On a project I was looking at it indicates all the branch circuits to terminate to ground bar located in a junction box, then run a single grounding conductor to the panelboard ground bar. For this specific project all the circuits being 15A-1P GFCI breakers, my question is will the GFCI still operate correctly using a common ground for multiple circuits(10 plus)? I am concerned because looking at it from a fault perspective if you have a fault on a single device it runs thru the grounding system smaller ground conductor, the ground bar and then through the larger conductor to the panel with the larger conductor being able to handle a smaller fault how will the breaker operate? Is there a code reference to this. Thanks in advance for your help.:-?
Grouping Ground Conductors??
- Thread starter Mike01
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If you're talking about joining all of the (branch circuit) Equipment Grounding Conductors together in a JB and then running one large grounding conductor to the breaker panel, I don't believe that it will affect the operation of the GFI breakers that power those circuits.
A (single pole) GFI breaker moniters the current between the un-grounded (hot) conductor and the grounded (neutral). If it senses return current from the load to anywhere other than the grounded (neutral) conductor, it will trip the breaker.
As far as I know, the grounding conductor plays no part in it's operation.
Examples....If there's a fault current flowing thru a person to earth, the grounding conductor will never carry any of this fault current and the breaker will still trip.
If you disconnected the grounding conductor, the GFI breaker would still trip.
Just a opinion.
steve
A (single pole) GFI breaker moniters the current between the un-grounded (hot) conductor and the grounded (neutral). If it senses return current from the load to anywhere other than the grounded (neutral) conductor, it will trip the breaker.
As far as I know, the grounding conductor plays no part in it's operation.
Examples....If there's a fault current flowing thru a person to earth, the grounding conductor will never carry any of this fault current and the breaker will still trip.
If you disconnected the grounding conductor, the GFI breaker would still trip.
Just a opinion.
steve
Remember that a GFCI does not require an equipment ground to operate. Also remember that if all of these conductors were run in a metalic raceway, the raceway could serve as the grounding conductor. With that in mind, it is easy to see that joining multiple grounds together and running one conductor bac to the panel will not cause a problem as long as the conductor is sized properly.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
hillbilly said:
haskindm said:
Why would the single EGC need to be any larger than a #14. All the circuits are 15 amp Art. 250.122(C)
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The only disadvantage that I see is if the EGC going back to the panel gets compromised then all the circuits would lose their EGC. No different than going to a sub panel and losing that EGC.Mike01 said:
Right and according to the OP that is 15 amps. So a #14 ground would work. unless they increased the conductors for VD.
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
Dennis Alwon said:
Isn't that a controversial statement? Something along the lines that you don't upsize conductors for VD, you rightsize them...?
In the general case, if there are enough circuits and enough distance then you could significantly reduce copper spend by using a common ground conductor.
Bob NH
Senior Member
- Location
- The "Live Free or Die" State
How does the described method of running all of the EGCs to a junction box, with a single conductor to the ground bar in the panel, comply with the requirements of 250.118 or 250.134(B) that the EGC be run with or within the same cable or raceway?
It seems like there would be a problem unless all of the circuit conductors ran in the same raceway.
It seems like there would be a problem unless all of the circuit conductors ran in the same raceway.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
This has been discussed before. Upsizing for VD is a 'voluntary' upsize, while upsizing for bundling, derating, etc., is mandantory. The former requires an upsized EGC, while the latter does not.dbuckley said:
The rationale is that upsizing for voltage drop is to minimize an increase in circuit impedance, which would also affect the EGC's performance, whereas upsizing to maintain the prescribed conductor ampacity does not affect the EGC's performance.
wbalsam1
Senior Member
- Location
- Upper Jay, NY
hillbilly said:
If that were exactly true, wouldn't the breaker be called a Short-circuit current interrupter? I think the equipment grounding conductor is the key player here..hence the name ground fault not grounded-conductor fault...
JMO Of course I'm just tweaking words....lol
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Bob NH said:
I believe that is what the op is planning to do. At least that is what I assumed. I conduit from the panel to the JB with one EGC.
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It?s not what I was planning on doing, I was asked to look at a set of drawings and give my opinion if I saw anything that was not code compliant, I noticed that the electrical contractor proposed a large j.b. they would route 1 1-1/4? conduit with multiple circuits (de-rated per the NEC) however the branch circuit would only include one larger EGC to a ground bar mounted in the junction box, approximately 6-8 circuits per j.b. with the load grounds terminated to the ground bar and one large ground routed with the circuit conductors back to the panel. Would this be a problem if more than one conduit were installed. It does not seem to be to be my preferred design but is it code compliant sounds like it is, I am still looking into this, and was just concerned about the operation of the GFCI breakers located in the upstream panels that the loads are connected to.
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It?s not what I was planning on doing, I was asked to look at a set of drawings and give my opinion if I saw anything that was not code compliant, I noticed that the electrical contractor proposed a large j.b. they would route 1 1-1/4? conduit with multiple circuits (de-rated per the NEC) however the branch circuit would only include one larger EGC to a ground bar mounted in the junction box, approximately 6-8 circuits per j.b. with the load grounds terminated to the ground bar and one large ground routed with the circuit conductors back to the panel. Would this be a problem if more than one conduit were installed. It does not seem to be to be my preferred design but is it code compliant sounds like it is, I am still looking into this, and was just concerned about the operation of the GFCI breakers located in the upstream panels that the loads are connected to.wbalsami1,
GFCI does not rely on a grounding conductor to work. It measures the current between the ungrounded conductor and the grounded conductor (or the ungrounded conductors in a multi-pole gfci). If the currents are not equal, then current is returning to the source through some other means. This could be the grounding conductor, a person, the earth, some other grounded (bonded) equipment or surface, etc. Whatever the path, the GFCI will open when the current is unbalanced beyond a predetermined value. That is why one of the accepted methods for replacing ungrounded receptacles is by using a GFCI, it will work fine without an equipment ground.
Perhaps they should be called "Unbalanced Current Interrupters"!
GFCI does not rely on a grounding conductor to work. It measures the current between the ungrounded conductor and the grounded conductor (or the ungrounded conductors in a multi-pole gfci). If the currents are not equal, then current is returning to the source through some other means. This could be the grounding conductor, a person, the earth, some other grounded (bonded) equipment or surface, etc. Whatever the path, the GFCI will open when the current is unbalanced beyond a predetermined value. That is why one of the accepted methods for replacing ungrounded receptacles is by using a GFCI, it will work fine without an equipment ground.
Perhaps they should be called "Unbalanced Current Interrupters"!
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Mike01 said:
Mike you have me confused. You asked
Do you mean more than one conduit back to the panel?? If you are using EMT then you don't even need an EGC unless the specs call for it. If they call for an EGC then I would probably run one in each conduit but I don't believe it is necessary since the EMT is an effective ground.
This should not be a problem with the GFCI circuits at all and I believe it is code compliant.
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