Service Bonding Question

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awc

awc

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Ok, I'm a first year apprentice and I've got another one of those apprentice questions. If you have a 100 Amp Residential service and it has a 100 Amp disconnect that is bonded as it's suppose to be. It has SE cable running to the main panel in the house (3 conductors-2 ungrounded and 1 grounded bare). Now the question is...........it's bonded in the disconnect so it shouldn't be in the main panel correct? But the grounds are to be seperated from the ungrounded conductors so what good are the grounds doing since they have no tie to anything??? :-? Am I missing something here?
 
awc said:
Ok, I'm a first year apprentice and I've got another one of those apprentice questions. If you have a 100 Amp Residential service and it has a 100 Amp disconnect that is bonded as it's suppose to be. It has SE cable running to the main panel in the house (3 conductors-2 ungrounded and 1 grounded bare). Now the question is...........it's bonded in the disconnect so it shouldn't be in the main panel correct? But the grounds are to be seperated from the ungrounded conductors so what good are the grounds doing since they have no tie to anything??? :-? Am I missing something here?
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[EDIT: You would need to run 4 wires from the disconnect to the main panel.]

This setup is no different then a sub-panel installation, but what you are accomplishing is so that dangerous (neutral) current will not flow on the metal parts of the electrical system.

Study this picture...
View attachment 1744
 
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stickboy1375 said:
[EDIT: You would need to run 4 wires from the disconnect to the main panel.]

This setup is no different then a sub-panel installation, but what you are accomplishing is so that dangerous (neutral) current will not flow on the metal parts of the electrical system.
Click to expand...


Ok, but the part that is confusing me is if it's not a bonded panel what gives the ground a conductive path back to the disconnect?? I hope this isn't one of the questions where you are like "wow, what the heck is he thinking"....maybe it's to late for me to be working the ole gray matter :smile:
 
1. I have never used SE cable... but in my estimation, the wiring from the first disconnect to the panel is a feeder, not service entrance. As far as I know, it needs to be 4-wire as stickboy notes.

2. Is a bare neutral permitted in this instance?

3. Are there any exceptions which would let us bond the neutral in the panel and use the grounded conductor as the EGC also?

I'm checking it out now. I am guessing there is no exception to the need for 4-wire.
 
like stated above, you need 4 wire to the panel from the disconnect. The bare would go soley to the ground bar which is bonded to the panel and the grounded conductor (neu) would go to the neutral bar. 2 hots, 1 neu, 1 gnd

if you have 3 wire from the disconnect to the panel, that is incorrect
 
Stickboy..............Sorry, I just realized I posted that before noticing your EDIT :roll: . I thought that missing the 4th conductor for the ground was an issue.
 
awc said:
Ok, but the part that is confusing me is if it's not a bonded panel what gives the ground a conductive path back to the disconnect?? I hope this isn't one of the questions where you are like "wow, what the heck is he thinking"....maybe it's to late for me to be working the ole gray matter :smile:
Click to expand...

By what you've described, there is no path. That's the problem. And it should be fixed.
 
frizbeedog said:
By what you've described, there is no path. That's the problem. And it should be fixed.
Click to expand...


That's what was hanging me up............because I didn't see where it had a path either so I didn't think this was correct but I wanted to make sure I wasn't missing something.
 
awc said:
That's what was hanging me up............because I didn't see where it had a path either so I didn't think this was correct but I wanted to make sure I wasn't missing something.
Click to expand...

That you noticed the hazard was the important part. :smile:
 
Thanks guys, I appreciate your help on this one :smile: . I feel better now that I see I wasn't off on my thinking.
 
View attachment 1745
Just when you thought I was done.
Ok, I ran across something and I'm a little confused...........is this picture showing the same thing I seen???:-? I realize it's referring to a totally seperate issue but maybe i'm studying the picture to close but it appeared that it was dipicting the same thing I seen today????
 
awc said:
Just when you thought I was done.
Ok, I ran across something and I'm a little confused...........is this picture showing the same thing I seen???:-? I realize it's referring to a totally seperate issue but maybe i'm studying the picture to close but it appeared that it was dipicting the same thing I seen today????
Click to expand...

If this setup in the picture was installed on a house, then you would run 4 conductors out of that disconnect to the panel.
 
Ok, so if there was no disconnect and it was coming straight from the Meter to the panel........then could you run 3 conductor and bond the panel? Would that be correct?
 
awc said:
Ok, so if there was no disconnect and it was coming straight from the Meter to the panel........then could you run 3 conductor and bond the panel? Would that be correct?
Click to expand...


Yep, because your disconnect would be in the panel....
 
3. Are there any exceptions which would let us bond the neutral in the panel and use the grounded conductor as the EGC also?




No .
Click to expand...

See 254.32(A) The fpn says volumes too.

Further clarification was added in the NEC that even outbuildings (the three wire vs four wire argument) now will be 4 wire. See the verbage in 254.32(B), the exception basically covers existing 3 wire set ups.

250.4(A)(5) and especially 250.4(A)(5) get into the meat of grounding and bonding.


Back to the apprentice's question...visit 250.24(A)(5) and 254.24(B).
 
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