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Old 07-03-2015, 11:04 AM   #15
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Originally Posted by wigginsjsr View Post
So much for the idea that the generators have built-in protection against high voltage. So many of the discussions regarding the need for surge/voltage protectors indicate that there is no need to worry about generator over voltage.
I wholeheartedly agree. A scenario like this is exactly why I put my Progressive EMS after the transfer switch. I want to protect the coach from as much as possible.

Granted, there is still the possibility that there could be a break in the neutral between the EMS and the breaker panel, but at least I've eliminated as many bad connection sources as possible.

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Originally Posted by nothermark View Post
The generator is working properly. Your wiring is broken.
I also agree.

L1 <--> N = 104, about 20 volts too low.
L2 <--> N = 145, about 20 volts too high.

One line being too high while the other line is too low by the same amount is the classic indication of an open neutral. I strongly believe that the neutral line is open somewhere between the generator and the main breaker panel. If the problem doesn't occur when on shore power, then it's safe to say the break isn't in the neutral path between the transfer switch output and the breaker panel. That leaves possible break locations at:
  1. The generator internal wiring
  2. The generator output connections
  3. The cable between the generator and the transfer switch
  4. The input connections to the transfer switch
  5. The transfer switch contacts
I think 2 and 4 are the most likely causes, followed by 5. 1 and 3 are less likely, but still possible.

I don't think it's the connection between neutral and ground, I think it's the actual neutral path that is broken.
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Old 07-04-2015, 06:39 AM   #16
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The safety ground will not be connected internally in the Generator. That is not what it is for. The RV spec is to connect it at the transfer switch. It would need to be done on the generator side because it should not be connected together when on shore power. That pretty well nails it to the wiring going into the transfer switch.

The other thing that could do it is an open safety ground. One can get strange readings on an open with a high impedance meter. I'd check continuity between the genset and safety ground to neutral bridge.
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Old 07-04-2015, 10:09 AM   #17
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Quote:
Originally Posted by ShapeShifter View Post
I wholeheartedly agree. A scenario like this is exactly why I put my Progressive EMS after the transfer switch. I want to protect the coach from as much as possible.



Granted, there is still the possibility that there could be a break in the neutral between the EMS and the breaker panel, but at least I've eliminated as many bad connection sources as possible.







I also agree.



L1 <--> N = 104, about 20 volts too low.

L2 <--> N = 145, about 20 volts too high.



One line being too high while the other line is too low by the same amount is the classic indication of an open neutral. I strongly believe that the neutral line is open somewhere between the generator and the main breaker panel. If the problem doesn't occur when on shore power, then it's safe to say the break isn't in the neutral path between the transfer switch output and the breaker panel. That leaves possible break locations at:
  1. The generator internal wiring
  2. The generator output connections
  3. The cable between the generator and the transfer switch
  4. The input connections to the transfer switch
  5. The transfer switch contacts

I think 2 and 4 are the most likely causes, followed by 5. 1 and 3 are less likely, but still possible.



I don't think it's the connection between neutral and ground, I think it's the actual neutral path that is broken.

Re #4, I already tried swapping the wires to the other side of ATS so I would think we can rule that out, no? They are seated and secured well. I would think that would rule out #5 as well? I got same weird readings on other side of ATS too.

I will open generator back up and start looking for loose screws or wires, but much of your alls talk about neutral/ground path, etc is getting confusing to me. In bed comfortable with 12v, but not as experienced in AC. I'm terrified to take my coach to the Cummins service center, as I feel they are not used to dealing with electrical issues as much as changing oils and parts out. I could rack up a pricy bill and still not get it fixed.... I just don't know who else to let look at it locally?


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Old 07-04-2015, 10:35 AM   #18
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If you want to do more troubleshooting yourself you can go to
flightsystems.com and take a look at their troubleshooting guide.
If your voltage issues are constant and not intermittent, any qualified generator place could locate the problem quickly. It could be a bad control board or voltage regulator or bad wiring. I would just bite the bullet and take it to Onan/Cummins
for at least a diagnostic review.
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Old 07-04-2015, 11:22 AM   #19
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Originally Posted by jdwky View Post
Re #4, I already tried swapping the wires to the other side of ATS so I would think we can rule that out, no? They are seated and secured well.
Yes! That would tend to rule out #4, at least for now. Move on to other areas, like you are planning. But if nothing else helps, don't be too reluctant to come back and revisit it.

Quote:
I would think that would rule out #5 as well?
Maybe, maybe not. It could still be an internal transfer switch problem, in the common circuit after the relays. However, everything works properly on shore power, that would tend to rule it out. Swapping sides like that does tend to rule out the generator side of the ATS and contacts.

Quote:
I got same weird readings on other side of ATS too.
This also tends to rule out the transfer switch. If there are bad readings, and the transfer switch is working properly, I would expect that you see the bad readings on both sides of the switch. If the readings are good on one side, and bad on the other, then I would suspect the transfer switch.
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Old 07-05-2015, 05:59 AM   #20
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Originally Posted by jdwky View Post
Re #4, I already tried swapping the wires to the other side of ATS so I would think we can rule that out, no? They are seated and secured well. I would think that would rule out #5 as well? I got same weird readings on other side of ATS too.

I will open generator back up and start looking for loose screws or wires, but much of your alls talk about neutral/ground path, etc is getting confusing to me. In bed comfortable with 12v, but not as experienced in AC. I'm terrified to take my coach to the Cummins service center, as I feel they are not used to dealing with electrical issues as much as changing oils and parts out. I could rack up a pricy bill and still not get it fixed.... I just don't know who else to let look at it locally?


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No, it will not rule out #4 unless you also tie the safety ground and neutral together. You also need to check the integrity of both connections back to the generator.
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Old 07-05-2015, 09:01 AM   #21
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Originally Posted by nothermark View Post
You also need to check the integrity of both connections back to the generator.
I agree that the integrity of all connections should be verified. But I'm still having a hard time wrapping my head around how a lack of neutral-ground bonding would cause what he's seeing.

The line voltages to ground are correct. To me, that says the ground line is intact.

The line voltages to neutral are wrong. To me, that says the neutral line is broken.

I'm certainly not saying you are wrong, I'm just trying to understand how an open bonding connection can cause the posted readings. Of course, with an open ground connection, all sorts of strange readings are possible, especially with a high impedance meter, but I would think it would cause the strange readings when referenced to ground, not neutral.

Any chance you can draw a picture that shows how your theory would cause valid line to ground readings, but invalid line to neutral readings?

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There's one thing that hasn't been specifically said by the OP (or if it has, I missed it.) Is everything working properly when on 50 amp shore power? I've been assuming it is, but I don't see that explicitly stated. But if screwy readings are seen on 50 amp shore power, then it points to an open neutral between the transfer switch and main breaker panel (an area not previously considered.)
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Old 07-08-2015, 06:32 PM   #22
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I will be installing a new transfer switch myself tomorrow. I went by Cummins Crosspoint after work today, they wanted $550 for a new transfer switch that even Camping world charges $260 for. Then $300-450 more to swap it out. My bill for their "diagnosis" of bad transfer switch = $439. Needless to say, I will never go back there again.



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Old 07-09-2015, 07:52 AM   #23
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Originally Posted by ShapeShifter View Post
I agree that the integrity of all connections should be verified. But I'm still having a hard time wrapping my head around how a lack of neutral-ground bonding would cause what he's seeing.

The line voltages to ground are correct. To me, that says the ground line is intact.

The line voltages to neutral are wrong. To me, that says the neutral line is broken.

I'm certainly not saying you are wrong, I'm just trying to understand how an open bonding connection can cause the posted readings. Of course, with an open ground connection, all sorts of strange readings are possible, especially with a high impedance meter, but I would think it would cause the strange readings when referenced to ground, not neutral.

Any chance you can draw a picture that shows how your theory would cause valid line to ground readings, but invalid line to neutral readings?

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There's one thing that hasn't been specifically said by the OP (or if it has, I missed it.) Is everything working properly when on 50 amp shore power? I've been assuming it is, but I don't see that explicitly stated. But if screwy readings are seen on 50 amp shore power, then it points to an open neutral between the transfer switch and main breaker panel (an area not previously considered.)

If you can understand it you can draw it yourself. The system is a center tapped transformer with the center tap as the neutral connected to ground. The point is that there has to be a connection between neutral and ground. It is placed the way it is so current flowing though insulation will return to the safety ground thus rendering it measurable by a GFI. When on the shore cord the connection is made at the pedestal. When on the generator it is made on the generator side of the transfer switch. If you put it on the other side it would interfere with the normal connected practice.

The fact that he saw more than a minimal difference between readings to neutral and ground says there is a high impedance path between the two. It would have been interesting if he measured the two but he did not. The fact that he saw a difference is disturbing in that it indicates there is no connection.

I think he said it works on shore power. That is what got me looking at how the ground and neutral are handled when on the generator. The specifications are available on the internet for both conditions.
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Old 07-09-2015, 02:02 PM   #24
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I've been reading this thread with great interest and have learned a lot, especially about floating neutrals and RV grounding. One thing has me confused. If the power output at the generator is wrong, how does that involve the ATS? Bad voltage after the ATS I could see the ATS being the suspect but before it gets to the ATS? I think I must have missed something here.
If you switch the breakers off at the generator would it still not produce voltage? Or is there some internal wiring that prevents that. I'm no expert, just trying to understand, thanks.
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Old 07-09-2015, 04:29 PM   #25
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If you can understand it you can draw it yourself. The system is a center tapped transformer with the center tap as the neutral connected to ground. The point is that there has to be a connection between neutral and ground.
I fully understand all that. I just don't understand how simply breaking that connection could cause the readings he's getting. If that were the only problem, the voltages between hot and neutral would be good, but the voltages between hot and ground would be wrong. This is the opposite of what is being reported.

Quote:
The fact that he saw more than a minimal difference between readings to neutral and ground says there is a high impedance path between the two. It would have been interesting if he measured the two but he did not. The fact that he saw a difference is disturbing in that it indicates there is no connection.
I agree that given the readings, there must be a voltage present between the neutral and ground, and that means that there is not connection. But I don't think that simply breaking that connection would cause the readings he's getting.

The voltages between hots and grounds are good: to me, that means that all of those connections are good.

However, the voltages between hots and neutral are wrong, and they are wrong by complementary amounts. That sounds very much like an open neutral -- there is no return path between the neutral and the generator, therefore no way for the neutral path to balance out the voltages. Therefore, the neutral voltage is floating relative to the generator and the ground.

I think the neutral ground bond is intact, but the neutral wire is broken between that bonding point and the point where he's making the voltage measurements. It looks like a broken/ground connection, but that's only an artifact of the broken neutral connection.

Quote:
I think he said it works on shore power. That is what got me looking at how the ground and neutral are handled when on the generator.
I can understand why it appears that way. But if the broken neutral is between the generator and the transfer switch, or in the transfer switch itself, you would get the same result: the shore power works, but the generator doesn't.

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I've been reading this thread with great interest and have learned a lot, especially about floating neutrals and RV grounding. One thing has me confused. If the power output at the generator is wrong, how does that involve the ATS? Bad voltage after the ATS I could see the ATS being the suspect but before it gets to the ATS? I think I must have missed something here.
If the problem is an open neutral, as I suspect, the break could be anywhere. It could easily be a contact in the transfer switch.

If the neutral line is broken, the voltages on the hot lines can vary widely depending on the loads: load one hot line heavily, and the other lightly, and you will end up with voltages that are high on one hot line, and low by the same amount on the other hot line -- exactly what is being reported.

Quote:
If you switch the breakers off at the generator would it still not produce voltage? Or is there some internal wiring that prevents that.
I'm not sure what you're asking. If the breakers at the generator are off, the generator itself will still be creating voltage internally, but it won't get outside of the generator box.
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Old 07-09-2015, 05:30 PM   #26
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What I'm asking is that if the generator is producing correct voltage with the breakers off then I see that the external wiring or the ATS is faulty. However, if the generator voltage is not within specs at the generator, while the breakers are off, why would anything down line be bad? It would seem to be an internal issue of the generator. Just trying to understand.
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Old 07-09-2015, 05:33 PM   #27
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Get an electric heater and plug it in someplace then check voltages again.

Check white to white and start at source connection at generator.
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Old 07-09-2015, 06:01 PM   #28
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What I'm asking is that if the generator is producing correct voltage with the breakers off then I see that the external wiring or the ATS is faulty. However, if the generator voltage is not within specs at the generator, while the breakers are off, why would anything down line be bad? It would seem to be an internal issue of the generator. Just trying to understand.
Yes, I agree that if the generator output breakers are off, which would isolate the generator internals from the RV, and you open up the generator box to measure the internal voltages and they are bad, then the problem is virtually certain to be in the generator and not the outside wiring. But I don't see any evidence that this is the case here. Did I miss some tests where the breakers were shut off and the generator internals were determined to be bad?

I'm looking back through this thread, and re-reading your first post up at the top. You are seeing voltage fluctuations and frequency shifts, which makes me think you are having a problem inside your generator. Your voltage shifts are not likely to be from the same cause as the OP's problems unless you are also seeing exactly complementary offsets as he is. For your fluctuations, are both lines going high or low at the same time? If so, I would suspect a generator control or speed problem, especially if you are seeing frequency variations. However, if you have one line going high while the other line goes low by the same amount (within a volt or so) then I would suspect a broken neutral, and that break could be anywhere from inside the generator to all the way to the breaker panel.
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