larry cad wrote: Bit Bucket, you are only quoting part of what Ca Traveler wrote and complaining about that partial quote. What he said is exactly correct, if you quote the entire post. What you say may be correct, particularly in a true residential situation, or perhaps more commonly in a commercial situation, however, in an RV, I don't believe they have shared neutral circuits and, as may be obvious, we are talking about an RV problem and trying to get an RV problem fixed. Discussing theoretical issues may be helpful in understanding how systems work, but practical discussions will help find the problem.
Bit Bucket wrote:
CA Traveler wrote: For an open neutral problem it can only occur in the main panel or upstream from the panel which includes everything to the pedestal and beyound. Once inside the main rig panel the individual circuit neutrals are all individual wires just for their circuit.
Just not true at all, never has been, maybe his will turn out to be that way by coincidence but not because it had to be...
Larry, wasn't trying to nit-pick. Sorry if it came off that way to you.
In the interest of examining all of the legitimate possibilities for his problem, it seems that keeping an open mind about the possibility of a shared neutral on a multiwire branch circuit that may or may not be in his RV could account for most of what he is seeing.
I also wasn't trying to take his statement out of context. It really isn't true, the part in red isn't true no matter how many words you put in front of it or behind it. There is literally no way the part in red is accurate no matter what scenario it is wrapped up in. That is why I only quoted part of it.
Both of you appear to not really understand what an Edison circuit is (re-read your first reply) and it seemed you dismissed it as a possibility because of this. I am not complaining about anything anymore than you or he were when you didn't get what Cheyenps was saying about shared neutrals and disputed it.
Just pointing out that the problem could be related to what he said, it doesn't only have to be the way you see it. There is also no relevance to a "true residential situation" or a "commercial situation". RV's 120/240 internal wiring practices are exactly like residential because the NEC says it is residential and they get wired that way if whoever wires it chooses to. There is no common practice or unspoken rules about shared neutrals in an RV. If you or I haven't seen a shared neutral circuit in an RV doesn't mean some don't get wired that way. There are no special rules governing shared neutrals on multiwire branch circuits in RV's. The reason for sharing neutrals is for shaving a few dollars off the install and it sometimes makes the run a little simpler so an RV is exactly the type of place this practice may happen. So yes, we are all talking about the same thing, RV wiring.
Why is your contribution practicle but ours is "theoretical"? Both sides tried to be helpful by pointing out what some possibilities might be. When you "corrected" the shared neutral discusion you were being practical but when it was pointed out that the shared neutral discusion didn't need "correcting" I am being theoretical?
And I know you have some electrical knowledge but if you read your reply:
larry cad wrote:
Cheyenps wrote: Do those two circuits share a neutral?
Another name for "neutral" is "common", meaning common to all circuits. There is always only one neutral and all the various neutral wires from the various plugs, etc. are connected together at one bus bar in the breaker panel, and then on to the power pedestal.
it does not sound like you knew what a "shared neutral" was so I was just trying to keep that as something to possibly look for.
In the end, the main wiring supply uses a "shared neutral". So the only difference between the two suggestions of what to possibly look for is whether or not the potentially bad neutral connection is at the source or possibly a little further downstream, in a main branch circuit.
Bit, my main point was that I don't believe RVs use shared neutral, or "multple wire branch circuits. Consider these points:
1. A shared neutral in a 30 amp RV is, by definition, impossible because there is only one phase.
2. A shared neutral in a 50 amp RV is a really bad idea since it is possible, and likely, that the two "phases" will become one phase when a 30 to 50 amp adaptor is used to power both sides of the 50 amp panel. With only one phase, there will be no current cancelling in the "shared" neutral and thus create the potential for an overloaded neutral. The shore power neutral will be fine as the total current will be 30 amps in a #6 conductor. This will not be a problem in a residential system, or in a commercial system since there is no practical way to connect the two phases together. That is what I meant by theoretical vs. practical.
It is certainly possible to have an open neutral in a 20amp residential branch circuit on a shared neutral, it is impossible to have an open neutral on an RV branch circuit on a shared neutral IF shared neutral circuits are not used in RV wiring. Unfortunately, since I am not at home, I have limited ability to research this topic and a definitive answer will have to wait.
The red text in your post, when taken away from the original post, could be considered untrue. However, when placed in context with the ongoing discussion about RV electrical systems, is totally true. It must be taken in context.
As an aside, I am well aware of what a shared neutral circuit is. I am a licensed electrical contractor in the state of Ohio, graduated with a degree in electrical engineering, and have taught numerous seminars on electrical systems and electrical safety. In addition, I have performed numerous repairs on many RVs and have never seen a shared neutral circuit in any of them.
Today is my personal best for most consecutive days alive.
larry cad wrote: A shared neutral in a 50 amp RV is a really bad idea since it is possible, and likely, that the two "phases" will become one phase when a 30 to 50 amp adaptor is used to power both sides of the 50 amp panel.
Agreed, very bad idea! But I have never been able to find any regulation or reference prohibiting it, bad idea that it is (I believe it is a bad idea everywhere, as I previously stated).
larry cad wrote: it is impossible to have an open neutral on an RV branch circuit on a shared neutral IF shared neutral circuits are not used in RV wiring.
Yes, if it is indeed the case where shared neutrals can be shown to be prohibited or not allowed in RV's then yes, you are right.
But if we cannot show or find reference to it not being allowed then one cannot assume that it is never done.
And if it has ever been done then... I stand by my statement.
And yes, I am well aware of your background and RV blog, you have provided some great stuff to a lot of people over the years. Some of us don't always agree with everything though!
larry cad wrote: A shared neutral in a 50 amp RV is a really bad idea since it is possible, and likely, that the two "phases" will become one phase when a 30 to 50 amp adaptor is used to power both sides of the 50 amp panel.
Agreed, very bad idea! But I have never been able to find any regulation or reference prohibiting it, bad idea that it is (I believe it is a bad idea everywhere, as I previously stated).
larry cad wrote: it is impossible to have an open neutral on an RV branch circuit on a shared neutral IF shared neutral circuits are not used in RV wiring.
Yes, if it is indeed the case where shared neutrals can be shown to be prohibited or not allowed in RV's then yes, you are right.
But if we cannot show or find reference to it not being allowed then one cannot assume that it is never done.
And if it has ever been done then... I stand by my statement.
And yes, I am well aware of your background and RV blog, you have provided some great stuff to a lot of people over the years. Some of us don't always agree with everything though!
Thanks for taking the time to respond!
And I let you drag me into this despite my own caution!
Gentelmen, Any branch circuit(after the main) in any load center that uses split neutral wiring method has to be protected by a double pole circuit breaker. Plain and simple. Most RV's don't use double pole c/b's for branch circuits. That being said there maybe some that do. You may pm me if you disagree. JMO.
This is what happened just last month to my m/h.
It is a 50 amp service with a Progressive surge protecter hard wired before the transfer switch.
I smelled smoke and began looking and found transfer switch burnt up. Voltages were 185v with a loose neutral. This zapped my new refrigerator, microwave, 2000w inverter. I checked the voltages with my meter before unplugging unit.
this was my real world incident. Not saying this is what happened to you but my cause.
donnie d wrote: This is what happened just last month to my m/h.
It is a 50 amp service with a Progressive surge protecter hard wired before the transfer switch.
I smelled smoke and began looking and found transfer switch burnt up. Voltages were 185v with a loose neutral. This zapped my new refrigerator, microwave, 2000w inverter. I checked the voltages with my meter before unplugging unit.
this was my real world incident. Not saying this is what happened to you but my cause.
donnie, sorry about your disaster. That is exactly the kind of thing that can happen with an open neutral. Thanks for sharing.
john&bet wrote: Gentelmen, Any branch circuit(after the main) in any load center that uses split neutral wiring method has to be protected by a double pole circuit breaker. Plain and simple. Most RV's don't use double pole c/b's for branch circuits. That being said there maybe some that do. You may pm me if you disagree. JMO.
Thanks! Agree!
Yes they do require double pole breakers or approved tie handles(since the 2008 NEC), no question.
The "some" that you say may exist are the ones I would be talking about.
I don't have first hand knowledge of any shared neutral circuits in RV's but I also realize tens of millions of RV's exist out there that I have never seen. I also have seen first hand what the typical "licensed" "RV tech" does to an RV and I bet Larry could tell a story or two. Knowing this and the cut throat nature of banging out RV's for the least expense and most profit, I would be suprised if there has never been an RV wired up in this way.
Maybe there is something in RVIA as Larry has said that disallows shared neutral circuits in RV's. That would be good if there is, they are a bad idea.
I am pretty sure there is nothing in the NEC that disallows them in RV's.
donnie d wrote: This is what happened just last month to my m/h.
It is a 50 amp service with a Progressive surge protecter hard wired before the transfer switch.
I smelled smoke and began looking and found transfer switch burnt up. Voltages were 185v with a loose neutral. This zapped my new refrigerator, microwave, 2000w inverter. I checked the voltages with my meter before unplugging unit.
this was my real world incident. Not saying this is what happened to you but my cause.
This is why I think any protection should be wired as close to the load center as physically possible. That's what my local utility recommends for the s&b house so why not the mobile house. JMHO.
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