equipment for wiring a corner grounded delta service

[Electron_Sam78]

I'm going to be rewiring my first corner grounded delta (200a, 3ph, 480V) service and am doing some research into it. I know I need to use straight rated breakers or if slash rated the minimum voltage rating must be that of the corner grounded system. I also know that the grounded leg must be identified by gray or white marking throughout the installation.

I need to set up one service with 2 individual 100a service disconnects. I'd like to use a MLO panel from the meter can with 2 100a circuit breakers installed for the service disconnects. How should I wire the grounded phase in this equipment?

1).Use 3 pole breaker/panelboard and grounded phase from meter can to the neutral bar then from neutral bar to a lug of panelboard?

or

2). Use a 2 pole breaker/panelboard and grounded phase from meter can to neutral bar and then grounded phase from neutral bar out to load?

Also, if I wanted to use fused disconnects instead of breakers, I couldn't use a 3 phase DC with the grounded phase fused since that wouldn't allow for simultaneous opening of all phases should the neutral be lost (I assume that's the reason behind the simultaneous opening). I would have to use a single phase DC with the grounded phase wired through a bus bar, correct?

 

[dhalleron]

I don't know much about delta systems, but here's my 2 cents worth.

This past weekend during my continuing education class, the instructor said you did not need to use a 3 pole breaker in that situation. The grounded phase can go to the neutral bar just like a regular neutral does.

 

[raider1]

I'm going to be rewiring my first corner grounded delta (200a, 3ph, 480V) service and am doing some research into it. I know I need to use straight rated breakers or if slash rated the minimum voltage rating must be that of the corner grounded system. I also know that the grounded leg must be identified by gray or white marking throughout the installation.

I need to set up one service with 2 individual 100a service disconnects. I'd like to use a MLO panel from the meter can with 2 100a circuit breakers installed for the service disconnects. How should I wire the grounded phase in this equipment?

1).Use 3 pole breaker/panelboard and grounded phase from meter can to the neutral bar then from neutral bar to a lug of panelboard?

or

2). Use a 2 pole breaker/panelboard and grounded phase from meter can to neutral bar and then grounded phase from neutral bar out to load?

I would use option #2 and a single phase panelboard with straight rated breakers for 480 volts.

Also, if I wanted to use fused disconnects instead of breakers, I couldn't use a 3 phase DC with the grounded phase fused since that wouldn't allow for simultaneous opening of all phases should the neutral be lost (I assume that's the reason behind the simultaneous opening). I would have to use a single phase DC with the grounded phase wired through a bus bar, correct?

You can't install a fuse in a grounded conductor, use a single phase disconnect and bring the grounded conductor through the disconnect.

Chris

 

[Electron_Sam78]

I would use option #2 and a single phase panelboard with straight rated breakers for 480 volts.



You can't install a fuse in a grounded conductor, use a single phase disconnect and bring the grounded conductor through the disconnect.

Chris

Whoa Deja Vu! :grin:

 

[raider1]

Whoa Deja Vu! :grin:

Yep, theres an echo on the internet.

Chris

 

[jim dungar]

Actually you need to be using "Grounded-B Phase" breakers.
Note that the AIC ratings will probably be lower than standard breakers.

Your panel also needs to be rated for grounded-B phase.
It is hard to purchase an over-the-counter 1-phase 3-wire 480V panel. You will either need to order one or use a 3-phase 4-wire panel instead.

 

[Electron_Sam78]

Actually you need to be using "Grounded-B Phase" breakers.
Note that the AIC ratings will probably be lower than standard breakers.

Your panel also needs to be rated for grounded-B phase.
It is hard to purchase an over-the-counter 1-phase 3-wire 480V panel. You will either need to order one or use a 3-phase 4-wire panel instead.

Could you direct me to any sources that confirm this statement?

 

[jim dungar]

Could you direct me to any sources that confirm this statement?

Confirm which statement?

Or will this do from the UL White Book/Marking Guide Molded Case Circuit Breakers:

2-Pole ? 3-Phase Rated ? ​

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A 2-pole circuit breaker marked ?1-Phase ? 3-Phase? or ?1? ? 3ؔ may be used on 3-phase, corner-grounded delta circuits, or on single-phase circuits.​

 

[Electron_Sam78]

Confirm which statement?

Or will this do from the UL White Book/Marking Guide Molded Case Circuit Breakers:

2-Pole ? 3-Phase Rated ?

A 2-pole circuit breaker marked ?1-Phase ? 3-Phase? or ?1? ? 3ؔ may be used on 3-phase, corner-grounded delta circuits, or on single-phase circuits.
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yeah that's fine. That's also stated in NEC section 240.85. Good to know. I wonder how many manufacturers provide breakers rated for this use...

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[jim dungar]

I wonder how many manufacturers provide breakers rated for this use...

All of the major manufacturers do, but they are often 'special' orders.

 

[Electron_Sam78]

What about safety switches/disconnects? Do they have to be listed for use with grounded B phase systems or just straight rated voltage? Any special fuses?

 

[jim dungar]

I am not aware of any special requirements for fusible equipment installed on corner-grounded systems.