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Another sub question?


Darren
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Please tell me that the feeders to the bus lugs are just some odd colored wire and not bare copper! [:-bigeyes

BTW...I see a neutral and a ground exiting bottom left. Just one of each though. I would want to know for sure what the circuits are for. Odd set-up. It doesn't seem like it could be right without the outer two breakers tied together...and even then...?

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I believe this sub panel is feeding an in-ground pool.

Should I be concerned about the lack of grounding & neutral wires going out?

That depends on what those circuits are feeding. If the center two breakers are just serving a 240v load and the two outside breakers are feeding a multi-wire circuit, it looks fine. Anything else and I dont' see how it could be correct.

- Jim Katen, Oregon

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I believe this sub panel is feeding an in-ground pool.

Should I be concerned about the lack of grounding & neutral wires going out?

That depends on what those circuits are feeding. If the center two breakers are just serving a 240v load and the two outside breakers are feeding a multi-wire circuit, it looks fine. Anything else and I dont' see how it could be correct.

- Jim Katen, Oregon

Aren't multi wire circuits supposed to be on adjacent breakers so that the loads are out of phase? Kinda hard to screw up in that panel, but really easy to end up with a 240v neutral if they're not.

Tom

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. . . Aren't multi wire circuits supposed to be on adjacent breakers so that the loads are out of phase? Kinda hard to screw up in that panel, but really easy to end up with a 240v neutral if they're not.

Before '08, they only had to be on two different poles. Since '08, they're supposed to be on two-pole breakers, which sort of makes it necessary to have them side-by-side.

In the panel in the picture, the two outside breakers are on opposite poles.

- Jim Katen, Oregon

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Aren't multi wire circuits supposed to be on adjacent breakers so that the loads are out of phase? Kinda hard to screw up in that panel, but really easy to end up with a 240v neutral if they're not.

The neutral would still have 120volts...it'd be carrying the sum of the loads instead of the difference in the loads.

That depends on what those circuits are feeding. If the center two breakers are just serving a 240v load and the two outside breakers are feeding a multi-wire circuit, it looks fine. Anything else and I dont' see how it could be correct.

Jim, even if the outer breakers are serving a mwbc..shouldn't the handles be tied? I've been buzzed by neutrals on circuits that were off so I'm a little jaded

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The neutral would still have 120volts...it'd be carrying the sum of the loads instead of the difference in the loads.

Wouldn't that be worse? Couldn't that exceed the ampacity rating of the neutral without tripping either breaker?

Jim, even if the outer breakers are serving a mwbc..shouldn't the handles be tied? I've been buzzed by neutrals on circuits that were off so I'm a little jaded

That was my initial thought also, but with if it's two single poles tied together then there is the risk that the tie will prevent a breaker tripping if there is a fault on only one side of the circuit. I would guess that's why the NEC states double pole breakers now.

Tom

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Jim, even if the outer breakers are serving a mwbc..shouldn't the handles be tied? I've been buzzed by neutrals on circuits that were off so I'm a little jaded

You've been electrically shocked by a neutral? Neutrals, by design, do not carry significant voltages, only load currents that match the current in the corresponding un-grounded conductor. There's something seriously wrong when any neutral has sufficient voltage to shock you.

As for the original post, I don't see anything wrong except that the multi-wire circuit should be fed by a 2 pole breaker. I'm assuming that the existing 2 pole breaker is a 240V and not a 120/240V circuit.

Two pole breakers, by design, trip when a fault or overload exists on either or both poles, just as three or four pole breakers will.

Marc

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That was my initial thought also, but with if it's two single poles tied together then there is the risk that the tie will prevent a breaker tripping if there is a fault on only one side of the circuit. I would guess that's why the NEC states double pole breakers now.

Tom

Modern breakers trip internally and will still trip even if you forcibly hold the handle in the on position. While you can "lock" a breaker on to prevent someone from deliberately turning it off, you can't actually prevent it tripping in an overcurrent situation. So, a handle tie between two single-pole breakers is not a problem.

You can demonstrate this to yourself. Next time you test an AFCI breaker, try holding the handle in the on position when you hit the test button. The breaker will still trip. Other breakers have similar mechanical linkage.

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You've been electrically shocked by a neutral? Neutrals, by design, do not carry significant voltages, only load currents that match the current in the corresponding un-grounded conductor. There's something seriously wrong when any neutral has sufficient voltage to shock you.

I beg to differ that there's insignificant voltage or current. An ammeter meter in series with a neutral wire will show what ever load is imposed on the circuit. Current doesn't follow the easiest path to ground, it follows all paths.

Wouldn't that be worse? Couldn't that exceed the ampacity rating of the neutral without tripping either breaker?

Exactly. When you see neutrals the color of toast an incorrectly mwbc is often the culprit.

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Hello Chad,

I noticed that you're from Rochester, NY. I attended Rochester Institute of Technology there for 5 1/4 years as an EE major. Most beautiful country I've ever seen. Just loved Letchworth. Saw my first snowflake after Thanksgiving break during my freshman year there. I had been studying 'Probability & Statistics' when I took a break after midnight and walked over to my 3rd floor dorm window which overlooks a parking lot. All the cars were white. Asphalt was black as usual. So, I started figuring the probability of those cars all being white but I couldn't arrive at a credible number. Finally, I opened the window and stuck my hand out and snowflakes landed on my hand. It was a light snowfall, too light to see in the darkness or to color the asphalt, but enough to hide the color of the cars.

So many good memories.

Marc

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Jim, even if the outer breakers are serving a mwbc..shouldn't the handles be tied? I've been buzzed by neutrals on circuits that were off so I'm a little jaded

You've been electrically shocked by a neutral? Neutrals, by design, do not carry significant voltages, only load currents that match the current in the corresponding un-grounded conductor. There's something seriously wrong when any neutral has sufficient voltage to shock you.

As for the original post, I don't see anything wrong except that the multi-wire circuit should be fed by a 2 pole breaker. I'm assuming that the existing 2 pole breaker is a 240V and not a 120/240V circuit.

Two pole breakers, by design, trip when a fault or overload exists on either or both poles, just as three or four pole breakers will.

Marc

You may want to study neutral currents. If you think that you cannot receive a deadly shock from a neutral you are sadly mistaken.

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You may want to study neutral currents. If you think that you cannot receive a deadly shock from a neutral you are sadly mistaken.

Study neutral currents? Would you kindly explain, for the benefit of all TIJ users, how would it be possible for a neutral conductor on a properly installed and functional electrical installation to possess lethal voltages?

Marc

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I take a stab at it.

In my simple terms....A/C = alternating current. On a 120 volt circuit current flows both directions on both the conductors. Black and white. Out of the breaker on the black....to the light bilb and continues on through the white conductor to the panel. It's a circle. Then the current reverses and flows back along the same path.

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Let's work on our terminology for a minute:

Voltage: a measure of electromotive force. By 'carrying a voltage' is meant the presence or absence of a voltage on the surface of a conductor.

Current: a measure of the time rate flow of an electrical charge. By 'carrying a current' is meant the presence or absence of a flow of electrical charge through a conductor.

To check for voltage on a conductor, connect one lead of your voltmeter to electrical ground which means that terminal which is at ground potential. Connect the other lead of your voltmeter to the conductor being tested for the presence of voltage. Read the value of voltage on the voltmeter.

To check for current through a conductor, encircle the conductor with your clamp-on ampmeter or, if no such instrument is available, open the circuit, then close it again using your ampmeter or a suitable shunt.

Ok. Now what I mean when I say that neutrals do not carry significant voltage is that, without opening the circuit, if you check for the presence of voltage on a neutral, you should not get a significant reading, regardless of whether the circuit is carrying an electrical load or not.

All clear?

Marc

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I believe this sub panel is feeding an in-ground pool.

Should I be concerned about the lack of grounding & neutral wires going out?

Click to Enlarge
tn_20091216204037_FrankLakes%20080.jpg

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Hello Darren. To answer your question, I would say yes, you should be concerned about a possible lack of grounding. The 240 volt circuit may not need a neutral, but it still needs a ground lead going to the equipment. They may have grounded everything with that one green wire, but that is something that should be checked.

Concern #2, already mentioned but to clarify:

One of the reds is marked with black tape. We suspect the reds and the neutral are being used as a multi wire 120 v circuit (just a guess). If so, they really should be joined with a tie-bar for safety.

The reason is if someone is working on the circuit while one of those breakers is left on by mistake, he/she could get zapped. Right, Marc? [:)]

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. . . Ok. Now what I mean when I say that neutrals do not carry significant voltage is that, without opening the circuit, if you check for the presence of voltage on a neutral, you should not get a significant reading, regardless of whether the circuit is carrying an electrical load or not.

All clear?

Well, that's sort of clear. But it's not what you posted earlier, which was, quite clearly, wrong. All that someone has to do to be killed by neutral current is get in series with it. Electricians are killed by neutral current every year.

- Jim Katen, Oregon

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