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#41
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Sub Panel neutral bonding
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#42
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Sub Panel neutral bonding
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#43
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Sub Panel neutral bonding
On Tuesday, June 11, 2019 at 11:19:22 PM UTC-4, wrote:
On Tue, 11 Jun 2019 16:55:43 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 7:46:48 PM UTC-4, wrote: On Tue, 11 Jun 2019 14:20:47 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote: On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote: On 6/11/2019 8:32 AM, wrote: Why is the ground rod at the service any better than the one at the shop? I agree 4 is better than 2 but they are already bonded together via the neutral in a 3 wire feeder. I doubt he wants to dig up the yard. This was done this way for 90 years and we didn't pile up a lot of bodies. The code change was mostly just to make the language consistent with the rest of the code. Same with ranges and dryers. The grandfather clause is still there for things done pre 96 adoption. It does mean you have to be more careful with your bonding and grounding tho. the ground connection serves 2 purposes 1) a path for lightning the ground rod is to provide a path for lightning etc. this NEEDS to be a path to actual Earth ground because that is where lightning will go. 2) protection from shock due to equipment faults this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance. #2 is an important safety feature, I would not skimp on this. So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone. You can also add a ground rod there to help for lightning. If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V. mark Â* Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible .. This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . -- Snag Yes , I'm old and crochety - and armed . Get outta my woods ! That's what I would have done too, except probably adding a second ground rod. IDK how you're going to install 3 phase eqpt though, without redoing what you just did and a whole new service, for that matter? You can get a VFD that is single phase in and 3 phase out I see, well that solves that. So here's another puzzling question. In that thread about solar panels that has now run amok, Danny brought up the issue of preventing backfeeding into the grid. AFAIK, that's built into the inverters, but how do they do it? It would seem like the chicken and the egg problem. You need to detect the grid power going off, but you are connected directly to it and also powering it. So, how do they detect it? Obviously before connecting they must first monitor the voltage, freq and phase and sync to it, but once you connect, how do you then tell the other grid sources are gone? I guess you could look for voltage drop, since with the grid down you'd expect 99.9% there will be big voltage decrease. But is that sufficient? And what do they really do inside those inverters? Hypothetically, suppose there are 6 houses on a utility line that have solar and that segment is connected to the whole distribution system. The sun is shining, those houses are using significantly less than the panels put out. I cut the line to the rest of the grid, leaving just those 6 connected. What happens? Is the "grid" down? How do those inverters detect it? Do they? What happens? We got a pitch on these things a while ago. Basically a grid tie inverter is clocked from the grid. No grid, no output. But the question remains, the inverter is part of the grid, the inverters along the block are part of the grid, in addition to some generators somewhere. So, how does it know that the "grid" is down? Hypothetically, suppose there are 6 houses on a utility line that have solar and that segment is connected to the whole distribution system. The sun is shining, those houses are using significantly less than the panels put out. I cut the line to the rest of the grid, leaving just those 6 connected. What happens? Is the "grid" down? How do those inverters detect it? Do they? What happens? That is an interesting question but theoretically each grid tied inverter would lose clocking and shut down. But they don't really lose clocking, because if you have six houses, each was following the "grid" which is whatever sources, including the other solar. So, they would then follow collectively what is there which at the moment the segement is cut off, it 60 hz and A-OK. So they would be following each other. But I think what happens is that since they are each following the other and constantly trying to match, it does lead to the freq starting to vary slightly. I have posed this question to everyone I have talked to without an answer. What happens if you disconnect from the grid, drop all of your loads and connect a battery powered inverter. Will that clock your grid tie and allow you to add loads until you overwhelm it? Right, same idea. Would the grid tie inverter recognize that the battery powered inverter isn't the "grid". Whatever the "grid" even means. I guess the grid they are looking for would be defined as having at least one power company generator source. But wait, not sure even that's right. Power companies have solar and wind today too. If a disconnected segment had power solar, it's like the solar from home we're talking about. Wind, IDK, but that would seem to have the same issues, I assume they are using inverters too and not a generator where the rotation speed governs the freq. They run at a voltage that can be potentially slightly higher than the grid so if there is any power left over, it flows backward into the grid. A smart meter will see that and meter based on your local tariff agreement. The old style would just run backward if net flow was out instead of in. If you netted more use than you fed back in, no harm, just a lower bill. If you showed a negative bill I guess you would be talking to the PoCo. That is how people used to steal power, plug the meter in upside down it runs backward so there is a chance you would be starting in the fraud department if they did not know about your solar. The "plug in" collectors plug in just like your toaster and will boost the power on that side of your service. These things are usually too small to ever feed back into the grid if you have anything running at all. But from everything I see, a 10KW home solar system behaves exactly like the plug in ones and needs to detect when to disconnect. That is the way I understand it. Each inverter should detect loss of grid and shut down. It would be interesting if you had something else feeding the grid like your generator idea that the plan might fail. I also doubt there is enough power going into the grid to sustain it if you are not getting utility power, even if you have a lot of people with a black roof. I agree. In 99.9% of the cases of a segment coming disconnected from the rest of the utility, you'd think there would be big, obvious problems, starting with a big voltage drop. I also ran across a study of whether this is such a big deal or not. In terms of being a possible danger to linemen, the study concluded it really isn't, that they take precautions and it's extremely unlikely they would be injured. Higher chance of first responders, but even there very low incidence. Even damage to eqpt that was connected was rated very low. The biggest issue was that automatic reclosers on the grid that try to close to restore power could be affected and not close like they should. This might work if you had one guy on a street full of solar power systems with a generator back feeding the street to tickle everyone's inverter, all residents being frugal and a line cut isolating that street from the rest of the grid. It would work until sundown anyway ;-) I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ |
#44
Posted to alt.home.repair
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Sub Panel neutral bonding
I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m |
#45
Posted to alt.home.repair
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Sub Panel neutral bonding
On Wednesday, June 12, 2019 at 1:31:12 PM UTC-4, wrote:
I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Agree. When solar electric was first rolling out, I assumed that would be a big advantage, that you could have power during the day with the grid down. If someone could figure out a way to do that without batteries, it would be a big selling advantage. The essence of the problem I guess is that the sun varies and it would be difficult to maintain constant power. Still, you'd think if it's say a 8KW system, couldn't they provide 2KW to whatever loads you wanted to have emergency power? If the sun isn't sufficient, then it shuts down. If it gets sun sufficient for 3KW, then it turns back on. Software could impose off time delays and lengthen the off times if starts cycling too much, etc. But I guess a lot of people wouldn't pay much for that, having unpredictable power that comes and goes and only during the day. |
#47
Posted to alt.home.repair
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 09:17:16 -0700 (PDT), trader_4
wrote: On Tuesday, June 11, 2019 at 11:19:22 PM UTC-4, wrote: On Tue, 11 Jun 2019 16:55:43 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 7:46:48 PM UTC-4, wrote: On Tue, 11 Jun 2019 14:20:47 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 5:05:03 PM UTC-4, wrote: On Tue, 11 Jun 2019 10:21:46 -0700 (PDT), trader_4 wrote: On Tuesday, June 11, 2019 at 12:47:52 PM UTC-4, Terry Coombs wrote: On 6/11/2019 8:32 AM, wrote: Why is the ground rod at the service any better than the one at the shop? I agree 4 is better than 2 but they are already bonded together via the neutral in a 3 wire feeder. I doubt he wants to dig up the yard. This was done this way for 90 years and we didn't pile up a lot of bodies. The code change was mostly just to make the language consistent with the rest of the code. Same with ranges and dryers. The grandfather clause is still there for things done pre 96 adoption. It does mean you have to be more careful with your bonding and grounding tho. the ground connection serves 2 purposes 1) a path for lightning the ground rod is to provide a path for lightning etc. this NEEDS to be a path to actual Earth ground because that is where lightning will go. 2) protection from shock due to equipment faults this is to protect you from a shock if the hot wire shorts to the metal case inside an appliance. Think of a motor with all those windings of enameled wire. If the insulation should fail and connect the power to the metal case of the appliance, you can be shocked by touching the appliance. If the case is grounded however, when the short happens, a large fault current will flow and blow the breaker. For a LARGE fault current to flow, the ground must be low resistance. So you want a BOND WIRE between the neutral and ground in the system. This provides a path for the fault current to flow sufficient to blow the breaker if there is a ground fault. Often a ground rod alone is too high resistance. #2 is an important safety feature, I would not skimp on this. So if have only 3 wires between the buildings and you can't add the 4th wire, I think bonding the outbuilding neutral and ground together at the entrance to the outbuilding is the safer option compared to relying on a ground rod alone. You can also add a ground rod there to help for lightning. If you don't need 240V and need only 120V in the outbuilding, you can use the 3 wires as hot neutral and ground. That is 100% safe and legal but you give up having 240V. mark Â* Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible . This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . -- Snag Yes , I'm old and crochety - and armed . Get outta my woods ! That's what I would have done too, except probably adding a second ground rod. IDK how you're going to install 3 phase eqpt though, without redoing what you just did and a whole new service, for that matter? You can get a VFD that is single phase in and 3 phase out I see, well that solves that. So here's another puzzling question. In that thread about solar panels that has now run amok, Danny brought up the issue of preventing backfeeding into the grid. AFAIK, that's built into the inverters, but how do they do it? It would seem like the chicken and the egg problem. You need to detect the grid power going off, but you are connected directly to it and also powering it. So, how do they detect it? Obviously before connecting they must first monitor the voltage, freq and phase and sync to it, but once you connect, how do you then tell the other grid sources are gone? I guess you could look for voltage drop, since with the grid down you'd expect 99.9% there will be big voltage decrease. But is that sufficient? And what do they really do inside those inverters? Hypothetically, suppose there are 6 houses on a utility line that have solar and that segment is connected to the whole distribution system. The sun is shining, those houses are using significantly less than the panels put out. I cut the line to the rest of the grid, leaving just those 6 connected. What happens? Is the "grid" down? How do those inverters detect it? Do they? What happens? We got a pitch on these things a while ago. Basically a grid tie inverter is clocked from the grid. No grid, no output. But the question remains, the inverter is part of the grid, the inverters along the block are part of the grid, in addition to some generators somewhere. So, how does it know that the "grid" is down? Hypothetically, suppose there are 6 houses on a utility line that have solar and that segment is connected to the whole distribution system. The sun is shining, those houses are using significantly less than the panels put out. I cut the line to the rest of the grid, leaving just those 6 connected. What happens? Is the "grid" down? How do those inverters detect it? Do they? What happens? That is an interesting question but theoretically each grid tied inverter would lose clocking and shut down. But they don't really lose clocking, because if you have six houses, each was following the "grid" which is whatever sources, including the other solar. So, they would then follow collectively what is there which at the moment the segement is cut off, it 60 hz and A-OK. So they would be following each other. But I think what happens is that since they are each following the other and constantly trying to match, it does lead to the freq starting to vary slightly. I think they are smart enough to each know the grid dropped and they all shut down. I have posed this question to everyone I have talked to without an answer. What happens if you disconnect from the grid, drop all of your loads and connect a battery powered inverter. Will that clock your grid tie and allow you to add loads until you overwhelm it? Right, same idea. Would the grid tie inverter recognize that the battery powered inverter isn't the "grid". Whatever the "grid" even means. I guess the grid they are looking for would be defined as having at least one power company generator source. But wait, not sure even that's right. Power companies have solar and wind today too. If a disconnected segment had power solar, it's like the solar from home we're talking about. Wind, IDK, but that would seem to have the same issues, I assume they are using inverters too and not a generator where the rotation speed governs the freq. Since the net flow of that clock would be "in" I think it would keep going but I can't get a real answer. The battery inverter would need to be strong enough to handle the connected load at the time tho. PoCo connected sources are probably monitored in a different way. They run at a voltage that can be potentially slightly higher than the grid so if there is any power left over, it flows backward into the grid. A smart meter will see that and meter based on your local tariff agreement. The old style would just run backward if net flow was out instead of in. If you netted more use than you fed back in, no harm, just a lower bill. If you showed a negative bill I guess you would be talking to the PoCo. That is how people used to steal power, plug the meter in upside down it runs backward so there is a chance you would be starting in the fraud department if they did not know about your solar. The "plug in" collectors plug in just like your toaster and will boost the power on that side of your service. These things are usually too small to ever feed back into the grid if you have anything running at all. But from everything I see, a 10KW home solar system behaves exactly like the plug in ones and needs to detect when to disconnect. That is the way I understand it. Each inverter should detect loss of grid and shut down. It would be interesting if you had something else feeding the grid like your generator idea that the plan might fail. I also doubt there is enough power going into the grid to sustain it if you are not getting utility power, even if you have a lot of people with a black roof. I agree. In 99.9% of the cases of a segment coming disconnected from the rest of the utility, you'd think there would be big, obvious problems, starting with a big voltage drop. I also ran across a study of whether this is such a big deal or not. In terms of being a possible danger to linemen, the study concluded it really isn't, that they take precautions and it's extremely unlikely they would be injured. Higher chance of first responders, but even there very low incidence. Even damage to eqpt that was connected was rated very low. The biggest issue was that automatic reclosers on the grid that try to close to restore power could be affected and not close like they should. My neighbor is a lineman for FPL doing local distribution and he says that would not be an issue for him safety wise since they assume every wire is hot before they ground it to work on it. He did say if they track power back to your generator, your drop will be laying in your yard until every street light and rusty transformer is replaced. Then they will go to lunch and think about handling your call ... maybe next week. This might work if you had one guy on a street full of solar power systems with a generator back feeding the street to tickle everyone's inverter, all residents being frugal and a line cut isolating that street from the rest of the grid. It would work until sundown anyway ;-) I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ I think that is just a complicated way of saying that without a stable clock, these things will just go nuts and shut down |
#48
Posted to alt.home.repair
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote:
I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. There is not much of an advantage with a construction generator but a little inverter generator might be able to run at idle speed for days on a tank of gas while the solar array does all of the heavy lifting, Same with a 12v inverter, except you could use your solar power to keep your 12v battery up. I just have not found a guy with a grid tie system who was brave enough to try it. To really be effective you would need a 240v centertapped supply. That might be as simple as a transformer tho. |
#49
Posted to alt.home.repair
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Sub Panel neutral bonding
On Wednesday, June 12, 2019 at 2:51:36 PM UTC-4, wrote:
On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. I think if you read that description I provided of how they detect the loss of the grid, the answer is almost certainly not. They are looking for stability in voltage, freq, power factor and it's unlikely a typical home generator is going to fool it. Especially with variable load, which you'd have when a fridge cycles on, etc. Of course that description looks like it's for a bigger solar install than a home one, but the home ones have to comply with regs and must use similar techniques. Most interesting in that was that the inverters described there actually deliberately screw with the grid when they think they may be in an island situation, the idea being that you can't perturb a true grid, but if the "grid" is an island with just some other solar sources, you can and then other inverters will see the deviation and shut down too. There is not much of an advantage with a construction generator but a little inverter generator might be able to run at idle speed for days on a tank of gas while the solar array does all of the heavy lifting, Same with a 12v inverter, except you could use your solar power to keep your 12v battery up. I just have not found a guy with a grid tie system who was brave enough to try it. To really be effective you would need a 240v centertapped supply. That might be as simple as a transformer tho. |
#50
Posted to alt.home.repair
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 10:59:23 -0700 (PDT), trader_4
wrote: On Wednesday, June 12, 2019 at 1:31:12 PM UTC-4, wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Agree. When solar electric was first rolling out, I assumed that would be a big advantage, that you could have power during the day with the grid down. If someone could figure out a way to do that without batteries, it would be a big selling advantage. The essence of the problem I guess is that the sun varies and it would be difficult to maintain constant power. Still, you'd think if it's say a 8KW system, couldn't they provide 2KW to whatever loads you wanted to have emergency power? If the sun isn't sufficient, then it shuts down. If it gets sun sufficient for 3KW, then it turns back on. Software could impose off time delays and lengthen the off times if starts cycling too much, etc. But I guess a lot of people wouldn't pay much for that, having unpredictable power that comes and goes and only during the day. Probably the easiest way would be an inverter generator capable of providing 120/240. It could just loaf along at idle when the sun was shining and kick it up if a cloud came over or the sun went down. You would still need transfer equipment tho. |
#51
Posted to alt.home.repair
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Sub Panel neutral bonding
dpb posted for all of us...
Still have all the old mother-of-pearl inlaid pushbutton light switches that are classic in looks but not up to 120 VAC, sadly. Ahh, still remember them from my childhood. -- Tekkie |
#52
Posted to alt.home.repair
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Sub Panel neutral bonding
Terry Coombs posted for all of us...
* Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible . This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . I have a couple of 'projects' for you -- Tekkie |
#53
Posted to alt.home.repair
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Sub Panel neutral bonding
On 6/12/2019 2:44 PM, Tekkie® wrote:
Terry Coombs posted for all of us... * Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible . This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . I have a couple of 'projects' for you * Whatcha got ? -- Snag Yes , I'm old and crochety - and armed . Get outta my woods ! |
#54
Posted to alt.home.repair
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Sub Panel neutral bonding
On 6/12/2019 1:33 PM, wrote:
On Wed, 12 Jun 2019 11:14:35 -0500, Terry Coombs wrote: On 6/12/2019 8:48 AM, wrote: Â* Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . snip... I agree using the 3 wire system and bonding the neutral and ground is the most practical solution. But be aware, if that third ground/neutral wire should fail open, there will be a dangerous condition in the outbuilding. Everything that was ground, can become energized. mark Â* The likelihood of that 3/0 cable failing is very very slim ... I'll also be bonding the metal frame of the shop to the panel , it has some serious ground contact , including either 6 or 8 5/8" rods a couple of feet long driven thru the bottom member into the ground before I poured the concrete . I've been running stuff out there with a 3 wire ungrounded neutral bonded supply for 5 years or so , never had a problem . That was with lighter wire , part of the install of the new panel included running the 3/0 aluminum cable all the way to the shop to replace that section of smaller wire . If there is a total of 10' or more of steel in contact with that concrete footer you have a Ufer (concrete encased electrode) and that is far better than the rods you drove. In fact with a Ufer, you don't even need the rods. You should be using a #4 or larger to connect the Ufer, Rods only require a #6. That should tell you something right there. If I was doing it I would have run another #5 rebar around the footer, tying all of the down rods together and then you have serious contact with the concrete and a stronger footer. Â* There is a total of 40 linear feet of galvanized 2" square tube in contact with concrete on 2 sides - I spaced the tubes off the ground and worked the concrete under them . I think a 5/16" lag screw thru the side of the enclosure and into the square tube oughta do it ... I do have some #4 stranded and some solder on lugs if that's necessary . The rods into the ground are to keep the dern thing from blowin' in the wind . -- Snag Yes , I'm old and crochety - and armed . Get outta my woods ! |
#55
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 12:17:50 -0700 (PDT), trader_4
wrote: On Wednesday, June 12, 2019 at 2:51:36 PM UTC-4, wrote: On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. I think if you read that description I provided of how they detect the loss of the grid, the answer is almost certainly not. They are looking for stability in voltage, freq, power factor and it's unlikely a typical home generator is going to fool it. Especially with variable load, which you'd have when a fridge cycles on, etc. Of course that description looks like it's for a bigger solar install than a home one, but the home ones have to comply with regs and must use similar techniques. Most interesting in that was that the inverters described there actually deliberately screw with the grid when they think they may be in an island situation, the idea being that you can't perturb a true grid, but if the "grid" is an island with just some other solar sources, you can and then other inverters will see the deviation and shut down too. My generator was pretty stable, looking at it on a scope and the frequency doesn't drift that much when the engine grunts looking at a frequency counter. An inverter generator should not change at all. I think the author was just trying to dumb down his talk. When he says "screw with the grid" what he really means is these things do not have an internal clock and without a stable clock coming in they just go nuts. It detects that condition and shuts down, probably in a cycle or two. .. |
#56
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote:
I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Which is why lolar grid-tie, to me, is just a scam - particularly in Ontario where thr OPG paid 3 times as much for solar power than thay sold it for - - - |
#57
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 14:51:14 -0400, wrote:
On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. There is not much of an advantage with a construction generator but a little inverter generator might be able to run at idle speed for days on a tank of gas while the solar array does all of the heavy lifting, Same with a 12v inverter, except you could use your solar power to keep your 12v battery up. I just have not found a guy with a grid tie system who was brave enough to try it. To really be effective you would need a 240v centertapped supply. That might be as simple as a transformer tho. The question is what dioes the generator/inverter think of having power supplied to the output?? Now, if you could iso;ate the "clock" a small inverter would do the job - all it would produce is the "sync" signal. You could produce that from the sound output of a cell phone or tablet - - - |
#58
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 15:43:06 -0400, Tekkie®
wrote: dpb posted for all of us... Still have all the old mother-of-pearl inlaid pushbutton light switches that are classic in looks but not up to 120 VAC, sadly. Ahh, still remember them from my childhood. Had them for 120 volt too - lots of old houses here had them. There is at least one company producing them for use in modern electrical systems for the "retro" look. |
#59
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Sub Panel neutral bonding
On 6/12/2019 8:52 PM, Clare Snyder wrote:
On Wed, 12 Jun 2019 15:43:06 -0400, Tekkie® wrote: dpb posted for all of us... Still have all the old mother-of-pearl inlaid pushbutton light switches that are classic in looks but not up to 120 VAC, sadly. Ahh, still remember them from my childhood. Had them for 120 volt too - lots of old houses here had them. There is at least one company producing them for use in modern electrical systems for the "retro" look. Yeah, I've not looked for a number of years now, though--last time I did the only ones I found at the time were outrageously priced even for a low volume specialty product... I've thought one could replace the workings behind the buttons on the plate w/ new mechanical pushbutton switches but never had sufficient initiative to actually do so. -- |
#60
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Sub Panel neutral bonding
On Wed, 12 Jun 2019 21:25:43 -0500, dpb wrote:
On 6/12/2019 8:52 PM, Clare Snyder wrote: On Wed, 12 Jun 2019 15:43:06 -0400, Tekkie® wrote: dpb posted for all of us... Still have all the old mother-of-pearl inlaid pushbutton light switches that are classic in looks but not up to 120 VAC, sadly. Ahh, still remember them from my childhood. Had them for 120 volt too - lots of old houses here had them. There is at least one company producing them for use in modern electrical systems for the "retro" look. Yeah, I've not looked for a number of years now, though--last time I did the only ones I found at the time were outrageously priced even for a low volume specialty product... Last one I saw was $37 us each plus shipping. That was a few years ago. They are about $15 now from house of antique hardware or Classic Accents on Amazon. I've thought one could replace the workings behind the buttons on the plate w/ new mechanical pushbutton switches but never had sufficient initiative to actually do so. |
#61
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Sub Panel neutral bonding
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#62
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Sub Panel neutral bonding
On Wednesday, June 12, 2019 at 3:43:07 PM UTC-4, Tekkie® wrote:
dpb posted for all of us... Still have all the old mother-of-pearl inlaid pushbutton light switches that are classic in looks but not up to 120 VAC, sadly. Ahh, still remember them from my childhood. -- Tekkie We had them when I was a kid. We had a visitor with an intention tremor. Watching him try to stab those buttons when his finger was shaking was painful. |
#63
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Sub Panel neutral bonding
On Wednesday, June 12, 2019 at 8:43:28 PM UTC-4, wrote:
On Wed, 12 Jun 2019 12:17:50 -0700 (PDT), trader_4 wrote: On Wednesday, June 12, 2019 at 2:51:36 PM UTC-4, wrote: On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. I think if you read that description I provided of how they detect the loss of the grid, the answer is almost certainly not. They are looking for stability in voltage, freq, power factor and it's unlikely a typical home generator is going to fool it. Especially with variable load, which you'd have when a fridge cycles on, etc. Of course that description looks like it's for a bigger solar install than a home one, but the home ones have to comply with regs and must use similar techniques. Most interesting in that was that the inverters described there actually deliberately screw with the grid when they think they may be in an island situation, the idea being that you can't perturb a true grid, but if the "grid" is an island with just some other solar sources, you can and then other inverters will see the deviation and shut down too. My generator was pretty stable, looking at it on a scope and the frequency doesn't drift that much when the engine grunts looking at a frequency counter. "That much", is likely a world of difference compared to the normal grid and would be instantly detected. An inverter generator should not change at all. Maybe. I think the author was just trying to dumb down his talk. When he says "screw with the grid" what he really means is these things do not have an internal clock and without a stable clock coming in they just go nuts. It detects that condition and shuts down, probably in a cycle or two. . He didn't say "screw with the grid" and he actually explained what he meant. "For the active anti-islanding function, we use a technique called Slip Mode Frequency Shift. This varies the reactive power output of the inverter. The goal of this protection method is to destabilize an islanded feeder by trying to influence the frequency. This diagram, from the IEEE 1547 testing procedure, shows how we test the anti-islanding function in the inverter. We intentionally force the frequency out of spec and push against the grid, so we can properly detect and dissolve the island. We actually turn the anti-islanding function off, create an island, turn the anti-islanding function back on, and test the ability to disturb the island within two seconds. In our tests, we actually do it much faster." You could try to fool a grid tie inverter with another inverter. You don't even need a generator inverter, you could use a car battery and an inverter. If it worked, you could keep the battery charged from the solar power. I doubt it would work. It would depend on the actual anti-islanding methods used in the particular solar inverter. And then there is the problem of how does a typical battery inverter or generator inverter react when the solar inverter is fooled into thinking the grid is there, powers up, connects and tries to put power into the "grid", which in this case is just a small inverter or generator? I would think that would produce a condition that if it didn't blow up the other inverter/generator, would result in conditions that the grid tie inverter would recognize as not right and it would shut down. |
#64
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Sub Panel neutral bonding
On Thu, 13 Jun 2019 07:55:03 -0600, bud-- wrote:
On 6/10/2019 11:53 AM, wrote: On Mon, 10 Jun 2019 09:09:50 -0700 (PDT), trader_4 wrote: On Sunday, June 9, 2019 at 10:40:23 PM UTC-4, wrote: On Sun, 9 Jun 2019 20:01:54 -0500, Terry Coombs wrote: Â* When is it necessary ? I've just replaced the panel out in the shop (aluminum buss bars on the old one were giving problems) and I have a 3 wire service run out there . At this time the only place the neutral is bonded to ground is in the meter box . It has been suggested to me to bond them in the main panel too ... but that seems redundant to me , they're only the thickness of a piece of plywood apart . I have considered installing a ground rod at the new panel but am concerned about the potential for ground loop currents . If you only have 3 wires in the feeder going to the shop you need to bond the neutral and ground out there too or there is no path for fault current. You also need a ground electrode out there. Current code requires a 4 wire feeder and isolating neutral and ground in sub panels but if the wire was already there when the 1996 code was adopted the 3 wire feeder is grandfathered in. Ground loops are not an issue but carrying circuit current in the grounding conductor is, That is why you do need another ground electrode. Essentially you are creating another service in the second building and creating a new ground reference there. In the electrical biz, you can't have too many ground electrodes but they all need to be bonded together. His main question appeared to be whether the neutral and ground need to be bonded in the MAIN panel if they are already bonded at the meter which is right next to it? That is open to debate. A strict reading of the NEC says the PoCo should not have bonded the neutral in their can but since they do not have to follow the NEC, the language was tweaked a little (again 96 as I recall) so it is all "service equipment" and you still rebond the neutral in the service disconnect enclosure where the code says the "Main Bonding Jumper" is supposed to be. That is usually just a green screw on the neutral bus or a strap. The hitch is that the MBJ "shall remain accessible" and inside the meter can isn't. Sanity prevailed. Meter cans are usually made so the can is bonded to the neutral anyway. There is no way to avoid it. Some inspectors require that there be no metallic paths between the meter can (a PVC sleeve) and that you only bring 3 wires in. Then we did not care what they did in the can, the MBJ was clearly in the service disconnect enclosure. The grounding electrode conductor can land anywhere from the service point (usually the mast head on an overhead drop) to the service disconnect enclosure. That is how they can land it in the meter can. If you have an underground service lateral, the service point is usually the transformer connection at the street. Yes you usually own that wire in the yard. You typically do not own an overhead drop. A slightly broader view - the requirements for grounding-bonding on a service entrance are much tougher than past the service. Assume an overhead drop and EMT service entrance. The EMT from the meter can to the service panel is likely to be connected through concentric/ecentric knockouts at each end. That is not allowed for bonding and the meter can and EMT section are then not "grounded". Around here the practice was for the GEC exiting the panel to go through a ground clamp on the EMT then to the electrodes. That bonded the EMT but left the meter can. The bond between neutral and meter can is then critical. The EMT riser above the meter is connected through a hub, which is good for bonding. I am too lazy to look it up, but I think if the EMT between the meter can and service panel does not have concentric/ecentric knockouts, an EMT connector through the right sized hole is also not an approved bond and a "grounding locknut" (not an ordinary locknut) or other means has to be used. The EMT between the meter can and service panel is in parallel with the neutral wire but that was not considered a problem here. If PVC conduit is used, more likely now, the bonding problems go away, but bonding the neutral to the meter can is then also critical. The way I read Terry's post there is a utility meter separated from the panel by 1/4" of plywood. Sounds like a service panel, not a feeder-subpanel. Or that discussion may be in addition to a "new panel" at a separate shop building run off of a 3-wire feeder. Neutral-ground bond and earthing electrode(s) apply to both. More stringent bonding (above) only applies to a service. I would want a Main Bonding Jumper in a service panel (is required in a separate building 3-wire feed subpanel). For a service with no MBJ in the service panel the bonding (as above) on the ?metal pipe? from the meter can is a particular question. Raceways for service conductors get extra protection because there is no real overcurrent protection on a service conductor. Feeders are protected at their ampacity but service conductors are not. . A bolted fault on a service conductor is as likely to burn out the drop as it is to blow the primary fuse on the transformer. It will certainly get hot enough to roast that squirrel running along it. That is why your typical branch circuit breaker has a 10,000a AIC but the service disconnect/main breaker will be 65ka AIC or more. |
#65
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Sub Panel neutral bonding
On Thu, 13 Jun 2019 10:25:59 -0700 (PDT), trader_4
wrote: On Wednesday, June 12, 2019 at 8:43:28 PM UTC-4, wrote: On Wed, 12 Jun 2019 12:17:50 -0700 (PDT), trader_4 wrote: On Wednesday, June 12, 2019 at 2:51:36 PM UTC-4, wrote: On Wed, 12 Jun 2019 10:31:06 -0700 (PDT), wrote: I found this that explains a lot. We're on the right track of thinking about what happens and that it's kind of a paradox as to how to detect the loss of the "grid". They call this problem "islanding". This talks about the ways they detect it, it's complicated and even includes active action by inverters to deliberately try to destabilize the grid so that it goes off kilter and all the other inverters can more quickly detect it. It looks like they use voltage changes, freq changes and power factor changes as possible parts of the algorithms and that it's not a trivial problem. I think this gear is more for a larger commercial array, but the same principles should apply to all inverters. https://www.solectria.com/blog/anti-...-pv-inverters/ that is interesting it is also what makes the frustrating situation for people that spent a lot of money for a solar system, and they still have no electricity when the grid is down, even when the sun is out. m Hence my question, could you disconnect from the grid and use a small inverter or a little Honda to clock your solar inverter and rock on. I think if you read that description I provided of how they detect the loss of the grid, the answer is almost certainly not. They are looking for stability in voltage, freq, power factor and it's unlikely a typical home generator is going to fool it. Especially with variable load, which you'd have when a fridge cycles on, etc. Of course that description looks like it's for a bigger solar install than a home one, but the home ones have to comply with regs and must use similar techniques. Most interesting in that was that the inverters described there actually deliberately screw with the grid when they think they may be in an island situation, the idea being that you can't perturb a true grid, but if the "grid" is an island with just some other solar sources, you can and then other inverters will see the deviation and shut down too. My generator was pretty stable, looking at it on a scope and the frequency doesn't drift that much when the engine grunts looking at a frequency counter. "That much", is likely a world of difference compared to the normal grid and would be instantly detected. An inverter generator should not change at all. Maybe. I think the author was just trying to dumb down his talk. When he says "screw with the grid" what he really means is these things do not have an internal clock and without a stable clock coming in they just go nuts. It detects that condition and shuts down, probably in a cycle or two. . He didn't say "screw with the grid" and he actually explained what he meant. "For the active anti-islanding function, we use a technique called Slip Mode Frequency Shift. This varies the reactive power output of the inverter. The goal of this protection method is to destabilize an islanded feeder by trying to influence the frequency. This diagram, from the IEEE 1547 testing procedure, shows how we test the anti-islanding function in the inverter. We intentionally force the frequency out of spec and push against the grid, so we can properly detect and dissolve the island. We actually turn the anti-islanding function off, create an island, turn the anti-islanding function back on, and test the ability to disturb the island within two seconds. In our tests, we actually do it much faster." That is still flowery rhetoric for saying an unclocked inverter will go nuts. I think if it got a stable clock it would run. |
#66
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Sub Panel neutral bonding
Terry Coombs posted for all of us...
On 6/12/2019 2:44 PM, Tekkie® wrote: Terry Coombs posted for all of us... * Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible . This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . I have a couple of 'projects' for you * Whatcha got ? I will find the list, it is buried somewhere here. I will need your personal advice as my schemes can be questionable when the synapses' misfire. -- Tekkie |
#67
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Sub Panel neutral bonding
Clare Snyder posted for all of us...
Had them for 120 volt too - lots of old houses here had them. There is at least one company producing them for use in modern electrical systems for the "retro" look. That is what you could classify me: the retro look. -- Tekkie |
#68
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Sub Panel neutral bonding
On 6/14/2019 2:39 PM, Tekkie® wrote:
Terry Coombs posted for all of us... On 6/12/2019 2:44 PM, Tekkie® wrote: Terry Coombs posted for all of us... * Done is done , I have bonded the ground/neutral in the sub panel and added a ground rod out in the shop . Doing without 240V is unacceptable , I have 2 welders and an air compressor that all need 240V . And plans are to install a 240V 3 phase motor with a VFD on the mill in the future . Lightning is unlikely down in The Holler , but still possible . This is a "hobby" shop , but is very well equipped - pretty much a full machine and welding shop . I have a couple of 'projects' for you * Whatcha got ? I will find the list, it is buried somewhere here. I will need your personal advice as my schemes can be questionable when the synapses' misfire. * My reply-to is good . Hit me there and I'll give you my main email address . -- Snag Yes , I'm old and crochety - and armed . Get outta my woods ! |
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