Sub-Panels w/o ground

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  #1  
Old 11-14-06, 06:36 PM
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Sub-Panels w/o ground

Hi again, guys:

Just checked my two "non-service panels" (dating from 1974) and find that they do not have the required separate ground wire--only a three-wire feed.

Is it "legal" to just run a #4 ground wire (green jacket) to get the job done, or am I required to totally replace the feeder wires with a four-wire jacketed cable?

Sure would be nice to just add the ground wire!

Cheers,
 
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  #2  
Old 11-14-06, 07:37 PM
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If these are sub-panels in detached buildings from the service equipment panel that do not have any metal water lines or other metallic paths between them then 3-wire feeders are fine. You need ground rod/rods though at a detached building with a sub-panel.
If they are panels in the same structure with the service panel then 4 wire feeds are required with neutral and ground isolated electrically from one another in the sub-panels.

As for the ground wire size can you tell us the size of the feeder in awg for each sub-panel and what size ocpd's protecting those feeders?

Roger
 
  #3  
Old 11-15-06, 06:43 PM
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Hi Roger:

Both "sub-panels" are within the residential structure. The "main" panel is 125A and the shop panel is 100A.

Don't remember the size of the original jacketed cable to the "main" 125A subpanel" but the shop panel has AL wire correct for a 100A feed (but can't go look right now).

The main 125A disconnect is on the side of the house with the meter; the "main" panel" in the house is about 40 feet away, and the shop panel is about 20 feet away (from the disconnect).

Cheers,
 
  #4  
Old 11-15-06, 07:26 PM
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Sorry to interupt, This answer can wait.

If these are sub-panels in detached buildings from the service equipment panel that do not have any metal water lines or other metallic paths between them then 3-wire feeders are fine.

Would this include a metal raceway? I assume yes. detached or not.
 
  #5  
Old 11-15-06, 07:36 PM
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Originally Posted by billybard
Hi Roger:

Both "sub-panels" are within the residential structure. The "main" panel is 125A and the shop panel is 100A.

Don't remember the size of the original jacketed cable to the "main" 125A subpanel" but the shop panel has AL wire correct for a 100A feed (but can't go look right now).

The main 125A disconnect is on the side of the house with the meter; the "main" panel" in the house is about 40 feet away, and the shop panel is about 20 feet away (from the disconnect).

Cheers,
*The main 125A disconnect is on the side of the house with the meter; the "main" panel" in the house is about 40 feet away, *

This makes the primary panel (125A) a "SUB". From the disco at meter,there should be 4 wires HHNG (hot,hot,neutral,ground). From here to the next panel (100A-SUB) should be the same HHNG.

Is this wireing in metal conduit? or cable?

You don't meet any tap rule.
 
  #6  
Old 11-15-06, 07:50 PM
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Hi Lectriclee:

Yup, "main" panel is really a sub (inside the house) from the disconnect (outside the house with the meter).

Both sub-panels are fed with jacketed cable.
I am hoping that I can just run a separate ground wire (along the original wire path) and not have to remove the 3-wire cables and replace them with 4-wire cables.

Both sub-panels are fed from the disconnect (the smaller sub is NOT fed from the bigger panel).

Cheers,
 
  #7  
Old 11-15-06, 08:04 PM
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I see.... you have an outside main disconnect. In this case the disconnect is the service equipment and the 125 amp mlo (possibly a main breaker) panel inside is a sub-panel and then a 100 amp sub-panel is fed from the 125 amp panel. In this case you will have a 3 wire feed from the meter to the disconnect. Then a four wire feed to the inside panel. The equipment ground and neutral will be bonded in the main disconnect enclosure. The equipment ground can be an approved/listed metal raceway instead of a ground wire if the feeder is individual wires. Both panels will have H_H-N-Grd feeds.
The equip. grd can be a metal raceway as mentioned. Both neutral and ground must be electrically isolated in both subs.

OOPs I see this has already been replied to. In regards to running a seperate equipment grounding wire article 300.5 forbids wires of the same circuit to be ran outside of the same cable or raceway.

Roger
 
  #8  
Old 11-15-06, 08:30 PM
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Question

Both sub-panels are fed from the disconnect (the smaller sub is NOT fed from the bigger panel).*

Question to others. Would the 100A panel fall under A tap rule?
At 20' from main, no ground?

BillyBard, Are these panels fed in metal conduit?
When was this dwelling built (age of service/home)?

It doesn't sound right, But at one time (age of home) it may have been.
 
  #9  
Old 11-15-06, 09:55 PM
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Hi guys:

Thanks for taking the time to answer.

My home was built in 1974, but was done by a one-man-show who was prevalent in the area back then.

I have now lived in the home for six years, and I continue to find things that just don't seem right--although everything works OK.

Both sub-panels are fed with jacketed wire (like a very heavy Romex), but the shop sub-panel is fed with SEU (or is it SEC).
[Maybe someone can be kind enough to explain the difference.]

I think the previous post about ALL wires must be in the same jacket really answered my question, though. Darn....

Cheers,
 
  #10  
Old 11-16-06, 06:25 AM
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Billy.... Lectriclee points out that both panels are fed from the single main disconnect. How is that done? Have they tapped on the load side of the disconnect or line side? Have they just doubled the feeder wires in the disconnects lugs? Or did they use split bolt connectors or the like? Do the subs have main breakers? Just trying to get a better understanding of what you have there.

In regards to the cables. SEU (service entrance U-type) is a flat looking cable usually but not always with a gray outer jacket. It has a concentric braided bare neutral/ground surrounding the ungrounded conductors (hot wires). If it is an SER cable (service entrance round style) the bare will be in a wire form not braided around the other conductors.

Roger
 

Last edited by Roger; 11-16-06 at 06:39 AM.
  #11  
Old 11-16-06, 06:49 PM
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Thanks for the reply, Roger:

Yes, neither sub-panel has a main breaker--both are fed directly from the main 125A disconnect at the meter.

Guess both sub-panels are fed with SER (both cables are round and jacketed).

I believe that the original installation is flawed (not legal), cuz both the sub-panel feeds are under one lug on each phase of the disconnect. (In my remodel, I am planning on switching to a two-hole lugs for the load side of the main disconnect.)
 
  #12  
Old 11-16-06, 08:48 PM
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Next questions:

Is the disconnect part of a meter main with main disconnect only...ie...same enclosure as the meter?

Or is the 125 amp disconnect in a seperate enclosure from the meter?

You are correct the installation you have is not what you want.

There are a couple ways that are commonly done when feeding two panels from the meter.

One is to install a 320 meter base ( check with utility) that has double lugs for feeding two panels or two main disconnects and then feeders from the disconnects to the panels. In your situation you want two disconnects on the outside close together since your panels are not close to one another. Your disconnects must be grouped is the reason for this.

Or you could install a meter main combination panel which is a panel that has the meter then below the meter is a breaker panel in which you can install breakers to run feeders to the two sub panels.

Roger
 
  #13  
Old 11-16-06, 10:15 PM
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Thanks for the response, Roger.

Nuther option...

Can I use a meterbase and single main disconnect combo, and put two-hole lugs on the one disconnect?

Or must I use two separate disconnects for the two sub-panels?

Cheers,
 
  #14  
Old 11-17-06, 06:29 AM
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Billy

I wouldnt be familiar with that type of installation, so maybe someone else could respond. I'm going to say that probably isnt acceptable unless as lectriclee asked about a possible tap rule applying. But this would be out of my level of experience in a residential application. So I'm going to differ to someone else on being able to feed 2 panels from one main ocpd in a single family dwelling. I've never seen a double lugged main breaker in a residential application either.
Your limited in that the two panels are a ways from the planned main disconnect. If you were feeding one panel from the main disconnect then feeding the 100 amp panel from a breaker installed in that panel then things simplify some.

EDIT: You also should probably get a handle on what your total connected load or maybe I should say your demand load is.... as theoretically you have capability of 225 amps which is possibly going to effect the utility service if you are anywhere near that load amount by demand additions in the future.

Roger
 
  #15  
Old 11-17-06, 06:53 AM
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Billy,
If you do use a single disconnect and two main lug only panels, both panels and all cabling must be rated as the shared breaker. (EG, if it's a 125A shared breaker, both panels and their feeder cables must be rated for at least 125A).

100A panels would not fall under the bus tap rule unless they had 100A main breakers. If so, and if the other requrements are met, you could be allowed to use 100A cabling.

If the 100A panels are MLO and fed from a 125A breaker, the breakers in the panel can add up to at most 100A. And even then, I'm not 100% sure there isn't some other paragraph that would prohibit it.
 
  #16  
Old 11-17-06, 06:43 PM
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Thanks, guys, for the replys.

yeah, I was thinking about this today while doing other stuff.

All of a sudden, I realized that having a 100A MLO panel and a 125A disconnect seems like a non-no.

Guess I will persue a 200A service with dual disconnects for 125A and 100A--the things should be more or less legal.

Cheers,
 
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