Bonding screw in the distribution (sub) Panel

[kwired]

Having GFCI's has no bearing on whether it is acceptable to use the neutral for equipment grounding, you will still have same voltage rise on EGC's with same load conditions regardless if there are GFCI's or not.

 

[FionaZuppa]

Having GFCI's has no bearing on whether it is acceptable to use the neutral for equipment grounding, you will still have same voltage rise on EGC's with same load conditions regardless if there are GFCI's or not.

if the egc is bonded to the N bar in sub and the sub has gfi ocpd's, whats wrong with that. any fault onto egc would bypass the ocpd gfi ckt and trip the gfi, regardless if the feeder itself has egc or not, thus the branch ckts hanging off of the sub are still well protected, no hazard there. and in the case where feeder had no egc then the only way gfi works at the sub is if the egc is bonded to the N bar.

 

[al hildenbrand]

. . . in the case where feeder had no egc then the only way gfi works at the sub is if the egc is bonded to the N bar.

You must be moving too fast . . . GFCI fault detection does not require an EGC, nor ANY connection other than hot(s) and neutral.

 

[GoldDigger]

if the egc is bonded to the N bar in sub and the sub has gfi ocpd's, whats wrong with that. any fault onto egc would bypass the ocpd gfi ckt and trip the gfi, regardless if the feeder itself has egc or not, thus the branch ckts hanging off of the sub are still well protected, no hazard there. and in the case where feeder had no egc then the only way gfi works at the sub is if the egc is bonded to the N bar.

By "works" do you mean "does not trip on normal neutral current" or "trips on any leakage outside the normal circuit conductors"?
In either case I think that some of your statements above are not correct.
Remember that you cannot assume that there is no other connection between the appliance frame and earth, via pipes, ducts, frame touching another appliance, etc.

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[al hildenbrand]

if the egc is bonded to the N bar in sub and the sub has gfi ocpd's, whats wrong with that?

Read Kwired's post #41 again, as he answered that.

 

[FionaZuppa]

Read Kwired's post #41 again, as he answered that.

i did read it the 1st time. what's the hazard i am asking. using the N CCC as egc is no, but you would never get there if sub had all gfi ocpd's, etc.

 

[kwired]

i did read it the 1st time. what's the hazard i am asking. using the N CCC as egc is no, but you would never get there if sub had all gfi ocpd's, etc.

The hazard is exactly the same as it is if you had same loads but no GFCI's. Current on the neutral will cause a voltage drop, connecting non intended to carry current objects (basically your EGC's) to that same conductor will result in same rise over true ground on everything connected to it. More neutral current, means more voltage drop, longer neutral conductor with no increase in size means more voltage drop.

The GFCI is only looking for same current that leaves one conductor to come back on the other conductor(s) of the circuit, does not care what, or even if any of those conductors are grounded.

 

[FionaZuppa]

The hazard is exactly the same as it is if you had same loads but no GFCI's.

any fault current onto the egc will trip gfi instantly. i dont see how this would be the same as having std ocpd's. so what hazard do you mean? if the gfi fails to do its job then perhaps an issue.
gray wire is N, etc.

 

[kwired]

any fault current onto the egc will trip gfi instantly. i dont see how this would be the same as having std ocpd's. so what hazard do you mean? if the gfi fails to do its job then perhaps an issue.
gray wire is N, etc.

GFCI does not monitor the EGC, it monitors all the normal current carrying conductors of the circuit and is looking for a same current that goes out to come back on all of the conductors of the circuit. If more then 4-6 ma leaks away via some other path, could be the EGC could be any other path, even another ungrounded conductor of another circuit, it trips.

If your GFCI in your picture were a feeder panel - you show the EGC to the pump connected to the supply side neutral the hazard that is the same here is the fact if you have neutral current on the feeder conductors then the neutral and everything bonded to it has a voltage rise over true ground, and a GFCI breaker will not know or care about it.

You could connect a second 120 volt circuit and use the EGC to that pump as the neutral of that circuit, though that is a code violation the GFCI for the pump circuit will not see that current on the EGC, it has no connection at all to the EGC other then the supply side neutral terminal, at which point that objectionable current is going around the GFCI and not through it. It will not trip in that situation.

 

[FionaZuppa]

yikes.
am i not asking correctly.

surely any ~6+mA that loops from any CCC (from gfi) to the egc will trip the gfi, yes? the egc creates a path around the gfi.

so what i am asking is, if thats the case then whats the hazard in connecting the egc to the N bar in sub panel ??

the gfi is the tiny box, the small squigly is the gfi ocpd pigtail, etc. light blue box is the sub panel with a 3 wire (L-N-L) feeder.


and just for clarity, doesnt gfi kinda monitor the egc, because any wrongful leakage between CCC's the gfi could care less about, its only that fault current that goes outside of those CCC's, which is either earth (technically egc) or the egc wire itself.

 

[kwired]

yikes.
am i not asking correctly.

surely any ~6+mA that loops from any CCC (from gfi) to the egc will trip the gfi, yes? the egc creates a path around the gfi.

so what i am asking is, if thats the case then whats the hazard in connecting the egc to the N bar in sub panel ??

the gfi is the tiny box, the small squigly is the gfi ocpd pigtail, etc. light blue box is the sub panel with a 3 wire (L-N-L) feeder.


and just for clarity, doesnt gfi kinda monitor the egc, because any wrongful leakage between CCC's the gfi could care less about, its only that fault current that goes outside of those CCC's, which is either earth (technically egc) or the egc wire itself.

"Kinda" is the key. Any GFCI protected conductor that contacts something that gives you an alternate path will trip the GFCI when current leaking the intended circuit is over 4-6 mA. Does not change the voltage drop on the neutral - which equates to voltage rise on the EGC to true ground if you use the feeder neutral for connecting to your EGC's, and such neutral to EGC bonding does not change the balance of load side of any GFCI's connected to that feeder, they work just like GFCI breakers installed in a service panel do neutral and EGC are bonded together at service panels. This all going back to my comment that any hazards are the same as a result of using the neutral for EGC beyond the service equipment/first disconnect of separately derived system whether you install GFCI's or not. Is also the same reason a rise in voltage on EGC results in shocks/electrocutions at docks and marinas even though GFCI's were on the circuits involved. The rise is not because of a fault in the branch circuit - it is simply voltage drop on a normally current carrying grounded conductor that gets bonded to EGC's.

 

[FionaZuppa]

The rise is not because of a fault in the branch circuit - it is simply voltage drop on a normally current carrying grounded conductor that gets bonded to EGC's.

good point. so then gfi ocpd on both sides??

if the load only uses L-L how much voltage would there be on the egc ?

 

[al hildenbrand]

I am a home inspector . . . I have asked building inspector locally and electricians locally and I can not seem to get a clear understanding. So, hopefully someone can lay this out in laymen terms so I can be a better inspector. Thank you in advance.

Just a reminder from the OP.

so then gfi ocpd on both sides??

Your returning again and again to ground fault detection is way out in the weeds from the OP asked question.

 

[kwired]

Your returning again and again to ground fault detection is way out in the weeds from the OP asked question.

My thought as well, has nothing to do with OP's question and GFCI at the load end of a feeder won't care if you use the grounded feeder conductor for equipment grounding, but any voltage drop on that feeder grounded conductor will result in elevated voltage to true ground on any EGC's you connect to it. It may only be a volt or two but in the right circumstances, like around a swimming pool, that is a lot.

good point. so then gfi ocpd on both sides??

if the load only uses L-L how much voltage would there be on the egc ?

Depends on how much voltage drop there is on the grounded conductor from the point in question to the point where the source is grounded.

 

[FionaZuppa]

Depends on how much voltage drop there is on the grounded conductor from the point in question to the point where the source is grounded.

what grounded conductor if all the loads are pole-to-pole 240v?

perhaps post #2 was a tad confusing, throwing in egc bonded to N ? not really sure why that came up.

for OP, egc (gnd) bar bonded to the panel itself makes sense to me, as long as all other CCC's are isolated from the panel metal.

 

[kwired]

what grounded conductor if all the loads are pole-to-pole 240v?

perhaps post #2 was a tad confusing, throwing in egc bonded to N ? not really sure why that came up.

for OP, egc (gnd) bar bonded to the panel itself makes sense to me, as long as all other CCC's are isolated from the panel metal.

From the OP: "I am a home inspector trying to understand what is correct and why in the distribution (sub) panel. My understanding is that beyond the service disconnect point (main panel) (in what I call the sub panel, I believe is called a distribution panel by NEC) ground (bare copper wire) and neutral (white wire) is separated and not bonded.


IMO the main topic of the thread is why do we separate the two beyond the service equipment?
If you have a panel with no neutral load - then it is acceptable to use the neutral bus as a grounding bus - you would seldom find such a panel in a dwelling though that didn't also supply loads that operate line to neutral though, and this is the situation where OP usually sees this.

Even though it isn't code compliant, IMO you are still better off using the feeder neutral for equipment grounding path beyond that subpanel then to not have any equipment grounding at all, and if you do it doesn't change how a GFCI in that panel or even downstream of that panel will function. It does increase the possibility of a rise in voltage on that EGC to true ground though, and a GFCI won't detect that either.