Thread: Why would anyone do this? "Phase Jumper"

First off, what is a "Phase Jumper"?

I see a lot of weird and bad thing in electrical panel around here, but this one has be completely confused. This is a secondary panel (some might incorrectly call it a sub-panel) in a detached barn; the feeder is from a 100-amp breaker at the main distribution panel on the outside of the house (breaker labeled 'Barn subpanel').

See the picture to follow this. At the panel in the barn, I see a 100-amp hot (ungrounded) conductor and the grounded conductor (neutral) that attach to the supply lugs (blue arrows). What throws me is that there is a #4 copper wire (red arrows) that connects from the UNused supply terminal (only one of the two supply conductors are attached) and wraps around to a 20-amp breaker on the panel. There is no branch circuit attached to this breaker. On the panel cover, this breaker is labeled as "Phase Jumper". Since no supply conductor is attached to this supply lug, I guess that it would not be carrying a charge. So, what is the benefit of running a loop between an uncharged supply terminal, to a breaker?

To clarify, only one of the two hot (ungrounded) conductors is attached to the disconnect breaker at the service entrance panel, and at the panel in the barn (there are no 220-volt devices or receptacles in the barn, so I suppose that's ok). The grounded conductor (neutral) goes from the house panel to the barn. No equipment grounding conductor was seen leaving the house panel into this conduit; a grounding wire is seen at barn panel so I assume it is locally grounded but I can't see where. I hope this makes enough sense.

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Terry, It looks to me that the barn panel is only 110 volts with the jumper back feeding the other side of the panel. Maybe the main panel box did not have enough room for a second breaker for 220 power. If the 30 amp breakers are not for a 220 outlet I see nothing wrong, except the breaker tie needs to be removed.

This is an example of the term I coined (at least I never heard anyone else use it) today at an inspection, Handymanitis.
I saw this everywhere I looked in the house. At least your example does not look particularly unsafe. They simply needed power to the dead phase to supply 110 power to those circuits without rewiring the whole panel. Now why you would do that rather than attach the second leg correctly... only the person afflicted with the handymanitis condition could tell you.

I suspect a problem, something blew, maybe from a lightning strike.

See that arced and burned area behind the feeder which is still connected?

My guess is that the other feeder arced through, possibly arcing through the insulation, shorting or ground faulting it out, making it useless.

They fed the other bus from that breaker.

It would have been better to have just jumped from one terminal to the other.

That still leaves that 240 breaker (it is a black and a red, so it is, at least was originally, most likely a 240 circuit) which only has 120 volts at it, and -0- volts between the two conductors. My guess would be that whatever it operated has now been 'abandoned' and either replaced with, or re-wired to, 120 volts.

If the above is anywhere near correct, I would (do) wonder about the insulation on the other conductor (hot and neutral).

Another strange thing is that the feeders are aluminum and the grounding conductor is copper, solid copper at that. Really strange.

That needs an electrical contractor to find out what happened, what was damaged by whatever happened, and what can be done, which may likely mean pulling new feeder conductors (and who knows what else).

Duhh, now I get it. My brain is fried this week, and I did not really want to do this house anyway (the buyer just plans on bull dozing it anyway at some future date). Shows how important attitude is.

I was thinking in a one-way manner. If I get it right, the feeder from the house panel is supplying power to the left bus only. For what ever reason, the feeder for the right bus is no good (bad breaker at the main panel, short or whatever). So trying to save a few bucks, the electrician runs a jumper from the 20-amp breaker on the left bus to supply power to the right bus (kinda like a sub-sub panel). Now the 30-amp breaker on the right side has power. And looking again at my other pics, I see that 30-amp breaker is labeled on the panel as "Sub-panel in storage room". I must have missed a panel in one of those three beat up pole barns and hay sheds. (Gotta love ranchers).

Jerry -
Don't quite understand your other concern:
"Another strange thing is that the feeders are aluminum and the grounding conductor is copper, solid copper at that. Really strange."
I couldn't see, but assumed the grounding conductor is to a local system ground (this is a detached building w\ no common connections). Why would it be strange for the local system grounding conductor to be solid copper?

Terry,

It looked like that bare copper ground was coming out of the same conduit as the feeder conductors, which would be strange to have solid copper coming out with stranded aluminum.

Isn't the single neutral now undersized for the two 30-amp conductors on the same phase?

Originally Posted by Richard Moore

Isn't the single neutral now undersized for the two 30-amp conductors on the same phase?

No, the neutral looks to be the same size as the phase conductors, and, with one phase conductor disconnected, that means this is a 120 volt 100 amp panel, and those conductor look like they are large enough for that (they should be, they were for use with a 100 amp panel to start with, and still are for that same use).

The difference is that the neutral would previously have only carried the unbalanced current, now there is no "neutral", there is a "grounded conductor" (it just is not a "neutral" any more), and the "ungrounded conductor" and both are the same size, both rated for 100 amp.

Hi Jerry,

I was talking about the NM cable with the #10 red and black conductors connected to the 2-pole 30-amp breaker. That cable assembly has a single #10 white which is now serving as the neutral for a total of 50 amps on the same phase (1 30-amp and the other pole limited by the 20-amp "jumper breaker). I know normal SECs can have reduced size neutrals but I didn't think it was allowed for a branch circuit. (?)

Originally Posted by Richard Moore

I was talking about the NM cable with the #10 red and black conductors connected to the 2-pole 30-amp breaker. That cable assembly has a single #10 white which is now serving as the neutral for a total of 50 amps on the same phase (1 30-amp and the other pole limited by the 20-amp "jumper breaker).

No, it is serving a total load of 30 amps, any more and the breaker it is fed off will trip (should trip). Kind of like not being able to add all the breakers up when there are 6 mains instead of just one main.

"I know normal SECs can have reduced size neutrals but I didn't think it was allowed for a branch circuit. (?)[/quote]

"Used to" be able to reduce the neutral by two sizes. Now, the neutral 'must be sized for the load placed on the neutral'.

That change came about after it was discovered that in many cases the current on the neutral was *more* than the current on the phase conductors - due to harmonics.

The old theory was, if the neutral is only carrying the unbalanced load, the neutral will never (not very likely) carry the same full load current as the phase conductor.

The new knowledge is that the neutral *could very well* carry more current than the phase conductors, and thus 'must be sized to its load', meaning that the neutral could very well have to be *larger* than the phase conductors.

Thanks for that last bit...I didn't know it had changed.

However, I'm going to have to disagree about "No, it is serving a total load of 30 amps, any more and the breaker it is fed off will trip (should trip)."

As the two poles of the breaker are on the same phase it's effectively a parallel connection and the amperage is cumulative. Kind of similar to those 200-amp quad main breakers made up of 4 100-amp units (two per phase).

Forget the handle tie for a bit and you have two separate breakers, one with a 30-amp capacity (#A) and the other (#B) with 20, limited by the jumper. We don't know what they are feeding, but let's say they are serving separate circuits. You could have a 30-amp load on circuit #A AND a 20-amp load on circuit #B without tripping any breaker (50-amps). More than 30 on #A and breaker #A will trip (and yes, trip both because of the handle-tie). More than 20 on #B and the jumper breaker will trip...but #A could still be carrying 30-amps.

There's really no difference to having completely separate 20 and 30 amp single-pole breakers on the same phase in a normal panel.

The other scenario is the black and red are parallel (same phase) feeders to a single lug in the "Sub-panel in storage room" as Terry said it was labeled. In that case, the amperage or current is going to be shared between the two conductors...we'll say evenly assuming all else is equal. In that case you could still draw 40-amps before the 20 on the #B conductor tripped the jumper breaker (followed very shortly by a now overloaded #A breaker)

But that's still 40-amps with a neutral rated for 30.

And then there's the possibility that they feed separate lugs in the storage room making that panel very weird and my eyes cross. But in theory...etc, etc.

Originally Posted by Richard Moore

However, I'm going to have to disagree about "No, it is serving a total load of 30 amps, any more and the breaker it is fed off will trip (should trip)."

As the two poles of the breaker are on the same phase it's effectively a parallel connection and the amperage is cumulative. Kind of similar to those 200-amp quad main breakers made up of 4 100-amp units (two per phase).

The problem with the above assessment is that this is fed off a 100 amp breaker, there will still be 'no more than' 100 amps feeding that panel, no matter how you look at it.

100 amps in the phase conductor and 100 amps out the neutral conductor (I should say 'grounded conductor' as it is no longer a 'neutral' conductor).

Thus, regarding the feeder neutral, it was sized for (looks to be the same size as the phase feeder conductors) 100 amps, and that is all that will go through it, the 100 amp breaker protecting the feeders should trip.

Regarding the 30 amp breaker feeding to the other phase bus, making that the same phase, no more than 30 amp will go through that conductor, which looks like it is sized more than adequate for 30 amps.

You can hook 4 fire hoses together, but if you only feed them with one fire hose through a 1-4 special fitting, you will not get any more water from those 4 than you can get through the 1 feeding them.

Now, *IF* (that big IF) the abandoned phase feeder conductor were to be connected to the same terminal as the remaining phase feeder conductor, then you would have a point regarding the current on the now-grounded-conductor-but-not-a-neutral-conductor.

In the case above, you would have two conductors feeding in and one feeding out, and you could get 100 amps in on each parallel phase feeder conductor, and only 100 amps out on the now-grounded-conductor.

Yeah, under *full load*, that could be a problem ... but ONLY *IF* that *IF* were done, and it was not. So it is not part of the equation ... at this time ... under the conditions shown in the photo.

Of course, with the condition that abandoned phase feeder likely is (based on my other guess), *IF* it were connected as described above, I'm guessing it would short or ground fault out and would need to be disconnected.

Thus, regarding the feeder neutral, it was sized for (looks to be the same size as the phase feeder conductors) 100 amps, and that is all that will go through it, the 100 amp breaker protecting the feeders should trip.

Yes, but I'm not concerned about the feeder to this panel.

Regarding the 30 amp breaker feeding to the other phase bus, making that the same phase, no more than 30 amp will go through that conductor, which looks like it is sized more than adequate for 30 amps.

That's a 20-amp, but again, that wire size is not what I'm concerned about.

You can hook 4 fire hoses together, but if you only feed them with one fire hose through a 1-4 special fitting, you will not get any more water from those 4 than you can get through the 1 feeding them.

Aha! OK. I can go with that analogy. In this case we have a 1-2 fitting but the openings and hoses are not equal sizes. We have a 100-amp firehose capable of forcing water through a 20-amp and 30-amp hose at the same time before the special hydraulic sensing valves on those smaller hoses shut down. 50-amps worth of water (getting silly now).

I gotta get back to my report.
Maybe later we can arm wrestle for it.

Originally Posted by Richard Moore

Aha! OK. I can go with that analogy. In this case we have a 1-2 fitting but the openings and hoses are not equal sizes. We have a 100-amp firehose capable of forcing water through a 20-amp and 30-amp hose at the same time before the special hydraulic sensing valves on those smaller hoses shut down. 50-amps worth of water (getting silly now).

You are forgetting that there is a 1/2" gate valve and pressure regulator in that 20 amp hose system. The pressure regulator keeps the pressure below 80 psi and the gate valve automatically closes when the flow exceeds 7 gpm.

Thus, it does not matter how much you try, or how many fire hoses you connect up to it, the gate valve will automatically close and prevent the 20 amp 3/4" garden hose from rupturing.

You might spring a leak at the fire hose to 1/2" gate valve / pressure regulator connection, but you will not have to be concerned with that 3/4" garden hose bursting, it will never have enough pressure on it to burst and excess flow will close the gate valve.