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#1
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Code question on generator grounding
I will be installing a standby generator located about 50 ft. from the
grounding rod for my house. If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? Please provide a code reference (or quote) if you can. Many thanks for any help. |
#2
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Code question on generator grounding
On Sep 7, 1:35*pm, wrote:
I will be installing a standby generator located about 50 ft. from the grounding rod for my house. *If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. *If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? *Please provide a code reference (or quote) if you can. Many thanks for any help. Ground the frame where it is installed |
#3
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Code question on generator grounding
wrote in message ... I will be installing a standby generator located about 50 ft. from the grounding rod for my house. If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? Please provide a code reference (or quote) if you can. Many thanks for any help. There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. |
#4
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Code question on generator grounding
John Grabowski wrote:
There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. Lightning protection? You got wire that'll handle 7,000 Amps? |
#5
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Code question on generator grounding
"HeyBub" wrote in message m... John Grabowski wrote: There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. Lightning protection? You got wire that'll handle 7,000 Amps? LOL. What do you think ground rods are for? For a generator a #10 may only be required. For a house a #6 or #4 will suffice. |
#6
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Code question on generator grounding
On Sep 7, 4:08*pm, "John Grabowski" wrote:
wrote in message ... I will be installing a standby generator located about 50 ft. from the grounding rod for my house. *If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. *If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? *Please provide a code reference (or quote) if you can. Many thanks for any help. There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. *This would get connected to your grounding electrode conductor for lightning protection. *There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. The gen only needs small wire attached to even a long nail driven into the ground, a lightning rod is overkill |
#7
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Code question on generator grounding
Lightning protection? You got wire that'll handle 7,000 Amps?
Actually up to a record 200,000 amps has been measured, however it lasts for only about a millisecond so the wire will not heat appreciably during that short time. Most commonly, the lightning current ceases in about a millisecond for a given stroke, but sometimes there is a continuing current on the order of 100 amps following one or more of the strokes. This is called "hot lightning" and it is the cause of lightning fires. The continuing current only lasts for only 0.2 seconds and so a typical ground wire is sufficient. |
#8
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Code question on generator grounding
"ransley" wrote in message ... On Sep 7, 4:08 pm, "John Grabowski" wrote: wrote in message ... I will be installing a standby generator located about 50 ft. from the grounding rod for my house. If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? Please provide a code reference (or quote) if you can. Many thanks for any help. There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. The gen only needs small wire attached to even a long nail driven into the ground, a lightning rod is overkill LOL. You guys are making me laugh tonight. Thanks. This reminds of the person a few years back who posted about sticking a wire from her computer out the window to a coat hanger in the ground because her house was not a grounded system. Maybe on the next job I'll connect a ground wire good for 7000 amps to a long nail and show the inspector this thread. LOL |
#9
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Code question on generator grounding
I really do appreciate all you folks who took the time to reply. However,
the subject began "code question" amd so far none of the replies have tried to answer the question based on code. Also the question asked was "How, according to the NEC, should the generator be grounded?" Does anyone have an answer based upon their knowledge of the NEC? As to the long nail suggestion you may be very certain that the nail will not be connected well to the ground when it is new and much less so after it begins to rust. That is why long ground rods are used and why two are sometimes required. That is also why they are made of copper. Yes the outside of the copper will corrode but the copper oxide, unlike rust, is conductive. |
#10
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Code question on generator grounding
On Sep 7, 11:35*am, wrote:
I will be installing a standby generator located about 50 ft. from the grounding rod for my house. *If I ground the generator only in main panel, then there is a possibility that the generator frame will be at a slightly different potential than the adjacent earth on which someone touching the generator may be standing. *If I install a ground rod at the generator location, then I will be introducing a ground loop with its associated problems. How, according to the NEC, should the generator be grounded? *Please provide a code reference (or quote) if you can. Many thanks for any help Grounding and bonding depend on whether or not is a seperatley derived system or not. I assume you are permanantly mounting the generator and it is not a portable unit. I also assume you are installing a transfer switch. Is this correct? NEC 2005 Article 250 is where to look. |
#11
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Code question on generator grounding
John Grabowski wrote:
"HeyBub" wrote in message m... John Grabowski wrote: There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. Lightning protection? You got wire that'll handle 7,000 Amps? LOL. What do you think ground rods are for? For a generator a #10 may only be required. For a house a #6 or #4 will suffice. Well, they sure as hell ain't for lightning protection! |
#12
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Code question on generator grounding
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#13
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Code question on generator grounding
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#14
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Code question on generator grounding
"HeyBub" wrote in message m... John Grabowski wrote: "HeyBub" wrote in message m... John Grabowski wrote: There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. Lightning protection? You got wire that'll handle 7,000 Amps? LOL. What do you think ground rods are for? For a generator a #10 may only be required. For a house a #6 or #4 will suffice. Well, they sure as hell ain't for lightning protection! LOL. I printed this thread to show some of my fellow electricians. They will get a good laugh like I did. Thanks for making my week. |
#15
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Code question on generator grounding
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#16
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Code question on generator grounding
Caesar Romano wrote:
On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code question on generator grounding: That breaker has a mechanical interlock which prevents both it and the main breaker being on at the same time. (It is impossible to turn on the backfeed breaker on unless the main is off, and impossible to turn the main breaker on unless the backfeed breaker is off.) Where do you get such an interlock? Do you have a product name & manufacturer? Even better, do you have a link? They differ by panel model within manufacturer and are all hideously expensive. Here's what I did on a Square D panel. The connection to the generator goes to a double circuit breaker located in the upper right column. For normal, non-emergency, operation, this breaker is OFF. It's possible to fashion a metal or plexiglass plate that nudges against both the main circuit switch and this odd circuit breaker. This plate is bolted to the panel cover via elongated holes in the plate that allow the plate to slide, making contact with the two switch handles. The trick is to match the sliding with the positions of the main switch and the odd breaker. The breaker can't be turned ON unless the main switch is OFF. The main switch can't be turned ON unless the breaker is OFF. On a Square D, main switch ON is to the right and circuit breaker OFF is to the right. If you have a block plate between the levers, it's obvious the circuit breaker can't be moved to the left (ON) unless the main is first moved to the left (OFF) and the blocking plate moved likewise. Similarily, the main can't be moved right (ON) unless the circuit breaker is first moved right (OFF) and the blocking plate scooted over with it. Get the model and make of your panel and do a search on "{make} {model} interlock" The results will give you an idea of how the manufacturer of your panel wants the thing to work. You can then either find the best price on the "approved" device or, as I did, fashion your own. |
#17
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Code question on generator grounding
Some of the panel makers make them. Square D makes them for their Q0
panels and I think they now have them for their Homeline panels. Others also have them. Google "generator interlock kit" or see http://www.interlockkit.com/ On Mon, 08 Sep 2008 07:38:29 -0500, Caesar Romano wrote: On Sun, 07 Sep 2008 22:05:03 -0400, wrote Re Code question on generator grounding: That breaker has a mechanical interlock which prevents both it and the main breaker being on at the same time. (It is impossible to turn on the backfeed breaker on unless the main is off, and impossible to turn the main breaker on unless the backfeed breaker is off.) Where do you get such an interlock? Do you have a product name & manufacturer? Even better, do you have a link? Thanks |
#18
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Code question on generator grounding
On Mon, 8 Sep 2008 09:54:16 -0500, "HeyBub"
wrote Re Code question on generator grounding: Get the model and make of your panel and do a search on "{make} {model} interlock" The results will give you an idea of how the manufacturer of your panel wants the thing to work. You can then either find the best price on the "approved" device or, as I did, fashion your own. Thanks for the detailed description. I can easily visualize the "field" modification that you made. Very creative. Nice going. |
#20
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Code question on generator grounding
John Grabowski wrote:
"HeyBub" wrote in message m... John Grabowski wrote: There should be grounding requirements in the installation instructions. Generally there is an external ground lug on the frame or housing of the generator. This would get connected to your grounding electrode conductor for lightning protection. There should also be an equipment grounding conductor that is run with generator conductors to the transfer switch or panel that you will be supplying the generator power to. Lightning protection? You got wire that'll handle 7,000 Amps? LOL. What do you think ground rods are for? For a generator a #10 may only be required. For a house a #6 or #4 will suffice. This was my question as I read this thread. The OP said something about standing next to the generator and having different potential. But my understanding about "grounding" in this case is that its about lightning. I don't think there will be any current flow from the generator through a person's feet and into the soil no matter how its wired or what he touches. Is that correct? CLG |
#21
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Code question on generator grounding
I did this in my previous house before interlock kits were available. It
was not hard and worked very well. After checking the cost of the kits (ridiculous!) I plan to do it again, esp. since I have two 200 Amp panels, the kits would cost $300 to $400 depending on where you bought them. In my situation, I do not want a gen large enough to power the whole house so I won't use autostart anyway. I will manually turn off the HVAC brakers before starting the gen. Then everything else in my house will have power available, even if I cannot run it all at the same time. I had a 6KW gen hooked up this way before. Had a 21 day power outage and another 10+ day power outage and never a moment's trouble and no overloads of tripped breakers occurred. Saved a lot of $$$ on fuel by not having a huge generator. On Mon, 08 Sep 2008 10:38:11 -0500, Caesar Romano wrote: On Mon, 08 Sep 2008 11:02:09 -0400, wrote Re Code question on generator grounding: Some of the panel makers make them. Square D makes them for their Q0 panels and I think they now have them for their Homeline panels. Others also have them. Google "generator interlock kit" or see http://www.interlockkit.com/ Thanks! It looks like it can be an interesting "home-made" project: 1) Make a template out of cardboard 2) Use the cardboard template to fabricate a working interlock from 1/8" aluminum plate. |
#22
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Code question on generator grounding
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#23
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Code question on generator grounding
On Mon, 08 Sep 2008 13:11:23 -0500, Caesar Romano wrote:
You have two 200A panels in one house? Or is one of the panels in a work shop building? This is standard for homes with 400 Amp service. |
#24
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Code question on generator grounding
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#25
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Code question on generator grounding
On Mon, 8 Sep 2008 09:54:16 -0500, "HeyBub"
wrote Re Code question on generator grounding: Get the model and make of your panel and do a search on "{make} {model} interlock" The results will give you an idea of how the manufacturer of your panel wants the thing to work. You can then either find the best price on the "approved" device or, as I did, fashion your own. Thanks for the detailed description. I can easily visualize the "field" modification that you made. Very creative. Nice going. But you had better check your local codes. It's likely they will not allow that setup. NEC et al are only starting points; then the local guys get into the act and add their own idiocy, I mean, opinions of how things should be. KNOW BEFORE DOING is the proper mantra. Otherwise you could be doing it more than once. |
#26
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Code question on generator grounding
On Mon, 08 Sep 2008 16:52:13 -0400, metspitzer
wrote: I don't understand why anyone would want to select the circuits on the generator. To me, having the whole panel on the generator would be much easier to set up and much more flexible. But this is what you have to do if you use a transfer switch/panel that has only a few circuits. That's why I plan to backfeed the main panels. |
#27
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Code question on generator grounding
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#28
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Code question on generator grounding
On Mon, 8 Sep 2008 20:04:46 -0400, "TWayne"
wrote Re Code question on generator grounding: Thanks for the detailed description. I can easily visualize the "field" modification that you made. Very creative. Nice going. But you had better check your local codes. It's likely they will not allow that setup. NEC et al are only starting points; then the local guys get into the act and add their own idiocy, I mean, opinions of how things should be. KNOW BEFORE DOING is the proper mantra. Otherwise you could be doing it more than once. Very true. However I am fortunate enough to live in a rural area not subject to codes. Nevertheless I generally do my own projects to code where the code make sense. |
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