What is a "wild" leg?

Archive Public Archive
#1

Originally Posted By: Ed Griffin
This post was automatically imported from our archived forum.


What is a “wild” leg and what should I know about voltage to ground? I have encountered the term a couple times now, but have not found any particular definintion anyplace?


Thanks

#2

Originally Posted By: dbush
This post was automatically imported from our archived forum.


Edward, try this forum:


http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=11;t=001762

--
Dave Bush
MAB Member

"LIFE'S TOUGH, WEAR A HELMET"

#3

Originally Posted By: Mike Parks
This post was automatically imported from our archived forum.


In Ohio a “wild leg” is icon_lol.gif


Mike P.

#4

Originally Posted By: Bob Badger
This post was automatically imported from our archived forum.


Ed as wild legs are only found in some 3 phase services you should not be running into any “wild”, “high”, “bastard” or “Orange” legs in homes.


I have been in the commercial electrical trade 20+ years and have not seen this type of service.

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum

#5

Originally Posted By: roconnor
This post was automatically imported from our archived forum.


Thanks Bob … I would have posted something crude since I really don’t know the term … icon_lol.gif


Isn't it just one conductor on a 4-wire feeder that can have a higher voltage under special circumstances ... I think whats really called a "high-leg"?

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

#6

Originally Posted By: roconnor
This post was automatically imported from our archived forum.


Looks like this was a dupe post, and Joe Todesco gave a code quote for it here too


http://www.nachi.org/bbsystem/viewtopic.php?t=2341

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

#7

Originally Posted By: rpalac
This post was automatically imported from our archived forum.


A wild leg in electrical terms refers to the leg or tap on a Delta wound transformer.


These are 3 phase instatations.


This is used in commercial industrial application mostly. The common transformers you see in most construction today are "Y" connected transformers.

If you look at the letter "Y" it explains how the legs and taps are formed. Each outer end of the "Y" configuration represents the end of the coil winding . The center is the ground tap. The length of each leg is set exactly 120 degrees out of phase. .This means that from each leg end to ground you get 120 volts. Between each end you get 240 volts.

On a delta connected transformer the delta symbol looks like a tri-angle. each outer point is the leg tap. You mid tap one coil half way to create the ground tap. This divides one coil in witch you get 120 volts to ground from A leg and C leg. B leg is opposite and you run through a longer coil to get to it so you have a higher derived voltage to ground at around 176 to 209 volts. The wild leg. This leg is always marked with orange tape as part of the color code. If you go between legs you will still get 240 volts between A& C, B& C, or A & B.
Now that voltage is for 120 / 240 Red, Black, Blue for Y, red Black Orange for Delta.
If it is 277/480 it's brown, orange, yellow.

The delta type transformation is for high power demand industrial. If you loose a transformer coil the winding is still completed by the other side of the Delta. There-fore you never loose power. If your light safety system tells you that you lost a leg. You can do the repairs when the system is shut down later. You don't loose production that way.


I've worked on many, many, many of these systems.

Now for a real challenge try 2 phase 5 wire. I have only met a couple of people who work on this system. I was lucky enough to be a trouble shooter for it. Very rare, only found in old city Philly, part of New York, and Chicago that I know of.

If you found this in residential, I can't imagine it.

Bob P.

#8

Originally Posted By: rsummers
This post was automatically imported from our archived forum.


I’ve have had them referred to as the stinger leg in the past. I have ran into them on Commercial Air conditioning equipment. I think the extra voltage is used to start the compressor! That’s a guess I was just always sure that I marked what terminal the leg with the higher voltage attached to so when I reinstalled the unit it wouldn’t smoke.

#9

Originally Posted By: roconnor
This post was automatically imported from our archived forum.


RP … Your explanation of the difference between a delta and wye transformer is one of the most practical and easy to understand ones I have ever heard … eusa_clap.gif

–
Robert O’Connor, PE


Eagle Engineering ?


Eagle Eye Inspections ?


NACHI Education Committee


I am absolutely amazed sometimes by how much thought goes into doing things wrong
#10

Originally Posted By: Bob Badger
This post was automatically imported from our archived forum.


Quote:
Now that voltage is for 120 / 240 Red, Black, Blue for Y, red Black Orange for Delta.
If it is 277/480 it's brown, orange, yellow.


I would just like to point out that the NEC does not assign certain colors to certain voltages.

120/208 could be brown, orange, yellow or pink, purple, gold

Never determine voltage by colors, that is a dangerous assumption, use a volt meter.

Orange must be used for the high leg when it exists but no mention voltage for colors.

Quote:
I think the extra voltage is used to start the compressor! That's a guess


Well good guess but the compressor does not see the "extra voltage" as it is connected phase to phase and not phase to ground.

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
#11

Originally Posted By: rpalac
This post was automatically imported from our archived forum.


R. O’C.,


Thank’s for the compliment…Geeeee why can’t my =kid’s understand me when I explain things?


R.B.
You make a good point. The code only specifies the grounding conductor be green or bare (Article 110.54), Neutral or Grounded conductor being white, grey (Article 200.6, 200.9 and 200.10-B), or bare for grounding and orange for the wild leg in a delta (Article 215.![icon_cool.gif](upload://oPnLkqdJc33Dyf2uA3TQwRkfhwd.gif).

The voltages in many commercial buildings are a combination of all types and variations. The lest company I worked at had 120/240 and, 120/208 and 277/480 and 320 and 200 DC and some crazy European and military voltages that were un grounded every time you went to certain areas you had to think clearly what you might be exposed to. As you point out you better check with a circuit tester and know how to use it cause Ac and DC don't show the same and ungrounded systems don't read to ground.

I was tagged with 480 by an ungrounded system and I still chew my food backward, I think.

Another bad item was a time I was tagged by inductance on 13,200 from a cable that swung into the transformer. It lit up an disintegrated.....we hit the bar early.

Bob P.