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OleMiss29 10-30-2012 02:32 PM

Subpanel Wiring Help
 
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I have been a reader on these boards for quite some time, but have run into a situation where I need some guidance. To make a long story short, I completely gutted my shed in the backyard that was neglected by the previous owner. The subpanel (Square D Q06-12L100F) and the main wire (8-2 I believe) feeding into this were left in place and I installed 4 20 amp circuits in this sub panel to supply power throughout the shed . The subpanel looks to be described as "LOAD CENTER QO MLO 240V 100A 1PH 6SP N1". It also says on the panel that is is 240V/120V. The breaker from the main panel feeding the wire into the shed is a double pole 50 amp breaker.

1.) I want the outlets/circuits in the shed to run 120 v circuits. So to me it looks like the main wire previously installed was incorrect (8-2 into 50 amp double pole breaker-shouldnt this be an 8-3?)

2.)Could I just switch out the main breaker feeding into the shed a 30 amp single pole and be good? Thus making the main feed 120v and my hot wire-hot and nuet-nuet (not hot like it seems to be)?

Any thoughts or feedback would be greatly appreciated. I will do my best to better explain if any of this does not make since. I have attached a picture of the subpanel setup in the shed. The main neutral is unplugged in this picture. Thanks for your help!

mpoulton 10-30-2012 02:46 PM

Yes, you will need to change that to a 120V feed. A 3-wire (two hots plus neutral/ground) feed used to be legal, but that was changed several years ago. However, the type of three wire feed installed there was never legal. Your panel is using the bare grounding wire as a current-carrying neutral conductor. This is the opposite of the three wire configuration that used to be allowed, where an insulated current-carrying neutral conductor could also be used for grounding at the subpanel. So regardless, it needs to be changed. You can replace the double-pole breaker with a 40A or smaller single-pole and you'll be all set.

Julius793 10-30-2012 02:47 PM

If I understand correctly there are some serious issues..... This is the way it should be black will be hot connected to where it is currently, the white should be changed to neutral and should be where the ground is. then you should add a ground bar for all the grounds. Then lastly you will need a jumper from the black to where the white wire was previously installed to feed the other hot bus.

About the breaker size if its Romex it should be a 40a.

funkjosh 10-30-2012 03:30 PM

Quote:

Originally Posted by Julius793 (Post 1041115)
If I understand correctly there are some serious issues..... This is the way it should be black will be hot connected to where it is currently, the white should be changed to neutral and should be where the ground is. then you should add a ground bar for all the grounds. Then lastly you will need a jumper from the black to where the white wire was previously installed to feed the other hot bus.

About the breaker size if its Romex it should be a 40a.

thats sounds about right, however you may want to just change the wire to 8/3 and wire it to be more balanced.

and using a separate ground bar mounted in the panel is a plus. not sure why or if its a code, but i was always told subpanels should have separate ground bar.k

k_buz 10-30-2012 03:40 PM

What it looks like to me is that they are using the ground as a neutral. As the others have said, you need to replace the wire to a 3 wire feed plus ground.

jeffsw6 10-31-2012 04:00 AM

Quote:

Originally Posted by mpoulton (Post 1041114)
You can replace the double-pole breaker with a 40A or smaller single-pole and you'll be all set.

My understanding of 250.32(B)(1) is that the pictured panel should NOT have a bond between the grounded conductor ("neutral") and the equipment grounding conductor ("ground"), or the GEC required to be present at the shed and attached to that panel.

The picture looks like there is one bus bar serving as both neutral and ground. If so, I don't see how that can be brought up to date.

Also 225.33 applies to this panel. Because the OP only wants to install four circuits, it is not an problem for him; but he should be aware that he cannot populate the panel with more than six circuit breakers without breaking that rule. The reason is all the electricity in the shed must be able to be disconnected with no more than six switch-throws.

busman 10-31-2012 05:37 AM

Just wrong in SO many ways.

Julius793 10-31-2012 06:53 AM

Quote:

Originally Posted by jeffsw6
The picture looks like there is one bus bar serving as both neutral and ground. If so, I don't see how that can be brought up to date.

Very simple add a grounding bar

Quote:

Originally Posted by jeffsw6
Also 225.33 applies to this panel. Because the OP only wants to install four circuits, it is not an problem for him; but he should be aware that he cannot populate the panel with more than six circuit breakers without breaking that rule. The reason is all the electricity in the shed must be able to be disconnected with no more than six switch-throws.

Nice to see you know the nec......if you look at his panel it's a 6 circuit panel

OleMiss29 10-31-2012 11:38 AM

Thanks for all the responses. From what I gather, there looks to be a couple of options here. The way its currently configured, if simply I add a seperate ground bus bar, how would I wire this with the current configuartion and would this solve the problem? Or is the only real option to change the wire from 8-2 to 8-3?

funkjosh 10-31-2012 12:31 PM

Quote:

Originally Posted by Julius793 (Post 1041115)
Then lastly you will need a jumper from the black to where the white wire was previously installed to feed the other hot bus.

ive never done or seen this done but i guess it would work making your panel 120v. you jus wont be able to use double pole breaker. this may create an explosion, im not sure.

it shouldnt be hard to change wire tho. jus tape & tie the old cable to the new one and pull it thru the other end.

jeffsw6 10-31-2012 03:30 PM

Quote:

Originally Posted by OleMiss29 (Post 1041717)
if simply I add a seperate ground bus bar, how would I wire this with the current configuartion and would this solve the problem?

Modifying the box isn't exactly proper but it can be done safely. The easiest thing will be to mount a new neutral bus bar using a non-conducting stand-off, because the existing ground bar is probably tied to the frame of the panel (VOM will show if this is true.) Now use your new neutral bar in the obvious way -- connect it to the feeder neutral and all the branch circuit neutrals.

In your main panel, wire the shed feeder in the obvious way again -- black to the breaker, white to the neutral bar, bare to the ground bar.

Back in the shed panel, you are also required to have a GEC for that building. This is a safety issue because there can be significant voltage between the grounding system of your house and of the earth at your shed! You do not want to get shocked by a tool because your shed's electrical ground is not tied to the earth correctly. Maybe this already exists at the shed, but I doubt it. Drive a ground rod and connect it to an 8awg or larger wire using a ground wire clamp. Run that 8awg wire (can be bare wire or insulated but if insulated, must be green) to the bus bar in your panel. The easiest place to install it will be the lug on the left side of the bar. Now you have a safe grounding system for the shed. You can buy the ground rod and clamp for around $15 or $20 at a home improvement store.

Honestly, if it was me, I would think about replacing the panel instead of fooling around with mounting an extra bus bar in it, because you really aren't supposed to simply screw this new bus bar into the panel -- it is supposed to be electrically isolated.

k_buz 10-31-2012 03:39 PM

The panel isn't the problem, as someone said earlier, you can easily add a ground bar and remove the bonding jumper. The problem is your feed. They/you are using a bare conductor as a neutral, and that neutral is bonded to the case of the panel. You need to run a new 4 wire feed to the sub panel. You cannot safely continue to use the current feed.

mpoulton 10-31-2012 04:03 PM

Quote:

Originally Posted by jeffsw6 (Post 1041846)
Modifying the box isn't exactly proper but it can be done safely. The easiest thing will be to mount a new neutral bus bar using a non-conducting stand-off, because the existing ground bar is probably tied to the frame of the panel (VOM will show if this is true.) Now use your new neutral bar in the obvious way -- connect it to the feeder neutral and all the branch circuit neutrals.

That's backwards, and would violate the panel's UL listing. The existing ground/neutral bar is already isolated, and can be bonded or unbonded by installing or removing a bonding jumper (usually a green screw). The proper way to handle this is to remove the bonding jumper and install a ground bar kit in the panel (easy and cheap).


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