High leg delta systems--explanation and NEC requirements

This video covers high-leg delta-connected systems, including an explanation of the voltage system and the NEC code requirements for them.

[@jabbarvalenzuela9444]

I'm an apprentice electrician and recently came across to a high leg delta, and i didn't realize the color on the phases but the readings on my meter and the questions started, i was so confused and this video really help me a lot, i understand more about it and I'm more careful , just trust your meter right .. thanks....

[@Sparky-ww5re]

Thank you for explaining. A good buddy of mine, is a master electrician and has been in commercial and industrial for nearly 40 years, only ran into a 480/415/240 volt delta, once in his career, so far, which is how unusual they really are. It was in a woodworking plant somewhere in northern Kentucky, about 30 years ago. The larger motors were running 480 3ø, while they were running the metal halide high bays as well as some smaller equipment off of 240 volts, or it appeared that way anyway.

[@johnmaranuk1842]

Thank you, Ryan! Very thorough and easy to understand. Keep up the great work 👍

[@camoapajafa]

Thanks for another video, Excellent Mr Ryan.

[@Luuuke420]

Great video ! Covered all the code and why, straight to the point.

[@davidsonbolian9248]

Thank you Ryan for your very educational videos

[@lgrantcdg]

A very clear and complete tutorial. Thank you!

[@chrisf3875]

Really nice job. On explaining the breaker ratings.

[@SteigerSnacks]

Great video! Highly informative.

[@MrMaxyield]

Thanks again Ryan... One of the most informative channels on the tube...🔥🤘

[@felixsandoval486]

Excellent video Ryan, You defenitely have the gift to teach and make NEC contents clear, nice and easy. Thanks a lot for your great job and for sharing it with all of us.

[@travisbruno5964]

I just found your channel ive been a commercial/ industrial electrician mechanic for only 7 yrs now and i have to say thanks because how you explained all that was brilliant i know im gonna learn from your vids

[@felixsandoval486]

Also very good resources, pictures, slides and everything is high quality.

[@chadg6874]

Thank you. Subscribed! I'm just starting to learn the language of electrical work and code as a 2nd year apprentice. Even though a lot of these concepts are not fully intelligible for me yet, it really helps hearing thorough and careful explanations from you. Looking forward to watching more.

[@MrTom38ncalif]

Thank you for your educational expertice. I am grateful for your knowledge sharing. Here in San Antonio, I asked CPS to provide a High Leg to my home to power several 220 high current devices (welders , plainers, band saws ,and a few other 7.5 HP equipped devices). Their response was that we dont run these to homes given that the feeds are 1) underground and 2) the cost of installing a transformer might make you change your request. I settled on 320 Main with (2) 200 amp pannels and never looked back. Thank you CPS for an education and pulling it together for me. That being said, I dont mind paying more for power given their accomodation ..

[@tw4328]

Very Very informative sir !!!! you have cleared a lot of questions up. Thank you.

[@MarcMallary]

Thank you for this video. It helped me a great deal.

[@jakeupmickey8175]

the video was excellent and well-explained

[@j.anibalcueva662]

i always find in your videos very instructional and the explanation is really clear very knowledgeable; glad to have you as an instructor by this means, thanks for your help Ryan.

[@RyanJacksonElectrical]

Thank you!

[@bitsandpeace]

Great video again!

[@matthewstringer4424]

This is the lords work.

[@jovetj]

Love your videos!

[@donnieralph3993]

Great explanation of good information.

[@elc2k385]

Thanks again, Ryan.

[@monsooncustoms9100]

Great Explanation!

[@VegLuv]

Thank you for this!!!

[@wyliesdiesels4169]

We still have a few corner grounded deltas here in town. can easily tell because the metering cabinet is on the base of pole, and there are only 2 CT cores up on the crossbar on the pole. also, you can see a small bonding wire coming from the third unmetered leg going to a ground wire running down the pole.

[@tonyhddodge4282]

Great video. Thanks

[@salenahontz8001]

Amazing. Thank you!

[@ignacioflores7781]

Mr. Jackson, The best 23:07 minutes ever . Charlotte NC 2:24 am

[@RyanJacksonElectrical]

Thank you!

[@edgar20109]

Thank you for teaching

[@HumbleBrownWarrior]

Awesomeness, Thanks!!

[@lawtonsegler1923]

Fantastic!

[@chadrowland5234]

At the pool where I work, I have replaced panels before and a lot of our older facilities have high leg deltas and a good chunk of our newer pools as well. Our second and newest water park has a high leg delta. Our first and oldest water park has a Y system. I always like to call the high leg the "bitch phase". And, I always like to mark the wild leg with orange. Neutral is marked white. But I leave the other two wires alone. And, I only trust my meter and I always like to mark the panel with the label, "CAUTION: B PHASE TO GROUND HAS 208 VOLTAGE". And, the decoy spots that are traps, I mark them with a label, "HIGH LEG". And, on the panel door, I put a label, "BE CAREFUL! 210 VOLT HIGH LEG!" I do all of this to make double sure that either I or someone coming in after me don't blow out equipment like computers, TVs, VCRs, DVD player, garage door openers, ceiling fans, fluorescent lights, vacuum cleaners, Christmas lights and trees, and other equipment. That bitch phase has a voltage that can damage equipment and will bite equipment. When you see a breaker space skipped every third spot, it means beware of the bitch phase. Another thing that I want to add to your video. If I am putting a double pole breaker in a high leg delta, if I need 120 voltage from both sides of that breaker, make sure that both poles are not on the bitch phase, if you need 120 voltage from both sides. If you have a 240 volt window unit, good idea to keep both sides of the breaker off the bitch phase. If not possible, label the pole of the breaker on the bitch phase as "HIGH LEG".

[@Sparky-ww5re]

Great story. I call the high leg as the stinger leg, because it stings equipment and your bank account if you screw up and connect this to 120 volt stuff. That's one reason I'm not a particular fan of this system, but I'm not afraid to work on or install this, because I'm armed with knowledge so as not to cause damage or injury.

[@user-pp8tq7gm9w]

nice video, good info. Thank you sir

[@zhumusic-ng9tr]

Very useful thank you sir.

[@duecemcd7102]

Very informative 👍🏽

[@jolyonwelsh9834]

Most transformer manufacturers make a 240 volt delta primary to 208Y/120 secondary 3 phase transformer in all of the standard KVA ratings. You would have to special order it as most supply houses don't stock them. You can put all of your 120 volt loads on any of the phases of the secondary of this transformer. You can therefore balance the secondary of this transformer as well as the primary. You can therefore balance the overall load on the high leg service.

[@jolyonwelsh9834]

I came across a 480 volt high leg delta system once. It was at a waste water facility in north-east Ohio.

[@Sparky-ww5re]

Very cool. I didn't know that even existed until I watched this video, and I bet many electricians probably never will run into that. Personally I have worked on a few 240 volt delta systems in Southeast Michigan. They are (were) fairly common in rural areas and on farms that had 3 phase motors for grain dryers , augers and conveyors, while the majority of the load was 120 and 240 volt single phase. In that instance they would often install a second transformer and create an open delta high leg. In this day and age, though, it's pretty common to use a rotary phase converter, if you are in a situation where you have a few pieces of 3 phase equipment but only single phase is available, as it's typically much cheaper and most cost effective.

[@m-bigzadaproductiontm7262]

Love it

[@JayRamboe]

Good informative video.

[@jolyonwelsh9834]

You can connect modern LED light fixtures to the high leg with either hard wired fixtures or with mogul base sockets (120-277 volt 50 or 60Hz). Make sure that you use a Straight rated 240 volt circuit breaker.

[@carls6359]

Excellent video, and very timely for me, complacency just led me to burn up the 120v coils on 2 contactors, because, in a rush trusted the colors, did not use the meter, and connected the high leg to the control circuit. Won’t happen again.

[@Sparky-ww5re]

Yep, easy mistake to make,

[@raptorms773]

Thanks for the reminder i just looked at rooftop with this configuration and just couldnt figure out why they supplied me that voltage to the service discconect when i asked for 3 phase 208-240 60A service. I thought someone made a mistake i googled it saw this video. Went though my old books andnsure enough in my own hand writing in my notes a have a drawn a delta high leg confugiration where i noted how its where the ground is and even have the calculation written down. Jeez i think im old lol. I actually measured 220 on that leg but il chock that up to meter calibration and supply voltage

[@bretthouser13]

As a HVAC technician I would love a marking in a box with no neutral. We often connect 120v equipment by grabbing a leg and using ground for a neutral when we don't have 120 on the roof

[@RyanJacksonElectrical]

You need to stop doing that before you kill somebody.

[@bretthouser13]

If only that was an option

[@knowsenough2bdangerous]

"If you ever run up against a high leg delta, now you know what to do and you know what to look out for..." Well, not quite (actually I do - "Call an electrician") - but I certainly know a lot more about this area than I did 30 minutes ago. I always wondered about that 208 volt thing and now understand that _much_ better. I can also now glance up at transformers on a pole, stroke my beard, and make sage statements like "That's looks like a open delta high-leg drop" and then wander away before anyone asks any more questions.

[@ceetwarrior]

Service call: its uour lucky day! Lol that got me laughing. We've all been there before

[@jotarokujo4333]

Thanks

[@garbo8962]

Kind of remember from my vo tech class over 50 years ago said something like not to load the center tap more then 10% on a delta center tap because of creating too much voltage difference in phases. To me best pratice would be to always install a seperate transformer to get 120 volts like the secondary on a 120/208 3 phase transformer.

[@jasonparkinson7621]

👍👍

[@realvanman1]

I would imagine many of these requirements also apply to a system derived from a 240 volt single phase to 240 volt three phase phase converter, since the end result is also a high leg delta...

[@nickontario4681]

Wow Why wasn't I taught this ? Thanks for the info

[@koarivera9151]

I had a 230v h20 heater that I did a service call for and I used the high leg on a single pole breaker didn't get as hot but it worked

[@minabenjamin3660]

Thanks for the video! Do you have videos on 3 single-phase transformer wiring and power calculations?

[@tracyhawley2740]

Used 480 delta in saw mill for motors .

[@Michael-xx8bw]

I have a 480V H-L Delta in three single phase cans with each center tapped. It is providing 480/3ph and 240/3ph and a 415V stinger leg. If 480V Delta HL is rare, this set up with center taps on all the windings to give 240V/3ph has to be a unicorn.

[@jefferymurray9685]

There is no 'problem' with the voltages on a high-leg system! They are what they are- it's simple mathematics. It's just one of the available options for end users to choose. In Chicago there are many mixed use buildings with both commercial and residential occupancy.

[@jolyonwelsh9834]

Brown-purple-yellow for a 480Y/277 system is also common.

[@CNau88]

If there were a dedicated 3 phase 240v feed to a piece of equipment from the main service panel, but that piece of equipment also had a 120v control installed that pulled from a 120/240 sub panel (with an unbonded ground), is it conceivable that an equipment fault could potentially backfeed 208 through the neutral and fry things running on 120v?

[@realestateservicessaleshea99]

Thank you for the brush up we had 13200 volts into our buildings from two separate sub stations and multiple transformer configurations and panels 🥃🥃🍺🍺🍺🍇🏌 Stay safe. Retired(werk'n) keyboard super tech. Wear your safety glasses.

[@garbo8962]

At a large hospital that I retired from they had four 13,200 services feeding 2 switchgear rooms in lower basement. Also had 13.2 KV transformers on the 7th & 10th floors. Had 4 natural gas gens at 760 KW each and three 2000 KW diesel gens.

[@waynenocton]

Just last week I ran into this, and like you said every 3rd breaker slot was empty. There is one set of wires from the pole connecting to two heads with two separate line sets going down to separate disconnects. But one panel has the orange, center, high leg fuse missing, then at the two panels they lead to it changes to the C phase, and is marked high leg orange. Is anything different as far as bonding neutral to ground, at the first panel only? Reason I ask is one of the sub panels has a sticker saying it would need an isolation kit to separate grounds from neutrals, and both were attached to same screw terminals. Wondering too about balancing the phases, thought I’d connect all the 240v HVAC units and ovens etc that are truly 240v, meaning no neutrals to the high leg to try to balance things, but not sure if I should or if I should just keep not using the high leg. I’m doing what I can before the electricians come in.

[@ricardobejar1325]

What’s the max load /amps available at 120 volts on delta transformer?

[@shawngabriel7397]

I worked on a system that had a corner grounded delta.

[@shawngabriel7397]

That system was a480vac system

[@RyanJacksonElectrical]

@@shawngabriel7397 Those are pretty rare. Interesting systems. In almost every application the grounded phase is not identified correctly (must be white or gray).

[@shawngabriel7397]

@@RyanJacksonElectrical a lot of industrial facilities around colorado use corner grounded delta transformers.

[@nathanarmstrong7662]

These are all over in metro Detroit area.

[@Sparky-ww5re]

marking the high leg orange with pink stripes or something unusual would probably be more effective than orange, if you were installing a 480 volt high leg delta, because normally Brown, Orange , Yellow & Gray is used for 277/480Y. So in case of a 480 with a high leg, brown, orange/pink, yellow & gray could be used. just a suggestion.

[@davidw7015]

Ryan, I started my career as an electronics tech on B52 bombers in the USAF right out of HS. I took up Electrical wiring (Commercial then Residential) in 1972 and got my Journeymen's license. About 1980 I went on to designing mechanical and electronic equipment and programming embedded microcontrollers and PLCs. Skip 40 years, I now am building my first and last house. That being a 40 year span I need to learn the NEC again. I do have a licensed contractor to guide me and pull the permit and check my work before inspection. I am designing the electrical and mechanical of the house. I have watched many of your UTubes and just came upon this one. I have to disagree with your usage of 120/240 volt 2 pole breaker on the high leg. The breaker contacts have voltage across it only when it is OFF. When ON it has 0 volts across the contacts. So the two connections possible using it would be two 120 circuits to neutral. Not really functional unless you wanted to to drop out both circuits (120)when one tripped. This is one of my intended uses for it! The other connection is two legs connected to a 240 volt load. Phase does not matter because the load is not connected to neutral.. The only restriction is the same as a single breaker connected to the high leg with the load connected to neutral. I plan to use the high leg for 240 volt loads. What I'm looking for is where I need GFI and or AFI protection. Thanks for your excellent teaching. Dave

[@RyanJacksonElectrical]

See 240.85.

[@dylantaylor3921]

We wire high leg on phase B but, in the panel C phase is 208 or every 3rd breaker ??

[@jolyonwelsh9834]

"I want my high leg now" "power for nothing and your heat for free"

[@RyanJacksonElectrical]

Nah, that ain't working. 😉

[@jolyonwelsh9834]

@@RyanJacksonElectrical "What's with this funny voltage. That's the way you do it. You plug your heater into the high leg"

[@bitsandpeace]

Hi Ryan...just wondered if you have or might do something on ambient conductor adjustment factors. .. or just temperature adjustment factors in general. Thank you.

[@RyanJacksonElectrical]

I'll put it on my to-do list.

[@bitsandpeace]

@@RyanJacksonElectrical thank you Ryan!

[@reemasuresh1670]

Hi Ryan thank you for the explanation, it was very insightful. I am having trouble understanding why "every third space" will be empty on a high leg? Is it only in the context of not having 208V to N loads in the system?

[@RyanJacksonElectrical]

Yes, that is correct. Here in the U.S. there is no practical application for a 208V line-to-neutral power source.

[@reemasuresh1670]

@@RyanJacksonElectrical thank you :)

[@stephanielyons6983]

This is the clearest explanation of a high leg delta system out there. You should do education for kiln manufacturers/installers. There are a lot of installers that believe 240 3 phase is a thing of the past and don't know the system.

[@ronsbeerreviewstools4361]

A very good informative post. Is the high leg always phase A or phase B. ??

[@RyanJacksonElectrical]

For NEC installations it is B, for utilities it is usually C.

[@GlenDark-pq2mk]

High leg Deltas can have trouble with Variable Frequency Drives VFD as the drive will see the high leg as an overvoltage. Just my 2 cents for anyone out there struggling with this.

[@glennmcgurrin8397]

How often do electricians swap b and c instead of rotating all three phases creating a trap for those who install three phase motors or other phase rotation sensitive equipment without confirming phase rotation?

[@TransTurbine]

Good day, I have a delta transformer with high leg. I was curious if its possible to remove the center tapped configuration so it gives me three equal phases as opposed to the two 120v and one 200v

[@wim0104]

if you remove the center tap, you have no 120V at all, and you'd need another set of transformers to get 3 phase 120V

[@manuellastrollo2168]

why is that missing beside of being a high leg sir Ray? are there any explanations beside that?

[@nathanlindley5354]

So I have a question not covered. 240v high leg is 208. I have seen in the past and worked on equipment connected to the high leg by a single pole breaker at 208 volt. Example would be a mini split AC unit. Everything worked ok. But if the breaker is rated at 240v is there any violation?

[@RyanJacksonElectrical]

No.

[@estifloco]

Hi Ryan, I can't find any information regarding a 230v single phase motor and wiring it to a high leg panel. Can the motor be wired with the 120v A phase and High leg B phase?

[@Sparky-ww5re]

Yes it can. Any 240V line to line piece of equipment can run on phase A-B because it's "seeing " 240V, it cannot tell which phase if any, is the high leg. If you think about it, voltage is the "electrical pressure " or difference of potential between two points. The only thing you would need to watch out for, is that the breaker must have a straight rating of 240V, and you won't find that at your local home depot or Lowe's, you'll need to go to an electrical supply store and they'll most likely have to special order it for you; the breakers at your big box stores are slash- or slant rated 120/240V. Also, if the 230V motor in question is used in a piece of machinery with 120V controls, a CNC machine is a good example, using phase A & B (high leg) could be a decision you'll immediately regret, if the control circuits are inadvertently connected to phase B - neutral.

[@jigzzzz808]

When would this system configuration be used and what benefits does it have?

[@Sparky-ww5re]

Great question! This system is often found in older commercial and industrial buildings which have mostly 3 phase motors, and where the overall 120 volt loads are small in relation to the overall loads, and is seldom installed today. The benefits are 240v instead of the more common 208 means the same amount of power can be transmitted at a lower amp draw, and slightly smaller conductors and raceways can be used, saving costs in labor and material. This system has two major disadvantages. The biggest is that it's easy to mistakenly connect the high leg where 120 volts is desired and smoke up everything on that circuit. Also load balancing will be poor if there's substantial 120 volt loads.

[@andrebadel8257]

What does 408.36 (c) equate to ? Does that mean a breaker can no longer be installed in the high leg slot/phase Or that delta high breakers ( main ) the six space ones,may no longer be used..

[@RyanJacksonElectrical]

A delta breaker was a way to get three phase power out of a single phase panelboard connected to a three phase system. They haven't been manufactured since (I believe) the 1970s.

[@Sparky-ww5re]

@@RyanJacksonElectrical I have done research on these, they were banned in 1978 for new installs. What stirred up my curiosity was in the house I was renting last year in Charlotte, NC. I was told the property was built in 1969. Anyway the breaker box was a split bus, ITE panel, on the door it had two different wiring diagrams one of which illustrated a 120/240 3ø w/ high leg, and wondered what the heck that meant. Essentially it was a very oddball breaker that clipped onto the two bus bars like a regular two pole, but also had an additional wire, from the meter, that was connected to the breaker to feed it the high leg. It allowed for one three phase load, in a single phase box. Typically used for a 5 ton air conditioner in the 50s and 60s.

[@brianwhite905]

My shop has 208v bastard leg. Very difficult to find electricians that's even heard of it yet alone know how to deal with it. They always act like something's wrong. One even tried to fix it. blew out all the ballast in the fluorescent lights

[@user-mt7kn7qy7j]

I’ve never connected a 2 pole breaker in a panel to a high leg on a L6-20 receptacle in a server room( no neutral needed). I never felt it was secure. Maybe I’m wrong. Please advise me for future connections. Thanks for your teaching!!!

[@undaware]

Only reason I can think to avoid a high leg is to keep the phases balanced since the center grounded winding MAY see more load.

[@Sparky-ww5re]

I don't see any problem with using a two pole breaker on the high leg as long as it's ONLY running line to line loads because the load sees 240 (or rarely, 480) volts, no different than the electric water heater in your home running off a 120/240 single phase system. The only issue is the breaker is a straight rating, not a slash rating Most two pole breakers are 120/240, a straight 240V two pole breaker is a specialty item and you'll not going to pick that up at your local home depot.

[@davidrickert4925]

Why do they still install high legs?

[@theseattlegreen1871]

I don't think I've ever seen a 3-pole circuit breaker with 240 volts phase-to-phase. It's always been 208 V phase-to-phase🤷‍♂️ Or it would read 480v phase to phase

[@Sparky-ww5re]

That's because you're thinking of a wye system, 120/208 & 277/480. A delta system gives phase to phase voltage of 240, 480 , 600 and higher.

[@jakeupmickey8175]

Question, Why is it that you are referring to the 208V leg as the high leg when you have 240V that reads higher voltage I am asking not to be smart but maybe there is a reason for

[@RyanJacksonElectrical]

Because there is only one that is 208 to ground. The other two are 120.

[@tedlahm5740]

Three phase OPEN DELTA, only uses two phase power from the utility? Question please.

[@RyanJacksonElectrical]

Two windings, yes. This is where the word "phase" becomes problematic.

[@tedlahm5740]

@@RyanJacksonElectrical Thank you.

[@tedlahm5740]

Correction: All three phases are used from the power company but only 2 transformers.

[@andrebadel8257]

408.3 (e) 408.3 (f) (1)

[@ianbarry6615]

Good news here in the UK, we use 240v equipment, so you can buy and run any of our stuff, bad news your concept of electrical distribution is so overly complicated it's a wonder you make it to work in the morning, we and I think most of the rest of Europe use a balanced 3 phase 4 wire delta/ star electrical distribution network the final step down transformer star point being neutral and earth connection,UK any phase to phase 415volt any phase to neutral/ earth being 240volt, and no such thing as a high leg!

[@nhzxboi]

Color blindness forced me into engineering and I enjoy that. Stupid colors. Brown? Red? What's the difference? None to me. When speccing multi-conductors, I spec numbered conductors...they're usually black. Makes it so I can understand what's going on. Screw the colors, let's use numbers.

[@Ormaaj]

I only buy red and black. Why? Because I can get any kind of wire in red or black. Even so, go look at some exotic wire types (e.g. some of the mil spec stuff) on mouser or whatever. The weird and ugly colors are a fraction of the cost! Should really just use whatever is cheapest and disregard color. :D

[@nhzxboi]

@@Ormaaj I buy nothing, I just spec it. Color codes on a CAD drawing are easy. distinguishing blue from pink or brown from green is what I'd have trouble with. I'm fine with the letter codes though. Fear not, ,my DWGs are good but would be sorta tricky if I were wiring the thing. Color blindness is a serious handicap.

[@poordueto401k]

Good basic video and information. Just a couple of nits to pick. 1) Utility requires the high phase to be on the right side of a meter socket because that is the way the meter is designed. It has always bugged the hell out of me that the code making committee that decided the high phase must be the middle phase was so out of touch. The meter is NOT looking for 120 volts on phase B as the speaker suggested. The meter has two stators. One is a three wire stator just like is found in a residential meter. It consists of (2) 1/2 current coils and a 240 volt potential coil. The 1/2 current coils each measure 1/2 the current of 120 volt loads and twice the voltage due to the 240 volt potential coil. So, the coil must be energized at 240 volt so it is connected A-B The other stator is a 2 wire stator consisting of a full current coil and a 240 volt potential coil. It must be connected C-N which is 208 volts. 2) Although the speaker quickly realized his error in saying a 480 volt 4W delta has a high leg of 277 volt instead of the correct 416 volt, that makes me wonder if the speaker understands the math involved. Was it just a brain fart?

[@RyanJacksonElectrical]

Well I explained the math at the beginning of the video, so what do you think?

[@robertochavez8196]

Thanks

[@mikeadler434]

👍👍