I'm working at a plant where in the olden times they use 480 single phase to power 277 volts power lighting circuits (no neutral), just 480 volt to ground. Note the ground wire is insulated back to the panel (kinda of acting like a neutral). I know this is bogus today but was it ever legal ? I'm talking some 40 years ago. Are these types of installations grandfathered? Or is this just a royal screw up?
480 volt / 277 volt lighting
- Thread starter cornbread
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Buck Parrish
Senior Member
- Location
- NC & IN
Why are you calling it a ground? Do you mean grounded conductor? Or is it the equipment ground? Chances are it is a neutral (Grounded Conductor).
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
If the wire is white, it's a neutral and it's legal If the wire is green, it's an EGC and it was never legal.cornbread said:
The MCC that feeds the lightinh panel is fed from a xfmr with a grounded Wye 2ndary. The feeds to the lighting panel is 3 phase with a ground. Looks like they made a neutral at the panel. So the return path from the neutral at the light goes back to the lighting panel but from the lighting panel to the MCC / transformer use the ground.
billsnuff
Senior Member
- Location
- East of 480sparky
a learning opportunity
a learning opportunity
i ain't much when it comes to xfmrs, just curious what the name plate says on yours. i have several 480 delta - 208 wye LPs. x1 , x2, x3 = 208 3p xo neut. with EGC. x1, x0 = 110. or do you have a zig zag connected 480 - 277 lighting set up, with center tap neut.??? is raceway used for EGC???
a learning opportunity
i ain't much when it comes to xfmrs, just curious what the name plate says on yours. i have several 480 delta - 208 wye LPs. x1 , x2, x3 = 208 3p xo neut. with EGC. x1, x0 = 110. or do you have a zig zag connected 480 - 277 lighting set up, with center tap neut.??? is raceway used for EGC???
peter d
Senior Member
- Location
- New England
cornbread said:
I'm really confused by this description.
Unless you have something totally off the wall, 480 volts is obtained from two separate phase conductors, whether the service or downstream transformers are connected delta or wye.
Perhaps you may be dealing with a corner grounded delta. But in that case you are not dealing with an EGC, you are dealing with a grounded phase.
Is that ground insulated?cornbread said:
If so, it is a neutral... and it is grounded... and it is a 480Y/277 system. Line to line = 480V... Line to Neutral = 277V.
Also, I believe there are some instances in which the neutral was (is?) permitted to be bare.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
cornbread said:
If the system is 480 volts to ground as you stated then how can it power a 277 volt lighting circuit. Do you mean it is 277 volts to ground. That is common today.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
cornbread said:
Why are you calling the insulated wire from the panel to the light "the ground".
The ground wire is usually the green conductor or possibly bare conductor that does not ordinarily carry current. It is the grounding conductor. The white wire is the grounded conductor but sometime called a neutral.
What is it that you have? The white wire with a phase conductor is still legal today. You see it often with fixtures that have a 277 volt ballast.
steelersman
Senior Member
- Location
- Lake Ridge, VA
then why in your original post did you say that it was 480 single phase? Now you say 480 phase to phase which would mean more than one phase (3).cornbread said:
billsnuff
Senior Member
- Location
- East of 480sparky
just following along
just following along
most of my xfmr experience is 480 - 208 delta wye and 480 - 240/120 control.
don't use any 277 lighting. what type of xfmr is the op refering to. all i can find for 277 is zigzag connected with center tap gnd.
could someone enlighten me?
(no highjack intended, just curiosity)
just following along
most of my xfmr experience is 480 - 208 delta wye and 480 - 240/120 control.
don't use any 277 lighting. what type of xfmr is the op refering to. all i can find for 277 is zigzag connected with center tap gnd.
could someone enlighten me?
(no highjack intended, just curiosity)
Where is the system [intentionally] earth grounded? That is, where is(are) the grounding electrode system(s) bonded to the grounded conductor?cornbread said:
What type of raceway encloses the feeder between MCC and lighting panel?
Is the feeder a cable or individual conductors?
Is what you call the "ground wire... (kinda of acting like a neutral)" in any way bonded to non-current carrying metal parts at the load end?
jrannis
Senior Member
- Location
- Fort Lauderdale/ Miami
cornbread said:
Look again. Just by telling us that they are 277 volt fixtures leads me to believe you have a neutral and one of the phases feeding the light fixture.
You can for sure use 480 to feed a light fixture but, when you mentioned the 277, that kind of got me. What type of ballasts and fixtures are they?
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