neutral bonding at the generator

[DJones]

You only want one point of bonding. It is to be done at your point to disconnect (your main breaker). make sure the frame of your gen set is grounded for safety.

 

[coyote62ny]

mistaken1 if you or any one else reading this i would not use one of the cheap plastic battery disconnect switches i dont think they would handle the possible amps that could be passed through the switch the switch i used was from an old bulldozer we had all metal switch and marked 200 amp rated

 

[bones1]

The key to the whole seperately derived system nomenclature is "are you switching the neutral when you transfer to the generator". If you do switch to an isolated generator neutral like coyote62ny just described, you have a seperately derived system. If you connect your generator neutral to your house neutral solidly (not switched), then you have a non-seperately derived system (90% of systems are connected this way). Remember, if you do switch the neutral during transfer, the generator should be treated like its own seperate electrical service. This means it needs its own grounding electrode conductor - least a ground rod, plus one other grounding electrode (cold water pipe, metal gas line, auxillary ground rod, etc) AND your neutral and ground are tied together in the generator (because this is now the first means of disconnect). Confused yet?

The way I read this, you only need the ground rod at the generator when you are not connected to the house service panel.

Whoops, this original post is years old. Sorry. Can't find how to delete mine.

 

[steelandcanvas]

The way I read this, you only need the ground rod at the generator when you are not connected to the house service panel.

Whoops, this original post is years old. Sorry. Can't find how to delete mine.

Correct!

 

[Keith_J]

And to muddy the waters further, the latest NEC requires the single point ground to be tested with a special meter to insure a ground of 25 ohms or less. In lieu of such testing, a second, 8' ground rod can be installed 6 feet or more way from the first ground rod and connected to the grounding/neutral bond at service entrance point with its own ground wire. Confusing?

Just had my service entrance upgraded and had to do this before inspection sign off, the electrician allowed me to do this..actually he dislikes driving rods in our rocky soil. I drilled it in past the caprock and used my pneumatic t post driver to finish. 5 minutes of easy work. While I lack the special test meter, I measured 0 ohms between the two and <3 ohms between them and service entrance neutral.

 

[bones1]

This is correct as well. I had to do this about 3 years ago with my new panel install. Thanks guys. I will now put my generator grounding questions to bed.

 

[steelandcanvas]

Just had my service entrance upgraded and had to do this before inspection sign off, the electrician allowed me to do this..actually he dislikes driving rods in our rocky soil. I drilled it in past the caprock and used my pneumatic t post driver to finish. 5 minutes of easy work. While I lack the special test meter, I measured 0 ohms between the two and <3 ohms between them and service entrance neutral.

There were areas I worked in that I absolutely despised attempting to drive ground rods. One trick an inspector showed me was to drive the rod at an angle, you can do this up to 45 degrees. The angle trick combined with an electric jack hammer made this task bearable.

 

[shazam]

To once again revive a necro-thread...sorry....I want to make sure I do this right. Genset will be connected via 4-wire to the main house box. After reading the post twice, still confusnicated. Do I understand that....

The neutral bond bar in the genset should be disconnected, and the 4 wires go from the corresponding terminals in the genset to their respective places in the main box (two hot wires to the bus (thru a breaker/transfer switch of course), and neutral and ground to the grounding bar)?...and....

a separate grounding rod is/is not used at the genset? If 'is'....to ground the frame only, or to the ground terminal?

My newbieness is showing, and I thank you all for your expertise!

 

[DieselAddict]

With a 4 wire setup your generator is grounded through the main power system ground BUT you can drive a ground rod at the generator if you wish. No code against that. There is a ground terminal in the generator that you can parallel a local ground rod or you can install a ground lug on the frame. Either way is fine. There is debate whether a ground rod at a generator is a good thing or a bad thing. I personally think its a good thing so long as your grounding conductor is beefy (6 awg or larger). You can search the web and find many arguments on either side of that fence.

You are correct that the neutral/ground bar at the generator is to be disconnected when you are using a 4 wire connection and there is a neutral to ground bond elsewhere in the system. I know people don't agree with this but from a code perspective its clear. Only one ground to neutral bond per system.

 

[shazam]

Thanks, Chris! We'll be doing the final wiring Tuesday, including a remote start switch to the basement, and a small solar panel charger. Can't wait to be up and running!

Jim

 

[peapvp]

I am reviving this thread as shazam asked this question back in November 2018 and it was answered by Dieseladdict pointing out the debatable nature of this topic.

Very unfortunately, shazam experienced lighting related issues, which hopefully did not damage his Generator.

https://www.steelsoldiers.com/threads/lightning-auto-start.210434/#post-2457840

We were not asked back in 2018 of our opinion in this matter, neither where we aware of this thread.

We WOULD STRONGLY ADVICE AGAINST REMOVING THE BONDING BAR BETWEEN L0 AND GENSET CHASIS