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Split Neutral Wiring
I thought I was pretty good when it comes to wiring. I thought I knew
enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Are shared neutrals avoided where possible? An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? Thanks. |
Split Neutral Wiring
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Are shared neutrals avoided where possible? An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? Thanks. If you share the neutrals within the circuit to a breaker, then when that breaker is off no one is turning anything on, right? I wouldn't share neutrals between different breakers. Brian |
Split Neutral Wiring
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. When done properly, the two breakers would be tied together, so either both would be on or off. |
Split Neutral Wiring
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Are shared neutrals avoided where possible? An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? Thanks. That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box and then you have much bigger problems. They reduce voltage drop, save a little material, reduce congestion in the breaker box and maybe save a little labor. The big downside as I see it is that they can be confusing to people who don't know what they are. My house had one with both hots on the same leg. Didn't matter since not much was plugged into them, but it could have been a disaster. Also, I doubt you can use AFCI breakers, if that matters to you. |
Split Neutral Wiring
When done properly, the two breakers would be tied together, so either both
would be on or off. Good point. I did read something about a double pole breaker. That IS what I should have in my box. So either I don't have one or the neutrals that I was disconnecting actually weren't part of my intended circuit at all. There were a lot of wires in that box, perhaps another group was actually the neutral for my circuit. The wiring is 50 years old and it's hard to tell what color these wires were supposed to be! |
Split Neutral Wiring
On 13 Apr 2007 10:31:05 -0700, "Ben" wrote:
I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Are shared neutrals avoided where possible? An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? Thanks. I've never seen a neutral that wasn't tied together at the box and that was then tied to the earth ground. Me thinks your wiring is screwed up. |
Split Neutral Wiring
On Apr 13, 1:52 pm, "Wade Lippman" wrote:
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Are shared neutrals avoided where possible? An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? Thanks. That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box and then you have much bigger problems. They reduce voltage drop, save a little material, reduce congestion in the breaker box and maybe save a little labor. The big downside as I see it is that they can be confusing to people who don't know what they are. My house had one with both hots on the same leg. Didn't matter since not much was plugged into them, but it could have been a disaster. Also, I doubt you can use AFCI breakers, if that matters to you.- Hide quoted text - - Show quoted text - Or GFCIs for that matter, unless you use a double pole GFCI. nate |
Split Neutral Wiring
In article , "Wade Lippman" wrote:
That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box FALSE! The neutral is a current-carrying conductor under normal operation. Contrary to common belief, electricity does not follow "the path of least resistance." Rather, electricity follows all possible paths, and when you touch the neutral, you create with your body a second, parallel path to ground for the current flowing in the neutral. Granted, that's probably (though not necessarily) a fairly high-resistance path, which makes it *unlikely* that you will be shocked. But definitely *not* impossible. Your statement is false twice, actually: suppose the neutral is connected just fine *at* the breaker box, but is disconnected somewhere between there, and where you're working. In that case, you're putting yourself in *series* with the neutral current, not in parallel with it, and that makes a shock from touching it *likely* (if the circuit is energized). -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
According to Ben :
I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. This is more of a "independent feeds into a single box" than a shared neutral issue per-se. In a properly wired shared neutral circuit, getting zapped by the neutral can't happen - the neutral cannot be more than a volt or two away from ground. If you disconnect the neutral, then someone fires up a lamp on the other side, yes, you can get zapped. But: 1) Electrical code requires that neutrals on shared neutral circuits are pigtailed, so that it's possible to disconnect devices without breaking the neutral to downstreams. 2) There's a very strong hint that the neutral might be shared if you see 4 conductor wire (eg: 14/3 or 12/3 plus ground). Electrical code (at least ours) requires that, at least until the hots go off in different directions, that it's in a common cable. Since you can't parallel cable in normal residential wiring (eg: rejoin neutrals after splitting cable), at least theoretically, you'll always see /3 cable where the neutral is actually shared. Past the split point, it don't matter. 3) Because of (2), and electrical code requirements for common trip ("same strap" _requires_ common trip in the NEC, all shared neutrals in the CEC require common breaker trip), you'll almost always see a single cable connected to adjacent common-trip breakers You can't deenergize one hot without de-energizing the other. Are shared neutrals avoided where possible? Actually, until our (CEC) kitchen counter requirements changed a few years ago, at least two shared neutral circuits were mandatory in every house. An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? I wouldn't worry about it. Most of the concerns about neutral stupidities regarding what you've read is for industrial wiring botches, which is largely inapplicable to housing. The electrician probably won't be tempted to use it much anyway. What you _should_ do is insist that the electrician use tie-barred/common trip breakers everywhere he'd consider using common neutral (or two feeds into the same box - even a switch box), regardless of whether the NEC requires it for that specific instance. The only times I've ever been zapped is where the electrician violated the CEC rule about having non-common-trip feeds into the same box. They weren't shared neutrals. -- Chris Lewis, Age and Treachery will Triumph over Youth and Skill It's not just anyone who gets a Starship Cruiser class named after them. |
Split Neutral Wiring
According to Doug Miller :
In article , "Wade Lippman" wrote: That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box FALSE! The neutral is a current-carrying conductor under normal operation. Contrary to common belief, electricity does not follow "the path of least resistance." Rather, electricity follows all possible paths, and when you touch the neutral, you create with your body a second, parallel path to ground for the current flowing in the neutral. Granted, that's probably (though not necessarily) a fairly high-resistance path, which makes it *unlikely* that you will be shocked. But definitely *not* impossible. If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. You won't notice it anymore than you'll notice a shock from a D cell. Your statement is false twice, actually: suppose the neutral is connected just fine *at* the breaker box, but is disconnected somewhere between there, and where you're working. In that case, you're putting yourself in *series* with the neutral current, not in parallel with it, and that makes a shock from touching it *likely* (if the circuit is energized). If the neutral is cut between you and the panel, for all intents and purposes it's a hot if anything is switched on with the corresponding "real" hot. The dangers with common neutral arise when the neutral is broken without killing both hots. That's impossible in most code-compliant situations (unless you do your rewiring on hot circuits). [In the CEC, it's _all_ code-compliant residential situations. The NEC has an exception for circuits "not on the same strap"] -- Chris Lewis, Age and Treachery will Triumph over Youth and Skill It's not just anyone who gets a Starship Cruiser class named after them. |
Split Neutral Wiring
"Doug Miller" wrote in message t... In article , "Wade Lippman" wrote: That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box FALSE! The neutral is a current-carrying conductor under normal operation. Contrary to common belief, electricity does not follow "the path of least resistance." Rather, electricity follows all possible paths, and when you touch the neutral, you create with your body a second, parallel path to ground for the current flowing in the neutral. Granted, that's probably (though not necessarily) a fairly high-resistance path, which makes it *unlikely* that you will be shocked. But definitely *not* impossible. Your statement is false twice, actually: suppose the neutral is connected just fine *at* the breaker box, but is disconnected somewhere between there, and where you're working. In that case, you're putting yourself in *series* with the neutral current, not in parallel with it, and that makes a shock from touching it *likely* (if the circuit is energized). -- Regards, Doug Miller (alphageek at milmac dot com) Gee Doug, with all the millions of dryers and ovens that have the chassis attached to the neutrals and are touched daily by wet hands, how many shocks do you think people get? What the hell is wrong with you? |
Split Neutral Wiring
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. You can test for hot wires and verify at least one circuit is off, but then somebody comes along and turns on a light and suddenly the neutral is live. Not to mention the fact that if somebody came along who didn't know about split neutrals who knows what they may have mistakenly done in the past. So what is the best way to proceed when trying to determine if a box has any live wires or wires which could become charged if somebody turns on a light upstream? Always treat the wires as though they are hot. Every once in a while I get zapped by a neutral. Even though the ground and neutral are bonded together at the main you don't know what the condition of the neutral going back to the transformer is. You also don't know how good the neutral connections are at the panel. There is always the possibility of having a difference in potential between the ground and neutral at the load. In an old house it is a good idea to be extra cautious as you don't know what changes have been made over the years. Are shared neutrals avoided where possible? Some states are requiring arc fault circuit interupter circuit breakers for bedroom wiring. You cannot use a shared neutral on these circuits. An electrician is about to rewire just about my entire house. Should I request no shared neutrals or is this a silly request? It is not a bad idea to discusss with him what his plans are. Afterall you are paying for it, you have a right to ask. |
Split Neutral Wiring
On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski"
wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. |
Split Neutral Wiring
"Terry" wrote in message ... On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski" wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. Coming off of the power company's transformer to a single family residence are two hot conductors and a neutral conductor. The neutral conductor is the return path for the current to go back to the transformer from the two hot conductors. The neutral conductor is bonded to earth via the water pipe and ground rods. If you were to disconnect the neutral conductor the current will need to find another path back to the transformer. It can go through the earth via the ground rods and water pipe directly to the transformer ground rod and grounding conductor. However, depending on the location of the transformer and the neighbor's house (Or the quality of the transformer ground) the current might find a better path back to the transformer by going through the neighbor's water pipe and ground rods into the neighbor's electrical panel and then continuing through the neighbor's neutral conductor back to the transformer. |
Split Neutral Wiring
On Apr 13, 5:39 pm, "John Grabowski" wrote:
"Terry" wrote in message ... On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski" wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. Coming off of the power company's transformer to a single family residence are two hot conductors and a neutral conductor. The neutral conductor is the return path for the current to go back to the transformer from the two hot conductors. The neutral conductor is bonded to earth via the water pipe and ground rods. If you were to disconnect the neutral conductor the current will need to find another path back to the transformer. It can go through the earth via the ground rods and water pipe directly to the transformer ground rod and grounding conductor. However, depending on the location of the transformer and the neighbor's house (Or the quality of the transformer ground) the current might find a better path back to the transformer by going through the neighbor's water pipe and ground rods into the neighbor's electrical panel and then continuing through the neighbor's neutral conductor back to the transformer. I would think it would take the path back to the other winding in the transformer. |
Split Neutral Wiring
"Terry" wrote in message oups.com... On Apr 13, 5:39 pm, "John Grabowski" wrote: "Terry" wrote in message ... On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski" wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. Coming off of the power company's transformer to a single family residence are two hot conductors and a neutral conductor. The neutral conductor is the return path for the current to go back to the transformer from the two hot conductors. The neutral conductor is bonded to earth via the water pipe and ground rods. If you were to disconnect the neutral conductor the current will need to find another path back to the transformer. It can go through the earth via the ground rods and water pipe directly to the transformer ground rod and grounding conductor. However, depending on the location of the transformer and the neighbor's house (Or the quality of the transformer ground) the current might find a better path back to the transformer by going through the neighbor's water pipe and ground rods into the neighbor's electrical panel and then continuing through the neighbor's neutral conductor back to the transformer. I would think it would take the path back to the other winding in the transformer. The primary? I thought that it is only the secondary that is grounded.. |
Split Neutral Wiring
Noozer wrote:
"Ben" wrote in message ups.com... I thought I was pretty good when it comes to wiring. I thought I knew enough to be safe and have good quality work when I do it on my own. Then I learned about shared neutral lines for different hot phases. I am shocked I never heard of this. No book I ever read mentioned shared neutrals for household wiring. Given that a shared neutral is a possibility, I don't understand how anybody can do electrical work without shutting off power to the entire house. When done properly, the two breakers would be tied together, so either both would be on or off. I have shared neutrals in my box, done by the original builder on separate breakers. I know that doesn't make it right. BTW, the house is 35 years old. Also, in my local village hall building, they have 3 phase shared neutrals (208 Y connected) and all are separate breakers. So I don't think there is a requirement for common trip. |
Split Neutral Wiring
In article , "Wade Lippman" wrote:
"Doug Miller" wrote in message et... In article , "Wade Lippman" wrote: That is not really a concern; you can't get a shock off a neutral unless it is unconnected at the breaker box FALSE! The neutral is a current-carrying conductor under normal operation. Contrary to common belief, electricity does not follow "the path of least resistance." Rather, electricity follows all possible paths, and when you touch the neutral, you create with your body a second, parallel path to ground for the current flowing in the neutral. Granted, that's probably (though not necessarily) a fairly high-resistance path, which makes it *unlikely* that you will be shocked. But definitely *not* impossible. Your statement is false twice, actually: suppose the neutral is connected just fine *at* the breaker box, but is disconnected somewhere between there, and where you're working. In that case, you're putting yourself in *series* with the neutral current, not in parallel with it, and that makes a shock from touching it *likely* (if the circuit is energized). Gee Doug, with all the millions of dryers and ovens that have the chassis attached to the neutrals and are touched daily by wet hands, how many shocks do you think people get? What the hell is wrong with you? The question is, what the hell is wrong with *you*, continuing to insist that the neutral has no potential for danger? That just isn't true. It's NOT the same as ground, despite your persistent misunderstanding of that fact. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
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Split Neutral Wiring
"Doug Miller" wrote in message t... In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... and you might have 5% as much conductivity as the neutral and see 6v. Not likely but possible. Harmless, but possible. Stupid, but possible. Doug, but absurd. Oh, that is redundant. |
Split Neutral Wiring
On Fri, 13 Apr 2007 20:02:46 -0400, "John Grabowski"
wrote: "Terry" wrote in message roups.com... On Apr 13, 5:39 pm, "John Grabowski" wrote: "Terry" wrote in message ... On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski" wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. Coming off of the power company's transformer to a single family residence are two hot conductors and a neutral conductor. The neutral conductor is the return path for the current to go back to the transformer from the two hot conductors. The neutral conductor is bonded to earth via the water pipe and ground rods. If you were to disconnect the neutral conductor the current will need to find another path back to the transformer. It can go through the earth via the ground rods and water pipe directly to the transformer ground rod and grounding conductor. However, depending on the location of the transformer and the neighbor's house (Or the quality of the transformer ground) the current might find a better path back to the transformer by going through the neighbor's water pipe and ground rods into the neighbor's electrical panel and then continuing through the neighbor's neutral conductor back to the transformer. I would think it would take the path back to the other winding in the transformer. The primary? I thought that it is only the secondary that is grounded.. I should have said other leg of the transformer. I am only talking about the secondary side. Loosing the neutral on the secondary side will cause 240V across any connected loads. I can't see taking a neutral path to your neighbor's house. |
Split Neutral Wiring
On Apr 13, 6:36 pm, (Doug Miller) wrote:
In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. I discovered a shared neutral in my old house by working in a box that _should_ have been safe. Found the shared circuit is a yardlight on a 3 way switch in the back yard. I still haven't figured out how to correct it without running new wires underground. They only used 12/2 WG for the wiring. Harry K |
Split Neutral Wiring
In article , "Wade Lippman" wrote:
"Doug Miller" wrote in message et... In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... and you might have 5% as much conductivity as the neutral and see 6v. Pardon me if I don't simply take your word for it. Got any calculations to back that up? I didn't think so... Not likely but possible. Harmless, but possible. Stupid, but possible. Doug, but absurd. Oh, that is redundant. How much does it take to kill, Wade? Hint: the trip threshold on a GFCI is 20 mA. When are you going to figure out that neutral and ground are NOT the same? -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
Doug I hope you have all these responses canned in word or something. Seems
we just had this thread about a month ago. G -- Steve Barker "Doug Miller" wrote in message t... In article , "Wade Lippman" wrote: "Doug Miller" wrote in message . net... In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... and you might have 5% as much conductivity as the neutral and see 6v. Pardon me if I don't simply take your word for it. Got any calculations to back that up? I didn't think so... Not likely but possible. Harmless, but possible. Stupid, but possible. Doug, but absurd. Oh, that is redundant. How much does it take to kill, Wade? Hint: the trip threshold on a GFCI is 20 mA. When are you going to figure out that neutral and ground are NOT the same? -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
"Terry" wrote in message ... On Fri, 13 Apr 2007 20:02:46 -0400, "John Grabowski" wrote: "Terry" wrote in message roups.com... On Apr 13, 5:39 pm, "John Grabowski" wrote: "Terry" wrote in message ... On Fri, 13 Apr 2007 16:45:45 -0400, "John Grabowski" wrote: Shutting off power to the entire house is not a guarantee that the neutral won't be hot. Under rare circumstances if your neighbor lost his neutral connection it is possible that his return current would travel through the earth to your neutral connection and then back to the transformer. Could you explain this a little more, really slow. Coming off of the power company's transformer to a single family residence are two hot conductors and a neutral conductor. The neutral conductor is the return path for the current to go back to the transformer from the two hot conductors. The neutral conductor is bonded to earth via the water pipe and ground rods. If you were to disconnect the neutral conductor the current will need to find another path back to the transformer. It can go through the earth via the ground rods and water pipe directly to the transformer ground rod and grounding conductor. However, depending on the location of the transformer and the neighbor's house (Or the quality of the transformer ground) the current might find a better path back to the transformer by going through the neighbor's water pipe and ground rods into the neighbor's electrical panel and then continuing through the neighbor's neutral conductor back to the transformer. I would think it would take the path back to the other winding in the transformer. The primary? I thought that it is only the secondary that is grounded.. I should have said other leg of the transformer. I am only talking about the secondary side. Loosing the neutral on the secondary side will cause 240V across any connected loads. The only circuits that will be affected by that are the ones that share a neutral. Loads are not always perfectly balanced so the neutral will most likely always have current going to it. I can't see taking a neutral path to your neighbor's house. I figured. End of discussion. |
Split Neutral Wiring
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Split Neutral Wiring
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Split Neutral Wiring
In article , deke wrote:
On Sat, 14 Apr 2007 01:33:12 GMT, (Doug Miller) wrote: The question is, what the hell is wrong with *you*, continuing to insist that the neutral has no potential for danger? That just isn't true. It's NOT the same as ground, despite your persistent misunderstanding of that fact. I'm sorry Doug, but my neutrals are tied to ground in the breaker box. Same was true of the last 2 houses I owned. The service entrance is the *only* place where they *are* the same. In branch circuits, the ground conductor does *not* carry current in normal operation. It carries current only if there has been a failure somewhe either the hot or the neutral has faulted to ground somehow. By contrast, the neutral *is* a current-carrying conductor under normal operation. And that's why you can't presume that it's safe to touch. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
Doug Miller wrote:
In article , "Wade Lippman" wrote: "Doug Miller" wrote in message t... In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... and you might have 5% as much conductivity as the neutral and see 6v. Pardon me if I don't simply take your word for it. Got any calculations to back that up? I didn't think so... Not likely but possible. Harmless, but possible. Stupid, but possible. Doug, but absurd. Oh, that is redundant. How much does it take to kill, Wade? Hint: the trip threshold on a GFCI is 20 mA. When are you going to figure out that neutral and ground are NOT the same? In the USA the trip threshold on a class A GFCI is five milliamperes. On a class B GFCI such as the ones built into AFCIs the trip level is thirty milliamperes. Class B GFCIs are only intended to protect equipment. -- Tom Horne |
Split Neutral Wiring
In article , deke wrote:
I regularly install new switches and receptacles with the power on. There's a saying that there are old electricians, and there are bold electricians... but there are no old, bold electricians. I touch the black (hot) and white (neutral) wire regularly with the power on, just not at the same time. It is much faster and you don't have to reset any clocks. That's just foolish. If you are slightly cautious, there is absolutely no way you are going to get hurt. Make sure your life insurance is paid up. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
Doug Miller wrote:
That's just foolish. If you are slightly cautious, there is absolutely no way you are going to get hurt. Make sure your life insurance is paid up. Hmm. There are hundreds of electricians touching live wires every day. With the proper precautions, it's not only safe, but required. Think those who maintain the high-voltage distribution network. |
Split Neutral Wiring
On Sun, 15 Apr 2007 11:09:24 -0500, deke wrote:
On Sun, 15 Apr 2007 02:40:31 GMT, (Doug Miller) wrote: In article , deke wrote: On Sat, 14 Apr 2007 01:33:12 GMT, (Doug Miller) wrote: The question is, what the hell is wrong with *you*, continuing to insist that the neutral has no potential for danger? That just isn't true. It's NOT the same as ground, despite your persistent misunderstanding of that fact. I'm sorry Doug, but my neutrals are tied to ground in the breaker box. Same was true of the last 2 houses I owned. The service entrance is the *only* place where they *are* the same. In branch circuits, the ground conductor does *not* carry current in normal operation. It carries current only if there has been a failure somewhe either the hot or the neutral has faulted to ground somehow. By contrast, the neutral *is* a current-carrying conductor under normal operation. And that's why you can't presume that it's safe to touch. I regularly install new switches and receptacles with the power on. I touch the black (hot) and white (neutral) wire regularly with the power on, just not at the same time. It is much faster and you don't have to reset any clocks. If you are slightly cautious, there is absolutely no way you are going to get hurt. Very famous words. Last words. |
Split Neutral Wiring
In article , "HeyBub" wrote:
Hmm. There are hundreds of electricians touching live wires every day. With the proper precautions, it's not only safe, but required. Think those who maintain the high-voltage distribution network. Of course -- but you're talking about professionals, who do that on a daily basis. *And* have had proper safety training, besides. This is a homeowner forum. Most of the posters here are *not* pros, and have not had the training and experience that the pros do. Furthermore, I expect that the guys here who *are* pros would never advise a non-professional that it's safe to work "hot". -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
Split Neutral Wiring
I don't do it anymore, cause I really don't like the feeling when I do get
shocked. BUT , when I was 13, my parents built on to the house. The electrician was a man my dad worked with. I personally landed some 40-45 duplex outlets and a dozen or more switches all with the power on. Like was said, stand on wood, touch one wire at a time and no problem. AND like I also said, I don't do it anymore. There was another electrician where my dad worked (a large steel fab plant) who would probe voltages with one hand up to 440v. It all depends on the individual's personal resistance . There was a hired hand on the farm he grew up on who would shut down the 4 cylinder tractor by putting his arm across all 4 bare spark plug terminals. -- Steve Barker "deke" wrote in message ... I regularly install new switches and receptacles with the power on. I touch the black (hot) and white (neutral) wire regularly with the power on, just not at the same time. It is much faster and you don't have to reset any clocks. If you are slightly cautious, there is absolutely no way you are going to get hurt. |
Split Neutral Wiring
According to Doug Miller :
In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... I'll repeat what I said. In those circumstances, the voltage between neutral and ground is at most a volt or two, dependent on IR voltage drop on the neutral due to the load. It doesn't matter how sweaty you are, you're not going to feel it. How sweaty do you have to be to feel 3V off two AA batteries? The minimum "feel voltage" is at least 10V, and usually considerably higher. If the neutral was connected to ground yet was still showing 10V or more relative to the ground, it'd probably be glowing red hot. Now, if you skewered yourself in the heart muscle with the ground and neutral, you'd feel it. But people tend to avoid that. The hazard with shared neutrals is contacting a disconnected-from-the-main neutral without having all the hots shut off. -- Chris Lewis, Age and Treachery will Triumph over Youth and Skill It's not just anyone who gets a Starship Cruiser class named after them. |
Split Neutral Wiring
According to Larry Caldwell :
In article . com, (Ben) says... Are shared neutrals avoided where possible? Shared neutrals are handy where you need a lot of power in a small area, like a kitchen. However, they are rarely used nowadays, because a shared neutral will trip a GFI every time. I'd put that a different way. Shared neutrals are incompatible with single pole GFIs. They aren't incompatible with double-pole GFIs, and single GFIs can be used _after_ you split the neutral. Shared neutral double pole GFIs would be code here for kitchen counters, except that they're so bloody expensive. Shared neutral non-GFI _were_ code, but not anymore. We've adopted a modified version of the NEC for kitchen counter outlets. You can still use shared neutral, IF you're willing to pay for the dual GFIs, but otherwise, you use 20A singles. I have one split neutral circuit in my shop to a triple gang box. I split the receptacles from top to bottom, so half of each receptacle is on a different circuit. It's a simple way to get 40 amps of 120 volts to one location with one run. I have 5 split neutral circuits in my shop ;-) -- Chris Lewis, Age and Treachery will Triumph over Youth and Skill It's not just anyone who gets a Starship Cruiser class named after them. |
Split Neutral Wiring
In article , (Chris Lewis) wrote:
According to Doug Miller : In article , (Chris Lewis) wrote: If the neutral isn't broken between you and the panel, the _maximum_ ground-neutral voltage you'll see in the OP's scenario is a volt or two. That depends entirely on how well you are (or aren't) grounded. Under normal circumstances, there won't be enough current to do any damage. One sweaty hand on a grounded junction box, and the other sweaty hand touching an active neutral, though... I'll repeat what I said. In those circumstances, the voltage between neutral and ground is at most a volt or two, dependent on IR voltage drop on the neutral due to the load. It doesn't matter how sweaty you are, you're not going to feel it. Assuming all the connections in the neutral wire between that point and the service entrance are good.... no imperfectly-formed splices, no high-resistance connections due to corrosion, or improper Al-Cu splices... nothing of that sort... -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
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