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Old 10-11-2017, 09:00 AM   #21
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If you had experience with this stuff, then you would load the circuits and read current and voltage. Then you would know what was wrong. If I was standing there, I could show you. But from a screen and keyboard, not so much.


Again measure resistance from neutral to ground. The sub panel should not be bonded. That's why it's not a main panel. You should have only one bonding jumper. You can also take everything loose at the main panel and short a hot to a neutral to use it to check continuity...line to neutral would then be open on one hot and shorted on the other if it's good or open on both if the neutral is bad. Obviously by loose I mean totally disconnected and isolated from power.

You have some small leakage on the breakers that cause an imbalance. Stuff like little pilot lights or electronics in light switches and GFCIs for example is all it takes.

Aluminum does not disintegrate with soil contact unless you mess up your galvanic isolation. Contact with soil completes the galvanic cell and the copper eats out the aluminum often in as little as 12-18 months. Using al:Cu lugs alone doesn't cut it. Read the entire Alcoa guide. Building siding, some boxes, overhead lines, bass boats, and most large transformers can't all be that susceptible. And they all touch soil without insulation.


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Old 10-11-2017, 09:09 AM   #22
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Originally Posted by paulengr View Post
Again measure resistance from neutral to ground. The sub panel should not be bonded. That's why it's not a main panel. You should have only one bonding jumper. You can also take everything loose at the main panel and short a hot to a neutral to use it to check continuity...line to neutral would then be open on one hot and shorted on the other if it's good or open on both if the neutral is bad. Obviously by loose I mean totally disconnected and isolated from power.

You have some small leakage on the breakers that cause an imbalance. Stuff like little pilot lights or electronics in light switches and GFCIs for example is all it takes.

Aluminum does not disintegrate with soil contact unless you mess up your galvanic isolation. Contact with soil completes the galvanic cell and the copper eats out the aluminum often in as little as 12-18 months. Using al:Cu lugs alone doesn't cut it. Read the entire Alcoa guide. Building siding, some boxes, overhead lines, bass boats, and most large transformers can't all be that susceptible. And they all touch soil without insulation.


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If it's three wire, it has to be bonded. If it isn't, the ground and neutral could have a difference in potential. And AL wire isn't a boat. If you nick the insulation, it will fail a lot faster than 12 months, depending on the moisture of the soil and minerals. And last time I checked, overhead lines don't contact the ground in a normal situation.
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Old 10-11-2017, 11:05 PM   #23
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If it's three wire, it has to be bonded. If it isn't, the ground and neutral could have a difference in potential. And AL wire isn't a boat. If you nick the insulation, it will fail a lot faster than 12 months, depending on the moisture of the soil and minerals. And last time I checked, overhead lines don't contact the ground in a normal situation.


It is bonded at the system bonding jumper, one point. Utilities run multiple grounds but not residential. If you have multiple bonding jumpers then you get ground loops, possible voltage on equipment during faults, and the potential to bypass the breaker coordination during a fault. This becomes a variation on peg grounding, something I still see that should be illegal. Subpanels don't have system bonding jumpers. If a neutral is connected properly it is grounded at the system bonding jumper in the main panel. The ground in turn is connected there and bonding carries the potential through the system. Absent this or with either one not connected you will still see the correct voltages with no load because everything is insulated so we have Earth which is a conductor insulated from the power conductors. That's the definition of a capacitor. So "bad" neutrals or grounds are still connected but via a capacitor. A high impedance meter will read the correct voltages (120/120) but the moment you connect even a tiny load like a lighted GFCI the balance is upset by the resistive connection and the voltages become unbalanced while big loads like a space heater simply won't work.

Which reminds me...if the system is ungrounded (no jumper in the main panel) voltage to ground would do the same kinds of things (massively unbalanced) but line to neutral would still look normal (120/130) but the symptoms are referring to the neutral. I have also seen a miswiring situation recently where the standard wire colors weren't used and so it wasn't obvious that the neutral and ground were swapped at a welding receptacle. Voltages looked normal until they put a load on it.



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Old 10-12-2017, 12:47 AM   #24
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You are wrong. There are millions of three wire feeds to detached garages, barns, outbuildings. They need a GEC and bonding of the neutral to it. I suspect you aren't an electrician with experience in this.
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Old 10-12-2017, 01:00 AM   #25
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might be the other hot conductor that is bad. you say one is 120 to neutral & the other is 20 volts if the load on one side(120) works fine & the other doesn't the hot may be bad.you really want no till a load is put on it. a hi wattage bulb between each hot to neutral may confirm my suspicion.but also the neutral could be bad because of the voltages.

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Old 10-12-2017, 06:28 AM   #26
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Again measure resistance from neutral to ground.
How will this help find the problem?

The symptoms mentioned are (like 220/221 said) "a classic neutral problem".

The OP has something in his head and is not willing to listen to the good advice given on this forum.

To the OP, you have a neutral problem. If you can't figure out how to find it, you really need to call an electrician. You can keep not believing what everyone is telling you, but that won't change the fact that you have a neutral problem. Most likely it's the feeder between the house and the outbuilding, but ... does the house show any signs of voltage fluctuation?
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Old 10-12-2017, 07:45 AM   #27
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You are wrong. There are millions of three wire feeds to detached garages, barns, outbuildings. They need a GEC and bonding of the neutral to it. I suspect you aren't an electrician with experience in this.


First off you don't put system bonding jumpers in sunpanels. They only go at the main where the service disconnect is at or at the transformer.

https://iaeimagazine.org/magazine/19...nding-jumpers/

A subpanel is neither a service disconnecting means nor a separately derived system. It is possible to double tap the main and set up the feeder as a service feeder to an outbuilding to make it a second main panel downstream of the metering socket but then the feeder is always hot so it isn't done that way normally. It is a common wiring error to put a bonding jumper in a subpanel. A fault in the feeder to it can flow through the subpanel and not back through the main breaker where it belongs.

Second a GFCI does not actually need a ground. It measures current differences between any two conductors, grounded or not. If there is excess current imbalance it trips. The GFCI is bonded but not connected to ground except it might have something in the test circuit or a pilot light but those are not required for the fundamental function and UL would fail one that can't detect current imbalance on a hot/neutral regardless if the path is ground fault or another hot or neutral or just lab instruments.

In an ungrounded separately derived system obviously the first ground fault in a nonarcing fault has zero current so the prevailing wisdom is that it shouldn't trip. In practice it almost always does due to current flow from the system capacitance but those types of systems are illegal in North America on 240/120. It might show up with 208/120 wye where X0 was not connected or the ground strap corroded off.


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Old 10-12-2017, 07:58 AM   #28
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The system bonding jumper has nothing to do with the OP's problem and I understood backstay to be saying just that.

It seems you keep coming back to this bonding jumper as the source of the problem which makes me wonder why.
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Old 10-12-2017, 08:00 AM   #29
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@paulengr I am betting you're under 30, am I right?
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Old 10-12-2017, 08:03 AM   #30
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I am looking at @Dillon01 's report that the subpanel is not bonded as a clue. That one breaker is another clue. My guesses would be

1. It's an error in testing
2. There's something wrong right right in that panel (how many neutral bars are there, is there really no N-G bond?
3. There's something crossed up in the branch circuit wiring that's completing the circuit in an unexpected way
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Old 10-12-2017, 09:36 AM   #31
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Originally Posted by paulengr View Post
First off you don't put system bonding jumpers in sunpanels. They only go at the main where the service disconnect is at or at the transformer.

https://iaeimagazine.org/magazine/19...nding-jumpers/

A subpanel is neither a service disconnecting means nor a separately derived system. It is possible to double tap the main and set up the feeder as a service feeder to an outbuilding to make it a second main panel downstream of the metering socket but then the feeder is always hot so it isn't done that way normally. It is a common wiring error to put a bonding jumper in a subpanel. A fault in the feeder to it can flow through the subpanel and not back through the main breaker where it belongs.

Second a GFCI does not actually need a ground. It measures current differences between any two conductors, grounded or not. If there is excess current imbalance it trips. The GFCI is bonded but not connected to ground except it might have something in the test circuit or a pilot light but those are not required for the fundamental function and UL would fail one that can't detect current imbalance on a hot/neutral regardless if the path is ground fault or another hot or neutral or just lab instruments.

In an ungrounded separately derived system obviously the first ground fault in a nonarcing fault has zero current so the prevailing wisdom is that it shouldn't trip. In practice it almost always does due to current flow from the system capacitance but those types of systems are illegal in North America on 240/120. It might show up with 208/120 wye where X0 was not connected or the ground strap corroded off.


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Did you miss the part where it's a 3 wire feed? If neutral and ground aren't bonded in that sub panel, then anything connected to the ground bar is not serving its purpose, as a fault to the ground conductor won't trip a breaker. You need an NG bond for a fault to ground to trip a breaker. With a 3 wire feed, the outbuilding needs ground rods and an NG bond the same as the incoming service does.

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