Ground to Feeder Panel

[mjhutchins]

I'm working on a project where no grounding wire was run to a feeder panel. The feeder panel is over 500 feet from the main panel. A grounding rod was used to ground the panel. Do I need to run a ground to the new feeder panel

 

[Dennis Alwon]

I'm working on a project where no grounding wire was run to a feeder panel. The feeder panel is over 500 feet from the main panel. A grounding rod was used to ground the panel. Do I need to run a ground to the new feeder panel

If the feeder is run in a metallic raceway than the conduit itself can be used as the equipment grounding conductor.

 

[jumper]

Is feeder panel in the same building as supply panel?

 

[iwire]

I'm working on a project where no grounding wire was run to a feeder panel. The feeder panel is over 500 feet from the main panel. A grounding rod was used to ground the panel. Do I need to run a ground to the new feeder panel

Yes, an equipment grounding conductor of some type is required, it is dangerous without it.

But as Dennis mentioned a metal raceway can serve as the EGC.

 

[mjhutchins]

Is feeder panel in the same building as supply panel?

Thanks for the reply. The feeder panel is on another building. The existing feeder panel is being replaced. The existing cable didn't have a ground wire run with it. The existing panel has a grounding rod next to it and this was used for the equipment ground. Acr-fault breakers do not require a ground wire be run to the equipment as they detect arc and ground faults. Ground faults also don't require a ground wire. If arc faults and grounds faults were used is the ground wire from the main panel required? Many feeder panels don't have provisions for grounding wires. I've installed ground bars in past panels because they lacked one.

 

[iwire]

Thanks for the reply. The feeder panel is on another building. The existing feeder panel is being replaced. The existing cable didn't have a ground wire run with it. The existing panel has a grounding rod next to it and this was used for the equipment ground. Acr-fault breakers do not require a ground wire be run to the equipment as they detect arc and ground faults. Ground faults also don't require a ground wire. If arc faults and grounds faults were used is the ground wire from the main panel required? Many feeder panels don't have provisions for grounding wires. I've installed ground bars in past panels because they lacked one.

OK, up until I think the adoption of the 2005 NEC it was code compliant to run a feeder to a seperate building with out an EGC. You would use the neutral as the EGC and set the panel up in the remote building just as you would a service. You would bond the neutral to the panel, add grounding electrodes and you where good to go.

Now the code has changed any you cannot do a new installation like that.

However there is an exception for existing feeders.

250.32 Exception No.1: For installations made in compliance
with previous editions of this Code that permitted such connection,
the grounded conductor run with the supply to the
building or structure shall be permitted to serve as the
ground-fault return path if all of the following requirements
continue to be met:

( 1) An equipment grounding conductor is not run with the
supply to the building or structure.

(2) There are no continuous metallic paths bonded to the
grounding system in each building or structure involved.

(3) Ground-fault protection of equipment has not been installed
on the supply side of the feeder(s).

There is more to the exception but I am having some computer issues.

 

[mpoulton]

Thanks for the reply. The feeder panel is on another building. The existing feeder panel is being replaced. The existing cable didn't have a ground wire run with it. The existing panel has a grounding rod next to it and this was used for the equipment ground. Acr-fault breakers do not require a ground wire be run to the equipment as they detect arc and ground faults. Ground faults also don't require a ground wire. If arc faults and grounds faults were used is the ground wire from the main panel required? Many feeder panels don't have provisions for grounding wires. I've installed ground bars in past panels because they lacked one.

Need to clarify if there was a metallic raceway used as a grounding conductor for the original feeder. If so, no separate grounding conductor was required (and none is required now as long as you reuse the continuous metallic raceway). If not, then the next question is whether there was a neutral-ground bond at the subpanel. There better be! Without it, that's an extremely dangerous system - any ground fault will energize all "grounded" metal on the system. That is completely unacceptable and has never been code compliant.

Regardless of how the panel was set up before, your new installation requires an equipment grounding conductor returning to the main panel. That can be a wire or a metallic raceway. There are no exceptions. AFCI devices are not rated or allowed to be used for ground fault protection in lieu of a grounding conductor, and GFCI devices can only be used this way on unmodified existing branch circuits. You must have a fault clearing path from the EGC to the system neutral. The installation is unsafe and not code compliant without it.

 

[iwire]

Regardless of how the panel was set up before, your new installation requires an equipment grounding conductor returning to the main panel.

Maybe, please see the exception I posted.

 

[mjhutchins]

OK, up until I think the adoption of the 2005 NEC it was code compliant to run a feeder to a seperate building with out an EGC. You would use the neutral as the EGC and set the panel up in the remote building just as you would a service. You would bond the neutral to the panel, add grounding electrodes and you where good to go.

Now the code has changed any you cannot do a new installation like that.

However there is an exception for existing feeders.



There is more to the exception but I am having some computer issues.

iwire, and the other guys and gals on this forum are great. Thanks it is much appreciated. Something I'll keep handy for the inspector.

Do you have any insight as to why the code now requires a grounding wire to be run back to the main panel? What is the difference between sinking a EGC and bonding to it? Since the code changed, there must have been some reason that made the change necessary.

 

[mjhutchins]

Need to clarify if there was a metallic raceway used as a grounding conductor for the original feeder. If so, no separate grounding conductor was required (and none is required now as long as you reuse the continuous metallic raceway). If not, then the next question is whether there was a neutral-ground bond at the subpanel. There better be! Without it, that's an extremely dangerous system - any ground fault will energize all "grounded" metal on the system. That is completely unacceptable and has never been code compliant.

Regardless of how the panel was set up before, your new installation requires an equipment grounding conductor returning to the main panel. That can be a wire or a metallic raceway. There are no exceptions. AFCI devices are not rated or allowed to be used for ground fault protection in lieu of a grounding conductor, and GFCI devices can only be used this way on unmodified existing branch circuits. You must have a fault clearing path from the EGC to the system neutral. The installation is unsafe and not code compliant without it.

The supply cables are run in PVC conduit underground. Yes, the neutral is bonded to the EGC and all the grounding wires are tied to the neutral. Thanks, you and the other guys and gals on this board are great. Its much appreciated.

Any insight as to why an EGC is not acceptable at a subpanel but has to be run back to the main panel?

 

[iwire]

Do you have any insight as to why the code now requires a grounding wire to be run back to the main panel? What is the difference between sinking a EGC and bonding to it?

If you mean just putting a ground rod and tying only the branch circuit EGCs to it that would be extreamely hazerdous and would not provide any protection at all. You must have a wire or raceway type EGC from the panel all the way back to the source which is the utility transformer.

You cannot use the earth for the EGC.

Since the code changed, there must have been some reason that made the change necessary.

I think you missed the part about the code used to allow the neutral to be used as wire type EGC. You could run just two hots and a neutral to the remote building. At that building you would be required to bond the neutral to the panelboard exactly like we do for a service.

Then you would add the grounding rods and connect those to the bonded neutral in the panel, again like a service.

The neutral would be the EGC for clearing ground faults and the grounding rods are for lightning protection and ... well ... just to pass the inspection. It's hard to say if rods help at all for this type of installation but they (or some type of grounding electrodes) are required.

 

[FionaZuppa]

no egc ? yikes, lifted N or even high ohms N, and zap.
make every effort to get a egc back to main panel, keep N isolated at the sub. N's and egc's dont touch until they meet in service panel, etc.

buried PVC? can you blow a string through and pull an insulated egc wire?

 

[iwire]

no egc ? yikes, lifted N or even high ohms N, and zap.
make every effort to get a egc back to main panel, keep N isolated at the sub. N's and egc's dont touch until they meet in service panel, etc.

Are you aware that using the neutral as the EGC was allowed up until about 10 years ago?

Are you aware it is still allowed in existing installations?

Are you aware when doing it this way it is required to bond the neutral?

If you tell me that using the neutral as the EGC for this application is unsafe then every service in the US is also unsafe.

I know who put the proposal in for the change stopping this practice and the only substantiation given was to make it more in line with the rest of the NEC.

 

[FionaZuppa]

Are you aware that using the neutral as the EGC was allowed up until about 10 years ago?

Are you aware it is still allowed in existing installations?

Are you aware when doing it this way it is required to bond the neutral?

If you tell me that using the neutral as the EGC for this application is unsafe then every service in the US is also unsafe.

I know who put the proposal in for the change stopping this practice and the only substantiation given was to make it more in line with the rest of the NEC.

yep, uh-huh. my statement still stands.

250.32 Exception No.1: For installations made in compliance
with previous editions of this Code that permitted such connection...

i dont really follow what nec means here. so if i am doing a install to 2005 nec spec why would i be reading this passage from this newer nec ??

 

[iwire]

yep, uh-huh. my statement still stands.

So you are going to stand by a clearly false statement.

i dont really follow what nec means here. so if i am doing a install to 2005 nec spec why would i be reading this passage from this newer nec ??

I get called to a job, they want a panel replaced in a separate building supplied by a feeder. It happens this exsiting feeder is using the grounded conductor as the equipment grounding conductor as had been allowed for decades.

This exception makes it clear I can reuse this existing feeder for work I do today.

It is that exception that makes this statement by you ...

.
make every effort to get a egc back to main panel, keep N isolated at the sub. N's and egc's dont touch until they meet in service panel, etc.

.... false at least from a code perspective.

As far as the open neutral issue, it is no more hazardous for this feeder than it is for every service in the US.

 

[FionaZuppa]

in another conversation around 3-wire as a feeder

I think the EGC to a separate strutcure is a good rule. There should be an exception to a meter pedestal though.

imho, the nec might allow it, but if you can pull a egc wire then do it.
did OP ever say to what nec code the existing feeder was installed to? is it on a permit card?

 

[Dennis Alwon]

in another conversation around 3-wire as a feeder



imho, the nec might allow it, but if you can pull a egc wire then do it.
did OP ever say to what nec code the existing feeder was installed to? is it on a permit card?

By the OP's response my guess is the install was before 2005

 

[FionaZuppa]

By the OP's response my guess is the install was before 2005

so, ok, by ned, just swap the panel. or, to be safer per newer nec code, pull a egc if possible.

 

[iwire]

or, to be safer per newer nec code, pull a egc if possible.

Where we pulling this EGC too? All the way back to the utility transformer? If not I am not seeing any real safety improvement.

 

[FionaZuppa]

Where we pulling this EGC too? All the way back to the utility transformer? If not I am not seeing any real safety improvement.

if it were a new feeder would it be a 3 or 4 wire?