Changing old 120/120/208 Edison style breaker panel.

[patricknola]

Hey guys, I just took a job to change out a very old 200 amp 120/120/208 volt panel. The old panel has (20) 20 amp single pole circuits, (3) 3 phase circuits, and (3) two pole circuits. Where do I land the high leg? Wouldn't every third breaker be 208 from hot to nuetral? TIA.

 

[ptonsparky]

High leg is center.
I would be inclined give them both a single and three phase panels.

 

[LarryFine]

Sounds like you get it. Yes, an electrician must be aware of the high leg and terminate breakers accordingly.

 

[infinity]

Here's the relevant NEC code section.

408.3(E) Bus Arrangement.
(1) AC Phase Arrangement. Alternating-current phase arrangement on 3-phase buses shall 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. The B phase shall
be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements
shall be permitted for additions to existing installations and shall be marked.

 

[jim dungar]

Wouldn't every third breaker be 208 from hot to nuetral? TIA.

In general, yes.


But it may depend on the panel.
40 years ago, panelboards, not loadcenters, often had breaker to bus connections (i,e, fingers) that were moveable. It was possible to build the panel with (6) 3-phase spaces and the rest of the 42 circuit panel all 1-phase.

 

[Little Bill]

Hey guys, I just took a job to change out a very old 200 amp 120/120/208 volt panel. The old panel has (20) 20 amp single pole circuits, (3) 3 phase circuits, and (3) two pole circuits. Where do I land the high leg? Wouldn't every third breaker be 208 from hot to nuetral? TIA.

No one mentioned this but you won't have a high leg on a 208V service unless you meant 208V just on the high leg.
Be careful with "every 3rd breaker". You would need to start off with "B", which would be the 2nd breaker starting at the top. Then you can go every 3rd after that. It helps, if you have 120V loads on a high leg panel, to put tape on all the spots where B phase is. That way you can take a quick glance and see where the B phase is and avoid that for 120V circuits.

 

[domnic]

Number one rule identify what your working on or don't work on it !

 

[Coppersmith]

Number one rule identify what your working on or don't work on it !

That might be the number three rule. Number one rule is work safely so you don't die doing your job.