208v?

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ronlove

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If you have a 3 phase system (240v) between all three phases, 120 to ground on one phase, 208v on the middle, and 120 v on the third. Do you call this a 240 v three phase system? If you want to hook up a 208v device do you only use the 208v leg and neutral to the device?
 
This would generally be called a 240V 'high leg' system.

In theory it is possible to supply a 208V load, however there are practical issues that make such use uncommon. I've had no experience with such applications, and cannot tell you all of the practical issues involved. I do know one: you need to use a 240V OCPD (not a more common 120/240V 'slash rated' OCPD).

-Jon
 
ronlove said:
If you have a 3 phase system (240v) between all three phases, 120 to ground on one phase, 208v on the middle, and 120 v on the third. Do you call this a 240 v three phase system? If you want to hook up a 208v device do you only use the 208v leg and neutral to the device?
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The system is correctly called a 240/120V 3-phase 4-wire delta.
Slang terms for this type of system include: Wild Leg, High leg, Christmas Tree, and Red leg.

208V loads are not encouraged.
There are usually no single pole 208V rated breakers available for the common panels found on these 240/120V systems. The transformer bank that creates this system has usually not been sized for the unbalanced effects a 208V load would create.
 
jim dungar said:
Slang terms for this type of system include: Wild Leg, High leg, Christmas Tree, and Red leg.
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Christmas tree? Really? I never heard that one - what do you suppose the origin of that one is? :-?
 
George Stolz said:
Christmas tree? Really? I never heard that one - what do you suppose the origin of that one is? :-?
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You ever plugged Christmas decorations into 208 volts? :D
 
George Stolz said:
Christmas tree? Really? I never heard that one - what do you suppose the origin of that one is? :-?
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I am definitely showing my age with that one. I am sure it comes from the resemblence of a center-tapped closed delta to a kid's drawing of a tree.
 
Usualy the 208 panels are lighting panels and phase to phase isn't used. Just phase to neutral/ground. These are Y secondaries.
 
ronlove said:
If you have a 3 phase system (240v) between all three phases, 120 to ground on one phase, 208v on the middle, and 120 v on the third. Do you call this a 240 v three phase system? If you want to hook up a 208v device do you only use the 208v leg and neutral to the device?
Click to expand...

if your device won't work on 240v...you may want to think about a buck/boost transformer.
 
jim dungar said:
The system is correctly called a 240/120V 3-phase 4-wire delta.
Slang terms for this type of system include: Wild Leg, High leg, Christmas Tree, and Red leg.

208V loads are not encouraged.
There are usually no single pole 208V rated breakers available for the common panels found on these 240/120V systems. The transformer bank that creates this system has usually not been sized for the unbalanced effects a 208V load would create.
Click to expand...

often, what's up on the pole is 2 transformers in an open delta configuration,
not really designed for a single phase 208 volt load.

as far out on the edge as i've ever seen done is some old WW2 machine
tools that were 240 volt delta with across the line 240 control voltages
and they had to be rewired to run on 480.

the motors could be rewired without problems, they were 12 lead motors,
and the contactors were obviously fine, but the
polish and german contactors had coils that were unobtainable
anywhere, and were 240 volt. however, they were built like tanks,
and meggered well, and have been running for about 19 years on the
277 volt leg to ground of the 480 system without problems. no motor
burnups either. stuff built back then was built pretty sturdy. the only
shortfall was the heaters. correctly sized ones were not available,
so running overcurrent protection is virtually nonexistant.

it isn't something i would do, from a liability standpoint, but it has
stood the test of time.


randy
 
Fulthrotl said:
often, what's up on the pole is 2 transformers in an open delta configuration, not really designed for a single phase 208 volt load. /quote]

In Wisconsin, I would say that we hav e close to 50-50 open and closed delta systems. But neither system is normally sized for the effects 208V loads could have.
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To sum up Jim Dungar's answer I am not too far from him and yes we do have split pools of open and close delta's

But from my past experinces with 208 delta they are not much used at all and it will affect the voltage reading if not carefull and really I pretty much discouraged anyone try to use wild leg connecton for single phase load anyway { majotry of the transformer will useally not take oddball load very kindly }

Speaking of Christmas tree that I heard once a while but kinda rare for anyone to say that but yes that true.

Merci,Marc
 
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