NEC True of False Question: 240/120 High Leg - a/k/a 208 Delta

[jar546]

True or False:
On a 240/120-volt, 3-phase, 4-wire center-tap grounded delta system, the high leg, which is commonly found in the 'B phase' and may carry a voltage of 208 volts nominal, must be marked in orange or another effective means of identification according to Section 110.15. Additionally, for 3-phase buses, the alternating-current phase arrangement must always be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard, switchgear, or panelboard, without any exceptions.

 

[Paul Sweet]

The B phase in 120/240 V delta is 240 V, not 208. It is required to be orange.

 

[jar546]

The B phase in 120/240 V delta is 240 V, not 208. It is required to be orange.

I do not agree. No one said it is 120/240. In the original post I stated it was a "240/120-volt, 3-phase, 4-wire center-tap grounded delta system" in which the B phase is 208. There is no system in which a B phase is 240V.

 

[wwhitney]

The B phase in 120/240 V delta is 240 V, not 208. It is required to be orange.

The B phase is 240V relative to A or C, but 208V relative to N, which is required to be grounded.

Voltages are best described along with the reference point, although when that reference point is omitted, it is generally assumed to be ground, unless another reference point is clear from context.

Cheers, Wayne

 

[jar546]

The B phase is 240V relative to A or C, but 208V relative to N, which is required to be grounded

Yes, agree.

 

[wwhitney]

True or False:
On a 240/120-volt, 3-phase, 4-wire center-tap grounded delta system, the high leg, which is commonly found in the 'B phase' and may carry a voltage of 208 volts nominal, must be marked in orange or another effective means of identification according to Section 110.15.

True, that is what NEC 110.15 says.

Additionally, for 3-phase buses, the alternating-current phase arrangement must always be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard, switchgear, or panelboard, without any exceptions.

False, 408.3(E)(1) has some exceptions.

Cheers, Wayne

 

[Paul Sweet]

You're right. I was looking at phase to phase voltage. I don't think I've ever seen a stinger to neutral circuit.