Another shed subpanel question - proper grounding

[tmnutan]

I’m running power to my shed and I’ve got a few questions that I’m hoping somebody could help me with. Here’s an overview:

I’m doing a subpanel at the shed. Distance from the main panel (at the house) to the shed is about 100’. Using 10/3 wire (two hots, a neutral, and a ground).

At the main service panel I have a double-pole 20-amp breaker.

At the shed: I have a subpanel for two circuits, either two 20's or a 15 and a 20. I have two 8’ ground rods, 6' apart, connected with #6 wire.

These are my questions:

1) Grounding at the shed Part 1 - Where do I connect the #6 to the subpanel?

2) Grounding at the shed Part 2 - What do I do with the ground that’s coming from the main panel (the bare wire in the 10/3 “feed”)? I don't think it's supposed to be connected to the subpanel, is that right? Should it be connected at the main panel (that wouldn't make much sense to me)?

3) At the shed, should I get a subpanel with a main breaker, one switch that will shut the whole thing down? That seems like overkill if I only have 2 circuits, but I’ve seen it mentioned a few places.

4) GFCI – if I put an outlet on the outside of the shed, does the outlet need to be GFCI, or the breaker, or both?

Thanks very much for any guidance you can provide. I live in North Carolina, FWIW.

 

[Highbeam]

I’m running power to my shed and I’ve got a few questions that I’m hoping somebody could help me with. Here’s an overview:

I’m doing a subpanel at the shed. Distance from the main panel (at the house) to the shed is about 100’. Using 10/3 wire (two hots, a neutral, and a ground).

At the main service panel I have a double-pole 20-amp breaker.

At the shed: I have a subpanel for two circuits, either two 20's or a 15 and a 20. I have two 8’ ground rods, 6' apart, connected with #6 wire.

These are my questions:

1) Grounding at the shed Part 1 - Where do I connect the #6 to the subpanel?

2) Grounding at the shed Part 2 - What do I do with the ground that’s coming from the main panel (the bare wire in the 10/3 “feed”)? I don't think it's supposed to be connected to the subpanel, is that right? Should it be connected at the main panel (that wouldn't make much sense to me)?

3) At the shed, should I get a subpanel with a main breaker, one switch that will shut the whole thing down? That seems like overkill if I only have 2 circuits, but I’ve seen it mentioned a few places.

4) GFCI – if I put an outlet on the outside of the shed, does the outlet need to be GFCI, or the breaker, or both?

Thanks very much for any guidance you can provide. I live in North Carolina, FWIW.

1) To the ground bar in the sub which is bonded to the panel.
2) Also to the ground bar in the sub which is bonded to the panel.
3) You don't need a main since you only have 2 circuits in the sub but I would recommend it. Price is nearly the same.
4) Either. The outlet must be GFCI and that's where I would put it. You don't need or want both.

You are dancing around it so I want to be clear about this issue, you must keep the neutrals and grounds separate. You will have two bars on the back of the panel, one will be bonded to the panel and that is the ground bar, the second bar is for all of the neutrals and it must not be connected to the ground bar or bonded to the panel can. At your main panel in the house, neutrals and grounds are bonded so you'll see white and bare on the same bar.

Here's a photo of my shed's subpanel. I am a big fan of Siemens gear, this can is from the HD.

 

[tmnutan]

This is very helpful, thank you. Will the buss bar that's "bonded" to the subpanel be obvious? I don't have the subpanel in front of me, and it's hard to tell on the pic you sent.

And also (and please don't take offense at this question), are you sure I want both grounds (from the two ground rods and from the 10-3 wire) connected at the subpanel? I've gotten a bit of conflicting information about this, some sources seemed to be suggesting that this would cause a problem, that you should only ground it in one place or the other, that doing both could be dangerous...

Thanks again,
Mike

1) To the ground bar in the sub which is bonded to the panel.
2) Also to the ground bar in the sub which is bonded to the panel.
3) You don't need a main since you only have 2 circuits in the sub but I would recommend it. Price is nearly the same.
4) Either. The outlet must be GFCI and that's where I would put it. You don't need or want both.

You are dancing around it so I want to be clear about this issue, you must keep the neutrals and grounds separate. You will have two bars on the back of the panel, one will be bonded to the panel and that is the ground bar, the second bar is for all of the neutrals and it must not be connected to the ground bar or bonded to the panel can. At your main panel in the house, neutrals and grounds are bonded so you'll see white and bare on the same bar.

Here's a photo of my shed's subpanel. I am a big fan of Siemens gear, this can is from the HD.

 

[Highbeam]

This is very helpful, thank you. Will the buss bar that's "bonded" to the subpanel be obvious? I don't have the subpanel in front of me, and it's hard to tell on the pic you sent.

And also (and please don't take offense at this question), are you sure I want both grounds (from the two ground rods and from the 10-3 wire) connected at the subpanel? I've gotten a bit of conflicting information about this, some sources seemed to be suggesting that this would cause a problem, that you should only ground it in one place or the other, that doing both could be dangerous...

Thanks again,
Mike

On the grounding. Yes, you attach all grounds to the same bar. You should only bond the NEUTRAL and the gound at one place and that is at the main panel in the house. Think of it like a floating neutral in the subpanel, all whites together.

When you buy a panel the provided "ground" bar(s) will both be insulated from the can. There will be a screw on one of the bars that is to be bottomed out IF you want that bar to be bonded to the can. The screw is big, usually green, and usually has a sticker telling you what to do.

Some panels, mine, have a strap connecting the two ground bars that must be removed.

The neutrals are not to be bonded to the can or to the ground bar but they are to all be bonded together by landing on the ungrounded neutral bar.

When you get the panel, a lot of this will become clearer. Since you are buying such a tiny panel, some of this may already be done for you. Get the panel and we can doubel check.

You are getting this inspected aren't you? I have a nice green sticker on mine from the approval.

 

[Highbeam]

This is very helpful, thank you. Will the buss bar that's "bonded" to the subpanel be obvious? I don't have the subpanel in front of me, and it's hard to tell on the pic you sent.

On my zoomed in picture the grounded bar is on the right. Note the big green screw on the top of that bar. That big green screw is the one I had to tighten down to bond the ground bar to the panel.

 

[rwhite]

I faced some similar issues when I wired my own subpanel. Even if you are mechanically inclined electrical work has it's own quirks. I bought this book and it has been invaluable on my shelf for many years:


http://www.tauntonstore.com/wiring-a-house-revised-and-updated-rex-cauldwell-070639.html

 

[Highbeam]

Putting in a main or subpanel is about the hardest thing you can do in a residential wire job. The results of mistakes could kill someone so lets be real sure about the final setup. Don't be afraid to post your work photo so that we can look for booboos. Stupid little stuff like the bushing covering the threads where the conduit comes into the can will be hard to catch for a first timer.

 

[Former Farmer]

Using 10/3 wire (two hots, a neutral, and a ground).

What type of wire are you using? What methods of installation are you using? If underground, what depth are you burying it at?
If you are using type UF, I would recommend sleeving it in PVC, that way if you have an issues in the future, you can pull out the old wire and pull in new.

3) At the shed, should I get a subpanel with a main breaker, one switch that will shut the whole thing down? That seems like overkill if I only have 2 circuits, but I’ve seen it mentioned a few places.

You don't need a main breaker, as long as you stay below 6 breakers.

4) GFCI – if I put an outlet on the outside of the shed, does the outlet need to be GFCI, or the breaker, or both?

All outlets in the shed have to be gfci protected, whether inside or outside of the building. The outlet outside the shed will require a weather resistant type outlet and an in-use cover.

Stupid little stuff like the bushing covering the threads where the conduit comes into the can will be hard to catch for a first timer.

PVC bushings would not be required since the op is only running a #10.

 

[Highbeam]

PVC bushings would not be required since the op is only running a #10.

Interesting, what's the threshold when pulling a wire through a conduit into a can that you don't need to provide a bushing?

 

[Former Farmer]

#6 awg if memory serves me right. It may be larger than that. I usually will install bushings on long pulls regardless of wire size, just because it feeds in better.