got my pto-generator today.

[mahlers]

</font><font color="blue" class="small">( mahlers,
It is against "code" to use the Earth as the sole means to ground/neutral. And very dangerous, usually doesn't work and will get someone killed. )</font>

OK, now I'm totally confused. In your earlier post, you said that the neutral goes down the pole and into the ground, and is the ground for the transformer. Isn't that, by definition, using the Earth as a ground? Help me out here...

 

[mahlers]

</font><font color="blue" class="small">(

The neutral is the return line in a 115 volt circuit, it shouldn't actually be needed in a 230 volt system unless the load is being split--which appears to be your case.

)</font>

Yup - and I needed 120 volt service where there was previously only 240. I tried to take a short-cut by making my own neutral (I won't go into why I tried to go that way, but I will say that I went through a miserable time trying to run 700 feet of #2 cable through the trees and over a river to get back to the main service entrance common). It was pretty obvious right away that making my own neutral wasn't going to work, so I ended up running the common all the way back to the entrance.

It still does go back to my original question about what the utility neutral really is. If I understand Inspector507 correctly, the utility neutral goes down the utility pole and into a coil of wire at the base of the pole - buried pretty deep down. That seems like a ground to me, and my twisted logic would tell me that I could drive four or five ten-foot copper ground rods into the soil and accomplish exactly the same thing. It didn't work, and I'm still curious if there's some other magic done at the utility transformer that I'm overlooking here.

 

[johnbilt]

Hi

Let me give this a try. I've read a few of the responses and am not sure if they answered your queston directly.

1) There are three wires from the "service side" feeding your meter and panel. The transformer on the pole has a center tap which provides a neutral (grounded conductor per NEC). This is the electrical return path for the two 120volt circuit legs.

2) The neutral (grounded conductor) is connected to earth ground at the service pole, as well as the service entrance (your panel and meter). This allows the center tap transformer to reference the potential at earth ground. Otherwise the system will "float" with respect to earth ground.

3) The neutral (grounded conductor) carries the return electrical current. This is different from the earth ground connection, which does not carry any current except in a ground fault condition.

4) Be careful with the NEC. This is primarily written for the service entrance and distribution beyond. I think there is another code for electrical service providers.

I hope I haven't created more questions !! /forums/images/graemlins/crazy.gif

I believe that your service pole must be wired correctly. Consult a professional electrician or the power company if there is really a suspected problem with your service.

Be careful out there !
/forums/images/graemlins/cool.gif
John

 

[KennyV]

John
You are absolutely right …
at the transformer the center tap is grounded AND also sent to your meter which is also grounded, and then to your panel where it is grounded again.
If you have a situation where you have a 240 volt but no 120, this is not impossible, but the only way you can get 120 safely and reliably is either use a 2:1 transformer, this will effectively making this an isolation transformer, or you can rewire and run three conductors. That is, Both legs of the 120 AND a common.

The first can be expensive if you have any real current requirements, transformers are not cheap. The second is more practical in almost all situations.

Don’t use the earth for your return. That path will be a variable resistance, due to contaminate and moisture levels in the soil.
If you are not sure, have a pro check it out ... alittle electricity can take the fun out of everyones day.
Good luck, KennyV

 

[ns_in_tex]

Hi Snowman,

On mine, I ran a single fused circuit, fed above the main disconnect to a hall light, we seldom use. When the generator is in use, we flip this hall light on. It tells us when the power company has the service back on.

 

[v8dave]

</font><font color="blue" class="small">( To v8dave:

I was thinking that neutral should only be bonded to ground at one point only(main panel). If it was bonded at more than one point, ground loops would be created. Neutral and ground should not be bonded at the barn, current should only flow back in the neutral for a split voltage configuration ?????????? )</font>

Yup, and that logic was exactly what I thought too. But the county inspector (El Dorado County, California) made the electrician bond the new shop's panel at it's power entrance. I questioned the request and got an unintelligible answer, but interpreted it to have something to do with GFCI might not work properly--too many false trips. I wanted the approval, so I just shut up. The shop panel is about 150' away from the house, main, panel.

 

[_RaT_]

"John
You are absolutely right …
at the transformer the center tap is grounded AND also sent to your meter which is also grounded, and then to your panel where it is grounded again.
If you have a situation where you have a 240 volt but no 120, this is not impossible, but the only way you can get 120 safely and reliably is either use a 2:1 transformer, this will effectively making this an isolation transformer, or you can rewire and run three conductors. That is, Both legs of the 120 AND a common"

I have done this in the past on small parking booths where they have 240V only. Much of the equipment needs 120V so in order to get it I would have needed to run a neutral well over 1000'. By using a relatively small indoor transformer fused for the transformer size since the incoming feed was 60 amp 240V and the transformer about 3000 watts I was easily able to run the various calculators, a light and a very small AC unit (the booth was 4'X8'). I did need to bond the transformer. Mark

 

[Inspector507]

<font color="blue"> OK, now I'm totally confused. In your earlier post, you said that the neutral goes down the pole and into the ground, and is the ground for the transformer. Isn't that, by definition, using the Earth as a ground? Help me out here... </font>

No, what I said was, the neutral is attached to that wire. The neutral is already a grounded conductor and this is supplemental to that.
The ground in your house is for a safe return path back to the neutral conductor at the service equipment. Grounding electrodes will not do anything to provide a safe low-impedence path. The butt wrap the utilities use are for "transient" voltage....i.e. lightning.

 

[Inspector507]

Okay, I decided to post a reply to myself and try to clear up what the NEC® says about running power to a separate building as far as grounding/bonding.

(1) If you only run one branch circuit, and include a grounding conductor, no electrode or neutral bonding is required. But a connection to the neutral is not to be made.

(2) If you run a feeder to the building with no equipment grounding conductor, a grounding electrode must be installed and the neutral bonded to that electrode and the panel enclosure. This is provided you do not have any continous metallic paths back to the main building such as metal water/air lines, etc. And provided you do not have ground fault protection for EQUIPMENT. The average residential property will not have GFPE which is different than a GFCI

(3) If you run a feeder with an equipment grounding conductor, a grounding electrode must be installed at the building and connected to the grounding conductor in the feeder and to the enclosure.

All of this is in NEC® 250.32

 

[v8dave]

</font><font color="blue" class="small">( Okay, I decided to post a reply to myself and try to clear up what the NEC® says about running power to a separate building as far as grounding/bonding.

. . .

(3) If you run a feeder with an equipment grounding conductor, a grounding electrode must be installed at the building and connected to the grounding conductor in the feeder and to the enclosure.

All of this is in NEC® 250.32 )</font>

Ah ha, and this is the case in my situation. Why the county inspector didn't say this is a mystery to me. I suppose his explaination was good too, just not understandable.

Thanks Inspector.