Three phase panel used for single phase service. Violation?

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jaggedben

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I found a closed thread on a similar subject but I wanted to solicit fresh opinions.

A three-phase panel is being used for a single phase (120/240V) service. The two hot service conductors land on a 'backfed' breaker in the top left two positions. Thus A and B are 240V apart. B is jumpered to C with the same ampacity conductor. Thus the panel positions are (simplifying):

1-A -(Main)
2-B -(Main)
3-B
4-A
5-B
6-B

So... Code violation? Or not? Inspectors, would you pass work that involved adding a 240V breaker to this panel?
 
I do.

Nothing about the labeling of the panel would indicate the "Whodunnit" configuration behind the cover.

JAP>
 
jap said:
I do.

Nothing about the labeling of the panel would indicate the "Whodunnit" configuration behind the cover.

JAP>
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It should be fairly obvious from the configuration of the back fed breaker that something is a little different.

I think code also requires you to label where it is fed from which would be another clue.

I just do not see it is a code violation. Whether it is a good idea or not is something else.

I wonder why they jumped phase B and C together. Maybe a neutral bar has been added and the C phase spots are used for 120V circuits.
 
One big concern is to make sure no two circuits on the two B-phase buses are wired to share a neutral.
 
well you end up with alot of wasted space with the 2 pole breakers.. but- i've seen one passed with a green sticker!
do you have a picture of this panel? make sure any doubled up hot legs are in rated lugs!
 
petersonra said:
...

I wonder why they jumped phase B and C together. Maybe a neutral bar has been added and the C phase spots are used for 120V circuits.
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Because if they didn't jump them together they'd have had an 8 space panel instead of a 12 space panel. And they only needed 120V circuits anyway.

Panel came with a neutral bar, label has diagrams for 280/120 or 240/120 high-leg.

LarryFine said:
One big concern is to make sure no two circuits on the two B-phase buses are wired to share a neutral.
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True. (Plus the handle tie issue.) But I can determine whether I can fix that up or not. I'm looking to see if there's consensus on whether the panel itself is a no-no.
 
rambojoe said:
well you end up with alot of wasted space with the 2 pole breakers.. but- i've seen one passed with a green sticker!
Click to expand...

Good to know. Maybe. :lol::roll:

do you have a picture of this panel? make sure any doubled up hot legs are in rated lugs!
Click to expand...

I know why you're saying that, but in this case with the backfed breaker there are no doubled up hot legs. If people really want pictures I'll post when I have a bit more time.
 
petersonra said:
It should be fairly obvious from the configuration of the back fed breaker that something is a little different.

I think code also requires you to label where it is fed from which would be another clue.

I just do not see it is a code violation. Whether it is a good idea or not is something else.

I wonder why they jumped phase B and C together. Maybe a neutral bar has been added and the C phase spots are used for 120V circuits.
Click to expand...

It wont be obvious if you don't take the cover off.

Hence my original statement "behind the cover"

And,

If a label to a 3 phase panel indicates a single phase source, that would just confuses the issue.

If I were an inspector, and couldn't gig em on this type of unprofessional panel install, I'm sure I could find something else to sting them on to make up for it.

JAP>
 
rambojoe said:
make sure any doubled up hot legs are in rated lugs!
Click to expand...

There's not going to be any doubling up "hot legs" in this scenario.

It was stated they back fed a 3 pole breaker in the top 2 left positions.

I'm sure they simply jumpered B and C phase on the empty Main Lugs in the panel.

But, I may be giving them too much credit considering what they did already.

JAP>
 
This might be a code violation (AND a hazard) if it's a service entrance and the B-phase conductor is "protected" by two breakers in parallel, which would allow double the B-phase conductor's ampacity to flow before tripping.

Even if not, it seems like a really bad idea. The next person to come along and add something will face several non-obvious opportunities for trouble. For example:
- The above-mentioned shared-neutral MWBC, which will seem to be OK when installed & tested but will eventually overheat the neutral.
- Trying to supply a three-phase device from this "three-phase" panel, which won't work and might damage a motor.
- Trying to supply a 208-volt single-phase load from the B & C phases, which won't work.
- Trying to supply a 208-volt single-phase load from the A & B phases, which might overheat on 240 volts, ...

At worst, the next person trying to add something might place a hex on the original installer, resulting in a lifetime of bad luck and torment.
(sorry, watching too many old Halloween Week movies)
 
jap said:
There's not going to be any doubling up "hot legs" in this scenario.

It was stated they back fed a 2 pole breaker in the top 2 left positions.

I'm sure they simply jumpered B and C phase on the empty Main Lugs in the panel.

But, I may be giving them too much credit considering what they did already.

JAP>
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Sorry, I meant 2p breaker in slots 1&3.

JAP>
 
To me, this panelboard would be a violation of 408.58.

This panel is being used for a different number of phase conductors than for what it was designed.

JAP>
 
jap said:
There's not going to be any doubling up "hot legs" in this scenario.

It was stated they back fed a 3 pole breaker in the top 2 left positions.

I'm sure they simply jumpered B and C phase on the empty Main Lugs in the panel.

But, I may be giving them too much credit considering what they did already.

JAP>
Click to expand...

my bad- I assumed a mlo…. point is its 240/120 no? I wasn't sure how the "B" leg was jumped to"C" buss...
 
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