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Old 01-17-2013, 10:53 AM   #16
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Sub Panel over 10g-2 Help Needed


The whole reason for the need for 220v was so I could run a 220v window ac w/ heat in my shed/shop. Instead of going through all the work to change out the old wiring to get 220v, I am going to purchase a 110v ac w/ heat and change out the units.

I now understand the problems with my setup. I plan on leaving the sub panel in there and just using one side. So here's the new plan:

New 30a single pole breaker in the main panel
Keeping the existing 10-2 wire
Hook up to one lug in the sub panel - black wire
White and bare ground to the neutral bar
Install new sub panel breakers for light circuit(15a) and outlet circuit(20a) and dedicated 15a for window unit

What I will be running is this:
1 - 120v 15a window unit (dedicated circuit)
6 - 120v 0.5a T8 2 bulb light fixtures
(Maybe) 2 - 400w (not sure about the amps) ceramic radiant wall heaters

Do I need to install a ground wire to a ground rod at the shed or will the existing ground to the main panel work?

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Old 01-17-2013, 11:06 AM   #17
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Sub Panel over 10g-2 Help Needed


I'm pretty sure from my reading says that any subpanel must NOT join the neutral and ground, i.e. they have to be isolated and feed back to the main breaker panel. So you would have 2 separate bus bars, and NO separate grounding rod at the subpanel. I am NOT an electrician, so someone would have to verify that.

So to correct your statements, I believe, you can not hook up white (neutral) and bare ground to the same bus bar, they must be separate (you can buy and mount another one). You must use the ground coming from the main panel, and you should not create a separate ground at the sub panel.

I hope I'm not way off... btw, amps are just watts divided by volts (roughly), so 400w = 400/120 = 3.3 amps.

Last edited by Ocelaris; 01-17-2013 at 11:10 AM.
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Old 01-17-2013, 11:39 AM   #18
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Quote:
Originally Posted by Ocelaris View Post
...any subpanel must NOT join the neutral and ground ... So you would have 2 separate bus bars,
... you can not hook up white (neutral) and bare ground to the same bus bar, they must be separate (you can buy and mount another one).
I believe you are correct.

As for load calc, 1800W A/C + 800W heaters + 360W lights = 2960W, and your 30A breaker can handle up to 3600W. As as long as you don't run more than 660W or 5.5A of power tools while all the heat is on, things should work.

Note that something big like a table saw may pop the breaker as it will draw over 3x it's rated current on startup. So you may need to shut off the heaters long enough to start bigger tools.
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Old 01-17-2013, 12:01 PM   #19
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Sub Panel over 10g-2 Help Needed


You need to add a seperate ground bar in the sub and separate the neutral and ground. You also need 2ground rods.
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Old 01-17-2013, 08:39 PM   #20
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Ok. I am getting conflicting information. Some are saying I do not need to separate the ground and neutral wires on different bars. Some are saying that I need to have a separate bar for each.

Let's do this.....

New information.

The house I live in is a rental. I have the landlords permission to make alterations.

I have scrapped the 240v idea. I have ordered a 120v 15a window ac w/heat.

When I changed out the main panel 20a breaker to a single pole 30a breaker, I found that there were two wires attached to the breaker. After investigating what the second wire went to, I found that one wire is for the lights (12-2) in the shed and the other is for the outlets (10-2). I moved the wire for the lights to a 20a breaker by itself. The wire in the shed for the lights must come up from the ground and run through the wall and ceiling. So now I have removed the light circuit from my calculations because they do not run through the sub panel.

The wire for outlets run into a metal junction box in the front of the shed. That single wire coming into the shed had two wires wire nutted to it. One of those wire runs to a power bar with 8 outlets. The other wire runs 8 double outlets around the perimeter of the shed.

Overview:
Shed lights run off a 20a breaker in the main panel with 12-2 wire. No longer a factor.
I installed a sub panel in the shed
I changed the 20a shed breaker in the main panel to a 30a over a 10-2 wire.
I hooked the 10-2 black wire to the main lug on the right side of the sub panel, white wire and bare ground to the neutral bar.
I installed a 15a breaker that now runs the power bar 8 outlets.
I installed a 20a breaker that now runs the 8 perimeter outlets.
I will install a 15a breaker dedicated to the window unit.

Everything now works but is it right? Do I need to install another bus bar for the ground coming from the house? Do I need to ground the sub panel to ground rod(s)?
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Old 01-17-2013, 08:43 PM   #21
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You are not allowed to run more than one feeder to an outbuilding like a shed.
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Old 01-17-2013, 08:45 PM   #22
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Quote:
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You are not allowed to run more than one feeder to an outbuilding like a shed.
I didn't run it. The shed was already here. The power was already run.

I could locate the light circuit were it comes into the shed, cut it loose from the house and install it in the sub panel if that would help. Then there would only be one feed coming into the shed.

If I did that.....

Do I need to install another bus bar for the ground coming from the house? Do I need to ground the sub panel to ground rod(s)?

Last edited by hamblinh; 01-17-2013 at 08:50 PM.
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Old 01-17-2013, 08:50 PM   #23
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Sub Panel over 10g-2 Help Needed


You need to separate your neutral and ground and install two ground rods. Only one feeder allowed for a separate building.
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Old 01-17-2013, 09:03 PM   #24
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Are there any short term issues to not having the ground and neutrals separated? I would like to at least have the ceramic heaters on tonight. I don't have a problem installing the ground wire and grounding rods but I won't be able to get the materials until tomorrow. And I won't be able to install them until tomorrow night. But I really need some heat out there so I don't ruin some stuff that is out there. I don't have the room to move the material to a heated location in the house.

Quote:
Originally Posted by hamblinh View Post

I could locate the light circuit were it comes into the shed, cut it loose from the house and install it in the sub panel if that would help. Then there would only be one feed coming into the shed.
I have a question that is mainly curiosity. What is the purpose for the sub panel grounds? I am not an electrician obviously. Otherwise I wouldn't be asking the questions. But the sub panel ground rods seems redundant to the house ground.
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Old 01-17-2013, 09:19 PM   #25
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Sub Panel over 10g-2 Help Needed


Quote:
Originally Posted by hamblinh View Post
Are there any short term issues to not having the ground and neutrals separated? I would like to at least have the ceramic heaters on tonight. I don't have a problem installing the ground wire and grounding rods but I won't be able to get the materials until tomorrow. And I won't be able to install them until tomorrow night. But I really need some heat out there so I don't ruin some stuff that is out there. I don't have the room to move the material to a heated location in the house.



I have a question that is mainly curiosity. What is the purpose for the sub panel grounds? I am not an electrician obviously. Otherwise I wouldn't be asking the questions. But the sub panel ground rods seems redundant to the house ground.
All required by code no other way that I could think to suggest it be done.
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Old 01-17-2013, 09:36 PM   #26
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I guess I should rephrase my question. Will my shed burn to the ground before tomorrow night when I can separate the ground and neutrals and install the ground rods?
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Old 01-17-2013, 09:40 PM   #27
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Sub Panel over 10g-2 Help Needed


Quote:
Originally Posted by hamblinh View Post
I guess I should rephrase my question. Will my shed burn to the ground before tomorrow night when I can separate the ground and neutrals and install the ground rods?
No.............
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Old 01-17-2013, 09:48 PM   #28
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Thank you everyone for your help with this problem. I have a lot of new information and I think my problem has been solved.
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Old 01-18-2013, 12:45 AM   #29
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Quote:
Originally Posted by hamblinh View Post
Thank you everyone for your help with this problem. I have a lot of new information and I think my problem has been solved.
What is your soluation ??

For the subpanels which I know majorty of the time you will have to buy a seperated ground bussbar and screw that in the factory holes which it allready punched. Do not bond the netural bussbar ( some will have green screw and some will have jumper wire or peice of hevey alum or copper jumper bar ) so that will be only legit way you can do this.

As other mention above moi., ditch that circuit and run a real MWBC circuit the cost of new conductors will be justified compared to the cost of the transfomer.

A typical 5 KW transfomer will set you back about 500 to 1000 Euros ( Dollars ) depending on what model it is.

Now you know why I rather run a real MWBC instead of transfomer.

The cost of running new MWBC is peanuts compared to the cost of transfomer is.

Merci,
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Old 01-18-2013, 07:54 PM   #30
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Sub Panel over 10g-2 Help Needed


Here's what I now have....

Ditched the 240v idea. Using only one lug in the sub panel 120v supply.

30a breaker in the main panel
10-2 existing wire to the shed
Sub Panel...
#6 ground wire attached to 2 8' ground rods 6' apart
Installed ground bar
Attached all ground wires to ground bar
Attached all neutral wires to neutral bar
15a breaker dedicated to 120v 1800w 15a window ac/heat 12-2 wire
15a breaker dedicated to water proof exterior outlet 12-2 wire
15a breaker for power strip w/8 outlets 12-2 wire
20a breaker for 8 perimeter outlet 10-2 wire (Runs the 2 400w 3.3a ceramic heater)

Cut off all but 2" of exterior wire insulation inside sub panel (not off each individual wire, just the bundle)
Clamped each wire coming into sub panel

If my math is correct I can run an additional 1000w 8.3 amps without tripping the 30a main panel.

Good???


Last edited by hamblinh; 01-18-2013 at 10:23 PM.
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