You could still take a picture of the panel. If it is 3 phase, it should have 3 large connectors for three phase conductors. It should then have a large neutral bar for another large neutral conductor and another buss bar (maybe) for the grounds, depending on how old the panel is.
If you have three phase power then what the electrician did is probably OK.
So if it's three phase it means that the neutral is never carrying more than one of the "returns" from any one of the three branches at the same time?
Even if that's true, isn't it still in some sense more heavily loaded then the three "hot" legs. Each hot leg is "hot" for one third of the time whereas the neutral is carrying "return" current ALL the time, at least if something is plugged in and running on each of the three legs.
No. At least if my memory is correct, it's been a while since I worked in a plant with 3 phase power, but if the loads are balanced I think there is no return current at all in the "neutral." 3P is a way of doing 3 separate circuits that would normally need 6 wires (hot and return for each circuit ) with only 3 wires by taking advantage of the phase difference.
Given that each of the hot legs is 120 degrees out of phase with respect to the others, the current in the grounded conductor (aka neutral) will sum to zero when all of the hot legs are pulling max current. In the worst case, where only one leg is pulling max current, the grounded conductor also conducts max current.
Thanks Tim and Scott. Also saw some other similar explanations further down the thread. I assume there's only zero current when all the loads are the same inductively as well as resistively so there's equal phases shift on all legs??
I'd have to go back to the text to answer that, probably someone else here is more current (pun) than I.
However, there's a complication. You can run 3P power without a neutral at all. 3 wires is enough to keep your equipment running, and any two of tho se three to run single phase equipment. But you have only phase to phase v oltage. For common US residential 3P, that means you would have only 208, from any hot leg to any other hot leg. To get 120 you run hot to neutral. It seems likely to me that this puts more current on the neutral. But as I said I'm rusty at this stuff. In the plant where I worked we had 440 fro m leg to leg to run motors, and 277 from leg to neutral to run lighting. W e had 3P in residential when I lived in Germany but I didn't work on it, it was a rental.
e is more current (pun) than I.
I don't see how that's a complication. It's the case that he's citing. If the load or loads are balanced, on all 3 phases, then you have no curren t in the neutral.
ree to run single phase equipment. But you have only phase to phase voltag e. For common US residential 3P, that means you would have only 208, from any hot leg to any other hot leg. To get 120 you run hot to neutral. It s eems likely to >me that this puts more current on the neutral.
If it were balanced to begin with and you placed an additional load from one phase to neutral, then the load through that load would flow through the neutral. If you put two more identical loads on the other two phases, then the overall load would be balanced again and there would be no load through the neutral again.
three to run single phase equipment. But you have only phase to phase volt age. For common US residential 3P, that means you would have only 208, fro m any hot leg to any other hot leg. To get 120 you run hot to neutral. It seems likely to >me that this puts more current on the neutral.
I'm not sure I'm following you.
I have L1, L2, L3, and N.
I can put a load between L1 and L2, L1 and L3, and/or L2 and L3, at 208 V ( thinking residential). No current should flow through the neutral. Even if the loads are unbalanced, maybe.
I can put a load between L1 and N at 120 V. That full load current will fl ow through the neutral.
Now add a load between L1 and L2. Will that reduce the load through the ne utral? Doesn't seem like it should. Adding a load betwen L2 and N might?
I'm pretty sure I had to solve problems like that in the basic circuits cou rse. Trouble is that was way back in the 80s and I disremember.
e three to run single phase equipment. But you have only phase to phase vo ltage. For common US residential 3P, that means you would have only 208, f rom any hot leg to any other hot leg. To get 120 you run hot to neutral. It seems likely to >me that this puts more current on the neutral.
(thinking residential). No current should flow through the neutral. Even if the loads are unbalanced, maybe.
flow through the neutral.
Put additional equal loads between L2 and N and L3 and N. The current in the neutral is now zero.
neutral? Doesn't seem like it should.
You're right, it won't reduce the current through the neutral because the current has only one place to go, there is nothing else connected to the neutral.
Adding a load betwen L2 and N might?
Yes, per the example given.
>
There are only two incoming cables. Cannot be 3 phase.
Maybe it's just me, but I find it a little weird that instead of just saying, this is in Katmandu, or wherever it is, you're expecting answers based on "it's not in the USA". Nor is there much other pertinent information. If safety is the issue, maybe you should ask the local inspection authority, assuming they have one in wherever it is.
I'm not an electrician. What are pertinent information? I don't know. I thought I was asking a question in physics. Physics doesn't change from country to country. What is changed is code. I don't think my question is code related.
If I were in France, Britain, or Germany, I would have said so in the beginning because maybe somebody knows something there. But I am in Myanmar (and I have said so six days ago). Does it help anything? I doubt. There is no code in Myanmar. Once I asked the electric company which did a job for me to give me a conformity letter. They did not know what a conformity letter is. I then said I wanted a letter from them stating the work they did complied with government regulations. They said government did not regulate these things. If I had said in the very beginning I am in Myanmar, maybe people would think "Oh! I don't know anything about Myanmar" and just ignore my question.
If you want any definite answers, we have to know exactly what kind of service you have. The next step is either a voltage tester or maybe a few photos.
Are the breakers all single pole? (one switch each) If one is double pole, you still may be ok.
On Friday, November 28, 2014 6:20:14 PM UTC-5, yyy378 wrote: There are only two incoming cables. Cannot be 3 phase.
It does, because a quick google shows that you have single phase 230V or 3 phase. You've said you only have two conductors entering the building, so it sure sounds like you have single phase 230V service. You said you had several outlets installed on 3 breakers. Are these outlets all 230V?
And actually your question is code related, because you asked what is "safe". The safety standards are to a great extent, embodied in the codes and they vary from country to country. What is considered safe in one, may not be considered safe enough in another.
ILet's assume you have 230V, single phase service. You said you have:
several new outlets on 3 breakers serving them are 3 hots, one neutral, one ground
You want to know if it's safe. First, we don't know for sure how it'w wired, so it's impossible to say for sure. But let's assume that one breaker is for each of the hots and that they all share one common neutral. That seems a reasonable assumption. Let;s also assume the grounds are done properly. That leaves two main aspects of safety that I see:
1 - Are the conductors and breakers sized and adequate for the max current? That would seem to mean the neutral would have to be larger than the hots. 2 - Since it sounds like it's almost certainly a shared neutral situation, then are the breakers sharing that neutral tied together so that they trip together? That's where you get to the finer points of safety. Here in the USA it's required to be wired that way for safety, so that someone working on it, won't make the mistake of having a neutral still carrying current when they have opened only one of the breakers that they think are associated with that neutral. Will it burn your house down? No. Is it allowed and considered safe in some other countries? Probably, especially if you have no codes.I'd say if you're really concerned about the safety, then the only way you're going to know is get someone in there that's qualified to take a look.
All breakers are single pole and all wires are 2.5 mm, which is close to gauge 13.
I am convinced that the electrician wires the single phase circuits in 3 phase way.
All wires are 2.5 mm and all breakers are single pole. I'm convinced that the electrician wires the single phase circuits in 3 phase way which is quite common here.
Not sure how to find a qualified electrician. Since the government doesn't regulate it, there is no license, hence, no licensed electrician.
Once I saw a plug of a piece of equipment being cut off and two leads are inserted into an outlet. I asked around to see who did it and was told an electrician did it. I was shocked. I'm no electrician but I know that is wrong.
IDK how it would ever be possible to wire a single phase as 3 phase. Also, if you're knowledgable enough to know that, then I would think you could figure out what you actually have and how it's wired.
But for sure, to have single phase, 3 hots feeding outlets, only one netural, all same gauge, does not sound right as from what is given, the current on the neutral would be greater. The other possibility is the hots are over-sized, but that defeats the purpose of a shared neutral.
I have seen an old farmer do that in the USA, but only to test and see if some thing worked.
He would then wire on a real plug, and do it more safely.
- . Christopher A. Young Learn about Jesus
Then it is wrong.
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