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Old 02-28-2010, 01:04 PM   #1
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Sub panel wiring


I have been reading everywhere about separating ground and nuetral in sub panel and noticed mine in my garage is not! So I basically went ahead and fixed it so it would be right. I am pretty positive I did it correctly but I wanted to post this pic to get an expert answer...


Basically I removed the big green screw in the middle of the nuetral bar, added an additional bar on the right for the grounds, and then moved all grounds to the new bar. Is this correct?

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Old 02-28-2010, 01:14 PM   #2
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The only problem I see, is splitting the strands on the ground wire to connect it to the bar.
Not sure if it is a code violation or not, just something I avoid.

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Old 02-28-2010, 03:59 PM   #3
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Yup. Code violation. You need a larger lug adapter on that ground bar.

Here is a typical one:

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Old 02-28-2010, 04:16 PM   #4
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Sub panel wiring


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Originally Posted by kbsparky View Post
Yup. Code violation. You need a larger lug adapter on that ground bar.

Here is a typical one:

...And what about connecting a Black wire (subp. feeder) (regardless of polarity) to the Neutral bar?! And the White ("Neutral") wire disconnected!

Last edited by spark plug; 02-28-2010 at 04:17 PM. Reason: (Unnecessary) Duplication.
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Old 02-28-2010, 04:30 PM   #5
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Originally Posted by spark plug View Post
...And what about connecting a Black wire (subp. feeder) (regardless of polarity) to the Neutral bar?! And the White ("Neutral") wire disconnected!
Black with white stripe.....allowed ?

The other white wire...looks like the wires only feed a 30a 240v device ?
If the wire is run (like to a dryer) I connect it & upgrade to a 4 prong plug/outlet
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Old 02-28-2010, 04:38 PM   #6
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Sub panel wiring


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Originally Posted by Scuba_Dave View Post
Black with white stripe.....allowed ?

The other white wire...looks like the wires only feed a 30a 240v device ?
If the wire is run (like to a dryer) I connect it & upgrade to a 4 prong plug/outlet
Yeah. I didn't see the White strip. Maybe I need a new pair of glasses!!! Thanx!!
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Old 02-28-2010, 09:38 PM   #7
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Is this garage attached? If not, you may have a separate grounding rod for the garage depending on local code. I know when I put power to an outbuilding, I put a rod in and so my neutral and ground shared a bar.
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Old 03-01-2010, 07:29 AM   #8
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Is this garage attached? If not, you may have a separate grounding rod for the garage depending on local code. I know when I put power to an outbuilding, I put a rod in and so my neutral and ground shared a bar.
Just because you have a ground rod, the neutral and ground still must be seperated inside the sub panel.
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Old 03-01-2010, 09:55 AM   #9
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Thanks for straightening me out on that, then.
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Old 03-01-2010, 11:52 AM   #10
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Sub panel wiring


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Originally Posted by dukeofsolidsrfc View Post
I have been reading everywhere about separating ground and nuetral in sub panel and noticed mine in my garage is not! So I basically went ahead and fixed it so it would be right. I am pretty positive I did it correctly but I wanted to post this pic to get an expert answer...


Basically I removed the big green screw in the middle of the nuetral bar, added an additional bar on the right for the grounds, and then moved all grounds to the new bar. Is this correct?
Okay, I give up: What's with the white wire that comes down the left side, but doesn't appear to be attached to anything? Did you just take this photo before finishing the re-wiring of the panel, or is it something else?
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Old 03-01-2010, 12:01 PM   #11
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Okay, I give up: What's with the white wire that comes down the left side, but doesn't appear to be attached to anything? Did you just take this photo before finishing the re-wiring of the panel, or is it something else?
Looks like a 3 wire cable used for a 220 volt branch circuit that does not require a neutral.
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Old 03-01-2010, 04:40 PM   #12
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Originally Posted by J. V. View Post
Looks like a 3 wire cable used for a 220 volt branch circuit that does not require a neutral.
Okay, guess that makes sense (although, honestly, I've never wrapped my brain around how a 220v outlet can have two hots, but no neutrals to complete a circuit......).

Is it common practice to leave it dangling in the panel as shown? It appears it may be partially taped, but you can still see the exposed wire. However, since it's not hooked up to anything, guess it's not a big deal. Just looks sloppy (compared to the rest of the panel, which is nicely laid out).
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Old 03-01-2010, 05:24 PM   #13
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Okay, guess that makes sense (although, honestly, I've never wrapped my brain around how a 220v outlet can have two hots, but no neutrals to complete a circuit......).
Think of it this way:

Your Panel is fed from the POCO with +120v, -120v, and 0v.
+120v is the 1st HOT, the -120v is the 2nd HOT, and 0v is the neutral.

If a device needs 120v, you connect it to 0v and either the +120v or the -120v (either way, you get 120v of AC across the device).

If a device needs 240v, you connect it to -120v and +120v. That gives 240v of AC across the device.


[Edit]
Oh, and the reason to design a device to use 240v rather than the typical 120v is so that you only need half as much current. So if an A/C unit is wired with 240v and a 30amp breaker, you'd need a 60amp breaker (and much larger wire) to get the same power from only 120v.

Last edited by HooKooDooKu; 03-01-2010 at 05:26 PM.
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Old 03-02-2010, 12:44 AM   #14
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Sub panel wiring


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Originally Posted by HooKooDooKu View Post
Think of it this way:

Your Panel is fed from the POCO with +120v, -120v, and 0v.
+120v is the 1st HOT, the -120v is the 2nd HOT, and 0v is the neutral.

If a device needs 120v, you connect it to 0v and either the +120v or the -120v (either way, you get 120v of AC across the device).

If a device needs 240v, you connect it to -120v and +120v. That gives 240v of AC across the device.


[Edit]
Oh, and the reason to design a device to use 240v rather than the typical 120v is so that you only need half as much current. So if an A/C unit is wired with 240v and a 30amp breaker, you'd need a 60amp breaker (and much larger wire) to get the same power from only 120v.
Sure, I knew the the 1/2 amps from 240V. Inverse relation between currrent and voltage. That's why I'm planning to change my table saw to its optional 240V setup.

Your explanation helps about the 240V scenario. The two 120V's are out of phase, allowing the alternating current to work "both ways," while doubling up. I think this makes sense (it's been QUITE a while since my HS and college physics classes ).

Of course, it begs the question why some 240V outlets DO have a neutral wire. I'm looking at diagrams of 240V plug wiring options in a home improvement book, showing two different options using 3-wire (plus ground) connections -- two hots, a neutral and a ground.

Why neutrals in these cases?
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Old 03-02-2010, 02:39 AM   #15
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Sub panel wiring


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Originally Posted by Itsdanf View Post
Of course, it begs the question why some 240V outlets DO have a neutral wire. I'm looking at diagrams of 240V plug wiring options in a home improvement book, showing two different options using 3-wire (plus ground) connections -- two hots, a neutral and a ground.

Why neutrals in these cases?
To allow both 240v AND 120v circuits inside what ever get plugged in for one. As an example, an electric dryer needs the 240v for the heating element, but might only use 120v for the motor that turns the drum, the control circuitry, and the light that comes on when the door is open.

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