Branch circuit voltage limitations

Status
Not open for further replies.
G

garydarling

Member
A project I am bidding asks for 480 volt fluorescent lighting, indoors in an industrial workroom at about 35' elevation. The existing 1000w, 480v hibays are being replaced. I am curious about the legality of 480v lighting indoors.

Article 210.6(C) would appear at first glance to govern this installation, except that it is limited to conductors "not exceeding 277 volts, nominal, to ground". The definition of 'Voltage to Ground' in article 100 is, "...for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit". The question would appear to be, is a 480v circuit, with no neutral conductor present, an "ungrounded circuit"? If so, 210.6(D) would then appear to govern, which would prohibit the use of 480 volt lighting indoors. Electricians I posed this question too said 'What about the conduit, it's grounded?' But I don't think a raceway would count as a part of the circuit.

Does the code intend to prohibit 480 volt lighting indoors, or is this a 'too-literal' reading of the code?
 
Re: Branch circuit voltage limitations

A 480 circuit originating from a 480Y/277 source does not exceed 277 volts to ground with or without a neutral included in the circuit.

Your all set. :)
 
Re: Branch circuit voltage limitations

Each one of the 480v legs is still 277v to ground. Take your meter and read from one leg to the enclosure, and you will get reading of 277v.
If not run like %^&((&^$#$ :D
 
Re: Branch circuit voltage limitations

Originally posted by iwire:
A 480 circuit originating from a 480Y/277 source does not exceed 277 volts to ground with or without a neutral included in the circuit.

Your all set. :)
Click to expand...
Presuming the wye is grounded, right? :confused:
 
Re: Branch circuit voltage limitations

Originally posted by rattus:
]Presuming the wye is grounded, right? :)

I am not aware of any code compliant way of installing an ungrounded wye system in a building. Of course all that means is I am unaware.
Click to expand...
 
Re: Branch circuit voltage limitations

Sorry for the delay on the reply: There is no neutral in the supply panels; it is a straight 480v industrial panel. While measuring from a current carrying conductor to a grounded raceway will no doubt give you a reading of around 277 volts, it is my understanding that the raceway is not a conductor and cannot be referenced.

I assume that a 'Grounded Circuit', as mentioned in Article 100 - Voltage to Ground, is a circuit that has a neutral conductor present. Absent the neutral, any other circuit conductor becomes your second point of measurement. If that is the case, it appears that 210.6(D) regulates this installation, prohibiting it's use indoors.
 
Re: Branch circuit voltage limitations

I assume that a 'Grounded Circuit', as mentioned in Article 100 - Voltage to Ground, is a circuit that has a neutral conductor present. Absent the neutral, any other circuit conductor becomes your second point of measurement. If that is the case, it appears that 210.6(D) regulates this installation, prohibiting it's use indoors.
Click to expand...
There is no requirement that there be a neutral to have a grounded system. If XO is grounded, it is a grounded system and suitable for this use. If XO is not grounded or if it is a delta system, then you are correct and you can't use it for this application.
Don
 
Re: Branch circuit voltage limitations

Put it another way: The identity of a system as being "grounded" or "ungrounded" is based on something that happens at the transformer, or at the first panel fed by the transformer. If a transformer has a 480/277 volt, WYE-connected secondary with the XO grounded, as Don described, the system is "grounded." Thereafter, it would not matter whether any feeders or branch circuits include a neutral conductor. The system is grounded, and the voltage between any phase and ground will be 277.
 
Status
Not open for further replies.
Top