subpanel explanation

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mg165

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I help some home inspectors in my area with questions they have. An inspectors asks:
"Here is my dilemma. My clients have their main electrical panel in the garage. It is a 200 amp panel, with shut off , likely only 5 to 8 years old. Since the panel is over 15 ft. from the meter (outside, with shut off) the clients have been told that the panel in the garage is a sub- panel and grounds/neutrals should be separated."

I replied -"2 thoughts.If there is an outdoor disconnect after the meter, any panel after that is considered a subpanel. Period. This would have also required that the cable AFTER the outdoor disconnect that runs to the panel be SER cable. Round not flat. 4 conductors. 2- hots, 1 neutral and 1 ground.
Regarding subpanels and unfused conductors. After the meter, the submain cable can run almost anywhere outside but when it enters the building it must be protected (breaker/fuse) within 3-5 feet, not sure).
I suspect the panel is on an interior wall, hence the outdoor disconnect."

He replied - "Thanks again for your fast response and knowledge. One question ?.do the neutrals and grounds have to be separated in the sub-panel, that is located on the interior wall. (Rear wall of garage) I do believe that the cable running to the panel is SER, but from memory I can not be 100% sure. One other question?..sorry ??what if the sub main cable is flat (3 conductor) ????"

He's not listening.

Please, a good, easy explanation of subpanel connections.....
 
Sometimes it is best just to tell them (laymen in general) something is either OK or not OK, it will help your stress level stay low. ;)

Roger
 
Regarding subpanels and unfused conductors. After the meter, the submain cable can run almost anywhere outside but when it enters the building it must be protected (breaker/fuse) within 3-5 feet, not sure).
I suspect the panel is on an interior wall, hence the outdoor disconnect."
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Your statement here is somewhat confusing. The panel would only become a subpanel after the service disconnect. If there is no OCPD between the meter and the panel, than the panel is the service and must contain the service disconnect. Service entrance conductors can run for any length on the outside of the building.

Once a service disconnect/OCPD is installed adjacent to the meter the conductors between that and the subpanel can be run either inside or outside of the building. The subpanel would require it's feeder to contain separate grounded and grounding conductors and separate terminations of each within the subpanel.
 
I replied -"2 thoughts.If there is an outdoor disconnect after the meter, any panel after that is considered a subpanel. Period. This would have also required that the cable AFTER the outdoor disconnect that runs to the panel be SER cable. Round not flat. 4 conductors. 2- hots, 1 neutral and 1 ground

read 250.32(B)(2) may have local codes that do not allow but also this was intalled several years ago and was propably exceptable at time do not have upgrade every time the NEC changes


Regarding subpanels and unfused conductors. After the meter, the submain cable can run almost anywhere outside but when it enters the building it must be protected (breaker/fuse) within 3-5 feet, not sure).
I suspect the panel is on an interior wall, hence the outdoor disconnect."

225.32 Location of disconnect readily accessible nearest the piont of entrance as per NEC this can interupted differently by local requirements but there is already a disconnecting means ahead of this one so it can be some what relaxed
 
Bea said:
read 250.32(B)(2) may have local codes that do not allow but also this was intalled several years ago and was propably exceptable at time do not have upgrade every time the NEC changes
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Good to tell your inspector friends to remember. An existing, compliant-when-installed service requires no alteration.

Also, remember that disconnect and over-current device have different purposes:

The location of the disconnect determines the neutral/grounding bond location, beyond which they must remain separate, and determines whether you need SE or SER to the breaker panel.

In order to run the service cable within the structure beyond "nearest the point of entrance", the over-current device itself must be outside. This in turn requires the SER, as above.
 
LarryFine said:
In order to run the service cable within the structure beyond "nearest the point of entrance", the over-current device itself must be outside. This in turn requires the SER, as above.
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That's kind of a broad statement, it depends on the interpretation of the AHJ, IMO. "Near" is a relative term.

Even here in CO, where almost all service disconnecting means are outside, there come occasions where running underground, coming up through the basement floor and installing the service disconnecting means there is the most practical option.

Sometimes meter sockets are installed outside with the service disconnecting means inside, on the other side of the wall.

Bear in mind the section quoted is dealing with the disconnecting means, the OCPD is dealt with in a different section, 230.91.

I could find no support for the idea of fusing the service conductors outside and running through the interior of the structure to get to the service disconnecting means...?

Not trying to pick on you Larry... :D
 
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infinity said:
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Once a service disconnect/OCPD is installed adjacent to the meter the conductors between that and the subpanel can be run either inside or outside of the building. The subpanel would require it's feeder to contain separate grounded and grounding conductors and separate terminations of each within the subpanel.
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I just came back from a job that I think ties to this subject. I am looking for a confirmation of what to do.

Situation: 100 amp service, two circuit outdoor panel at meter 100 amp breaker. From here the conductors travel to the panel in the basement, this is about 30 ft into the house. The 30 ft is a true crawl space. What I found in the house is in no way correct.

I'm proposing a panel change in the house, new conductors into the house panel.

1. This would be a sub-panel since there is an OCD outside. Correct?
2. When I start this job I need to take the water ground and driven ground to the OUTDOOR panel and then separate the Neutral and Grounds at the house panel. Correct?

I look forward to insight and options.
 
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1793 said:
I'm proposing a panel change in the house, new conductors into the house panel.

1. This would be a sub-panel since there is an OCD outside. Correct?
2. When I start this job I need to take the water ground and driven ground to the OUTDOOR panel and then separate the Neutral and Grounds at the house panel. Correct?

I look forward to insight and options.
Click to expand...


Norb
Your comments are correct.
 
JohnJ0906 said:
Did they run 4 conductors to the inside panel? (2 hots, 1 neutral, 1 egc)
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You would not believe what I found at this job. There is an old SE, cloth type, feeding this in house panel. 2 hots & 1 bare ground. A "sub-panel" off of this panel just inches away, 50 amp DP feeding 10/2 Romex to a 100 amp main breaker in the "sub-panel". There are three circuits in the "sub-panel". There is some triplex heading the length of the basement that feeds something in a detached garage. I did not get access to the garage.

What I have detailed are just a few of the main points.

With the panel change a rewire will follow.
 
georgestolz said:
I could find no support for the idea of fusing the service conductors outside and running through the interior of the structure to get to the service disconnecting means...?

Not trying to pick on you Larry... :D
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Not feeling picked on at all. My point is that, when conductors are run past the AHJ-determined distance inside the structure, the over-current device is outside to protect the conductors, or more specifically, to protect the house from the conductors.

The disconnect and the over-current device provide related, but different, purposes. The disconnect is a switch; the over-current device is protection. If you have a breaker outside, it also becomes the disconnect by virtue of being first in line.

You could have a switch only outside, as a disconnect, but it does not provide any protection beyond that as a switch. The conductors are not protected unless a breaker or fuses are installed appropriately.

The rules for both are slightly different. Access requirements are a good example.
 
JohnJ0906 said:
Did they run 4 conductors to the inside panel? (2 hots, 1 neutral, 1 egc)
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This then brings up another thought:

Since this is technically a sub-panel, can I still use Table 310.15(B)(6) -- #2 AL SER at 100 amps to the in house panel? :confused:

So: 1. Table 310.16 #1 AL SER @ 75deg
or 2. Table 310.16 #3 CU SER @ 75deg

Does 334.80 come into play for ampacity?

Edited to add: "So....
 
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1793 said:
Since this is technically a sub-panel, can I still use Table 310.15(B)(6) -- #2 AL SER at 100 amps to the in house panel?
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stickboy1375 said:
No.........
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No is correct. You're never allowed to use '15 (B)(6) for a sub-panel.
 
I disagree. I think this still qualifies as a main feeder under 310.15(b)(6). meter to main disconect outside to main panel inside. Ther is only one feeder leaving the main disconnect outside, right? You still need to seperate EGCs and neutrals though.
 
JohnJ0906 said:
I disagree. I think this still qualifies as a main feeder under 310.15(b)(6). meter to main disconect outside to main panel inside. Ther is only one feeder leaving the main disconnect outside, right? You still need to seperate EGCs and neutrals though.
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No, a sub panel is not a main feeder... so you cannot use table 310.15(B)(6) I see this code violation all too often...:mad:


Sorry just reread your post, yes you can use table 310.15(B)(6) after the service disconnect, because that feeder still carries the entire load....
 
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Larry, I see what you were saying, now. I was picturing fuses installed outside by the meter socket, and then OCPD-protected (but not switched) conductors running inside, through the structure.

I agree with the above posters that a feeder supplying a "sub-panel" supplied from the service disconnect could make use of 310.15(B)(6).

My advice to the original poster would be to instill in the person the mindset to follow the neutral paths back to the source, bearing in mind the rule that neutral current is not to flow on equipment grounding conductors. Anywhere neutrals and EGCs touch, current will take both paths. That's about as simply put as I can think to put it at the moment. :)
 
stickboy1375 said:
No, a sub panel is not a main feeder... so you cannot use table 310.15(B)(6) I see this code violation all too often...:mad:


Sorry just reread your post, yes you can use table 310.15(B)(6) after the service disconnect, because that feeder still carries the entire load....
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I could not see why the use of 310.15(B)(6) would not be allowed form the disconnect to the house panel but could not articulate my reason to fully discuss the point. I do appreciate the explanation and input from all. I'm here, as others have said, to learn.
 
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