Grounding/bonding question

[ggunn]

I'm pretty sure I know the answer to this one, but I have to ask...

We are doing work in a residential MDP which is in a closet inside the dwelling. There is an external service disco with OCPD. The neutral is bonded to ground at the disco.

Inside the MDP the neutral and ground bars are bonded (obviously a problem), the branch circuit neutrals and EGCs are all connected willy-nilly to whichever bar the electrician(s) fancied at the time, and the inside of the enclosure is a rat's nest.

My question is this: Is there any wiggle room in the NEC that would allow our guys to fix the problem by unbonding neutral from ground at the disco instead of untangling the rat's nest, unbonding the bars, and separating the branch circuit ECG's from the neutrals?

 

[augie47]

as you say, you know the answer

 

[charlie b]

Tell me that the MDP has a main breaker, and I will offer you some wiggle room. Remove the outside disconnect entirely, and put some type of enclosure in its place just to house the connections. The code requires the N-G bond at (or upstream of) the first disconnecting means. Your problem is that the external disconnect presently serves that role. So reassign that role to the main breaker in the MDP.

 

[ggunn]

Tell me that the MDP has a main breaker, and I will offer you some wiggle room. Remove the outside disconnect entirely, and put some type of enclosure in its place just to house the connections. The code requires the N-G bond at (or upstream of) the first disconnecting means. Your problem is that the external disconnect presently serves that role. So reassign that role to the main breaker in the MDP.

Thanks, but I am pretty sure the POCO requires an external service disconnecting means. I told our guys to bite the bullet.

 

[jap]

I'm pretty sure I know the answer to this one, but I have to ask...

We are doing work in a residential MDP which is in a closet inside the dwelling. There is an external service disco with OCPD. The neutral is bonded to ground at the disco.

Inside the MDP the neutral and ground bars are bonded (obviously a problem), the branch circuit neutrals and EGCs are all connected willy-nilly to whichever bar the electrician(s) fancied at the time, and the inside of the enclosure is a rat's nest.

My question is this: Is there any wiggle room in the NEC that would allow our guys to fix the problem by unbonding neutral from ground at the disco instead of untangling the rat's nest, unbonding the bars, and separating the branch circuit ECG's from the neutrals?

What you haven't told us is how the inside panel is fed from the outside disconnect.

3 wire or 4 wire or possibly 3 wire in emt or etc.....


JAP>

 

[ggunn]

What you haven't told us is how the inside panel is fed from the outside disconnect.

3 wire or 4 wire or possibly 3 wire in emt or etc.....


JAP>

I don't see what difference it makes, but it is 1P3W plus ground in EMT. The grounding electrode is under the disco on the exterior wall.

 

[ggunn]

Tell me that the MDP has a main breaker, and I will offer you some wiggle room. Remove the outside disconnect entirely, and put some type of enclosure in its place just to house the connections. The code requires the N-G bond at (or upstream of) the first disconnecting means. Your problem is that the external disconnect presently serves that role. So reassign that role to the main breaker in the MDP.

I misunderstood what is going on here. What has happened is since we are adding a PV system to the MDP, under "you touch it, you fix it", the POCO is making us install a service disconnecting means on the outside of the building. They did not require it at the time the house was built, but they do now.

The existing MDP in the building is for the moment the first disconnecting means on the service just as you suggested as a remedy. It was legal at the time it was installed, but now we have to install a disco on the outside of the building and there's no ground wire out there. The MDP is in a closet not near an exterior wall, and the cable to the outside goes through the walls. My opinion is that we need to drive a rod at the disco, bond it to neutral, run a ground wire through the attic to the MDP, and break the existing N-G bond (untangle the rat's nest) in the MDP. It's not a popular opinion.

This just in: Our guys are meeting the AHJ on site and will do what he tells them to do. Somebody else's problem...

 

[jap]

I don't see what difference it makes, but it is 1P3W plus ground in EMT. The grounding electrode is under the disco on the exterior wall.

Why do you have to run a ground through the attic if you've already got and EGC from the outside disconnect to the inside MDP?

Just separate the EGC's and the Neutral Conductors on the panel to their separated bars.

The Neutral and Ground will remain bonded together at the service disconnect, and , be separate at the indoor panel.

If you didn't have the 4th wire, or, the EMT as an EGC from the outside disconnect inside to the panel already, you'd have much bigger fish to fry.

JAP>

 

[ggunn]

Why do you have to run a ground through the attic if you've already got and EGC from the outside disconnect to the inside MDP?

Reread post #7.

 

[jap]

Reread post #7.

You had mentioned the existing Feeder to the panel was 1ph 3w with Ground in EMT, that indicates to me that there is already a means of overcurrent protection somewhere ahead of the existing panel. Possibly a meter/main remote from the structure.

Otherwise, there would not be a 4 wire feeder.

If the feed came from the utility transformer through the meter, then, directly to the existing panel with the main breaker, it would only be 3 wire, not 4.

So I guess I'll bail out for lack of completely understanding your situation.

JAP>

 

[ggunn]

You had mentioned the existing Feeder to the panel was 1ph 3w with Ground in EMT

Read my post #7 again. I was mistaken (I was given the wrong information, actually, or I misinterpreted what was told to me) about the ground wire from the outside wall. There isn't one. The existing conductors are service conductors, not a feeder.

 

[romex jockey]

So ggunn, if this is all about the PV introduction,could you just make it to the panel.....?

~RJ~

 

[jaggedben]

They are making you add a new service disconnect and not just an external PV disconnect?

 

[david]

Tell me that the MDP has a main breaker, and I will offer you some wiggle room. Remove the outside disconnect entirely, and put some type of enclosure in its place just to house the connections. The code requires the N-G bond at (or upstream of) the first disconnecting means. Your problem is that the external disconnect presently serves that role. So reassign that role to the main breaker in the MDP.

From his original description with the panel in a closet i was thinking manufactured home

if that would have been the case, the service may be required outside article 550

 

[david]

They are making you add a new service disconnect and not just an external PV disconnect?

Based on the utility requirement here, that was my thought, i would verify that first

 

[ggunn]

They are making you add a new service disconnect and not just an external PV disconnect?

Yes. There are a couple of AHJs around here that now require an external service disconnect where they didn't at some point in the past. "You touch it, you fix it" is enforced on us in those jurisdictions when we do anything to the customer's system where they don't have an external service disconnect. Usually we know about it in advance so that we can plan for it or punt the job.

My understanding (and I still don't have all the facts) is that this happened in a new jurisdiction for us where we were unaware of this requirement until we failed inspection for a system we had installed. At that point there was no backing out.

 

[ggunn]

From his original description with the panel in a closet i was thinking manufactured home

It's not.

 

[ggunn]

So ggunn, if this is all about the PV introduction,could you just make it to the panel.....?

~RJ~

It makes no difference in this situation where we make the interconnection.

 

[ggunn]

Yes. There are a couple of AHJs around here that now require an external service disconnect where they didn't at some point in the past. "You touch it, you fix it" is enforced on us in those jurisdictions when we do anything to the customer's system where they don't have an external service disconnect. Usually we know about it in advance so that we can plan for it or punt the job.

My understanding (and I still don't have all the facts) is that this happened in a new jurisdiction for us where we were unaware of this requirement until we failed inspection for a system we had installed. At that point there was no backing out.

I'll just add that those of us who install PV in many jurisdictions know that the information pertinent to this type of situation is not always easily or readily available from the AHJ. Sometimes we get blindsided.