MAIN BONDING JUMPER AT REMOTE PANEL BOARD

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florida-sparkey

Senior Member
Location
Pinellas Park, Florida
Occupation
Master Electrician
Now that I have your attention..:p I have a service call in a condo built in the 1960s. The service has a fused disconnect downstairs. I cannot find a main bonding jumper in it. There is a 208/120V 3 wire system up to the unit- L1,L2,N. Feeders terminate in a main breaker at unit. MBJ is connected at the panel. No original riser prints available. I cannot access any other unit to see if the replaced panel is a change from original design. My question is: If the EMT is the ground and I am looking at a "3 wire with ground" I would need to remove the bonding jumper in panel and isolate neutral block. Then I would need to add the MBJ at the first disconnect. My concern is that this is a change from the original design. Additionally, I do not like to use EMT as the sole ground conductor. But, Clearly, leaving it as it is keeps a parallel circuit in place for the neutral (unbalance) current. In other services, I have seen circuit breakers used as connection blocks in metering equipment. The AHJ and I agreed this was solely as a "terminal" to connect the feeders to the meter equipment stabs and that the main disconnect was at the panel in the units. The difference in those cases was that the conduit carring L1,L2,N was PVC. I can see no such purpose for the fuses in enclosures as the breakers were used. Any Ideas as to why to go one way or the other? Was there a time when the MBJ could be at a location not in the individual disconnect and I am just missing it? (NOT an assembly per 250.24(5)(B) exception 1, they are individual disconnects)
 
florida-sparkey said:
Now that I have your attention..:p
I have a service call in a condo built in the 1960s.
The service has a fused disconnect downstairs.
I cannot find a main bonding jumper in it.
There is a 208/120V 3 wire system up to the unit- L1,L2,N. Feeders terminate in a main breaker at unit. MBJ is connected at the panel. No original riser prints available.
I cannot access any other unit to see if the replaced panel is a change from original design.

My question is:
If the EMT is the ground and I am looking at a "3 wire with ground" I would need to remove the bonding jumper in panel and isolate neutral block.
Then I would need to add the MBJ at the first disconnect.
[No question yet???]
My concern is that this is a change from the original design. Additionally, I do not like to use EMT as the sole ground conductor.
But, Clearly, leaving it as it is keeps a parallel circuit in place for the neutral (unbalance) current.
In other services, I have seen circuit breakers used as connection blocks in metering equipment. [?????]
The AHJ and I agreed this was solely as a "terminal" to connect the feeders to the meter equipment stabs and that the main disconnect was at the panel in the units.
The difference in those cases was that the conduit carr[y]ing L1,L2,N was PVC.
I can see no such purpose for the fuses in enclosures [what fuses in what enclosures?] as the breakers were used.
Any Ideas as to why to go one way or the other? Was there a time when the MBJ could be at a location not in the individual disconnect and I am just missing it? (NOT an assembly per 250.24(5)(B) exception 1, they are individual disconnects)
Click to expand...

See if that helps any. :happyyes:

Where are the individual meters in this setup?

If the main fused disconnect is indeed the NEC service disconnect, you do not have much choice under the NEC.
If you can argue that this is just a safety disconnect required by POCO and the service disconnects are actually downstream by each of the meters, then the answer could be different.
The only recent changes in the NEC involved service and feeders to separate buildings, which does not seem to be the situation for you.
 
jumper said:
It does for me.:thumbsup:

Of course me being a persnickety old grouch you could also double space lines....yeah I am pushing it.:D
Click to expand...

Thanks for the replys I am sorry about the run together question. I cut and pasted it and something went wrong.

Sorry for the late reply... Its a long ago job now but because you took your time here is the end result:

The meters are up on the different floors in equipment rooms. Way away from the service entrance point floors below.

We bonded the one panel to the EMT and left the MBJ in place at this panel. We gained access to, and found, the same connection in another unit with original fuse box.

I advised the HOA pres to have an AHJ or PE look at it for possible safety concerns and sited some NEC codes on the ticket. He probably will do nothing but at least I tried...

Thanks again!!
 
florida-sparkey said:
Thanks for the replys I am sorry about the run together question. I cut and pasted it and something went wrong.

Sorry for the late reply... Its a long ago job now but because you took your time here is the end result:

The meters are up on the different floors in equipment rooms. Way away from the service entrance point floors below.

We bonded the one panel to the EMT and left the MBJ in place at this panel. We gained access to, and found, the same connection in another unit with original fuse box.

I advised the HOA pres to have an AHJ or PE look at it for possible safety concerns and sited some NEC codes on the ticket. He probably will do nothing but at least I tried...

Thanks again!!
Click to expand...


Thanks for the update. So few give updates after they receive help here. IT seems like you know what should be done: Bond main disconnect, isolate neutrals upstream. Note there is an exception that meter assemblies may be neutral bonded on the load side of the service disconnect, but I dont remember specifics/restrictions without looking it up.

A few comments on the EMT as equipment ground: It seems like long before I was in the trade, somehow this became frowned upon, and now nearly everyone wastes copper on an added wire EGC, despite studies that show most fault current takes the pipe when both are present. I was trained to "pull a ground" and had to fight the stigma of not doing so for a while, but now I rarely do.
 
electrofelon said:
...A few comments on the EMT as equipment ground: It seems like long before I was in the trade, somehow this became frowned upon, and now nearly everyone wastes copper on an added wire EGC, despite studies that show most fault current takes the pipe when both are present. I was trained to "pull a ground" and had to fight the stigma of not doing so for a while, but now I rarely do.
Click to expand...
Glad to hear you were set free from of the Cult of the Green Wire.
 
iwire said:
When I see pictures like that my first thought is not if the installer pulled a wire EGC or not. It is if they complied with the NEC regarding securing, supporting and conditions of use etc.

If you install conduits following those rules it should not be falling down.
Click to expand...
Depends on if they were hit with a front end loader and then ignored. The larger conduit is close to 15' or better.

I agree, most of it is conditions of use as is the smaller conduit where strapping has rotted away.
 
iwire said:
When I see pictures like that my first thought is not if the installer pulled a wire EGC or not. It is if they complied with the NEC regarding securing, supporting and conditions of use etc.

If you install conduits following those rules it should not be falling down.
Click to expand...

I think in my county the reason is because you often can go into an attic and see where, for whatever reason, that EMT has been separated by busted set screw coupler or the like. One step from an insulator or cable guy 20 years after install and you have a safety issue. Clowns will also intentionally bend it if its in there way for any reason and you cannot strap for that. I have seen this many times in condo remodels so I do agree with the spirit of the rule in my county and have no issue in following it. I also think an electrician go killed by separating EMT that had an unknown fault current on it and that is what triggered the rule but I could be wrong on that.
 
florida-sparkey said:
I think in my county the reason is because you often can go into an attic and see where, for whatever reason, that EMT has been separated by busted set screw coupler or the like. One step from an insulator or cable guy 20 years after install and you have a safety issue.
Click to expand...

The EMT was not supported or secured correctly or was run where it was subject to damage. Either of those are code violations.


Clowns will also intentionally bend it if its in there way for any reason and you cannot strap for that.
Click to expand...

I don't wire for clowns, it is not possible.
 
iwire said:
The EMT was not supported or secured correctly or was run where it was subject to damage. Either of those are code violations.




I don't wire for clowns, it is not possible.
Click to expand...

Ok I get it. your not a fan of the green wire. :thumbsup: I will argue one point on your comments.
The conduit could be straped perfectly by code and have something happen to it. Especially in a residential setting. I have seen it many times. The fact that it did or how or

why it got damaged after install and inspection 20 years ago is not the debatable item here is it? What is debatable is whether there is some value to the redundancy of the

ground path. In my area, smart people including inspectors and bureaucrats have ruled yes. This is also one of only a few changes to the NEC that the Florida state board

has looked at and approved within the state.

Thank you for your help, I really appreciate it!
 
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iwire said:
The EMT was not supported or secured correctly or was run where it was subject to damage. Either of those are code violations.
Click to expand...
I have to agree, about every broken or pulled apart fitting I have ever seen in an attic, probably would not have broken or pulled apart if the raceway were properly supported in the first place. Those being damaged by front end loaders, forklifts, etc. possibly should have been routed in a different location in the first place.

florida-sparkey said:
Ok I get it. your not a fan of the green wire. :thumbsup: I will argue one point on your comments.
The conduit could be straped perfectly by code and have something happen to it. Especially in a residential setting. I have seen it many times. The fact that it did or how or

why it got damaged after install and inspection 20 years ago is not the debatable item here is it? What is debatable is whether there is some value to the redundancy of the

ground path. In my area, smart people including inspectors and bureaucrats have ruled yes. This is also one of only a few changes to the NEC that the Florida state board

has looked at and approved within the state.

Thank you for your help, I really appreciate it!
Click to expand...
I'm not a fan of the green wire in every installation either. If attaching to an all steel structure, those mishaps when something gets damaged still has the steel structure to carry fault current. Yes NEC doesn't recognize this as an EGC, but reality is the structure may often carry more fault current then the green wire or the raceway in most incidents.
 
kwired said:
I have to agree, about every broken or pulled apart fitting I have ever seen in an attic, probably would not have broken or pulled apart if the raceway were properly supported in the first place. Those being damaged by front end loaders, forklifts, etc. possibly should have been routed in a different location in the first place.

I'm not a fan of the green wire in every installation either. If attaching to an all steel structure, those mishaps when something gets damaged still has the steel structure to carry fault current. Yes NEC doesn't recognize this as an EGC, but reality is the structure may often carry more fault current then the green wire or the raceway in most incidents.
Click to expand...

I think this went off the topic a little but thanks again for the input. Seems to be a hot debate on the green wire. In my case I can take the easy way out and simply say like it or not, I have to do the green wire in any new install or retro. Thems the rules for my neck of the woods and the AHJs do not have a sense of humor about it.:rant:

Thanks again to everyone for taking their time!!
 
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