generator ground

gww1 · January 2015

Though I have read the recent post on generator grounding, I am dence and decided to just ask a simple question that I do understand.

I have a devilbiss 5000 watt generator. If I wanted to hook it to my outback inverter with a manual transfer switch could I get my ground by running a wire from the frame of the generator to my house ground?

Thank you
gww

Ethan Brush · January 2015

Re: generator ground

gww1 wrote: »

Though I have read the recent post on generator grounding, I am dence and decided to just ask a simple question that I do understand.

I have a devilbiss 5000 watt generator. If I wanted to hook it to my outback inverter with a manual transfer switch could I get my ground by running a wire from the frame of the generator to my house ground?

Thank you
gww

So you have a battery inverter that feeds a breaker panel, and you want to put a transfer switch between the inverter and the panel? Is there a neutral to ground bond and if so is it at the panel or the inverter? Do you know if there is a neutral ground bond at the generator? Finally, do you intend to switch the neutral with the transfer or not? Sorry to ask so many questions....

gww1 · January 2015

Re: generator ground

I will do my best. My inverters are fed ac from a breaker box in my garage threw a 50 amp breaker. I have two inverters. They are on a mounting plate with an ac breaker box on the left and a dc breaker box on the right. The ac breaker box has a transfer switch that allows the grid ac to bypass the loads or go through the inverters. The ground to the inverter is from the ac breaker box that is in the garage to the ac breaker box on the inverter. I have ran a 50 amp fuse (240 volt) from the breaker box on the inverter to a critical load breaker box in my house.

My ideal is for a manual transfer from the garage breaker box so that the inverter breaker box would be getting power from either the grid or the generator. I believe that there is a nuetral ground bond in the garage breaker box and also the inverter input breaker box but I only ran a nuetral from the inverter to the house critical load breaker box. I looked at a link on another generator ground thread and it looked to be that most devilbiss generators where floteing ground "whatever that means" but not all. I can't remember if it was the devilbiss or craftsmen that had a place to hook a ground rod to the frame but one of them did.

As far as transfering the neutral or not, I have know ideal, If I hooked the generator frame to the house ground I wouldn't need any of that would I?

Thanks
gww

Ethan Brush · January 2015

Re: generator ground

gww1 wrote: »

I will do my best. My inverters are fed ac from a breaker box in my garage threw a 50 amp breaker. I have two inverters. They are on a mounting plate with an ac breaker box on the left and a dc breaker box on the right. The ac breaker box has a transfer switch that allows the grid ac to bypass the loads or go through the inverters. The ground to the inverter is from the ac breaker box that is in the garage to the ac breaker box on the inverter. I have ran a 50 amp fuse (240 volt) from the breaker box on the inverter to a critical load breaker box in my house.

My ideal is for a manual transfer from the garage breaker box so that the inverter breaker box would be getting power from either the grid or the generator. I believe that there is a nuetral ground bond in the garage breaker box and also the inverter input breaker box but I only ran a nuetral from the inverter to the house critical load breaker box. I looked at a link on another generator ground thread and it looked to be that most devilbiss generators where floteing ground "whatever that means" but not all. I can't remember if it was the devilbiss or craftsmen that had a place to hook a ground rod to the frame but one of them did.

As far as transfering the neutral or not, I have know ideal, If I hooked the generator frame to the house ground I wouldn't need any of that would I?

Thanks
gww

Oh so you are grid tied? For some reason I originally thought this was off grid. So this is a grid tied with battery backup? Sorry, Im still a little lost. Can you expand on this statement?

The ac breaker box has a transfer switch that allows the grid ac to bypass the loads or go through the inverters

here is the deal with generators connected to a "normal" utility supplied premise. The thing that determines how generator grounding is done is whether or not the generator is a separately derived system or not. Basically, if the transfer switch DOES NOT switch the utility neutral, than it is NOT a separately derived system, and this means you would have a separate neutral and ground at the generator, no generator ground rod, and a neutral and feeder with a neutral and ground between the panel and the generator. IF the transfer switch switches the utility neutral then it is an SDS and neutral and ground are bonded at the generator, no EGC is run with the feeder, and the generator needs a grounding electrode. Note that often consumer generators that have the bond are used without switching the neutral, but I see very little concern for this even though it is a code violation. The issue is then you have a parallel path for neutral current on the EGC, but the EGC is often insulated in a rubber cord and unlikely to be of any issue.

gww1 · January 2015

Re: generator ground

E......

The ac breaker box has a transfer switch that allows the grid ac to bypass the loads or go through the inverters

I have and outback set up and the ac breaker box has basically a transfer switch so that the inverter can be removed and worked on with out losing power to your loads.

here is the deal with generators connected to a "normal" utility supplied premise. The thing that determines how generator grounding is done is whether or not the generator is a separately derived system or not. Basically, if the transfer switch DOES NOT switch the utility neutral, than it is NOT a separately derived system, and this means you would have a separate neutral and ground at the generator, no generator ground rod, and a neutral and feeder with a neutral and ground between the panel and the generator. IF the transfer switch switches the utility neutral then it is an SDS and neutral and ground are bonded at the generator, no EGC is run with the feeder, and the generator needs a grounding electrode. Note that often consumer generators that have the bond are used without switching the neutral, but I see very little concern for this even though it is a code violation. The issue is then you have a parallel path for neutral current on the EGC, but the EGC is often insulated in a rubber cord and unlikely to be of any issue.

I am not sure exactly what you are talking about. I have read this alot and always end up confused when talking ground. I also ask more for an do a,b then c question as I know my limmitations. It sounds like you are saying that just running a plug from the generator to the transfer switch may not be code but would cause no real problim. I could have this wrong. It would not be your fault if I did but mine. I wired my whole system, grounded my panels but know there are issues that I don't understand when dealling with generators. I ran an rv ac with the craftsmen generatorn and never worried about grounding the generator. I read this is wrong the other day. I don't worry so much about code but don't really want anyone to get hurt.
Thanks for your help
gww

Ethan Brush · January 2015

Re: generator ground

Ok, lets see where to go from here.......I guess I still am not understanding what is going on. Are these grid tie inverters or stand alone inverters? IS there a DC system other than the batteries?

Well you cant go too wrong if you do the following:
1) run a separate equipment ground to the generator. I assume you will be running something like a 10-4 SO rubber cord and plugging it in to a L14-20 or L14-30 recep on the generator right?
2) bond the EGC going to the generator to the other system(s) EGC bars and the grounding electrode system
3) make sure the transfer switch doesnt interrupt continuity between the items mentioned in #2
4) the generator EGC should be bonded to the generator neutral through the main bonding jumper in you system somewhere (This should already be done). Imagine a fault at the generator to the generator frame. The fault is supposed to get back to its source (the generator windings) by traveling through the generator EGC, through the premise main bonding jumper, to the generator neutral, and back to the generator. I know it sounds a little convoluted but that is the way it is supposed to be set up.

Hope that helps and isnt just more confusing. I think if you "walk through" those 4 items you can figure it out.

gww1 · January 2015

Re: generator ground

Ethan

I will study your post. Here is what I ran power from the garage to and then ran from it for critical loads. ac is on left dc is on right.

http://www.mavericksolar.net/outback/inverters/my_ps2_gvfx3524_s.jpg

That is what I started with but with two inverters. Just to clarify what I am talking about.

I am going to have to study your post for understanding.

I put this on my favorites to try and figure this out but am not sure it is the same devilbiss generator cause they made more then one 5000 watt one I think.

http://members.rennlist.org/warren/gt5000c.html

I don't expect you to have to look at the links unless you are just bored.

Your post may cover it after I read it five times and rap my slow brain around it.
Thank you for your time.
gww

PS to answer your questions, It is a gridtie inverter that I run as off grid except once in a while to use the grid to charge it. I only run ac loads through the inverter.

gww1 · January 2015

Re: generator ground

1) run a separate equipment ground to the generator. I assume you will be running something like a 10-4 SO rubber cord and plugging it in to a L14-20 or L14-30 recep on the generator right?

I haven't got a cord yet but will probly hard wire the breaker portion.
gww

PS I am not sure what EGC is.

gww1 · January 2015

Re: generator ground

See if I got part of it.

The generator neutral is probly already bonded to the frame. "frame to windings"

The transfer switch that I use or make, should have the neutrals to both breakers wired to the main neutral buss so that no matter which breaker is ingaged it will be bonded. A green and white wire to the buss or just a white like goes to my critical load panel?

Will the cord I buy be grounded from the plug on the generator?

Is any of this close or am I missing the boat.
gww

Ethan Brush · January 2015

Re: generator ground

I agree with the link you posted. I greatly prefer generators operating as ungrounded systems ("neutral floating") when used In a portable manner. I was using an electric jackhammer down in my well, and I definitely didnt want the electric supply to have any association with ground - remember current travels back to its source not to ground. If the system is ungrounded, than it has no relationship to the earth.

Anyway,

Will the cord I buy be grounded from the plug on the generator?

yes get a 4 conductor cord and you will have two hots, a neutral, and a ground

PS I am not sure what EGC is.

equipment grounding conductor, AKA ground wire

The generator neutral is probly already bonded to the frame. "frame to windings"

Then technically you either have to remove that bond, or switch the neutral in the transfer switch. I would try to remove that bond. If you cant do that, dont worry about it as it would be extraordinarily unlikely to have a safety issue. Consumer generators are a pain as they are often technically not compatible with the transfer systems commonly used. Also, I dont really follow the logic in the NEC as it relates to generators and when they are or are not considered separately derived systems as the location of the connection to the grounding electrode system is not considered......Anyway, sorry to get off topic...

gww1 · January 2015

Re: generator ground

Ethan

Then technically you either have to remove that bond, or switch the neutral in the transfer switch. I would try to remove that bond. If you cant do that, dont worry about it as it would be extraordinarily unlikely to have a safety issue. Consumer generators are a pain as they are often technically not compatible with the transfer systems commonly used. Also, I dont really follow the logic in the NEC as it relates to generators and when they are or are not considered separately derived systems as the location of the connection to the grounding electrode system is not considered......Anyway, sorry to get off topic...

I had studied the post I linked to but was still abit confused by it.. I am not sure if I have a 3 prong or 4 prong plug on the generator or not. I can't remember sitting here.

I looked up a chart that some one posted on this site and it looked like the devilbiss generator had a floting ground but I was not sure exactly what that ment and out of the 3 5000 watt devilbiss listed, one was not floting ground. I would probly never use it but I would still like to hook it up and see if it would work in my system.

So lets see if I got it strait. If I just buy the plug and didn't worry about code it would probly work with out issue just wiring from the plug to the transfer switch and nothing else?

If it is a floting ground, does floting ground mean it is not grounded at all or that if you attach a ground rod to the frame it is grounded to the wiring?

If I want to do it correctly I need to take the plug cover off and trace the wire and if one of the wires goes to the frame, I need to snip it from the frame and connect The plug to the house?

If I use the generator anywhere else I need to reconnect what I had snipped?

In any case it will probly work with just building a cord to a plug that is made for the generator with out snipping anything?

I believe it is a floting ground.

I know you have answered and re-answered This basic question and am sorry if I keep repeating my question but when I type what I think you said back to you I have a better chance if I am still screwed up of finding it. Sorry

Did I get it right on the "Will be ok with just a plug that is made for the generator?"

Thank you
gww

Ps as long as I don't kill anyone, I live in the country and a county that has no inspections or building permits and no one will care.
I have only used it twice even though it is pretty old and when I welded with it I just made a plug to the lincoln ark welder and used it, I didn't even know then that grounding was an issue.

oil pan 4 · January 2015

Re: generator ground

If its a 240 volt generator, has any 4 prong plug plug with two lines, a neutral and ground. The neutral and ground are bonded inside the generator.
Check resistance from the neutral to the ground on the generator receptacle, you will have very low resistance if neutral and ground are bonded.

gww1 · January 2015

Re: generator ground

Oilpan
By checking resistance, you mean an ohms meter at the 2ook setting or lowest ohm setting? If I find resistance I need to dig in and remove the ground bond before hooking to my house? Am I getting the above correct?
Thank you
gww

Ps the generator has two 120 volt plugs and two 240 volt plugs on it.

gww1 · January 2015

Re: generator ground

The generator has a 3 hole 240 plug, the re-set/fuse is 20 amp.
gww

gww1 · January 2015

Re: generator ground

From the web site I linked to earlier;

DeVilbiss GT5000, GT5250
My former generator, a DeVilbiss GT5000 was supplied with a duplex outlet for 240VAC. The three wire connection with bonded neutral and ground was not suitable for my transfer panel. It was rewired to use a four conductor twistlock outlet, type NEMA L14-30 30A 125/250VAC. The outlet shown in the picture was later replaced with a L14-20 20A outlet. As a backup power supply for my home, I required the neutral line to be isolated from ground.

There are two output coils in the generator and four wires coming to the output panel.
They are paired as red/green and orange/black. Each coil generates 120VAC.
Orange and green are used as neutral and connect together and attach to the neutral connections on both outlets.
Red and black are used as live lines and both connect directly to the circuit breakers.
From the circuit breaker outputs, connect red to one of the 120VAC outlets and black to the other. Red and black also connect to the live lines on the twistlock plug.
Remove the jumper from ground to neutral, likely on the 120VAC duplex outlet and connect ground connections on both outlets to the chassis.
Note the green wire from the generator coil is not the same as the green wire used for grounding. Be careful not to get the two mixed up!
Make a new label for the electrical panel stating FLOATING NEUTRAL.

Each output coil creates 120VAC up to 2500 watts maximum, and when operated together supply up to 5000 watts. If required, both output coils can be permanently wired in parallel to provide full 5kW output at 120VAC. 240VAC will not be available in this configuration. Alternately, a switch can be installed to select either normal 120/240VAC operation or full 5kW output at 120VAC only.

I've hand drawn a diagram for both methods. Top of drawing shows twistlock 120/240VAC plug.
Bottom diagram has 4PDT switch to select either 120VAC only or 120/240VAC operation.

On the GT5250, there is a green jumper wire on the duplex wire going from the neutral connection to ground. Remove it for floating neutral.

Here are wiring diagrams for the full DeVillbiss generator lineup, including many Porter Cable models.
DeVilbiss equipment manuals can be found at DeVilbiss manuals/breakdown web site.

If I wanted to hard wire from the generator to my home breaker box;
Is the above saying;
1. Go in the generator and remove the jumper wire from the ground and neutral.

2. Hook the red wire to one breaker of a 240 volt dual breaker.

3. Hook the black wire to the other breaker of the 240 volt dual breaker.

4. Run the orange and green wire to the neutral buss in the transfer switch/breaker box.

5. Run a chassis ground wire to the ground/neutral buss in the transfer switch/breaker box.

This is what it is saying to me, have I got it wrong?
Thanks
gww

gww1 · January 2015

Re: generator ground

Generator manual;

http://www.allpartsinc.com/mmALLPARTS_NEW/Others/GENMAN.pdf

gww

oil pan 4 · January 2015

Re: generator ground

To better explain the difference between floating neutral and bonded is like this.
A bonded neutral means the generator is more or less a copy of the power coming into your house. You have 2 lines, about 120 volts each, neutral and ground are your 0 volt references.
Neutral is a current carrying 0 volt reference, ground is non current carrying 0 volt reference there for safety.

On a floating neutral, none of what I put above applies.
On a floating neutral your neutral is not a 0 volt reference. With a floating neutral genset you don't actually have a line and a neutral, what you really have 2 lines that give you about 60 volts each.
This is why floated neutrals do not have their neutral bonded to ground, if you did bond the N and G then your "ground" would be energized with 50volts too.
There is nothing inherently wrong with floating neutral gensets, its just that the potential to kill some one gets a lot higher if you don't know what you are doing when you try to go beyond plugging extension cords into them to power simple individual devices and start trying to use them to power up a house.

If your generator has an L14-20 or L14-30 then it will have a bonded neutral and ground.

gww1 · January 2015

Re: generator ground

Oil pan
I am pretty sure this is the plug that fits the generator.

http://www.northerntool.com/shop/tools/product_200321985_200321985

5-20p I think
Thanks
gww

gww1 · January 2015

Re: generator ground

Oil pan
Can I take an ohm meter and stick it in the round hole of the plug and touch the other lead to a bare spot on the frame. If the ohm meter keeps reading 1 then neutral is not bonded but if I get some other number it would mean that the neutral is bonded to ground. Is this a correct way to find out?
Thanks
gww

BB. · January 2015

Re: generator ground

That will work. Zero Ohms is a perfect bond. 10 ohms or less is "bonded" for this discussion.

-Bill

gww1 · January 2015

Re: generator ground

Bill
Thank you

My next question is, if it comes out as not bonded or after I disable the bond, I could just run three wire from one of those plugs to the transfer switch and when I hooked the neutral to the transfer switch ground/neutral buss bar the generator electrical circute would then be grounded to the house ground and the frame of the generator would no longer matter. If I decided to use the generator for other uses I could use the same kind of plug with only one wire to the round hole in the plug going to the frame and the generator would again be bonded.

Does this sound correct?
Thanks
gww

Ethan Brush · January 2015

Re: generator ground

gww1 wrote: »

Bill
Thank you

My next question is, if it comes out as not bonded or after I disable the bond, I could just run three wire from one of those plugs to the transfer switch and when I hooked the neutral to the transfer switch ground/neutral buss bar the generator electrical circute would then be grounded to the house ground and the frame of the generator would no longer matter. If I decided to use the generator for other uses I could use the same kind of plug with only one wire to the round hole in the plug going to the frame and the generator would again be bonded.

Does this sound correct?
Thanks
gww

No. Here is why. Remember the main thing we want to accomplish when we are talking equipment grounding is to provide a low impedance (resistance) path back to the source. This will cause a short circuit when a fault happens and trip an OCPD (overcurrent protective device) thus deactivating the circuit and informing you that there is a problem. The actual connection of an equipment metal frame or conduit to earth is of very minor importance and doesnt result in a decreased shock hazard. Yes read that last sentence again if you have to, it is a very very common misconception. Why? Because A) dirt has a very high resistance and thus does not allow enough current to flow through it back to the source to trip a breaker (unless dealing with high voltages i.e > 1000V)

during a fault to earth/dirt, because of the high resistance of dirt, only a very small patch of ground right where the fault is happening will be raised to the same potential as the metal equipment - stand a few feet away and you will be subject to nearly the full voltage of the system. So take your generator frame that has no EGC back to the source and say there is a 120V fault to the frame. The frame is now energized with at best only a few amps flowing from the frame into the ground/dirt so nothing happens until someone notices it because they get a shock. If you had the EGC connected to the generator frame and the other end connected to the ground bus at the electrical service, the fault current would now get back to the generator source windings through the neutral ground bond at the electric service, cause a short circuit, and trip a breaker. So just to reiterate, the fault current goes like this: generator frame -> generator EGC -> main electrical equipment ground bus -> neural bus via neutral ground bond (NEC code word is "main bonding jumper" or "system bonding jumper" -> generator neutral wire -> Back to source=short circuit, breaker trips

gww1 · January 2015

Re: generator ground

Ethan
So what is the purpose of removing the ground in the generator so that you don't have two ground sources Ie house/gen at the same time. If I hook to my house the grounds are already grounded. If I want a ground from the house (which is already bonded with neutral) not the gen then it seems that the only thing left is to run three three wires from the gen plug and one from the generator frame and bond them in the breaker box/transfer switch. Then the frame and neutral are still bonded, just in a differrent fasion/place.

Two to get the bond back if the generator is use away from the house, the second suggestion of bonding from the frame through the neutral position on a plug would seem to replace the bond that I removed if it is not a floting ground generator already.

Here is the equiptment I would like to work with, A two breaker transfer switch and the plugs that fit the generator and wire which I have in abundance up to 8 awg. The house and inverter already bond the neutral to the house ground rod. I would like to ground the gen in the same fassion and have a simple convertion back if I need to use it elsewhere.

So, Will doing it again like I posted on my last post WORK if I add a 4th wire from the generator frame to the ground/neutral buss bar in the transfer switch?

I read everthing on the website I posted again today and the previous hook up I wrote was what I seemed to get out of it. Are you tired of helping me or do you have one more shot at helping in you. Even if I still don't understand why it works, if I can just get it hooked up where it will work and be safe, that will be good enough. I have been through a million big grouding threads and eveytime one comes up they are about the longest threads on the forum which keeps me pretty confused. If I could possibly get a what wire goes where with the equiptment I am using I should be able to get it done.

Thanks
gww

gww1 · January 2015

Re: generator ground

Ethan

You posted this.

So just to reiterate, the fault current goes like this: generator frame -> generator EGC -> main electrical equipment ground bus -> neural bus via neutral ground bond (NEC code word is "main bonding jumper" or "system bonding jumper" -> generator neutral wire -> Back to source=short circuit, breaker trips

I posted this earlier.

If I wanted to hard wire from the generator to my home breaker box;
Is the above saying;
1. Go in the generator and remove the jumper wire from the ground and neutral.

2. Hook the red wire to one breaker of a 240 volt dual breaker.

3. Hook the black wire to the other breaker of the 240 volt dual breaker.

4. Run the orange and green wire to the neutral buss in the transfer switch/breaker box.

5. Run a chassis ground wire to the ground/neutral buss in the transfer switch/breaker box.

This is what it is saying to me, have I got it wrong?
Thanks
gww

I realize that number 4 mentioning the orange and green wire is confussing as that (per the website I posted) are the neutral wires for the two stators in the generator. so change that to white/neutral.

Is your post and and my earlier post saying the same thing?

Thank you
gww

Ethan Brush · January 2015

Re: generator ground

gww1 wrote: »

Ethan
So what is the purpose of removing the ground in the generator so that you don't have two ground sources Ie house/gen at the same time. If I hook to my house the grounds are already grounded. If I want a ground from the house (which is already bonded with neutral) not the gen then it seems that the only thing left is to run three three wires from the gen plug and one from the generator frame and bond them in the breaker box/transfer switch. Then the frame and neutral are still bonded, just in a differrent fasion/place.

IF you were to keep the neutral/ground bond at the generator in addition to the N/G bond at the house, you would have the neutral and ground in the interconnecting cord set operating in parallel meaning neutral current would be flowing on the ground wire. We want the EGC to only carry fault current not normal current. Got it? Police follow the money, electricians follow the current: From generator "hot winding" -> cord set, through transfer switch to house branch circuit -> through light bulb -> through neutral wire back to breaker panel neutral bus-> through N/G bonding jumper -> EGC in generator cord set -> generator frame -> bonding jumper to generator neutral winding -> home.....NO GOOD, we dont want normal current traveling through the equipment grounding conductors, thats why we dont want the bond at the generator. In practice its not that critical in your situation as the EGC will be insulated anyway and the neutral current flowing on the generator frame is very unlikely to cause a shock hazard for several reasons. Note that you are free to add a grounding electrode to the generator frame if you wish, it would be called an axillary electrode per NEC 250.54. I dont see what purpose it would serve however. Dont get confused, the auxiliary electrode would be equipment earthing, the N/G bond we are discussing concerns "system grounding" which involves referencing a system conductor to the same potential of the earth and effects how faults are dealt with. Just forget I even mentioned auxiliary electrode

Two to get the bond back if the generator is use away from the house, the second suggestion of bonding from the frame through the neutral position on a plug would seem to replace the bond that I removed if it is not a floting ground generator already.

You could do that. As I said before, I kinda prefer a generator to be ungrounded (no N/G bond). For the stuff I do, I think its much safer.

Here is the equiptment I would like to work with, A two breaker transfer switch and the plugs that fit the generator and wire which I have in abundance up to 8 awg. The house and inverter already bond the neutral to the house ground rod. I would like to ground the gen in the same fassion and have a simple convertion back if I need to use it elsewhere.

So, Will doing it again like I posted on my last post WORK if I add a 4th wire from the generator frame to the ground/neutral buss bar in the transfer switch?

I think that sounds fine.

Is your post and and my earlier post saying the same thing?

Yeah I think we are on the same page. Just note that your "4th wire"/ground wire/egc will be in the plug and receptacle - you wont have to physically land a ground wire on the generator frame. The ground terminal on the receptacle on the generator is already connected to the generator frame.

Hope this helps and isnt just getting more confusing

gww1 · January 2015

Re: generator ground

Ethan
No, I think I have it, I can't thank you enough for helping walk me through this. Now I have to put it in my favorites so it doesn't get lost till I use it. I also thank everyone else who helped get me here.

I may add to this thread but believe I have the ground portion worked out.
gww

gww1 · January 2015

Re: generator ground

Ok
Round two.

If I went from a service panel that I already have; could be the service to the garage or the ac breaker panel that came with the inverter, and put a new breaker in it and built a immovable plate that insured that only the generator breaker or the main panel breaker was on at a time, I would in effect have a safe ul aproved generator transfer switch.

Am I correct on this?
gww

oil pan 4 · January 2015

Re: generator ground

To avoid running current on your ground you wire the generator through a sub panel where the neutral and ground are separated.
If you wire it to the main panel then you end up hooking the neutral and ground to the same bus bar and the ground carries current.

gww1 wrote: »

Oil pan
Can I take an ohm meter and stick it in the round hole of the plug and touch the other lead to a bare spot on the frame. If the ohm meter keeps reading 1 then neutral is not bonded but if I get some other number it would mean that the neutral is bonded to ground. Is this a correct way to find out?
Thanks
gww

The round slot on a NEMA 5-20 should be grounded and should give you low resistance to the frame.
To find out if the neutral is bonded to the ground with a generator that only has 3 prong receptacles, first make sure the generator is off. Set the meter to read ohms then stick one meter lead in the taller/wider slot or the side ways "T" shaped slot in the receptacle, these are your neutral prong slots on your 5-15 and 5-20 receptacles.
Then take the other lead and touch it to the inside of the round ground prong hole and to the frame. You may have to dig around a little to find the metal conductor inside the round ground prong.
If you have a bonded neutral then the resistance from your neutral receptacle slot to your ground prong hole and frame should be very low.
If your neutral is floated, then you will see very high resistance, in the thousands of ohms between the ground hole and frame to the wide neutral slot.

gww1 · January 2015

Re: generator ground

Oil pan

To avoid running current on your ground you wire the generator through a sub panel where the neutral and ground are separated.
If you wire it to the main panel then you end up hooking the neutral and ground to the same bus bar and the ground carries current.

Did you read post 24 and 25. That is how I want to wire the generator. I want my whole system to use the house ground so that there is no switching of ground and the generator is not a secondary ground point. The house bond is with neutral. I am going to try to change the plug on the generator to a L14-20 four hole so I guess I will be digging further in the generator and tracing wires to get it correct. I see no way around the gen. ground at some point being with the house ground If the house ground is what I am going to use.

As far as the ohm meter. I am going to have to go stick it in some holes and then report back with what I have. Your description almost seems as I need three leads on the ohm meter. One thing that might not be considered is this is 240 volts and not 120 volts so the t hole is probly not neutral. I think the plug is 6-20 not 5-20 but they look the same. I am learning as I go. Thanks for any comments.
gww

gww1 · January 2015

Re: generator ground

I stuck the ohm meter in some holes. I got some pretty erratic readings. I couldn't see as well as I like and my meter probes are pretty short. I scraped a bit of powder coat off the frame for a bare spot. The end reading that I got atleast steady and twice was .03 ohms, so I say the generator is bonded. That was from the round hole to the frame. I got readings from the round hole to the other two holes also.
gww

gww1 · January 2015

Re: generator ground

To hard wire from a 4 prong plug to my breaker box.

1. remove the jumper That bonds neutral to the ground from inside the gen.

2. run the neutral from, each gen. stator, as one wire to the ac breaker panel neutral/ground buss bar.

3. Run the ground as one wire to the ac breaker panel neutral/ground buss bar.

4. Run the two gen stator hot wires independantly to breakers in the ac breaker panel.

5. Make an interlock for the ac breaker panel that makes it impossible for the ac breaker panel grid to provide power at the same time as the gen. breakers do.

This would be the exact way that the inverter ac breaker box on the inverter is set up now.

The gen would get its ground from the garage ac box where the neutral is bonded with ground but the paths from the generator to there would be independant.

If I put a sub breaker box prior to this it would have no ground untill it reached the garage anyway, so in the end seems to be the same thing.
Thanks
gww

generator ground

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