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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Relay and Contactor based GENSET BACKFEED PREVENTER?
Our 50amp transfer unit only switches power from grid to generator after
30 seconds from when it sees power from the gen. http://www.green-trust.org/wiki/inde...ransfer_Switch Steve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html Ignoramus25850 wrote: I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanks i |
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I don't claim to have really followed it, but do know that the contacts on
my TS relay fused closed. Unless your device accomodates that (on the line contacts) safely, it is no good. |
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"Ignoramus25850" wrote in message ... I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. Where I live the utilities require physcial and electrical interlocks. Most residential panels do not lend themselves to a physcial interlock. Square D is the only one that I know of that has a physical interlock between the main and another breaker. Then comes to the issue of the equipment being service rated. Then comes UL listings. A contactor/motor starter off the shelf I do not believe is service rated. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanks i Check with your local authorities and utility before embarking on the project. If you can build this in 30 minutes, your a lot better than I am. |
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"SQLit" wrote in message ... "Ignoramus25850" wrote in message ... I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. Where I live the utilities require physcial and electrical interlocks. Most residential panels do not lend themselves to a physcial interlock. Square D is the only one that I know of that has a physical interlock between the main and another breaker. Then comes to the issue of the equipment being service rated. Then comes UL listings. A contactor/motor starter off the shelf I do not believe is service rated. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. One piece of advice. I am not seeing it in your description, but I might be missing it. Do you have a plan for seeing that the incoming power from the street is back on? I only mention this as I once had a friend do something similar, and failed that part. Worse yet, he had to get into his car to drive by a few neighbors to see if power had been restored. Even worse yet he had to drive by two of them as they had generators. Remote area it was. -- Chris If you can read this, thank a teacher. If it is in English, thank a soldier. If it is in ebonics, thank your Congressman. |
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On Tue, 6 Sep 2005 11:47:41 -0400, "Chris" wrote:
"SQLit" wrote in message ... "Ignoramus25850" wrote in message ... I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. Where I live the utilities require physcial and electrical interlocks. Most residential panels do not lend themselves to a physcial interlock. Square D is the only one that I know of that has a physical interlock between the main and another breaker. Then comes to the issue of the equipment being service rated. Then comes UL listings. A contactor/motor starter off the shelf I do not believe is service rated. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. One piece of advice. I am not seeing it in your description, but I might be missing it. Do you have a plan for seeing that the incoming power from the street is back on? I only mention this as I once had a friend do something similar, and failed that part. Worse yet, he had to get into his car to drive by a few neighbors to see if power had been restored. Even worse yet he had to drive by two of them as they had generators. Remote area it was. On my brothers recreational property the meter is at the road (with a disconnect and main breaker) and there is a red pilot lite on the back of the service box that tells him power is on. His transfer switch is back at the buildings. When the light is on, he knows the grid is up. |
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On Tue, 06 Sep 2005 15:21:20 GMT, Ignoramus25850
wrote: I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanks i Sounds like a good idea - BUT. Can you ensure the generator contactor can NOT stay closed when the switch is shut off to turn the main disconnect on? You need a failsafe system that makes it IMPOSSIBLE for the generator to "lock on" - whether by killing the generator before being able to reconnect to mains or whatever. That is why virtually all transfer switches employ what boils down to a mechanical DPDT knife switch. |
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Since you are going for a manual changeover, you might want to consider one
of these simple kits: http://www.interlockkit.com/intro.html "Ignoramus25850" wrote in message ... I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanks i |
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Crossposts deleted
I'm all for building stuff that does what you want it to. But when you start talking 7 kw of power plus the potential to have life endangering consequences I start to drag out my "safety first" speech. Officious speech mode on There must be a POSITIVE interlock to avoid backfeeding to the grid. This interlock should satisfy BOTH the power company and the electrical inspector. Period. No discussion. Positive in this case means you, your neighbor, an electican, or your power company guy can all work it correctly without fear of screwing up. It should also be physically positive in the sense that it won't bend short of using a vice grip or prybar. Your description says something about some vague "mechanical device" to accomplish this. I don't buy it. Officious speech mode off Other than that, why are you going though all the hassle of relays, 9 volt batteries, etc when all you need to do is switch a couple of circuits? I also think you will have some issues with trying to power the whole house with the 7 kw generator. I see a few neighbors trying to run their houses with 5 kw (granted these are a bit smaller), modern houses take a LOT of power, if several things come on at once, you kill the generator. But with proper power management, you should have enough power to run a small window AC unit as well as the rest of the required items like refrigerator, freezer, well, and a few lights. Most folks just use the 60 amp (??) Square D transfer switch to have 4 circuits that can be cut over to the generator. $100 or so, UL listed, NEC compliant, looks like a sub panel, takes an afternoon to install. The even simpler route is to have the critical items (eg furnace)on plugs, just move the plug from grid to generator as required. Cheers. Ignoramus25850 wrote: I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed. There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor. This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer. I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanks i |
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"Ignoramus25850" wrote in message ... I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). Not a DIY job. Get a UL listed transfer switch, have a licensed electrician install it and get it inspected. |
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riggghhttt. anyone with a bit of sense can install a transfer switch.
Steve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html ATP* wrote: Not a DIY job. Get a UL listed transfer switch, have a licensed electrician install it and get it inspected. |
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"Steve Spence" wrote in message ... riggghhttt. anyone with a bit of sense can install a transfer switch. Steve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html I've seen plenty of simpler electrical jobs screwed up or just poorly executed by people with more than a bit of sense. In any case, it has to be listed and inspected per the local utility regulations. ATP* wrote: Not a DIY job. Get a UL listed transfer switch, have a licensed electrician install it and get it inspected. |
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maybe in your community, but not in mine. I wired my whole house, panels
and entrance. The power company only dropped to the meter on the pole. that was the end of it. I did the rest. Steve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html ATP* wrote: I've seen plenty of simpler electrical jobs screwed up or just poorly executed by people with more than a bit of sense. In any case, it has to be listed and inspected per the local utility regulations. ATP* wrote: Not a DIY job. Get a UL listed transfer switch, have a licensed electrician install it and get it inspected. |
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On Wed, 07 Sep 2005 18:51:51 -0400, Steve Spence
wrote: maybe in your community, but not in mine. I wired my whole house, panels and entrance. The power company only dropped to the meter on the pole. that was the end of it. I did the rest. Steve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html ATP* wrote: I've seen plenty of simpler electrical jobs screwed up or just poorly executed by people with more than a bit of sense. In any case, it has to be listed and inspected per the local utility regulations. ATP* wrote: Not a DIY job. Get a UL listed transfer switch, have a licensed electrician install it and get it inspected. In Washington state you are allowed to wire your own house. It then must pass inspection. After that you must live in it for five years before you can sell it. This is done to prevent bad wiring done by people who are building spec homes. Not that everybody who builds a spec home is going to do a bad job. Just that some people will skimp and not use qualified people to do the wiring. ERS |
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On Wed, 07 Sep 2005 18:51:51 -0400, Steve Spence
wrote: ATP* wrote: I've seen plenty of simpler electrical jobs screwed up or just poorly executed by people with more than a bit of sense. In any case, it has to be listed and inspected per the local utility regulations. Some of the most screwed up DIY installations I've ever had to rework were done by engineers and (literally) 'Rocket Scientists' who thought they knew better. I think half the parts the former owner used for the additions at this house (before we bought it) "fell off the loading dock" at Rocketdyne in the '60's, though I can't prove it. maybe in your community, but not in mine. I wired my whole house, panels and entrance. The power company only dropped to the meter on the pole. that was the end of it. I did the rest. In EVERY community I know of, the electrical utility won't tie onto a power panel and provide a meter unless the panel has been inspected and approved as safe by /somebody/ referred to as the Authority Having Jurisdiction or AHJ. If there isn't a city building inspector, the job falls back to the county or parish level. If it's on state or federally owned property, then their inspector has the authority. The power utility doesn't want the legal liability if someone gets hurt or killed, so they insist on it. Now after the AHJ has passed the installation, the utility has connected the feed, and both parties are long gone, /then/ you can do additional work without a permit, and cheat as much as you want, with one gigantic caveat: As long as they never see it. And if the AHJ comes back to check something else and sees you have cheated, now you have a problem. They can (and will) force you to fix it. If you don't, their ultimate recourse is to call the utility and tell them to cut the feed and pull the meter, the installation is no longer safe. Darkness and quiet quickly ensues. (*) (* At least on things run from utility power, noting the crosspost.) Except for mobile homes / manufactured housing in California, where inspection of the meter pedestal and outside wiring is a city or county responsibility like normal, but anything electrical inside or on the coach itself is inspected by a State bureaucrat. Our local mobile home inspector drives into Western LA County from Riverside, where the closest office is. -- Bruce -- -- Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop Electrician for Westend Electric - CA726700 5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545 Spamtrapped address: Remove the python and the invalid, and use a net. |
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Excellent suggestion.
Ig, you come across as an enterprising and resourceful individual. I would suggest focusing your talents on something that is not so dangerous to... - your finances - your power company employees If this homebrew setup would fail with fatal results for someone, you will be on the hook litigation wise. There are reasons why sometimes we spend the money on UL listed products, have a licensed electrician do the work and have inspections....all to cover us legally.It only takes one fatal failure to wipe you and your family out financially. Let know how you end up doing it. TMT |
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On Tue, 06 Sep 2005 15:21:20 GMT, Ignoramus25850
wrote: I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot. Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power). It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding. I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position. Go get yourself a UL Listed transfer switch of some sort. The cheapest way is a Double-Throw safety switch. Looks just like the fused disconnect for a motor, but the lever goes On-Off-On. Or do some heavy-duty scrounging and buy a new or good used automatic transfer switch that you can install. DO NOT TRY TO INVENT THIS YOURSELF. It is life-safety critical, and there is absolutely no reason for you to reinvent the wheel. Better you should pay a bit for the right equipment - Use a proven design. If your homebrewed transfer switch design is flawed, creates a backfeed and kills a lineman or two working on power restoration (or even just surprises the hell out of them when they find out the line is energized) I can guarantee that they will find you, and that the proceedings will not be pleasant. If you do anything permanent, get it checked out and passed by the local building inspector, and by the local utility. This is critical. -- Bruce -- -- Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop Electrician for Westend Electric - CA726700 5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545 Spamtrapped address: Remove the python and the invalid, and use a net. |
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