# High Leg on a 3 phase 120/240 4 wire delta system



## az101 (Feb 13, 2010)

I`m a journeyman electrician in Arizona and I recently encountered a very old warehouse building that has a 120/240 3 phase 4 wire with a high leg reading 240V to ground and neutral wire on the C phase coming from the service disconnect from the power company. I know the power company used to have the high leg on the C phase but changed it to the B phase. I would like to know if 3 phase 240V motors can be connected to the the 3 phase power with high leg and not damage the motor. I know I can use a rotary phase converter to create the 3 phase needed, but if not cool.


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## Bob Badger (Apr 19, 2009)

az101 said:


> I`m a journeyman electrician in Arizona and I recently encountered a very old warehouse building that has a 120/240 3 phase 4 wire with a high leg reading 240V to ground and neutral wire on the C phase coming from the service disconnect from the power company. I know the power company used to have the high leg on the C phase but changed it to the B phase. I would like to know if 3 phase 240V motors can be connected to the the 3 phase power with high leg and not damage the motor. I know I can use a rotary phase converter to create the 3 phase needed, but if not cool.


Yes you can connect a 3 phase motor to this supply, the motor is to stupid to care about the voltage to ground.


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## MDShunk (Jan 7, 2007)

Yes, you're fine with 3-phase motors. 

The only two things you have to worry about on a high leg system are 120V single phase loads on the high leg, or 240volt multiwire branch circuits that use the neutral inside the equipment for some 120V stuff (like clothes dryers and electric ranges). Treat your 3-phase motor loads as you would any other 3-phase load. Any three phase equipment that also has a neutral run to it should be investigated to determine what they're using the neutral for, so that you don't smoke something inside the machine that might use the high leg and neutral for something 120V. Some printing presses are this way, as one notable example. The cure there is to feed a transformer, instead of the equpment directly, and do delta primary and wye secondary. Omit the neutral with the branch circuit run from the high leg panel, and make a neutral with your wye secondary.


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## az101 (Feb 13, 2010)

I also talked to a motor tech and he had said that the high leg would burn the motor out in a few weeks or months. The tech said each leg on the 3 phase should read 120V and anything higher on any leg meaning the high leg can burn the motor. I think he believes the motor is very smart.


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## MDShunk (Jan 7, 2007)

az101 said:


> I also talked to a motor tech and he had said that the high leg would burn the motor out in a few weeks or months. The tech said each leg on the 3 phase should read 120V and anything higher on any leg meaning the high leg can burn the motor. I think he believes the motor is very smart.


He wasn't much of a motor guy if he told you that.


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## ohmontherange (May 7, 2008)

Just don't connect any 120V single phase loads to the high leg.

A-B, B-C, & A-C IS 240V phase to phase.

All the high legs I've seen are typically 210-216ish phase to ground


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## Magnettica (Jan 23, 2007)

az101 said:


> I also talked to a motor tech and he had said that the high leg would burn the motor out in a few weeks or months. The tech said each leg on the 3 phase should read 120V and anything higher on any leg meaning the high leg can burn the motor. I think he believes the motor is very smart.


Think of the motor as a painter, or a plumber. :laughing:


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## brian john (Mar 11, 2007)

az101 said:


> I`m a journeyman electrician in Arizona and I recently encountered a very old warehouse building that has a 120/240 3 phase 4 wire with a high leg reading 240V to ground and neutral wire on the C phase coming from the service disconnect from the power company. I know the power company used to have the high leg on the C phase but changed it to the B phase. I would like to know if 3 phase 240V motors can be connected to the the 3 phase power with high leg and not damage the motor. I know I can use a rotary phase converter to create the 3 phase needed, but if not cool.


You are reading 208 VAC on C phase to ground NOT 240 VAC.


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## micromind (Aug 11, 2007)

That 'motor tech' is way off. He needs a bit more education.

I can't even think of how many 3 phase motors I've connected to delta systems, and yet to have a problem. Some of these are 20 years ago. 

I've seen plenty of motors that were installed in the '60s and before that ran just fine on delta systems. 

One of the major reasons for the existence of the 240 delta system was to add a 3rd phase to a single phase system so that 3 phase motors could be installed. 

Anyone who says that a delta system will damage a 3 phase motor doesn't know much if anything about motors or power systems.

Rob


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## chenley (Feb 20, 2007)

I don't think I would take any advice from that "motor tech" from now on. 

All you really need to watch for in motor applications is the rotation of it so it doesn't damage the equipment it is attached to.


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## 220/221 (Sep 25, 2007)

> I also talked to a motor tech and he had said that the high leg would burn the motor out in a few weeks or months


 
:jester: 



> I know the power company used to have the high leg on the C phase but changed it to the B phase.


Actually, POCO still connects to C but past their terminations, NEC requires it on B.




> I would like to know if 3 phase 240V motors can be connected to the the 3 phase power with high leg and not damage the motor.


Sure. That's what you have. 120/240 3 phase as opposed to 120/208 3 phase where all legs are 120V

Although, IMO, it's not a great idea, you can connect any 240 load using the high/wild/bastard/stinger leg, even single phase, and it will work properly because you have 240V between any of the two phases. 

Just don't ask *me* how it works.



> You are reading 208 VAC on C phase to ground NOT 240 VAC


Even though the math says it should read 208, for some reason they seem to generally read in the high 190's.


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## brian john (Mar 11, 2007)

220/221 said:


> :jester:
> 
> 
> 
> ...


Because the phase to phase is 218-220 and single phase to neutral is 109-110.

HIgh Leg services were designed for INDUSTRIAL facilities, for areas with high number of motors.


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## jwjrw (Jan 14, 2010)

Magnettica said:


> Think of the motor as a painter, or a plumber. :laughing:


Why not an electrical inspector or a multi inspector???????:whistling2::laughing::jester::thumbup:


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## electron_theory (Feb 14, 2010)

Strange that a motor guy would say that, considering that Delta systems are designed for and used almost exclusively for pure power applications.


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## LGLS (Nov 10, 2007)

electron_theory said:


> Strange that a motor guy would say that, considering that Delta systems are designed for and used almost exclusively for pure power applications.


...And the situation is going to get worse before it gets better. "Motor guys" know motors, not power systems.


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## Marshall175 (May 23, 2009)

220/221 said:


> :jester:
> 
> 
> 
> ...


where does the NEC require the high leg to be B phase? Correct me if I am wrong, but I don't believe that is code, only common practice...


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## electron_theory (Feb 14, 2010)

Marshall175 said:


> where does the NEC require the high leg to be B phase? Correct me if I am wrong, but I don't believe that is code, only common practice...


Here is an interesting read....
http://www.mikeholt.com/mojonewsarchive/NECQ-HTML/HTML/NEC-Questions-017~20041220.php


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## Marshall175 (May 23, 2009)

yeah, I guess I posted too fast...I found the code section a little after I posted that...


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## TOO_SL:IM (May 13, 2010)

The utility makes the call on where you land the wild leg.Usually they come in on L3 on the line side then on the load side we swap it to L2 "B" phase>I run into this problem a lot as one of our utility is a Rural coop and we do all the wiring from the Transformer on in to the Building.Was told that is how the meter reads it correctly, my 2cents


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## Southeast Power (Jan 18, 2009)

az101 said:


> I`m a journeyman electrician in Arizona and I recently encountered a very old warehouse building that has a 120/240 3 phase 4 wire with a high leg reading 240V to ground and neutral wire on the C phase coming from the service disconnect from the power company. I know the power company used to have the high leg on the C phase but changed it to the B phase. I would like to know if 3 phase 240V motors can be connected to the the 3 phase power with high leg and not damage the motor. I know I can use a rotary phase converter to create the 3 phase needed, but if not cool.


Yes you can, that's exactly what it was made to do.


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## kolbychamberlain (Jun 21, 2010)

whats the color of the high leg of a 120/240 volt 3 phase 4 wire system?


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## wildleg (Apr 12, 2009)

usually orange. this is the third time you asked in 1 hour. Do you own a codebook ? 110.15


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## Murphy (Dec 10, 2009)

its not like the motor uses the 240 voltage to ground, when you are only using three phases and no neutra,l the voltage between any of them is the same


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## NolaTigaBait (Oct 19, 2008)

wildleg said:


> usually orange. this is the third time you asked in 1 hour. Do you own a codebook ? 110.15


Yeah, Orange....BUT, I did this the other day and confused the hell out of the lineman....They are used to RED...I'd check with them also:thumbsup:...Don't want to make the monkeys think.


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## Skipp (May 23, 2010)

kolbychamberlain said:


> whats the color of the high leg of a 120/240 volt 3 phase 4 wire system?


 I beleive the same as a 3 phase 3 wire high leg. Orange.


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## frenchelectrican (Mar 15, 2007)

kolbychamberlain said:


> whats the color of the high leg of a 120/240 volt 3 phase 4 wire system?


 
The modern delta system in USA typically are orange however if you run into old delta system there are some case it will marked RED !!

So very simple rules always test with your voltmeter to verify if you have see red conductor but no orange conductor show up.

Merci.
Marc


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## dronai (Apr 11, 2011)

kolbychamberlain said:


> whats the color of the high leg of a 120/240 volt 3 phase 4 wire system?





wildleg said:


> usually orange. this is the third time you asked in 1 hour. Do you own a codebook ? 110.15





Skipp said:


> I beleive the same as a 3 phase 3 wire high leg. Orange.



Ran into one of these in an area I would least expect it. The high leg was on the blue colored C phase. This was in a vault for an old condo complex for the pool equipment. *There was no breaker Panel*, just a feeder to a large can, and everything all motors taped off this !! 240V single phase motors for the pool equipt. Someone wrote on the J box cover Blue = High leg. I didn't even know this town had that service anywhere. There was a couple of county pump stations nearby, this may be why that service is available. Wondering how balanced the loads on there would be the way this was set up. I guess someone thought they could use the tap rule :laughing:


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## bkmichael65 (Mar 25, 2013)

kolbychamberlain said:


> whats the color of the high leg of a 120/240 volt 3 phase 4 wire system?


Don't trust the color, trust your meter


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## dronai (Apr 11, 2011)

bkmichael65 said:


> Don't trust the color, trust your meter


 First time in a bit, I have run into this. But usually in industrial areas, not at the beach. You can damage a lot of single phase loads !


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## Jlarson (Jun 28, 2009)

Zombie thread


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## dronai (Apr 11, 2011)

Jlarson said:


> Zombie thread


yes digging around in the archives
Seems like a lot of single phase 120V loads would unbalance this thing with people avoiding using the High leg.


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## Bill Blough (Sep 22, 2012)

Before the code required the High Leg to be marked Orange it was always marked Blue. I have never seen a High Leg marked Red around here. We have a lot of Open Delta 3 phase services around here. The power Co. can get away with running 2 primary phases to a 3 phase location, use 2 pots and hook them up in an open delta config. Saves them 1 phase primary to an out of the way agricultural irrigation pump and they only have to size the power pot for the pump load, usually 1/2 of the lighting pot.

In heavy industrial locations the normal system is a Delta system. This uses all 3 primary phases and 3 pots all the same size. You can still center tap one pot on the secondary to produce a neutral for the secondary.


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## RandyM (Apr 5, 2012)

dronai said:


> yes digging around in the archives
> Seems like a lot of single phase 120V loads would unbalance this thing with people avoiding using the High leg.


Basically it is a single phase house service (120/240) with a smaller third phase. 
The poco can supply 120/240 3 wire single phase services (Houses) and 120/240 3 phase 4 wire service (Industrial/Commercial) with one set of pots. 

Look for a large pot and one (open Delta) small pot or one large and two ( closed delta) small pots on the pole. 

If all three pots are the same size most likely its a Y system, 120/208 or 277/480.


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## Elephante (Nov 16, 2011)

wildleg said:


> usually orange. this is the third time you asked in 1 hour. Do you own a codebook ? 110.15


Your name is Wildleg. It is your job to answer those questions.


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## Introyble (Jul 10, 2010)

bkmichael65 said:


> Don't trust the color, trust your meter


I once was in an industrial facility where they had a 200 amp breaker box. If you open the box you notice that every other breaker was skipped with no blank covers. Turns out they were trial and error trying to find the voltage they needed to power heater zones on plastic extrusion. They couldn't figure out why some of the breaker positions were low voltage. It was a delta high leg xformer of course


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