120v 277v insame 3ph box

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Re: 120v 277v insame 3ph box

"Having the neutrals tied together in the panel will not cause any problems. It happens on every code compliant installation where there are two or more systems with grounded conductors in a building. All of the grounded conductors are tied together by the system bonding jumpers and the grounding electrodes.
Don "


Are you saying that there is continuity between the neutral conductor of a 120v system and a 277v system that are in the same building?
 
Re: 120v 277v insame 3ph box

Originally posted by pierre:
Are you saying that there is continuity between the neutral conductor of a 120v system and a 277v system that are in the same building?
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Pierre there is continuity between all the neutrals of grounded systems. The NEC requires it.

There is likely continuity between the neutral of the 120 circuit I am using now and the neutral of a 277 circuit out in your area.

Not that we want to 'advertise' this but any grounded conductor of any system can be used with any ungrounded conductor of any other grounded system.

Good idea? No not at all.

Would the circuit operate? Sure.

[ January 02, 2006, 07:35 AM: Message edited by: iwire ]
 
Re: 120v 277v insame 3ph box

It has been ten years so I do not remember the detail. I was gutting out an office building. Thought I had the area I was working on off. Got zapped by 277 neutral. Not smart since I had already figured out that neutrals had been robbed. Different system conduits had been tied together and all wires run together. I then went back to the panels and noticed the wrong color wires in the wrong panel. Things looked so bad I had not thought anything of it before. Just figured par for the course. The wires came from the 277 panel,through the 208 panel to steel the conduit. Figured out that the 208 read 277. Don't know if I took the time to figure out how it was backfeeding. I just pulled it all out and problem was solved. I replaced everything with room for expansion and all Jboxes clearly marked for voltage.

[ January 02, 2006, 07:46 AM: Message edited by: Fred S. ]
 
Re: 120v 277v insame 3ph box

Pierre,
Are you saying that there is continuity between the neutral conductor of a 120v system and a 277v system that are in the same building?
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If not, the systems have not been installed per the code.
Don
 
Re: 120v 277v insame 3ph box

I would still like to see this panel!
Here?s something else: This panel is probably a 120/208 3? 4W panel. Being such, the breakers in it are only rated 120 to ground! The 2pole breakers are probably dual rated 120/240 (slash breakers).
What is the rating of the 277V breaker? Using SqD as an example, did the installer use a QO120 for the 277V loads?
On the otherhand, if this is a NEHB panel then the voltage rating on the breakers is a mute point.
 
Re: 120v 277v insame 3ph box

Frank,
That kind of throws a wrench at the defintion of SDS?
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Not really...there is no direct connection of supply conductors of the different systems. There are direct connections of the grounding conductors of the different systems, but not not the suppy conductors.
Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.
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Don

[ January 02, 2006, 06:17 PM: Message edited by: don_resqcapt19 ]
 
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