground will less in center tap configuration, but either you get electrocuted by 120 or 240 you will get electrocuted....!!! Also in 240 volt system without center tap to ground connection wire sizing will also reduced for 240 volts for same kilowatts while center tapped live wire and neutral will be the same as before

[@totallyawesome80s55]

Excellent video. I'm pretty sure that this was explained in trade school, but definitely not this clearly.

[@martf1061]

10:54 I'm an electrician, and never understanded why the neutral ( X0 ) has to be " grounded " ?! I know what happens when it's not, but dont understand the reason... Is it only in case of unbalanced 120v loads in a star 120/208v ? But what if its 3 phases 208v star configuration, and we only put a load on phase A and B ( 208v single phase ) , and the X0 is not grounded, what happens?

[@rob0516]

"Ended up blowing up a bunch of stuff, cause they were RUSSIAN". - context😅

[@mcdrone3932]

@davegordon6819 Dave, I absolutely enjoy your topics and teaching method. I have a question I’d love to see you do a video on. There’s a debate in the RV industry about the use of voltage stabilizers. Some say not to use them, as they will drop the voltage for the rest of the RV users, as the stabilizers sacrifice current for voltage, therefore pulling more current and lowering the voltage at the post. My take is that if there is low voltage at the RV post, say 104V, instead of 120 per leg, the appliances, Air Con, refrigerator, etc.,inside the RV are going to pull more current, as they maintain their power requirements. Therefore, boosting the voltage with an autoformer, will reduce current consumption at the RV, but will consume more current at the post, making the current equal to that without the autoformer, minus some inefficiencies. Am I off base here?

[@preston2784]

Thank you! Really gonna help me with school

[@georgehirapetian1570]

I received dumpling machine from China and they made 220v single phase thinking it's good for using in the USA. There are five wires coming out of the machine. Electrician said its 3 phase, but he was afraid to make the connection because on my circuit breaker cabinet said 120v/208v. Can I use this machine without transformer?

[@whochecksthis]

This is not how I understood the 120/240 transformer works… I thought it was a single phase 240V transformer it’s a neutral midpoint… so only a SINGLE wave not two… it measures peak to peak not wave peak to wave peak…

[@angrykawata1992]

Hi dave, thanks for sharing, for the wye connection. in single phase 208V. How do we calculate the current for each phase. since the single phase 208vac running on two phases (L1&L2) . Does it means current in L1= L2 ? like single phase to neutral 120Vac. Current flow in neutral = current flow in L? or any other calculation. need it to calculate total load at each phase. thanks in advance

[@simplechristian1]

So what happens with the sin waves when you change 208 (2hot legs) to 120/240 via a transformer. I'm perplexed because you still keep 120 volts

[@markchidester6239]

On the 3rd drawing, is the 208 volts also called grounded B-phase? You are giving me information that the maintenance guy I use to work with wouldn't give me because it would have taken to long to explain.

[@beijing561]

Nice tutorial. But can you use the delta center tapped high leg 208v for single phase 208v appliance? Thanks in advance

[@irving_8194]

13:45 "They were Russian. They had to stay behind and fix everything" Looool I know he said "rushing" but it sounded like "Russian"

[@ryanstout5020]

I need help! Lol im trying to get 208 single phase and need 32 amps. What is the transfromer ill need? Supply voltage would be 240 v

[@makesaveinccomm]

Hi guy some one please tell me the different between home depot 2 gauge thhn copper wire and Lowes wire. They both made by southwire but why does lowe list it can only carry max 110 amp while home depot listed on their site 125 amp max. If I don't remember wrong, I think in store even said 130 amp. I plan to run 25-28 feet inside conduit over head inside garrage ceiling. 125 circuit breaker box. Thanks

[@georgeswindoll9138]

This man is a truly gifted teacher!!!!

[@mrindependent1]

He just schooled me so good! Thanks sir We love ur videos His diagrams are perfectly simple

[@xevierred6330]

Here the batteries did not blow up when he changed the direction. How come with 480vac if you do this you'll blow things blow up.

[@techmelts7860]

Under x2 there’s a tank ground bushing right underneath it. The green ground wire. How do I hook that up? Do I connect to only tank ground or both x2 bushing and tank ground bushing? I’ve seen people do both. Don’t know which one to do.

[@thelasttimeitried]

13:45 "Ended up blowing up a bunch of stuff, because they were Russian." This video aged well.

[@Festus2022]

At 2:20 you point with your finger the direction of current flow for the RED-half of the inductor. Is this correct or wrong? Appears to be a mistake. Are you using conventional current or electron current?

[@luckychohan3705]

Sir can u plz explain how current flow when we use just two line 208v wye system with neutral for one receptacle do they cancel each other the way they do in 240v split phase.

[@robertwasswa1631]

You may find instanes where you are given either a 3 wire cord or 4 wire cord and youre told the voltage supply is single phase, finding a starting point isnt always so easy, I kindly ask that you clarify slightly more so that we get a better understanding of your informative lecture. Thanks a lot, i hope to hear from you.

[@RalphSampson...]

That drives me nuts..."Hot Water Heater". You don't heat hot water. Nor is it a heater operating using hot water. You "plus them"? Dude, you are way too smart to say these things....way smarter than me.

[@fancy357]

Can you get 120v to ground without a neutral for single phase power from a 3 phase panel?

[@caseyburke6263]

Fantastic video! I recently took over management of a 160 year old theatre that has a high leg delta panel in the projection room. Wanted to get familiar with the system. This video was incredible informative. Don't be worried. It did not give me the the confidence to monkey with the panel. I'll call a pro anytime this panel needs works.

[@davidd1395]

While 208 volts is a 3 phase voltage produced by 3 phase transformer bank, it is commonly used as a network voltage by utilities as a leg to leg voltage for single phase residential loads instead of 240.

[@najentertainment5866]

So is it safe to use the 208v along with with neutral or earth?

[@abdelghanich7804]

Hello.i have a problem with a neutral of secondary coil of single phase transformers .the question is how I can make a difference between the neutral and the phase . thanks to everyone reply to my question

[@tedlahm5740]

In 1910-1920 era houses only had 30 amp 110 volt service. the way i remember it.

[@jaedonjackson3454]

So in the “Y” system you can touch the neutral (like in a splitter) because it’s grounded and not get shocked

[@mohammadfarzankia2636]

A complete transformer's ‏‪teaching wideo❤

[@stevenj100]

So there is a push and pull or alternating between the 240 lines but there never is a push from the neutral? So 120 is off and on but not back and forth between hot and neutral?

[@Sparky-ww5re]

another system worth an honorable mention, is, an open delta, typically 120/240, but occasionally corner grounded 240. I've seen this in rual areas, almost always on a farm setting, when most of the loads are single phase 120/240, with a smaller amount of 3 phase motors, typically a grain drier, augers and conveyer. The capacity of a full delta is not warranted, and the system can be easily recognized, by the two transformers, one being significantly larger, in terms of KVA, because all your 120V loads come off that one. the smaller transformer is the power transformer, this provide the high leg. Much like the full delta, open delta suffers from the same limitations, very difficult if not impossible to balance, along with the possibility of mistakenly connecting a single pole breaker to the high leg when 120 volts is needed. As such these systems are rarely encountered in new installations.

[@MrWaalkman]

I was wondering if someone would spot this. I actually did a job at a water treatment plant in Pueblo, Colorado that used an open delta service.

[@daltondelaney9534]

Great video, I do have one question at 10:25 when you said that if you take any vertical point on the 3 phase graph and add it up you get 0. Are you referring to where the one phase peaks and the other 2 phases are intercepting underneath that peak? I assume you are subtracting the value of the peak from the values of the negative voltage phases underneath the neutral. Just threw me off when I heard you say that.

[@aaron-ld9zv]

Searched for this explanation for way too long. Very well done Dave.

[@alicerey8946]

What about if I need to install a motor of 220V in an installation of 208 V? Can I take only 2 phases

[@epicredhead13]

They ended up blowing up a bunch of stuff because they were Russian....

[@sealstech8087]

I was nodding off to the debate and watched this instead, far more substance and I had an “ah-ha” moment. 🍻

[@lazarogonzalez1455]

You answer the question that I been looking for I don’t know how long

[@pjmcinnis1188]

You the fuckin man bro keep up the good work I really enjoy your teachings

[@stevebusby6618]

Thank you, Dave! I've just discovered your videos while looking for some information about transformers. You combine two of my favorite subjects: electricity and math. Fifty years ago I was an electrician in the Navy. At that time, we were trained in single phase and three-phase delta and wye transformers. I understood it completely at the time, but never had experience with them since then and lost my knowledge of them. Now I understand them a whole lot better.

[@happydays454]

I always have wondered what would happen if you get a center of a transformer coil and stick it in the ground

[@robertwasswa1631]

For this single phase connection at 8:45 minutes, do I need a neutral? Or just the 2 live wires? It isnt so esy to comprehend

[@edt2378]

Thank You Dave well done! Best teacher I seen yet! Thanks again.

[@robertwasswa1631]

Thanks a lot Mr. dave, I just need some more clarity around 8:45 minutes, it does not cut across that easily.

[@motorhead2392]

The left drawing implies two phase which is not true. Although the presenter makes note of this in the description, it is still misleading.

[@ryanmason9141]

I've been digging to find a good explanation and now I've found it. Thank you sir!

[@Bapuji42]

I like this channel. It's for smart people.

[@jolyonwelsh9834]

There are plenty of uses for the high leg. Many modern LED light fixtures are rated for voltages between 100 and 277 volts 50 or 60 Hz. If you use the high leg, make sure that you use a straight rated 240 volt breaker.

[@Sparky-ww5re]

So you're saying there are single pole, straight 240V breakers manufacturered ??? If so they're about as rare as a royal flush.

[@jolyonwelsh9834]

@@Sparky-ww5re No, but all 3 pole breakers are straight rated and some double pole breakers are. You can simply use the high leg as part of a multi wire branch circuit. There's nothing in the NEC that says you can't use the high leg to neutral. You can run three (2 wire) branch circuits from a three pole breaker. You can not however run a 4 wire branch circuit with a shared neutral from three single pole breakers. NEC 210.4B.

[@douglieberman6406]

Is there no such thing as 120 volts peak to peak or 60 vp+ and 60 vp- ?

[@bryanfrancisco-t7x]

Very good explanation. Crystal clear tome

[@simsjoshua8128]

A single phase has 240V how comes a three phase has 415V ?

[@jon-sig]

Can you run a single phase house on a 120/208 3 phase bank

[@cosmic1663]

So it's the difference in degrees that makes a it efficient and not the voltage.

[@itsjil7594]

What happen of voltage if one transformer not working?

[@alicerey8946]

Thank you so much! You are really good

[@jameskegel991]

Awesome job explaining

[@borderm3]

5:15 the math doesnt work. You have a sin and sin(x+pi) and if you add the two waves you get 0. Hope you can help me understand, thanks!

[@GH-oi2jf]

You don't add them. Voltage is the potential difference. Subtract.

[@tedlahm5740]

Question. Can i have 480 volts on the Delta transformer WITH a neutral? What would happen to the Wild Leg from the B phase to neutral?

[@carultch]

You can have a corner-grounded 480V system, and one of the three phases would be your grounded conductor. It wouldn't be a neutral by strict definition, and this is uncommon. In concept, you could have a 480V delta system that center-tapped between its A and C phases, and each of these would be 240V to neutral. Its B-phase would be 416V to neutral. This could exist in theory, but I don't think you'll ever see it in practice. Most 480V systems you'll see in practice, are either ungrounded 480V, corner-grounded 480V, or 277/480V wye systems that are either grounded wye (most common) or floating wye (less common). There simply isn't as much need to use exotic configurations of 480V, as there is for 240V. It's much less common now, to have 240V high leg delta services, as 120/208V wye services are much more common.

[@ajsebastian5529]

do you have a video about corner ground delta thank you

[@anthonyferreira1698]

Thank you Dave, easily explains the differences as well as applications. And thank you for the math lesson (brings back memories).

[@robertwasswa1631]

In case I wanted to connect a single phase load on 208V, the two wires I have to choose from can be any live combination that is from the three live wires, What I do not get and I want clarity on is if am choosing any two wires from these three for single phase connection, how do I incorporate the neutral? Because here in Canada we use Black, White and Green for any single phase load. When you say 208V single phase around 8:45 minutes, how do i do the arrangement so that I incorporate my live wire, a neutral and a ground?

[@martf1061]

Here in canada, we dont have single phase 208V ( line-neutral ). Its like he explains, ( Line to Line ) is 208v And ( Line to Neutral ) is 120v The colors of your wires dont matter. You can always put some red tape on your white wire if it not a neutral, just to prevent mistakes or accidents.. but if its clearly identified as 208v, usually, nobody will think that the white wire is neutral.

[@rexated5148]

Thank you for teaching.

[@Mike79555]

This makes since to what i do what i do

[@1kmoduzitbig]

Hey Dave. I'm new to your channel. This video really caught my attention with your detailed explanations. I'm an electrician and I have question. If I want to feed a 125A/1ph/120v-240v panel from a 3ph/120-208v panel what's the best method to do this? Will I need a phase converter or a transformer? I have some 1ph/240v/60hz equipment to hook up but only 3ph/277-408 & 120v-208v to the building.

[@davegordon6819]

Thanks for watching. In regards to your question, I would argue against a phase converter because you already have "single-phase 60 Hz" available in you current distribution system (assuming you're in North America, and your voltages imply that). You simply need to transform the voltage. Therefore, I would present one of the following options: 1) If you just have a couple pieces of equipment you could take two "hots" (either black and red, red and blue, or blue and black) which would give you 208 V single-phase and run them through a Buck-Boost transformer to boost the voltage up to 240 V. The two output leads would then have a 240 V potential between them and could run your "1ph/240v/60hz" equipment. We generally run a separate Buck-Boost transformer for each load, but that doesn't mean you can't run more loads on a single Buck-Boost. I wouldn't, however, recommend feeding a panel with one of these. I've found that the supply houses are generally helpful in helping you size the proper Buck-Boost(s) for your load(s). These handy little devices are about the size of a shoe box, and if you're unfamiliar with them, I have a video that could get you started: kzbin.info/www/bejne/l4DXhKGApJuDnK8 2a) If you want a single-phase 120/240 V panel you could have one, but this may well be a more expensive option. The 208Y/120 V part of your system already gives you 120 V so that aspect of this option would be redundant. However, if this is your objective, then you could get a single-phase transformer with either a 480 V or 208 V primary (depending on which of you panels you wish to feed it with), and a 120/240 V secondary. This would give you a secondary that would look like the usual single family home service with which to feed you new panel. 2b) Alternatively, you could get a 480 V or 208 V primary and a 240 V secondary (without the neutral, "X0") and feed the panel with just two hots (240 V only), BUT I'd want to clear that with your city electrical department as someone could be tempted to create an illegal, and potentially dangerous, 120 V at some point in the future... ***Look into costs, but if you only have a few single-phase loads at 240 V, the Buck-Boost option may be less expensive and an easier installation. IMPORTANT NOTE: Which ever way you go, because you are adding a single-phase load(s) to a three phase system you want to make sure that you add it to the most lightly loaded pair of phases in you distribution panel (calculated loads are often printed on panel schedules if they are kept up to date). This is more important if you are trying to feed a single phase panel because the goal is to keep your three-phase transformers as balanced as possible, within reason. However, if you only need two or three Buck-Boosts then you can alternate their feeds (one from phases A&B, the next from B&A, and the third from C&A out of your 208Y/120 V panels).

[@1kmoduzitbig]

@@davegordon6819 Thank you so much for the response! I appreciate you taking the time not just to respond but to go into the depth that you did with all the options. I'll be sure to spread the word about you and your channel. This is a massive help! Thank you and have a great day!

[@V21IC]

The best option is to get the service voltages from the PoCo. If you want 120/240 contract the split-phase 120/240. If you have 3-phase loads choose the compatible service (a transformer) from the PoCo. Also, look at the motor voltage options. Whiich is easier($)? Purchase/change loads that are compatible to curent service voltages? Or, to ontract /change another service from the power company to match current loads? It's like if your loads are 3phase, 50Hz then you need to get a 3-phase 50Hz source supply of the matching voltage. O if you have a 3phase 60Hz supply, you need to change current loads or acquire other loads so that thet would be compatible to the supply voltage. The PoCo handles the supply and you, the load. You can always get your own transformer configured to your special voltage needs. However, its primary voltage requirements hast to be one that the PoCo support.