Proper grounding for generator as a component of off grid solar / house system.

[rtrask]

I am pretty confused about how to ground my whole system. Originally I thought I would drive a grounding rod near solar panels, at the Conex box housing my batteries and charge controller / inverter, and the generator back up. I have come to learn that would be a bad practice that could fry my equipment due to a ground loop circuit . I watched this video by Mike Holt Bonding Video. My current thinking is that I should run a 6 gauge wire from the basement UFER (rebar running through the basement walls).

So what do you all think how should I ground the system as a whole. Should I ground the generator by bonding it to the whole system or treat it as a standalone ?

 

[chucky]

I dont see why you couldnt drive a couple rods for safe measure and use water and a couple things of morton table salt down the holes with the water then the 6 gauge wire to tie all the rods then to the rebar in your footing ! This is what a 35 year IBEW retiree instructed us to do when we couldnt get enough ground to feed a huge plasma cutting table that a friend of mine was wiring for a commercial shop and it worked so i always rememberd it !

 

[rickf]

Interesting video. I know on my generator I have it wired into my panel through a safety interlock and I have it wired with four wires. The two hots, neutral and ground. The ground is tied into the house ground so that is bonding the generator to the house wiring and ground, all above ground as he says. BUT, I also have the ground rod at the generator which is 25 feet from the house and the bonded ground wire is tied into that!! 25 feet from the house ground rod and at the base of tall trees at that! Not good from what he is saying, and what he is saying makes perfect sense.

 

[Icesythe7]

This video is one of the best imo because it uses great animations to show the path the electricity will take and goes over many scenarios.

 

[2Pbfeet]

There is lots of great advice on Mike Holt's forum. In many parts of my life, I have found that when an issue has lots of conflicting solutions, either there are gross misunderstandings, or incomplete, or inadequate solutions, or a poor understanding of the different use cases. I would nominate the whole grounding / bonding area as one them, at least for me, but I am not a professional electrician.

FWIW: Ufer grounds have much better grounding abilities than ground rods, so if you have one, I think setting up your grounding system to use the Ufer ground is superior- did I mention that I am not a professional electrician? I can recommend reading Ufer's original report(s), if you are curious.

Personally, I think that the NEC does an OK job for grounding/bonding of single family dwellings, but I think it does have some inconsistencies that are apparent on closer inspection. E.g. multiple grounds. 120/240 transformers generate the neutral by a center tap in the transformer, which is grounded at the transformer pad or pole. Every home is required to bond the neutral and the ground wires at a single point in the first service panel. So there are two ground to neutral connections, and the potential (pun intended) for ground loops. This is not only permitted, but required. If there are multiple homes on one transformer, then there are even more ground neutral connections. Yet a home with an out building that has a subpanel is supposedly required not to bond the ground at the subpanel. I have lived through how ugly things get when the transformer or home neutral, or both, aren't adequately grounded.

My takeaway is that if you follow the NEC, it will be hard for anyone to argue later if there is an issue. For me that feels uncomfortably close to "just following orders", but the insurance companies and courts would probably require anyone to prove that their deviation is/was "better", which is not going to be an easy bar to clear.

All the best,

2Pbfeet

 

[Guyfang]

If you are going to run your house on the gen set, then do not forget to remove the ground bonding link on the gen set. There are only about a million threads on this subject. You will not live long enough to read them all.

 

[rickf]

If you are going to run your house on the gen set, then do not forget to remove the ground bonding link on the gen set. There are only about a million threads on this subject. You will not live long enough to read them all.

So you are saying do not bond everything above ground and ground o earth at one point but instead ground at the house AND the generator and create a ground loop? I know there are a million threads pertaining to this but how many of those threads are referencing the bad codes? Not one of the 7 auxiliary generators for the college I worked at was grounded to earth. And I have never seen a professionally installed home genset grounded at the genset.

 

[Icesythe7]

So you are saying do not bond everything above ground and ground o earth at one point but instead ground at the house AND the generator and create a ground loop? I know there are a million threads pertaining to this but how many of those threads are referencing the bad codes? Not one of the 7 auxiliary generators for the college I worked at was grounded to earth. And I have never seen a professionally installed home genset grounded at the genset.

Did you quote the right person? He is saying to make sure that the genset running the home is not neutral and ground bonded and instead is a floating neutral as when you connect to your bonded and grounded main service disconnect/main inlet that will provide the path for all short circuits and ground faults, leaving the genset bonded would have a double bond.

 

[Guyfang]

Did you quote the right person? He is saying to make sure that the genset running the home is not neutral and ground bonded and instead is a floating neutral as when you connect to your bonded and grounded main service disconnect/main inlet that will provide the path for all short circuits and ground faults, leaving the genset bonded would have a double bond.

Correct. Still ground the gen set. When powering the house, the gen set gets its ground from the house. SOOOOOOOO, what happens if the house is not being powered up? No ground. I will tell people to get a pro to hook up your house. Back feeding and such shade tree stuff can kill you. Get a pro, or darn sure know what you are doing. Thats my 5 cents worth.

 

[rickf]

Correct. Still ground the gen set. When powering the house, the gen set gets its ground from the house. SOOOOOOOO, what happens if the house is not being powered up? No ground. I will tell people to get a pro to hook up your house. Back feeding and such shade tree stuff can kill you. Get a pro, or darn sure know what you are doing. Thats my 5 cents worth.

Ok, So Guy, You are saying to ground the genset only and hook up the three wires to the house but do not bond the house ground to the genset? This way when the genset is running but not connected to the house it is safe but when it is hooked to the house the neutral is the floating ground? That makes sense.

And Icesythe7, I am not a pro electrician but I did spend 12 years as a building maintenance tech so I have a pretty good knowledge of electrical design. I am also very anal about reading directions and codes so I have followed this forum for years and I have followed the directions. Note the lockout switch on the panel. No I am not backfeeding my welder plug! BUT, Did you people actually watch that whole video? And did you pay attention to what was said about real life compared to the obviously conflicting codes in the NEC book? Now, That video was in 2015 I think, I do not know if the codebooks have been changed but I doubt it. I will call a buddy of mine who just retired from PSE&G after 35 years. Pretty sure he will know the proper answers.

 

[Icesythe7]

Ok, So Guy, You are saying to ground the genset only and hook up the three wires to the house but do not bond the house ground to the genset? This way when the genset is running but not connected to the house it is safe but when it is hooked to the house the neutral is the floating ground? That makes sense.

And Icesythe7, I am not a pro electrician but I did spend 12 years as a building maintenance tech so I have a pretty good knowledge of electrical design. I am also very anal about reading directions and codes so I have followed this forum for years and I have followed the directions. Note the lockout switch on the panel. No I am not backfeeding my welder plug! BUT, Did you people actually watch that whole video? And did you pay attention to what was said about real life compared to the obviously conflicting codes in the NEC book? Now, That video was in 2015 I think, I do not know if the codebooks have been changed but I doubt it. I will call a buddy of mine who just retired from PSE&G after 35 years. Pretty sure he will know the proper answers.

I didn't watch the first video I try to watch recent ones like the one I linked, and genset running by itself (not connected to the house) with just extension coords for example the gen set should NOT be grounded but SHOULD be bonded, running a genset grounded while say using an extension cord if you was to have a ground that would in this scenario actually increase the risk of shock. Another scenario is if you are say using the genset at a cabin in the woods that does not have a ground system then the generator should be grounded and bonded, and lastly if connected to the house that is bonded and grounded the genset should NOT be ground and NOT bonded.

The entire goal at the end of the day is for the electricity to
1: Have a path back to the source, if there is no path back to the source in all circumstance (ground fault, short circuit, normal operation) then breakers will not trip and it is not safe
2: Ensure that there is only ONE path back to the source so that you can know exactly where the electric goes, if you have multiple paths to the source you may energize other components in the system in the event of a fault before reaching the source to clear the fault (trip the breaker)

The video I linked above uses animations and many scenarios to show the path the electric will take it is pretty decent, the bonding ordeal that comes up here often sounds complicated but it is actually extremely simple if you sit down and draw out the schematic of the circuit, simply ensure that the electric in any scenario has 1 path back to the source...easy

(Using a loop explanation I'm well aware AC is push and pull movement but for explanation)

Figure I should explain scenario 2 from above better, if you want to say run a torpedo heater off the convenience port of the genset and you ground the genset but it is not bonded in the event the black wire breaks off and you energize the torpedo heater itself, well no problem the electric goes out on black cant come back on neutral because it broke off and is laying on the frame of the heater so now it is coming back on the ground, but still has no path to the source only the ground so now you just have an electrified torpedo heater, but now you touch the torpedo heater you more than likely would not get shocked because there is no completed circuit back to the source.

Now if you ground AND bond the genset in this scenario and the same happens you now increase your risk of shock because when you touch the torpedo heater you become part of the circuit until the breaker trips, in this instance the power leaves on black comes back on green but is bonded at the genset to white so it will trip the breaker but not before briefly energizing the ground as well, so if you happen to be touching the genset and within x feet of the grounding rod you are part of the circuit and will get shocked

Now if only having the genset bonded but not grounded the electric leaves the black comes back on green is bonded to white at the genset and trips the breaker but you will not get shocked as there is no connection to ground(earth) so you can not complete the circuit, this is obviously the safest and why MOST portable gensets come bonded from the factory.

 

[rickf]

Interesting, I am going to have to go back over the threads covering this in the past but I am pretty sure you are going against what they are saying about grounding the generator. You are definitely going against what the manual says to do. And if I am interpreting what Guy said you are going against what he is saying also. I am not saying anyone here is right or wrong, I go by real world physical science which was used by Mike Holt and his associates. What I am hearing here on the forum is very contradictory and confusing. And basically if I had a pro come out and do the job then no matter how he did it it would be wrong according to someone's ideas on here. Again, very confusing. Who do you believe? The manual? Or choose one opinion over another? Do you see where I am coming from? If my 002 does not start for some reason I will use my 7500 watt gasoline generator, it has no provision for a ground rod. The instructions for it do not mention a ground. And when you think of it what about a mobile service truck? No separate ground there, just the extension cords going to whatever you are doing, including powering houses on more than one occasion. I am going to have to do some research on this one.

 

[Icesythe7]

Interesting, I am going to have to go back over the threads covering this in the past but I am pretty sure you are going against what they are saying about grounding the generator. You are definitely going against what the manual says to do. And if I am interpreting what Guy said you are going against what he is saying also. I am not saying anyone here is right or wrong, I go by real world physical science which was used by Mike Holt and his associates. What I am hearing here on the forum is very contradictory and confusing. And basically if I had a pro come out and do the job then no matter how he did it it would be wrong according to someone's ideas on here. Again, very confusing. Who do you believe? The manual? Or choose one opinion over another? Do you see where I am coming from? If my 002 does not start for some reason I will use my 7500 watt gasoline generator, it has no provision for a ground rod. The instructions for it do not mention a ground. And when you think of it what about a mobile service truck? No separate ground there, just the extension cords going to whatever you are doing, including powering houses on more than one occasion. I am going to have to do some research on this one.

Of course consult a professional and also read up on the current NEC codes according to NEC 250.53 the only time you should have more than 1 grounding rod is if the ohms on the main grounding rod is 26 or more

(2) Supplemental Electrode Required
A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(. The supplemental electrode shall be permitted to be bonded to one of the following:

1. Rod, pipe, or plate electrode
2. Grounding electrode conductor
3. Grounded service-entrance conductor
4. Nonflexible grounded service raceway
5. Any grounded service enclosure

Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.

furthermore section 250.34 states that the frame of the generator itself will server as the earth ground in situations u mentioned such as mounted to a truck etc

Section 250.34(C) Grounded Conductor Bonding
When the generator–portable, trailer- or vehicle-mounted–is a component of a separately derived system and contains a conductor to be grounded, this conductor must be bonded to the generator frame, providing a ground-fault current path to return to the generator.

Notice this says it must be grounded to the generator frame and NOT the earth

Again when using the generator and just using extension cords etc the generator MUST be BONDED but not earth grounded as common sense and the NEC will tell you this can briefly energize the ground around you allowing humans to complete the circuit i will post again

NEC 250.34 Generators- Portable and Vehicle Mounted (A) Portable Generators.
The frame of a portable generator is not required to be grounded to earth if:
(1)The generator only supplies equipment or cord and plug – connected equipment through receptacles mounted on the generator, or both and
(2) The metal parts of the generator and the grounding terminals of the receptacles are bonded to the generator frame.
(B) Vehicle - Mounted Generators. The frame of the generator is not required to be grounded to earth if:
(1) The generator frame is bonded to the vehicle frame.
(2) The metal parts of the generator and the grounding terminals of the receptacles are bonded to the frame.

When supplying a structure (house, barn, shop, etc) the generator should only be grounded to earth IF it is the first service disconnect (your powering a cabin in the woods by the generator only no other power options) in this case the generator should be earth grounded and neutral bonded.

When supplying power by backfeeding a disconnect (like a house that is on the grid etc) the first service disconnect "SHOULD" (always double check) already be earth grounded and bonded thus the generator should not be earth grounded and should have a floating neutral.

 

[G744]

A ground is just a ground, most systems I've seen/built for broadcast facilities have a lot of grounds to earth and metal electrical conduits/enclosures.

These have continuous copper connection between them, with a single point of bonding to neutral at the master disconnect.

Where else can one find a bunch of electronics gear (including many computers) connected to a 300' lightning rod, aka a tower or two.

Our main residence property has a 277/480V 200A 3PH service, where the NEC bond to neutral exists. The ground conductor starts there with an 8' rod, connected to a hefty surge supressor system, on to the 60kW genset automatic transfer box, then the 480 load center, the 45kVA distribution transformer (120-20, the 208 load center, then underground to the various structures on the property.

Each building has a ground rod tied to the grounding conductor, including the well casing.

In every case, the neutral conductor is not tied to ground anywhere, other than that in the main disconnect.

One really can't have too many grounds in terms of safety. If there is a difference in the real ground potentials, that is an indication a better connecting method is called for.

DG

 

[87cr250r]

Grounding is intended to provide a low impedance path for fault current to cause a magnetic trip of a circuit breaker.

That means your ground bus bar, wherever it is needs to connect to the neutral. At ONE point only. That is all.

Grounding is that one point where the ground bus bar and neutral are connected. Everything else gets bonded. Bonding ties the enclosures together so that they're at the same potential as the neutral which is connected to ground at one point.

 

[Valor]

I'm more confused as ever now.

 

[rickf]

I'm more confused as ever now.

Exactly, Each post seems to contradict the previous one.

 

[Icesythe7]

Exactly, Each post seems to contradict the previous one.

Stop going off posts and instead only follow the ones that show the latest nec codes to backup their claims, or as mentioned countless times hire a licensed electrician.

 

[glcaines]

I have an MEP003A connected to a Square D 400 Amp, 4-pole manual transfer switch. I have 400 amp service to my house. I am not switching the neutral so I'm utilizing the neutral / ground bonding from EMC and I do not have a ground rod installed. The neutral and ground on my trailer-mounted genset are not bonded. I ran cable from the genset through a 400 amp pin and sleeve receptacle and then about 200 feet underground to the transfer switch through conduit buried about 18 inches. I relied on information on this site from Guyfang and others on SS, which agreed 100% with the information from Blue Ridge Mountain EMC, that also permitted me to make all of the re-wiring and installation of the transfer switch and then inspected my work after I completed the work. The county building inspector also inspected my work along with the EMC personnel. EMC was very happy that I was installing a transfer switch. I did not use an electrician for the wiring, but again, the work was inspected by 5 people from EMC and the building inspector. I have never had any problems and my genset gets a regular workout due to numerous power outages. I'm on 40 acres surrounded by national forest way off the main highway.