High leg position?

[brinkmann27]

Using a 230/3/60 V.A.C. 4 wire system with a "high" leg, is there a code in which phase this wire must be placed on (L1 or L2 or L3) ? At times a 230 volt line & neutral is used for the control voltage (115 V) or for a GFI receptacle. Of course if the high leg is on either, many problems occur. Thanks !

 

[jbartos]

Suggestion: The 230/3/60 V.A.C. system is ambiguous. Please, would you clarify it.

 

[brinkmann27]

System Voltage 230 volts A.C. 3 Phase, with a neutral wire.( 4 wire) L1, L2 & L3 phase to phase is 230 V. If you take (measure between) a phase to neutral you get approx. 115 volts. Some systems have what's called a high leg. If you take a high leg to neutral you get approx 190-200 volts.
This is way to high for control voltage or a GFI. I would like to know if this high leg is always placed on a specific phase when connecting to a motor control panel.

 

[RHB155]

2002 NEC section 430.97(B) Phase Arrangement, covers your question. The phase arrangement on 3-phase horizontal common power and vertical busses shall be A,B,C from front to back, top to bottom, or left to right as viewed from the front of the motor control center. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems.

 

[advidana]

Watch out for these kind of sytems. What is happening is one of the 240 vac delta winding is center tapped to get 120vac from sides of the winding that is tapped . Some utilities use open deltas with one of the delta windings center taps, same logic.

This is not really a neutual conductor but what the nec code calls a grounding conductor. Only a 3 phase wye, center tapped transformer or a center tapped single phase transformer would that conductor be called the neutual.

 

[REDDOG]

Note: Some utilities require high leg to be C phase in the CT cabinet per their metering requirements. Then you transition to B phase in the switchgear.

 

[busbar]

Older 240/120V 3ø 4w ∆ systems may be found with the high leg in the Cø [righthand] position, based on some electric-utility metering standards.

 

[jbartos]

Suggestion: There may be a 3 phase 5 wire system. It includes 3 wires for 3x240V from open delta for three phase loads and 2 wires for 1 phase 120V loads from the transformer center tap to one delta corner of the center tapped transformer.

 

[rbulsara]

RHB155's repsonse is to the point and correct.

In addition:

NEC 215.8 requires high leg to be identified by either orange outer finish or tagging or other effective means at each locations (panel, junction boxes, etc) where a groudned condcutor i s also present.

NEC 408.3 (E) requires the B phase (center) to be the high leg.

This of course applies in the USA. Your local Codes may have slightly different requirements.

 

[resqcapt19]

advidana,
"This is not really a neutral conductor but what the nec code calls a grounding conductor. "
The conductor is not a "grounding" conductor. It is a "grounded" conductor. In the code, there is a big difference in these two conductors.
Don

 

[resqcapt19]

busbar,
Even when the utility requires the high leg to be in the right hand or "C" phase position in the metering equipment, the NEC requires a transition to the center or "B" phase position in the service equipment. There is an exception permitting the high leg to remain in the "C" phase position if the meter is in the same single section or multisection switchboard or panelboard.
Don

 

[busbar]

Isn't a Cø highleg also permtiied to "match existing" in a particular facility?

 

[peebee]

Yup -- "Other busbar arrangements shall be permitted for additions to existing installations and shall be marked".

 

[freddycor]

Here in Mexico, the " high leg " must be placed in phase C ( or 3, like you want ), according the good description of placements of phases descrites by RHB155.
You would be carefully when working in a delta conection of TR secundaries 3p-4w.

Saludos.

Alfredo Corona
Mexico

 

[jbartos]

Suggestion: Visit

http://www.intermatic.com/comind/guides/install/PG2000 Series.pdf

for the high leg connection to PanelGuard, high leg on L2 red, and 208V from high leg to the neutral and to ground.