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SeattleRain
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# Posted: 30 Mar 2010 12:56pm
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Hi Everyone,
I don't have power at my property, but have just completed wiring my cabin for generator power. I have a small electrical panel inside the house, which connects to my Honda 2000i generator outside. I know on new constructions homes, they usually require a 8' grounding rod to be sunk into the ground (usually through the foundation). Is this necessary if I'm just running power through the generator at my 16x20 cabin? The ground at my property is very hard and rocky and there is no way I'll be able to sink a rod 8' down. Also, is the ground rod necessary to ground the electrical or to serve as an outlet if lightning were to strike the house? Or both? Can someone with electrical experience in this area please comment?
Thanks!
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hallamore
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# Posted: 30 Mar 2010 03:36pm
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SeattleRain,
I am running your exact set up but with a Honda 3000i generator. I have not grounded it for three years but I did build a little shed about 50 feet away from my cabin and run underground heavy gague wire to a transfer switch that is equipped with breakers. Never had a single problem.
Good Luck,
Hallamore
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knottypine
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# Posted: 31 Mar 2010 11:01pm
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A ground rod provides a path the the ground for electricity in the event it has nowhere else to goes, which means a failure of your system. You should have one, but you might never need one. you have a box, generator has fuses, etc. Just pound a rod or two as deep as you can and hook a ground to it. you'll sleep better
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Rob_O
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# Posted: 1 Apr 2010 09:27pm
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Code requires a waterline ground in addition to a driven ground rod, or 2 rods 10' apart connected by an uninterrupted length of wire from the furthest rod to the panel
Ground the panel, or the generator, but not both
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Kithera
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# Posted: 3 Apr 2010 06:26pm
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Indeed, as with all safety devices, you never need it, but it's a lot better to be safe than sorry. Ground your system.
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bullelk
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# Posted: 30 Jan 2011 10:27pm
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I was planning on doing the same thing with my off-grid cabin. How did you connect the generator to the cabin? I do not want to use an extension cord with a male connector going to the building...basically a double male extension cord!
I there a weather proof box, that with a male connection, that will supply my sub panel in the cabin?
I have a 3300 watt Boliy Gen with a RV type 120.
Thanks in advance!
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Rob_O
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# Posted: 30 Jan 2011 11:12pm
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Quoting: bullelk I there a weather proof box, that with a male connection, that will supply my sub panel in the cabin?
How about this?
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MtnDon
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# Posted: 31 Jan 2011 12:33am
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You can usually find that type of connector, in 30 and 50 amp versions, at RV supply places. Most RV's have "shore" power hookups. Some use hardwired cords but many use a connector like Rob0) showed.
I just read this thread for the first time. About grounding rods... nowhere does the NEC say the rod(s) has to be driven straight down. Angles will do as will burying the rod in a trench. One rod will do if the resistance is below 25 ohms. Usually measurements are not bothered with and a second rod is installed. NEC actually just says no less than 6 feet apart, but 10 feet in good.
Lightning protection is an issue unto itself, If a lightning arrestor is used it connects across the hot and neutral in a 120 VAC system and across both hots and the neutral in a 240 VAC system. There is also a ground lead. This protects against lightning that may travel through the cabin wiring. The ground wire can be attached to the same ground rods.
Those with PV modules should have a separate DC arrestor at the panels.
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bobrok
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# Posted: 31 Jan 2011 07:30pm
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Excellent thread and one I was planning to start this spring since I am planning on doing the same type of generator-to-panel-box switch.
One thing I noted on my Honda manual was the recommendation to ground the generator itself. Of course I haven't done this yet but when I do my permanent install I guess this is probably advisable as well. What you you think? Ground everything.
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MtnDon
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# Posted: 31 Jan 2011 09:47pm - Edited by: MtnDon
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Grounding depends on how the generator is used or what is connected to it.
The NEC states; (250.34) Portable and Vehicle-Mounted Generators.
(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.
In other words when using a portable generator on a work site to power tools, most generators will not require a ground rod.
Connected to a cabin there is another issue. More later.
Part B for vehicle mounted systems reads....
(B) Vehicle-Mounted Generators. The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions:
(1) The frame of the generator is bonded to the vehicle frame, and
(2) The generator supplies only equipment located on the vehicle or cord-and-plug-connected equipment through receptacles mounted on the vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, and
(3) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.
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bobrok
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# Posted: 31 Jan 2011 10:35pm - Edited by: bobrok
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MtnDon: you are a wealth of knowledge. Thanks for popping in with that info.
I'm going to let this thread run it's course and absorb what I can from it.
Because my plans are a little different than powering solely from a generator I'll start a new thread sometime soon so as to avoid confusion. I have a solar panel that is hard wired through the charge controller and battery pack and then soft wired through the inverter and then via a thick lead through a 15a. panel breaker and then distributed through the wall outlets. I also have an unused breaker in that same box and would like to create a transfer switch so I could disconnect the solar power source and switch to gen-power. In other words one breaker would be connected to incoming solar power and the other breaker to the generator.
Without gong into great detail at this time is this a doable idea? As I said I'll open another thread on the subject soon.
Thanks for your help.
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MtnDon
Member
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# Posted: 31 Jan 2011 11:06pm - Edited by: MtnDon
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I made some edits here...
In any home/cabin 120 VAC electrical system there are three conductors; hot black, neutral white and green/bare ground. (I'm not going to address 240 VAC, simple off grid cabins normally do not have 240 VAC) We all know that. The system has what is known as a "bond". The bond is between the neutral and the ground. This connection should only occur once in the system. The usual place is in the main breaker panel. The bond connection is normally made with a green screw that connects the neutral block to the ground. This bond is onlky supposed to be made at one place in the system.
A generator that has a receptacle panel may have a bond between the generator neutral and the generator chassis ground. Not all generators will have such a bond. Check the manual or call the manufacturer If a ground rod is used with a generator there is no harm done. In the aforementioned scenario it's not needed, but won't hurt anything.
However, when connecting a generator to a properly wired (bonded) electrical system there may be a problem if there are two bonds. IF there is a transfer switch involved there are other things to be concerned about as well.
For now let's assume there is no transfer switch, that the generator is connected to the cabin system with a three wire cord, via plugs or hard wired.
There should only be a system neutral-ground bond at one place. Strange loops can be formed with more than one bond. This can cause issues with some GFCI, some generators and inverters, etc. To prevent that sort of thing the system must have only one bond.
It can be kind of confusing but the main thing is to only have one neutral-ground bond in the entire system.
Inverters that come with a panel mounted receptacle may also have a neutral-ground bond inside them from the factory. Again I said may, not will. Again check the user manual or check with the manufacturer.
I have read that any generator or inverter over 5KW must have bonds, but those smaller don't have to. But I have a small inverter that was bonded internally. Or I should say I had; it blew up when connected to a bonded cabin system.
Inverters like the high end units by Outback do not have an internal bond as they are not equipped with receptacles. They are meant to be hard wired to a service panel, with bond at the panel.
If the generator ground is connected to the cabin system ground, via the green/bare wire in the wiring, there is no real need to ground the generator frame to the earth.
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MtnDon
Member
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# Posted: 31 Jan 2011 11:08pm
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bobrock, when you open your thread list the equipment brand/model.
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bobrok
Member
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# Posted: 31 Jan 2011 11:27pm
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Thank you, MtnDon, will do.
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Rob_O
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# Posted: 31 Jan 2011 11:56pm
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Quoting: bobrok I also have an unused breaker in that same box and would like to create a transfer switch so I could disconnect the solar power source and switch to gen-power. In other words one breaker would be connected to incoming solar power and the other breaker to the generator.
While this will work, I don't think it's a good idea. Not sure exactly what would happen if you had line and inverter power engaged at the same time, but I can't see it being good for your equipment.
For the few bucks it costs, something like this Iota automatic transfer switch can be cheap insurance against human error
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Rob_O
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# Posted: 1 Feb 2011 12:12am
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You can also buy an electronic 3-way transfer switch that will seamlessly switch between line, generator and inverter power. A guy on another forum built a really cool home UPS with generator backup using one, I'm considering doing the same thing on a trailer so I can use it for power @ the cabin and have backup power @ the house
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MtnDon
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# Posted: 1 Feb 2011 12:57am
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I use one of those Iota transfer switches in our RV. The nice thing about using it is that when the generator is fired up, the ATS automatically switches. There's a delay that can be selected to allow the generator a little warm up time. And then when the generator is shut down it automatically switches back. I don't even notice a flicker. And it is a good price. And foolproof; no chance of operator error.
It's not NEC approved so if inspections are going to happen it won't pass. But there are lots of them in RV's.
Iota also makes a 50 amp unit I believe.
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dk1393
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# Posted: 1 Feb 2011 12:30pm - Edited by: dk1393
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I use a panel like this reliant to switch between my solar and generator. this switch feeds my breaker panel
http://www.amazon.com/Reliance-TCA1006D-Generator-15000-Watt-Generators/dp/B000HRWGPS /ref=sr_1_3?s=hi&ie=UTF8&qid=1296581452&sr=1-3
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MtnDon
Member
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# Posted: 1 Feb 2011 01:47pm
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I made some edits in the 31 Jan 2011 23:0 post
Small inverters and small generators can be tricky when it comes to the neutral-ground bond question.
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MtnDon
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# Posted: 1 Feb 2011 02:26pm
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Any transfer switch must switch both the hot and neutral wires in the 120 VAC circuit at the same time. The neutrals from one source and a second source should never be mixed. That would be an issue with the idea of using breakers to manually switch.
The Iota transfer switch switches both hot and neutral with the relay. Any proper transfer switch should do the same.
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Rob_O
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# Posted: 1 Feb 2011 06:28pm
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Quoting: MtnDon The Iota transfer switch switches both hot and neutral with the relay. Any proper transfer switch should do the same.
"Should" being the key word. I was installing a 15A furnace transfer switch, popped off the cover and found out it only switched the hot line. I don't use those anymore
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MtnDon
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# Posted: 1 Feb 2011 07:31pm
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That's why I used the should word. The Iota switches do; I have had their tech folks confirm that it did indeed use a double pole switch/relay. It appeared to have a DP setup but I had them confirm it via email.
BTW, I have found them very quick to answer any of my questions via email. Very good folks to deal with.
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bullelk
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# Posted: 2 Feb 2011 05:21pm
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Thanks for the information! I an going to put in two ground rods and ground at the panel...
I am still looking for an RV 120 (three pronged) recessed Receptacle that I can place on the side of the cabin to plug the gen into... does anyone know a good web site that I can look for this?
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MtnDon
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# Posted: 2 Feb 2011 05:53pm - Edited by: MtnDon
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I made one. I got a three prong, curved blade, locking type plug from Lowe's. I took a plastic box, drilled a hole that the plug just git inti and epoxied in in place. The lid closes when the ext cord is not plugged in..
I used a Cooper Model #: L630P-L (that's the male plug) I think that was the same as what plugged into my generator.
It was a lot cheaper making one. Not code approved but nobody was looking.
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bullelk
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# Posted: 3 Feb 2011 02:12pm
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OK, got my grounding rods! And now to decide if I should ground the gen or the panel? I don't want to have two bonds...Here is what my gen manual says:
GROUNDING REQUIREMENTS (Portable and Vehicle-mounted Generators)
Under the following conditions, OSHA directs that the frame of a portable generator need not be grounded
(connected to earth) and that the frame may serve as the ground (in place of the earth):
• The generator supplies only equipment mounted on the generator and/or cord- and plug-connected equipment
through receptacles mounted on the generator.
• The noncurrent-carrying metal parts of equipment (such as the fuel tank, the internal combustion engine, and
the generator's housing) are bonded to the generator frame, and the equipment grounding conductor terminals
are bonded to the generator frame.
Thus, rather than connect to a grounding electrode system, such as a driven ground rod, the generator's frame
replaces the grounding electrode.
If these conditions do not exist, then a grounding electrode, such as a ground rod, is required.
If the portable generator is providing electric power to a structure by connection via a transfer switch to a
structure (home, office, shop, trailer, or similar) it must be connected to a grounding electrode system, such as a
driven ground rod. The transfer switch must be approved for the use and installed in accordance with the manufacturer's
installation instructions by a qualified electrician.
BONDING VERSUS GROUNDING
Bonding and grounding are separate requirements for generators and other electrical distribution systems.
Grounding means the connection, or the establishment of a connection, of an electric circuit or equipment to
reference ground, which includes the generator's frame. Bonding is the intentional connection between the
grounded circuit conductor (neutral) and the grounding means for the generator, which includes the generator's
frame. Thus, effective bonding of the neutral conductor to the generator's frame is also a concern for the
safe use of the equipment. As with grounding terminal connections, proper bonding of the neutral terminal of
a power receptacle may be confirmed via testing by a competent electrician with the correct equipment, and the
ohmic resistance should measure near zero and must not be intermittent, which indicates a loose connection.
So after reading this, it sounds like my gen is bonded, right?
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MtnDon
Member
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# Posted: 3 Feb 2011 02:48pm - Edited by: MtnDon
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Right, you don't want to be incorrectly bonded.
The first part of that is lifted right from the OSHA regulation. There's nothing specific to your generator nor mine. The second section is also generic, a description of bonding vs grounding. Nothing really specific to any one generator.
If the manual does not clearly state that there is or is not a neutral - ground internal bond, the best sure way to tell is to inspect the wiring schematic. The schematic on mine made it clear there is no bond in the generator. But nowhere else was it stated. I don't know why the makers all can't clearly mark the machine. I have seen a generator that noted right on the panel that the generator was fitted with a bond and had simple instructions how to break the bond when it was necessary. I forget the make.
It's frustrating. Does your manual have a schematic? If not maybe a 'google' will find one.
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bullelk
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# Posted: 4 Feb 2011 01:26am
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Ha, no doubt it is frustrating!!!
Here is a link to the schematic:
URL
What do ya think?
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Rob_O
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# Posted: 4 Feb 2011 01:44am
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The wiring diagram you posted shows the ground is connected only to the ground lug on your generator. Bond/Ground the panel in your cabin and use a 3-wire cord and everything should play well together
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MtnDon
Member
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# Posted: 4 Feb 2011 10:59am
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What Rob_O said.
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bullelk
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# Posted: 4 Feb 2011 01:39pm
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Thanks! You guys have been a huge help...I will let you know how it goes!
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