3 phase grounding

WyoDave

Well-known Member
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Hopefully this is my last question on this matter. Today the electric company hung the transformers and set a meter. They then ran directly to this fused disconnect. Since this is my first means of disconnect, and since they connected the ground to the neutral, I assume from this point I need to keep them separate, which is what I figured I'd have to do. So I will need 5 wires to my distribution panel. 3 hots, a neutral, and a ground.

The question is, how much more do I need here for grounding. They hooked the ground lug to the copper wire running down the pole and into the ground. Do I need to drive and hook up additional ground rods, and if so, how many? I know I need one at each structure, but what do I need here to be code compliant?

They still needed one transformer, but I should be up on 3 phase power by the end of the week. Thanks for all your help with this.

David
 
At what point did they connect the ground to the neutral?
You need to hook that bonding wire/jumper that's fastened to the panel box to the small ground lug that's beside the neutral lug.
If you use AL wire do not allow that CU jumper wire to touch any bare part of it, that is CU to AL.
I would think that the Utility ground would be good enough at that point.

Dusty
 
At the bottom right corner of the neutral lug there is a long green screw that is inserted into the box. I figured that connected them.

David
 
(quoted from post at 17:03:32 01/07/14) At the bottom right corner of the neutral lug there is a long green screw that is inserted into the box. I figured that connected them.

David

I missed that. You don't need to connect that jumper. That green screw is doing that.

Dusty
 
I agree with my electrician buddy the good Dusty man (I think). Its a bit hard to tell from the picture, but it looks like the Equipment GroundING Conductor (the bare No 4 copper) is bonded to the metal case/frame of the disconnect, while the Neutral is on an insulated black plastic block, therefore NOT bonded to the metallic case and subsequently also NOT bonded to the Equipment GroundING Conductor. HOWEVER if that black plastic block does indeed have the Neutral to the case frame disregard the prior sentence, I JUST CANT TELL FROM THE PICTURE.

That being said and that I cant tell whats what from the picture, HERES WHAT NEEDS TO BE DONE::::

The Neutral Grounded Conductor needs to be attached to a GroundING Electrode Conductor (like No 4 bare copper wire) that leads to a GroundING Electrode such as a driven rod or rods subject to local authority requirements. TO DO THAT ITS LIKE DUSTY SAID I think, install a jumper so as to wire that No 4 bare copper also to the Neutral, that way the Neutral is bonded to the grounding Electrode Conductor which leads to a GroundING Electrode (driven rod or rods).

In addition, the conductive metal case/frame of the disconnect (just like conductive non current carrying metal boxes like junction boxes etc) needs to be attached to the Equipment GroundING Conductor/Buss. If a jumper is ran from the small terminal up to the Neutral (what I think Dusty meant??) that will accomplish all the above: The Neutral will then be bonded to the Equipment GroundING Conductor (No 4 bare copper) which leads to an Equipment Grounding Electrode (driven rod or rods) and also the metallic case/frame of the disconnect is grounded yayyyyyyyyyyyyyyy

I (nor anyone here) can speak for local authority, but if they drove a ground rod and to it that No 4 bare copper wire (GroundING Electrode Conductor) is attached, Id say that will suffice for a proper GroundING Electrode. IE no more GroundING Electrodes are required.

Now that you have single point grounding at the first means of disconnection, from that points I agree I would run 5 wires, 3 Hots, Neutral GrounDED Conductor, and an Equipment GroundING Conductor.

NOTE AND CAVEAT: Is the service 208Y 120 Volt Three Phase Four Wire????????? Or 120/240 Volt Three Phase Four Wire Center Tapped (Red Leg) Delta??????????? THAT MAKES A BIG DIFFERENCE. If its a center tapped red leg delta, its 120 from 2 legs to neutral but 208 from the red/high leg to neutral

NOTE Perhaps that center red taped leg is the red/high leg????????????? IF SO BE CAREFUL and remember that's 208 to Neutral while its 120 from either of the other legs to Neutral !!!!!!!!!!!!!!
KEEP NOTE OF SUCH AS YOU RUN TO SUBS KEEP THAT RED/HIGH LEG IDENTIFIED

Sorry I cant tell from the picture whats what so this may all be wrong as rain NO WARRANTY

DISCLAIMER, This is merely an opinion, and like any opinions here, regardless if it agrees with mine or not, may be right and it may be wrong, Im NOT saying one way or the other, take it or leave it.

John T (suspect its a red/high leg delta so be aware and careful)
 
After reading that below,,,,,,ifffffffffff the Neutral is bonded to the case/frame via the green grounding screw that accomplishes all I said needs to be done (in theory at least) HOWEVER that's still NOT the wiring method I specified or was used at our facility. I prefer a direct (so long as not copper to aluminum) Neutral to GroundING Electrode Conductor bond and from that bond to the case frame NOT use the case frame as a conductor...

John T
 
I took my meter out to confirm, but there is definitely continuity between the ground and neutral, so I'm sure the green screw is accomplishing that. What you're saying, is it might be wise, and perfectly legal to add a jumper wire, therefore not relying on the case to perform that task? That's easy enough to do to add some insurance. In that case, do I still need additional ground rods connected to this disconnect?

It is a high leg system, with the red tape indicating it on the center leg. I am aware, and fully understand what that means. It will only be ran to the shop though, the house only gets the 120 volt legs fed to it. The power company then used an oversize transformer to feed the lighting load, to make up for the imbalanced system.


David
 
that would be true only if the green screw were going thru the block and pushing against a bare spot on the box. Surely that is not the case. There would have to be a physical connection, such as a wire run from the grounding lug to the green screw to achieve bonding. And the way I have always understood the posts of this nature, this should be done at the first box on your side of the meter, as in this case
 

Yep like on Mobile homes, you must have a disconnect on the pole and then you run 4 wires to the MH main breaker box.

On most regular homes the breaker box is the disconnect after the meter so the neutral and ground bond there.
 
That is the case. The screw goes through the plastic and is threaded into the case. Yes, this is the first disconnect, so them being connected here would be correct as I understand it.

David
 
Thanks for the feedback Dave, that helps us help you.

Okay, from what you say with the green grounding screw making contact with the disconnects metallic case/frame ALL IS LEGAL based on my very rusty and outdated NEC knowledge so NO WARRANTY. However, again with proper Copper and Aluminum compatible junctions, I still prefer (even if NOT NEC required) the bare No 4 Copper Equipment GroundING Conductor bonded to the Neutral Grounded Conductor (at a single point) WITHOUT IT HAVING TO USE THE METAL CASE AND WIMPY GREEN GROuNDING SCREW AS CONDUCTORS. I just view the small grounding screw MORE as a method to bond the metallic case to the newly established Equipment GroundING Buss/Connection versus it and the case/frame being relied on for conduction and the electrical connection for bonding Neutral to Mother earth Ground THATS MY STORY N IMA STICKIN TO IT.

HOWEVER I would not use BOTH, if you run the bare copper to the Neutral (instead of the small case lug, with a proper junction method for copper/aluminum) Id then consider the green grounding screw as the method to bond the metal case/frame to the Equipment Ground. BUT THATS JUST ME DONT GET UPSET. The main thing you are doing (when you earth ground the Neutral) is to tie Neutral to mother earth for lighting and surge suppression and I like it direct NOT via green screws and metal cases. I don't have a problem with the green screw being used to bond the metal case/frame, that's how I've seen it.

GROUND RODS as I said before if your utility and local authority consider the single driven rod as sufficient I wouldn't worry with more (although sure drive all you want). In my day we drove one rod them tested it and if it failed we drove another rod and re tested, but if it still failed we didn't drive more rods. As I recall the NEC says tie to all readily available grounding electrodes which includes buried metal pipes and structural steel and "made electrodes" sucH as driven rod or rods. If there were no other electrodes then we used "made electrodes" such as driven rods.

I WISH AND HOPE SOME OTHER MORE CURRENT PROFESSIONAL electricians and engineers would comment on my method and tell how they preferred it, is this just me lol Anything wrong with my preferences??

John T retired, rusty and always willing to learn
 
Green screw came on a little piece of cardboard and goes through into a predrilled threaded hole. That is fine . That is why it was provided with the switch. Other than that I can't really see so I'm just going to slap a pass sticker wherever you desire. Red leg tape should be orange and not red but your not going to convince some salty old power co guy that because they don't read or use codebooks they just do what has always been done.Red leg how can it be taped orange. 110-15 ...''higher phase voltage to ground shall be permantly marked with an outer finish that is orange in color [or other effective means--- like red tape not orange--- interpetation]]. Power companies will always still use red because they do not like the confusion with a 277/480 system which is caused by the high leg taped orange. Not really relevent if you know to test things to always see what you are working with.
 

I see bare copper ground wire behind the box. Is there a ground wire running from anything anywhere to a ground rod(s) in some place?
 
The bare wire from the box is connected to that wire. Also there is a wire coming out of the meter hooked to it, and then the wire is staple the length of the pole. It grounds the utilities overhead equipment and disappears below ground with the pole.
 
(quoted from post at 20:35:34 01/08/14) The bare wire from the box is connected to that wire. Also there is a wire coming out of the meter hooked to it, and then the wire is staple the length of the pole. It grounds the utilities overhead equipment and disappears below ground with the pole.

Find out if there are one or two ground rods driven at the pole. If there are two , they should suffice to ground the fused disconnect box.
If that is a 100amp service a #6 bare copper would be legal.
What all equipment is planned to operate from that electrical service?
 

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