208 Volt High Leg
- Thread starter mcpritt
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Re: 208 Volt High Leg
208v commonly a wye voltage as in 208y/120. But the term "high leg" refers to a 3ph4w delta, such as a 240/120 system.
If you sketch a delta with a flat side at the bottom and mark the 'A' phase at the lower left corner, 'B' at the top, and 'C' at the lower right and make it as a simple 240v delta.
Now mark a point half way between the 'A' and 'C' marking it as 'X0'and is considered a neutral and grounded. Remember that you have 240v 1ph between A-C and with the X0 you have 120v between A-X0 and 120v between C-X0. So, between A-C you have basically a 120/240 1ph3w as you would have in a common residential service entrance.
Remember that 'B'? Between the 'B' phase corner, often referred to as the wild or bastard leg, and the X0 you will have 208v. With the X0 grounded you will have 120v to ground from the A and C phases and 208v from the b to ground. However, even so, I have not found a logical need for 208v 1ph.
Panels that are supplied for this application are marked as 240/120 3ph4w and the 'B' phase is conductor is orange and is terminated on the center bus.
If you have a couple of extra minutes check page 8 of this link out. Although the diagram is turned and flipped from my description it does show you how a panel is connected.
http://www.enm.com/training/siemenscourses/pnl_2.pdf
208v commonly a wye voltage as in 208y/120. But the term "high leg" refers to a 3ph4w delta, such as a 240/120 system.
If you sketch a delta with a flat side at the bottom and mark the 'A' phase at the lower left corner, 'B' at the top, and 'C' at the lower right and make it as a simple 240v delta.
Now mark a point half way between the 'A' and 'C' marking it as 'X0'and is considered a neutral and grounded. Remember that you have 240v 1ph between A-C and with the X0 you have 120v between A-X0 and 120v between C-X0. So, between A-C you have basically a 120/240 1ph3w as you would have in a common residential service entrance.
Remember that 'B'? Between the 'B' phase corner, often referred to as the wild or bastard leg, and the X0 you will have 208v. With the X0 grounded you will have 120v to ground from the A and C phases and 208v from the b to ground. However, even so, I have not found a logical need for 208v 1ph.
Panels that are supplied for this application are marked as 240/120 3ph4w and the 'B' phase is conductor is orange and is terminated on the center bus.
If you have a couple of extra minutes check page 8 of this link out. Although the diagram is turned and flipped from my description it does show you how a panel is connected.
http://www.enm.com/training/siemenscourses/pnl_2.pdf
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: 208 Volt High Leg
In other words, the factory doesn't do the marking. The electrician marks the conductor installed in the field.
In other words, the factory doesn't do the marking. The electrician marks the conductor installed in the field.
Re: 208 Volt High Leg
I have assumed that you are describing control panels, not load centers, panelboards or service equipment . These are covered by the NEC and definitely need proper installation and identification.
The control panels that I have installed at this voltage have had control transformers for the control voltage(s). This makes the need for identifying the high leg unnecessary. If you were actually using the neutral, labeling would be necessary to avoid legal issues...like smoking the 110volt controls because the installer didn't know where to put the 'high' leg.
I have assumed that you are describing control panels, not load centers, panelboards or service equipment . These are covered by the NEC and definitely need proper installation and identification.
Re: 208 Volt High Leg
Thanks for the reply's. I have a good understanding of how the 208 Volt system works. My problem is on a Generator. The manufacturer puts the high leg on the "A" phase because they want to. They say that they do not have to follow the recommendations of the NEC, that is for the installer. This is apparently true, I know need to know if UL has any requirements for this. I want to FORCE them to change, but I need something to back me.
Thanks,
Charlie
Thanks for the reply's. I have a good understanding of how the 208 Volt system works. My problem is on a Generator. The manufacturer puts the high leg on the "A" phase because they want to. They say that they do not have to follow the recommendations of the NEC, that is for the installer. This is apparently true, I know need to know if UL has any requirements for this. I want to FORCE them to change, but I need something to back me.
Thanks,
Charlie
Re: 208 Volt High Leg
The only way I know to 'force' much of anything is to shop around to other mfr's to see if you can find one that is more cooperative, ie, take your business elsewhere.
I wish you well. In our area, the POCO requires us to put the high leg on the right in a 3 phase meter socket. We then transition the high leg to the center at the main disconnect to satisfy the NEC.
The only way I know to 'force' much of anything is to shop around to other mfr's to see if you can find one that is more cooperative, ie, take your business elsewhere.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: 208 Volt High Leg
Can you please state the nominal voltage of this generator?
Is it 120/240, or is it 120/208?
The identification is to keep people from accidentally feeding line-to-neutral loads from the high leg. So do your job in the panel, and it won't be a problem.
The internals of listed equipment is not covered under the NEC anyway.
Can you please state the nominal voltage of this generator?
Is it 120/240, or is it 120/208?
Why? Do you forsee someone opening this generator up to add circuits?
The identification is to keep people from accidentally feeding line-to-neutral loads from the high leg. So do your job in the panel, and it won't be a problem.
The internals of listed equipment is not covered under the NEC anyway.
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