corner grounded delta panelboard

[lowvoltman]

we are building a portable panelboard that is being supplied by 480v grounded b phase. would you ground the b phase at the panelboard too?
or should it be grounded only at the transformer feeding it? also where would i look in the codebook about this subject?

 

[iwire]

Treat the grounded phase exactly the same way you would normally treat the neutral.

where would i look in the codebook about this subject?

Parts I, II, III, IV, V, VI and VIII or Article 250 and all of Article 200, that grounded phase needs to be marked white.

 

[cadpoint]

Heres a picture from Square D

WARNING: Three-pole circuit breakers must be used on three-phase 480 V corner-grounded delta systems. The outside poles are to be connected to the ungrounded phases and the grounded conductor connected to the center pole. Connecting the circuit breaker in a manner other than that described or shown may result in an unsafe application of the circuit breaker.

They cover both 240v and 480v B grounded service Square D

 

[iwire]

Three-pole circuit breakers must be used on three-phase 480 V corner-grounded delta systems.

Just want to point out that I do not believe that is an NEC requirement.

You could use fuses or perhaps someone else makes two pole breaker rated for 480 grounded delta.

 

[LarryFine]

I would be hesitant about grounding a phase in the panel for a "portable" panel, as it would be all to easy to energize the enclosure during a temporary hook-up.

 

[iwire]

I would be hesitant about grounding a phase in the panel for a "portable" panel,

You would not, you would treat the grounded phase just like neutral at a sub panel. :smile:

At the subpanel the grounded phase would need to remain remain isolated from the EGC that would be run with the circuit.

 

[lowvoltman]

I was thinking the phase should be grounded only at the transformer. just wan't to hear someone elses view of the subject. thanks!