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Old 07-15-2015, 08:12 PM   #57
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Ok now things are getting REALLY crazy. I'm at my wit's end! I opened the wire nuts on the connections in that junction box just outside of the generator, it must be the picture, the connections were beautiful. I still replaced the wire nuts with waterproof wire nuts and re-taped them up nicely. No luck. Now the worst part, I cut off the end of a 50-amp cord and wired it directly into the generator and plugged into my shore power cord. SAME PROBLEM. I've now eliminated the wiring and the transfer switch as the problem [Unless by some fluke of nature I had TWO bad transfer switches with the exact same problem....] Though now I'm even trying to run through the shore power side of the ATS and getting same problem. Now what?!?!? Cummins Onan themselves said, "We tested your generator for hours and it's fine", but the problem MUST be inside the generator!
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Old 07-15-2015, 08:13 PM   #58
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Quote:
Originally Posted by nothermark View Post
I'm starting to follow this thread just to see how long it will take for the OP to finally put a jumper between ground and neutral at the transfer switch as the wiring code calls for. If that was in place the voltages would be correct.
I don't follow you. You're saying to add a wire that was not part of the factory install? Which has worked fine for 3 years and all of a sudden stopped working?
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Old 07-15-2015, 10:30 PM   #59
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You have confirmed issue not generator.

As suggested before...Get a heater for a load and a voltmeter and start measuring along the neutral.

Use 50 amp cord as is to save fuel and noise and start at the point the cord is attached and work toward heater.

Verify good at your connection point first.
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Old 07-15-2015, 10:40 PM   #60
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Originally Posted by TQ60 View Post
You have confirmed issue not generator.

As suggested before...Get a heater for a load and a voltmeter and start measuring along the neutral.

Use 50 amp cord as is to save fuel and noise and start at the point the cord is attached and work toward heater.

Verify good at your connection point first.
I verified generator reads good under zero load.

I replaced transfer switch. I replaced 100% of wire from AC posts on top of generator to transfer switch.

I don't know what else it could be other than somewhere inside the generator.....? Are you saying cut the end off of a heater cord and wire directly to generator?
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Old 07-15-2015, 11:06 PM   #61
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I could not add this to my recent post.
And after reading your 6:12pm post, it looks like you have proven that connecting a shore power cord to drive the XFER switch input(the normal path for the genny) works fine. This says the genny has a problem.

Another test would be to simply connect a 115V duplex plug to one side of the genny. All else disconnected.

Blk to L1
White to Neutral
Grn to ground.

Then plug something in and check the voltage....it should be within 5 %

Then try it with L2.
This would be confirmation that the genny is good/bad under load.


A note on what the NEC requires:
The NEC recommends [FPN's to 210-19(a), 215-2(b), and 310-15] a maximum of 3% voltage drop for branch circuits, a maximum of 3% voltage drop for feeders, but a maximum of 5% voltage drop overall for branch circuits and feeders combined.

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Old 07-16-2015, 07:58 AM   #62
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Quote:
Originally Posted by jdwky View Post
Cummins Onan themselves said, "We tested your generator for hours and it's fine", but the problem MUST be inside the generator!

Did they test it under load? Or did they do what you did and disconnect loads and let it run for a while as they monitored normal voltages?

Quote:
Originally Posted by dpinvidic View Post
Shapeshifter....I don't understand why your are concerned with an unbalanced load. Any single 110V load on the system will create an imbalance. Consider plugging in a coffee maker or microwave.

The system should be able to run a full load on either leg.
Agreed. Everything you say is correct, as long as the wiring is correct.

Quote:
It is correct that if the loads are balanced, no current flows through the neutral.
And if the loads are unbalanced, the difference in the current runs through the neutral in order to balance the voltages.

BUT, if the neutral is broken, and the loads are unbalanced, then no current flows through the neutral to balance the voltages, and the voltages will be unbalanced. The total will still add up to 240 volts, but one line will read high, and the other will be low by the same amount. Without the neutral, it will act as two loads in series across 240 volts: the voltage on each load will be proportional to their impedance.

This sounds exactly like what is being reported in the first post.

Quote:
Originally Posted by TQ60 View Post
You have confirmed issue not generator.

As suggested before...Get a heater for a load and a voltmeter and start measuring along the neutral.

Use 50 amp cord as is to save fuel and noise and start at the point the cord is attached and work toward heater.

I think one of us read the post backwards, as it seems to confirm a generator problem. This is what I take from the most recent experiment:
  • He installed a 50 amp socket right at the generator, eliminating the wiring from the transfer switch to the generator.
  • He plugged the shore cord into that socket, and the problem remains while running the generator.
  • When he plugs that same shore cord into a 50 amp shore power pedestal, everything works properly.
jdwky: can you confirm this summary is accurate?

I draw these conclusions from this:
  • Because it works on the shore power pedestal, we can eliminate the shore cord, the shore power side of the transfer switch, and the rest of the coach's wiring.
  • Because it still fails when plugged into the new socket at the generator, we can eliminate the generator side of the transfer switch, and the generator to switch wiring that is now disconnected.
  • That means that the problem lies in the new socket or it's connections (I think it's unlikely that the new wiring is failing in the same manner as the bypassed wiring) or it's in the wiring from the new socket's connection point back into the generator.

Of course, this is assuming that the problem is an open neutral. It sure smells like that's the problem given the symptoms, but so many likely candidates are being eliminated that it's not a sure thing.

Quote:
Originally Posted by jdwky View Post
Are you saying cut the end off of a heater cord and wire directly to generator?
Yes, I think that's his suggestion. It has merit, but I would consider doing it a little differently. It might be worth an experiment to temporarily wire in a normal duplex outlet directly to the output of the generator: just beware that the breaker protection in the generator is much higher than the outlet wiring, so be sure not to overload it as it won't be protected, and don't leave it connected when the experiment is done. Break off the little brass tab between the two hot (brass) screws on the outlet so that the two hot screws are isolated from each other. Connect one hot line to each brass screw, neutral to the silver screw, and ground to the green screw. You now have two normal 120 volt circuits, one on each half of the outlet. Measure the two voltages and make sure they are correct with no load. Now, take something that can be set for 240 volts, like a travel hair dryer. Set it for 240, plug it into one of the outlets, turn it on, and measure voltages. Repeat for the other side of the duplex outlet. Do you still have the same issues?

Edit: I just read dpinvidic's post immediately above, and this is pretty much what he suggested. Sorry to step on your toes, sounds like we are thinking the same things.

Quote:
Originally Posted by jdwky View Post
I don't follow you. You're saying to add a wire that was not part of the factory install? Which has worked fine for 3 years and all of a sudden stopped working?
At this point, it's worth a try, it can't hurt. The only risk is that if it is a broken neutral, adding the bonding could cause a return path for the neutral current. While this would balance the loads, it would turn the ground path into a current carrying conductor which is a big no-no. You would need to measure the current in that bonding jumper to make sure there is no current flowing, a clamp-on type of ammeter would be ideal.

This could mask the problem and turn it into a different but still serious problem. That's why I haven't recommended doing it first. The system should still work properly without the ground bonding, which is a safety feature, not part of the primary power circuit. If a ground/neutral bonding were to fail, I see it causing strange voltages between ground and neutral, but it should not affect the line to neutral voltages.

The bonding is still something to investigate, as there could be an issue there, but I don't see it causing the line to neutral voltages you are reporting. But at this point, with all you've done and not being able to find the problem, it's anybody's guess...
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Old 07-16-2015, 08:35 AM   #63
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Quote:
Originally Posted by Shapshifter

  • Because it works on the shore power pedestal, we can eliminate the shore cord, the shore power side of the transfer switch, and the rest of the coach's wiring. Agreed
  • Because it still fails when plugged into the new socket at the generator, we can eliminate the generator side of the transfer switch, and the generator to switch wiring that is now disconnected. Agreed
  • That means that the problem lies in the new socket or it's connections (I think it's unlikely that the new wiring is failing in the same manner as the bypassed wiring) or it's in the wiring from the new socket's connection point back into the generator. Disaree - The "new" wiring is an extension cord...very unlikely
  • I think Shapeshifter (boy I would prefer to use real names) has a very valid point about an open neutral causing strange voltage readings. This results in a voltage divider baecasue you are running two 120v devices in series from a 240v source. Like two 6v bulbs from a 12v battery. however if you run a 3v and 9v bulb, you DON"T get 6v at the middle connection.

    HOWEVER: jdwky has proven that plugging his normal shore power cord into a pedestal works fine. THEN taking that same shore power cord and plugging into a temporary socket directly on the generator fails.
    This says a generator problem.

    I think you need to do some stress testing on the genny directly.
    Remove your modified power cord socket, and wire in TWO 120V sockets.
    Put them in a double box. One pair of plugs on each leg.
    Use this to load up each leg differently and see what you get.

    I would suggest it is a faulty neutral connection INSIDE the genny (not a complete open). This would line up with shapshifters comment on unbalanced loads causing different readings.

    Regards,

    Dan
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Old 07-16-2015, 10:09 AM   #64
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Quote:
Originally Posted by dpinvidic View Post
Disaree - The "new" wiring is an extension cord...very unlikely
Dan, I'm not sure what you are disagreeing to? You say you disagree, but everything you say in your post is very much what I'm saying. Are you saying that the new wiring is unlikely to be good because it's an extension cord? Or are you saying the new wiring is unlikely to be bad because it's new?

If you mean the former, then I don't see how you are drawing the rest of your conclusions.

If you mean the latter, then that's exactly what I'm saying: it's unlikely that the new bypass wiring is faulty in exactly the same way as the existing wiring, therefore the problem is most likely in the generator.

Cummins/Onan says they tested the generator, but did they test it under load? We already know it works without load, and that could be all the testing they did?

I just re-read what I wrote:

Quote:
Originally Posted by ShapeShifter View Post
  • That means that the problem lies in the new socket or it's connections (I think it's unlikely that the new wiring is failing in the same manner as the bypassed wiring) or it's in the wiring from the new socket's connection point back into the generator.
I guess I can see where it could be misunderstood. I say it could be the socket or new connections, but then I immediately dismiss it as being unlikely, leaving the generator as the most likely culprit. I can see where the wording is clumsy and easy to misunderstand if read quickly.

Quote:
I think you need to do some stress testing on the genny directly.
Remove your modified power cord socket, and wire in TWO 120V sockets.
Put them in a double box. One pair of plugs on each leg.
Use this to load up each leg differently and see what you get.
Precisely what I am suggesting, just that I was proposing using only one duplex outlet and separating the two halves. Your way is a little more work, but is safer because mine relies on properly breaking out the isolation tab.

I am also recommending using a test load that can tolerate 240 volts, since it is likely to see more than 120 volts.

The interesting thing about this test is that if it is truly an open neutral, then without anything plugged into the other line, he could see what would seem to be very strange results. Assuming he's plugged into line 1, and line 2 is open, he could could see:
  • no voltage across the load (because no current is flowing)
  • 240 volts across the open socket (because it's an open circuit)
This is because a small imbalance causes a small difference, a large imbalance causes a large difference: having one leg loaded and the other not loaded at all causes a complete imbalance.

-- Adam (If you couldn't guess from my signature...)
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Old 07-16-2015, 10:20 AM   #65
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Quote:
Originally Posted by ShapeShifter View Post
Dan, I'm not sure what you are disagreeing to? You say you disagree, but everything you say in your post is very much what I'm saying. Are you saying that the new wiring is unlikely to be good because it's an extension cord? Or are you saying the new wiring is unlikely to be bad because it's new?

If you mean the former, then I don't see how you are drawing the rest of your conclusions.

If you mean the latter, then that's exactly what I'm saying: it's unlikely that the new bypass wiring is faulty in exactly the same way as the existing wiring, therefore the problem is most likely in the generator.

Cummins/Onan says they tested the generator, but did they test it under load? We already know it works without load, and that could be all the testing they did?

I just re-read what I wrote:


I guess I can see where it could be misunderstood. I say it could be the socket or new connections, but then I immediately dismiss it as being unlikely, leaving the generator as the most likely culprit. I can see where the wording is clumsy and easy to misunderstand if read quickly.


Precisely what I am suggesting, just that I was proposing using only one duplex outlet and separating the two halves. Your way is a little more work, but is safer because mine relies on properly breaking out the isolation tab.

I am also recommending using a test load that can tolerate 240 volts, since it is likely to see more than 120 volts.

The interesting thing about this test is that if it is truly an open neutral, then without anything plugged into the other line, he could see what would seem to be very strange results. Assuming he's plugged into line 1, and line 2 is open, he could could see:
  • no voltage across the load (because no current is flowing)
  • 240 volts across the open socket (because it's an open circuit)
This is because a small imbalance causes a small difference, a large imbalance causes a large difference: having one leg loaded and the other not loaded at all causes a complete imbalance.

-- Adam (If you couldn't guess from my signature...)
All of this is making some sense, but I think we're all in agreement the problem must be inside the generator somewhere. It must be some kind of connection that has rattled itself loose or corroded. One other thing I will try today is to unhook the neutral wire from the back side post and wire-nut the 2 neutrals together, bypassing the AC post on top of generator, in case it is bad inside there. Beyond that, I will really have to crack open the genset to trace the wire farther back. Anyone have a service manual for this genset??, QD 10kw. Thanks Adam and Dan for the continued support!
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Old 07-16-2015, 10:28 AM   #66
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Originally Posted by ShapeShifter View Post
Did they test it under load? Or did they do what you did and disconnect loads and let it run for a while as they monitored normal voltages?
I do not know. They were awful to deal with. Rude, condescending, brief. They refuse to refund any of my money even though they admitted "they were wrong" on the diagnosis. They said they worked over 3 hours on it, and 3 different techs supposedly looked at it.


Quote:
Originally Posted by ShapeShifter View Post

I think one of us read the post backwards, as it seems to confirm a generator problem. This is what I take from the most recent experiment:
  • He installed a 50 amp socket right at the generator, eliminating the wiring from the transfer switch to the generator.
  • He plugged the shore cord into that socket, and the problem remains while running the generator.
  • When he plugs that same shore cord into a 50 amp shore power pedestal, everything works properly.
jdwky: can you confirm this summary is accurate?
Correct.
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Old 07-16-2015, 10:30 AM   #67
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Anyone have a service manual for this genset??, QD 10kw.
There should be a label with the identification information, including a series of letters, for example HDKAH, HDKAT, etc. There are internal variations within the generators, and knowing those letters will let us know just which one you have. Just saying 10kW isn't a unique identifier.

Best bet is posting a picture of that identification plate.
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Old 07-16-2015, 10:36 AM   #68
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Old 07-16-2015, 11:38 AM   #69
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HDKCA is the key identifier. The service manual is HERE

Some interesting things to note:
  • On Page 12-6 there is the troubleshooting for under and over voltage. In both cases, the first test is to turn off the circuit breakers and measure the output voltage. You are doing the same thing by disconnecting the output wires. This test passes, so the troubleshooting notes indicate the problem is external to the generator. Therefore, Onan probably did the same and assumed the generator is good. However, that is not 100% true in all cases.
  • On page A-1 is the wiring diagram, with a few interesting observations:
    • The ground/neutral boding that concerns nothermark so much is being done inside the generator (note how the wires from TB2-3 and TB2-4 run parallel for a while, but then are tied together.) But if the neutral wire were broken somewhere between the bonding point and the terminal block, you would get the measurements you are posting, it would appear that that the bonding is broken (but not really be the case) and adding a new bonding connection would simply turn the ground conductor into a current carrying neutral conductor, which would be bad.
    • The neutral outputs from the generator are T2 and T3. If you are to trust the way the lines are drawn, the two lines splice together into a single wire, then split apart into ground and neutral before reaching terminal block TB2. If the neutral wire were broken after this split and before the terminal block, you would get exactly what you are reporting: good voltages between lines and ground, and bad voltages between line and neutral. It would seem that the break would have to be after this split, if it were before the measurements to ground would also be bad.
  • On page A-3 is a picture of the wiring harness. It's a pictographic drawing, not a schematic, so we can't see the actual connections: the wires just disappear into some form of jacketing. There are separate ground and neutral wires, but are they separate all the way through, or do they combine together and split apart as shown in the schematic?

I would start with the output disconnected from the terminal block -- completely isolate the generator from the rest of the coach. Also, turn off your battery disconnects -- we don't want the generator starting during these tests. Make sure you can't start the generator.

Now, using a meter, measure the resistance between the ground and neutral lines at the terminal block (TB2-3 and TB2-4.) There should be very low resistance, but I'm going to guess it's open. Now, measure between TB2-4 and the chassis of the generator, it should be very low resistance, and I'm going to guess that's true. If ground/neutral is open, and ground/chassis is connected, that confirms it's in the neutral line.

Now measure between TB2-3 (the neutral connection on the terminal block) and the T2 and T3 terminals of the generator. They should be connected, but I'm guessing you will find them open. This confirms the diagnosis. Now, it's a matter of tracing the wires from the generator T2/T3 terminals to TB2-3 and finding the open.

My guess (and it's just that, a guess): the wire labeled NEUT on page A-3 should be connected to TB2-3, and I'm going to guess that one of the terminals is crimped poorly or corroded so that it's not making a proper connection.
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Old 07-16-2015, 12:00 PM   #70
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Good stuff, thanks Adam!! Will work on this today. I owe you many beers if I don't have to cancel my camping trip this weekend! Fingers crossed.....
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