Here is a question for someone who knows the code.
I will be installing a generator aboout 60 feet from my home. Could someone tell me what code requires for grounding it?
Do I put in a grounding rod/rods at the generator site or run its ground wire to the panel in the house? (It seems that the former could cause a ground loop and the latter would allow for some potential (voltage) between the generator and the adjacent earth.)
Thanks.
I BEL:IEVE you do ground rods at the generator bonded to a nice heavy line connected to the panel so ground loops cant occur.
this is kinda a leftover of my dish install days where bonding all grounds was AAA+++ IMPORTANT
The generator should have a grounding point specified. This should be attached to an 8 foot grounding rod. The ground connection on the output plug should be connected to the ground at the electrical panel in the house.
---MIKE---
What are you using it for, to power your house (through a transfer switch of course) or independent devices? Is it bonded or not? Can't really give an answer without knowing that.
Thanks for the reply.
The generator will be for powering the house. The house panel will be back-fed through a 240V breaker with a mechanical interlock preventing the backfeed breaker and the main breaker from being turned on at the same time.
I am not sure what you mean by "b>
On some generators the neutral is connected to the ground (bonded). On most it is not. (non-bonded). It should say on both the generator and manual.
If you have a unbonded generator you are all set. Your generator is grounded through the breaker box, and must not be grounded independently; the ground loop you referred to.
If you have a bonded generator you have a problem. The generator must be grounded, and the neutral connection on your main feed must be switched along with the hots; again to prevent loops.
I don't have it saved any more, but there is a wonderful website from a Canadian distributor that explains all of this in extreme detail with diagrams; but I gave you the heart of it.
If your interlock switch disconnects the neutral from the mains input, you will need to have or make your generator ground bonded to the neutral line. If your interlock only switches the two hot lines and keeps the neutral connection intact you want your generator without the ground bonded to the neutral line. Remember the house neutral should be bonded to the ground once in your service entrance switchbox.
Also:
That's why generators used in this manner need to have a bond link, a physical, removable bar that connects the generator frame to the generator neutral. When purchasing a generator, keep in mind that some generators do not have a removable bond link.
In your case, since you are not switching the generator neutral in the "transfer switch", I would recommend connecting the generator as follows:
1...Remove the bond link in the generator, which results in the generator neutral being isolated from the generator frame. 2...Run a **4 wire** circuit from the generator to the main house panel. (2 hots, 1 neutral, 1 equipment ground) 3...drive a ground rod (two would be better, at least 6 feet apart) at the generator. Connect a #4 bare wire from the generator frame to the ground rods AND to the equipment grounding wire that runs between the generator and the house panel. There is usually a lug on the generator frame just for this purpose. 4...at the main house panel tie the generator neutral and generator equipment ground to the house main panel neutral busbar (which in turn is connected to the house grounding electrode system (ground rod(s), underground water line, etc.) 5...connect the hots to your mechanically interlocked breaker.The above method will result in what is referred to as a non-separately derived system. Hopefully, to avoid confusion, note that the ground rods at the generator in the above are not technically required by NEC since an equipment grounding conductor is ran to the generator. HOWEVER, using the ground rods in this way at the generator, especially since the main panel is some distance from the generator, ensures that the generator frame stays at ground potential. Most engineers will specify this method when connecting a non-separately derived system.
The other way to connect the generator is as a separately derived system. In that case you would have to not only change your transfer switch so that the neutral is switched, but you would also have to install a subpanel with the equipment ground and neutrals isolated from each other. In that case the ground rods at the generator would absolutely be required by NEC and the generator bond link would have to be installed to bond the "separately derived" neutral and equipment ground.
Note that the generator neutral is bonded to the equipment ground at one place _only_ in both cases.
One way to look at it is that with a separately derived system, a separate system ground for the neutral MUST be established. In a non-separately derived system, the generator neutral is grounded by the normal electric supply grounding system and any ground rods at the generator are merely supplemental to help keep the generator frame at ground potential.
I hope this doesn't cause confusion, as the point of my post is to help you understand the function of the ground rod in each case.
I don't think he is putting the generator a quarter mile from the breaker box. But if he is, your method is great.
Hi,
There is often alot of confusion over this. This is because there are a few variables to the equation:
1) Do you have a switch neutral in your transfer switch? 2) Is the neutral in your generator bonded to ground? 3) Are the house and generator grounds connected? Or should they be connected?Depending on the circumstances there are various "Sets" or possible soultions. Rather than me explain it, the best web sites I found was this:
snipped-for-privacy@aol.com wrote:
OK, I've read all the responses to the op's question and I'm still confused. I know the goal is to make sure there is a ground in place before & after the transfer switch. But is there a problem if the generator is grounded to a rod and also connected to the service ground? When I googled "ground loops", almost all responses were in relation to hum in audio/electronics rather than electrical distribution. So you even if have a ground loop between the service ground & generator ground with maybe 1-2 volts differential, does that really make any difference for running lights, refrigerator, and maybe a radio while on generator power?
Bob S.
hey, if you don't want to follow our advice, do whatever you want.
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