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Old 04-26-2011, 07:32 AM   #91
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Do I need a sub panel here?


It easier and cheaper to buy panel with a main installed.

As far sixe breaker it can be any size in the subpanel providing it does not exceed the amperage of the conductors supplying he breaker.
If you have a 100 amp breaker in main panel and the conductors to subpanel are rated for 100 amps ie #4 copper, than the breaker at the subpanel can be any size up to rating of panel


Last edited by NJMarine; 04-26-2011 at 07:34 AM.
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Old 04-26-2011, 07:36 AM   #92
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Originally Posted by NJMarine View Post
It easier and cheaper to buy panel with a main installed.

As far sixe breaker it can be any size in the subpanel providing it does not exceed the amperage of the conductors supplying he breaker.
If you have a 100 amp breaker in main panel and the conductors to subpanel are rated for 100 amps ie #4 copper, than the breaker at the subpanel can be any size up to 100 amp.
I understand the fact that I should have bought a box with a main installed... but I didn't. I have what I have, and I have already pushed the knockouts out so I can't take it back. I'm going to work with what I have. I'm trying to focus on the box I have..

My main question now is if it is within code to backfeed a breaker to make it the main breaker.
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Old 04-26-2011, 07:54 AM   #93
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Do I need a sub panel here?


It is code compliant as long as the breaker can't pop off the bus bar. The hold down kit makes the breaker solidly mounted. If this were a GE main breaker panel, the breaker that would be mounted at the top is the same breaker - THQL - that would be snapped onto the bus bar in your case. In the GE's, that main breaker is held into place with a press down lock ring. So think of the term "back fed" as more to the position the breaker is attaching to the bus bar and the fact it has to have the physical protection from popping off the bus bar.
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Old 04-26-2011, 07:56 AM   #94
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Do I need a sub panel here?


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Originally Posted by a7ecorsair View Post
It is code compliant as long as the breaker can't pop off the bus bar. The hold down kit makes the breaker solidly mounted. If this were a GE main breaker panel, the breaker that would be mounted at the top is the same breaker - THQL - that would be snapped onto the bus bar in your case. In the GE's, that main breaker is held into place with a press down lock ring. So think of the term "back fed" as more to the position the breaker is attaching to the bus bar and the fact it has to have the physical protection from popping off the bus bar.
Thanks. I still have to pick up the hold down bracket and the main breaker itself.
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Old 04-26-2011, 08:19 AM   #95
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Do I need a sub panel here?


Quote:
Originally Posted by NJMarine View Post
It easier and cheaper to buy panel with a main installed.

As far sixe breaker it can be any size in the subpanel providing it does not exceed the amperage of the conductors supplying he breaker.
If you have a 100 amp breaker in main panel and the conductors to subpanel are rated for 100 amps ie #4 copper, than the breaker at the subpanel can be any size up to rating of panel
Not true!

If you feed 100 amps from the main panel, the disconnecting means at the subpanel must be rated at 100 amps or higher!

If you feed 60 amps from the main, the disconnecting means at the subpanel must be rated 60 amps or higher.
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Old 04-26-2011, 08:32 AM   #96
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Do I need a sub panel here?


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[/B]Not true!

If you feed 100 amps from the main panel, the disconnecting means at the subpanel must be rated at 100 amps or higher!

If you feed 60 amps from the main, the disconnecting means at the subpanel must be rated 60 amps or higher.
Curious to the reasoning behind that requirement, besides code compliance that is. Anyone?
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Old 04-26-2011, 10:52 AM   #97
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Do I need a sub panel here?


1 reason is you would not have use of the full capicity of incoming power.
You would be limited to the size of breaker you install in the panel.
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Old 04-26-2011, 11:35 AM   #98
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1 reason is you would not have use of the full capicity of incoming power.
You would be limited to the size of breaker you install in the panel.
Yes, indeed. You would be limited to the capacity of the sub panel disconnect. I just don't understand how that would create an unsafe condition. I thought the code was written as minimum standards to prevent such dangers. Wouldn't this just be 'overbuilding'? Is this requirement in the code, it would be good to know (no need to specify the actual article). Thanks.
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Old 06-02-2011, 07:32 AM   #99
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Do I need a sub panel here?


Hate to bring this thread back up, but I have another question. I finally got an electrician out to the house yesterday to see this building, and get some prices on doing everything. When we were talking about the sub panel, he told me I do not need a breaker in the sub panel to act as a disconnect. He says since this panel is the main lug type, the two hots will go to the lugs, the neutral will go to the neutral bar and the ground to the ground bar. I didn't argue, but I could have sworn that you guys said it needed a disconnect.

He also said that 2,2,2,4 aluminum wire (the feeder) was good for 100 amps, and I could put a 100 amp breaker in the main panel. Seems I had seen or read where it was good for 90 amps, and I had intended on putting a 90 amp breaker in the main panel.

Is there something in the code that says that I have to have a disconnect, or can it be done the way that he is saying by just running to the main lugs?

Here is the picture of the sub panel


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Old 06-02-2011, 07:51 AM   #100
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Do I need a sub panel here?


The next thing he will tell you is that you only need 3 wires for the feed and you don't need a separate ground bar or ground rod(s). You need a new electrician.
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Old 06-02-2011, 08:21 AM   #101
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The next thing he will tell you is that you only need 3 wires for the feed and you don't need a separate ground bar or ground rod(s). You need a new electrician.
He did say I needed 4 wires for the feeder.
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Old 06-02-2011, 08:42 AM   #102
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Do I need a sub panel here?


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Originally Posted by J S Machine View Post

Is there something in the code that says that I have to have a disconnect, or can it be done the way that he is saying by just running to the main lugs?
There is a reference in the NEC that applies to panel with 6 or fewer disconnects stating that a single disconnect is not required but I don't know all the details.
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Old 06-02-2011, 08:44 AM   #103
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Do I need a sub panel here?


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There is a reference in the NEC that applies to panel with 6 or fewer disconnects stating that a single disconnect is not required but I don't know all the details.
Do you mean that if I have less than 6 breakers I don't need a disconnect?
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Old 06-02-2011, 08:46 AM   #104
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He did say I needed 4 wires for the feeder.
JS, I was exaggerating. But you do need a disconnect (main breaker). And I am not sure which NEC amperacity table he is using for the 100 amp rating.
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Old 06-02-2011, 10:02 AM   #105
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Do I need a sub panel here?


For your disconnect, you can have no more than 6 operations of the hand. If you’re going to have 7 or more breakers (including tandems) you’d have to use handle ties to bring those down to the 6 operations of the hand rule. Personally, I’d use a single breaker to act as the disconnect if 7 or more.

#2 aluminum is good for 100A only in 120/240V, 3-wire, single-phase dwellings, where it is either the service entrance conductors, or the main power feeder. In other words, all of the power for that dwelling has to run through that feeder, not just part of the building. 310.15 (B)(6)

So in your case of only your shop being run off a feeder, you would use Tbl 310.16. Since most likely the terminals that this feeder is being hooked to are rated 75*C, the ampacity allowed for #2 AL is 90A if your running wire in conduit.

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