Finishing electrical upgrade to detached shop

[knobby97]

This is my first post on this forum and I have to say that there is definitely info here that has helped me with my latest project, but I wanted to get some opinions on my work/plan thus far to make sure everything is good to go.

Brief history:

Detached shop in SC that is a 100' run from the house's 200A main load center. 110v was already run to the shop when I bought the house via a 20A breaker out of the main panel. I do a lot of jeep and other off road fab, which requires my miller 211 MIG, miller 375 plasma, miller diversion 180 TIG, and a 35 gal 110v air compressor. So the 110v setup wouldn't support all of my gear, so I decided to upgrade the wiring to 220v and install a 6 slot sub panel in the shop.

Layout:

The shop has 3 florescent lights inside, two exterior halogen lights, and 3 duplex outlets currently installed.

Plan:

Install 30A 220v plug for welders, dedicated 20A 110v outlet for air compressor, puts exterior lights on one 20A breaker, and run the 3 current outlets and add another off of another 20A breaker.

I picked up 3 x 114' of 6 AWG THWN (black, red, white) and 114' of 10 AWG THWN for the ground. This is all going in 1" PVC conduit with the misc pull boxes, etc. This will run from a 50A double pole breaker in the main panel.

If I understood everything I read on the forum thus far I would run the red and black hots to the 50A breaker, white to neutral bar, and green to the ground bar (which is bonded) in the main panel. This would feed the homeline sub panel (which is main lug only) which will be non bonded and have the separate ground and neutral bars. As stated above the box will have a 30A double pole breaker which will feed the 220v plug via 6-2 NM-B, and the 3 other 20A breakers will use 12 AWG NM-B.

Questions:

I have the 8' copper grounding rod that I have no installed yet, but was wondering if I needed to use the bare copper conductor to link the rod to the ground bar or can I use more 10 AWG green wire? Also is one rod enough, or no I need to install 2 bars 6' or more apart?

Could I run more than the planned 50A to the sub panel via the 100' of 6 AWG wire?

Does everything check out, or do I need to adjust anything?

I did have a funny discovery when removing the 110v wire and 3/4" conduit earlier today. First, the 12 AWG that was run from the main panel, through the conduit, to the shop was regular household NM-B and the conduit was filled with water and mud. Second, something had crushed the 3/4" conduit in one place. So I was glad that I hadn't tried to run the new wiring through the old conduit, as there is no way it would have made it through the kinked spot nor the dirt and other funk.

 

[pattenp]

I would use #6 solid copper for the ground rod wire and use two rods. I'd only go to a max of 60A on the #6 THWN at 100', technically you can go to 70A. The wire on a 30A breaker only needs to be #10. And if you use a main lug panel then you can have no more than 6 breakers in it without a main disconnect.

Edit: electrode conductor smaller than #6 needs to be protected in conduit.

 

[knobby97]

I would use #6 solid copper for the ground rod wire and use two rods. I'd only go to a max of 60A on the #6 THWN at 100', technically you can go to 70A. The wire on a 30A breaker only needs to be #10. And if you use a main lug panel then you can have no more than 6 breakers in it without a main disconnect.

Edit: electrode conductor smaller than #6 needs to be protected in conduit.

Got it, thanks. Will go with the #6 solid and 2 grounding rods. Will the #6 solid need to be run in conduit? If so I will run it in a separate conduit. Do the 2 grounding rods need to be separated by 6 ft or more, or is distance between the rods not an issue? Got it on the 10 AWG for the 30A 220v plug, just using the 6-2 since I had a random 10ft piece laying around.

When you say that electrodes smaller than #6 need to be run in conduit, where exactly are you referring to? I have the 3 #6s and # 10 run in conduit from the main panel to the sun panel, but everything running from the sub panel to the outlets in the shop is all roughed in and held with staples.


Sent from my iPhone using Tapatalk

 

[pattenp]

The electrode conductor is the wire that runs from the ground bar in the panel to the ground rods, if it's smaller than #6 it needs to be in conduit. #6 or larger is not required to be in conduit if not exposed to damage. The two rods need to be at least 6' apart. The #10 ground that runs with the #6 is the equipment ground and #10 is fine. The equipment ground conductor and the electrode ground conductor are two different things.

 

[theoldwizard1]

I picked up 3 x 114' of 6 AWG THWN (black, red, white) and 114' of 10 AWG THWN for the ground. This is all going in 1" PVC conduit with the misc pull boxes, etc. This will run from a 50A double pole breaker in the main panel.

If I understood everything I read on the forum thus far I would run the red and black hots to the 50A breaker, white to neutral bar, and green to the ground bar (which is bonded) in the main panel. This would feed the homeline sub panel (which is main lug only) which will be non bonded and have the separate ground and neutral bars. As stated above the box will have a 30A double pole breaker which will feed the 220v plug via 6-2 NM-B, and the 3 other 20A breakers will use 12 AWG NM-B.

Questions:

I have the 8' copper grounding rod that I have not installed yet, but was wondering if I needed to use the bare copper conductor to link the rod to the ground bar or can I use more 10 AWG green wire? Also is one rod enough, or no I need to install 2 bars 6' or more apart?

Huh?

Are these grounding rod(s) to be installed at the house in replacement for ????

If they are installed at the out building, why is he running a 4th (green) wire ? That would give you 2 grounds at the out building.

 

[pattenp]

Huh?

Are these grounding rod(s) to be installed at the house in replacement for ????

If they are installed at the out building, why is he running a 4th (green) wire ? That would give you 2 grounds at the out building.

The ground rods are for his detached shop. He's got an equipment ground that runs in the feed from the house to the shop. He was asking if he could the same type of #10 green wire for the ground wire to the ground rods. At least this is what I thought he was asking.

 

[Alchymist]

Huh?

Are these grounding rod(s) to be installed at the house in replacement for ????

If they are installed at the out building, why is he running a 4th (green) wire ? That would give you 2 grounds at the out building.

Sub-panel in a detached building requires a 4 wire feed, AND ground rods at the sub-panel. ECG and neutral are bonded at the main panel, separate at the sub.

 

[theoldwizard1]

Sub-panel in a detached building requires a 4 wire feed, AND ground rods at the sub-panel. ECG and neutral are bonded at the main panel, separate at the sub.

Just when I thought I understood this whole "outbuilding, sub-panel grounding" thing !

So, in this example, neutral and ground from the main panel are run to the sub-panel but are NOT bonded at the sub-panel. Got it.

But if you have "ground" coming from the main panel and "ground" coming from the ground rods, what do you do connect to each of these buses in the sub-panel ?

"Bonding" these 2 ground buses does not make sense based on what litle I know of "ground loops".

 

[Alchymist]

Just when I thought I understood this whole "outbuilding, sub-panel grounding" thing !

So, in this example, neutral and ground from the main panel are run to the sub-panel but are NOT bonded at the sub-panel. Got it.

But if you have "ground" coming from the main panel and "ground" coming from the ground rods, what do you do connect to each of these buses in the sub-panel ?

"Bonding" these 2 ground buses does not make sense based on what litle I know of "ground loops".

A separate ground bus in the sub-panel picks up the 4th wire ground from the main panel, the earth ground, and all ground wires in the detached structure, it is not connected to the neutral in the sub-panel. As to ground loops, in most installations, there is a ground rod at the transformer, one at the main panel, one at each (detached) sub-panel, and occasionally one at the meter base, depending on the POCO's requirements. The only place the ground and the neutral are connected is in the main panel.

 

[theoldwizard1]

A separate ground bus in the sub-panel picks up the 4th wire ground from the main panel, the earth ground, and all ground wires in the detached structure, ...

For fun, next time you are wiring a sub-panel in a separate structure, before you combine the 4th wire ground from the main panel and the earth ground at that structure, measure the voltage between those 2. I will bet you will find more than a couple of millivolts !

The only place the ground and the neutral are connected (bonded) is in the main panel.

That I understand !

 

[knobby97]

The ground rods are for his detached shop. He's got an equipment ground that runs in the feed from the house to the shop. He was asking if he could the same type of #10 green wire for the ground wire to the ground rods. At least this is what I thought he was asking.

That was exactly the question that I was asking, so I went to lowes and picked up a second 8 ft grounding and 25 ft of #6 solid.

Started wiring up the sub panel and separating the circuits in the shop. Got the interior and exterior lighting circuits finished up, along with the main outlet circuit (all are 20A each). Also got the 30A 220v wire run, but need another NM-B clamp as the 6-2 isn't exactly going to fit in the 1/2" clamp that I had left over. Also need to get a 1/2" hub nut for the 1/2" conduit that has the #6 solid run in it. So as of this evening this is what the sub panel is looking like:

Tomorrow I have to finishing running the wiring in the 1" conduit under the house and then up into the main panel. Only question I still have regarding this is how should the conduit terminate under the house? Can I just run the conduit to where the wiring feeds up into the main panel or do I need to install a 90 degree elbow and run conduit all the way up until it meets the subfloor? Also are there any guidelines for how many of what size wires can fit through whatever size NM-B clamps going into a box?

 

[pattenp]

I know you don't want to hear this but if the wire you used to feed the sub panel is individual THWN wires they need to be in conduit all the way from the main panel to the sub panel.

 

[knobby97]

I know you don't want to hear this but if the wire you used to feed the sub panel is individual THWN wires they need to be in conduit all the way from the main panel to the sub panel.

Something told me that, so I have already run everything in conduit with the exception of the vertical piece running up from under the house into the box. Only issue I foresee is the drilling of the hole through the sub floor for the 1" conduit, as the location where all of the wiring is run up into the house is right against the center floor joist that is made up of 3 sandwiched 2 x 10s.

Another off the wall question; are there any issues with splicing a run of 12-2 NM-B into 12-2 UF-B as long as the splice is done with lugs and in the proper junction box? I'm wondering this as I was going to re-use the 20A 110v circuit that was previously running out to the shop for patio and deck outlets.

 

[pattenp]

There is no problem with splicing NM-B with UF-B. Just don't use the NM-b outside. And wire nuts are okay for the splice connection in the jbox.

 

[theoldwizard1]

Another off the wall question; are there any issues with splicing a run of 12-2 NM-B into 12-2 UF-B as long as the splice is done with lugs and in the proper junction box?

Lugs ?

Wire nuts (appropriate size) are adequate if inside of a proper junction box.

 

[Alchymist]

Something told me that, so I have already run everything in conduit with the exception of the vertical piece running up from under the house into the box. Only issue I foresee is the drilling of the hole through the sub floor for the 1" conduit, as the location where all of the wiring is run up into the house is right against the center floor joist that is made up of 3 sandwiched 2 x 10s.

Once inside the house, terminate the conduit in a junction box. Use #6 NM-B from the junction box to the panel.

 

[knobby97]

Once inside the house, terminate the conduit in a junction box. Use #6 NM-B from the junction box to the panel.

Thanks for the suggestion, I never would have thought of that one. I picked up 15 ft of 6-3 NM-B to finish the run out.

Now the only issue is getting the 6-3 up into the main box. There are only 3 hubs in the bottom of the box, which are pretty much full. My initial though is to just drill out one of the available 1/2" knock outs to 3/4" or 1" if possible. Then the the 6-3 up the through it.

Another question regarding the equipment ground and grounding rod at the sub panel. How is having the bonded neutral/ ground at the main panel linked to the isolated ground buss bar in the sub panel (via the 10 AWG green wire) effected if say there is a lightening strike picked up by the earth ground at either end? Would it just be transferred from one box to the other then out through the opposite boxes earth ground? Anyway, still trying to wrap my mind around that one.


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[pattenp]

The rods are for lighting strikes. Hopefully which ever set of rods is closest to the strike will take the strike to earth. It's possible for the strike to travel over the equipment ground but hopefully the path of least resistance is going to be to one set of the rods, either at the house or at the shop.

 

[nwav8tor]

... And if you use a main lug panel then you can have no more than 6 breakers in it without a main disconnect.

Is this true for a main lug sub panel that is installed in the same room as the main panel?

My sub is a ML with 6 single pole and 2 double pole breakesr installed right next to the main panel in the garage and it was approved by the inspector without a main disconnect in the sub...

Thanks,
Paul

 

[pattenp]

Is this true for a main lug sub panel that is installed in the same room as the main panel?

My sub is a ML with 6 single pole and 2 double pole breakesr installed right next to the main panel in the garage and it was approved by the inspector without a main disconnect in the sub...

Thanks,
Paul

The six breaker limit only applies to panels that are supplied from a main panel located in a different structure. Since your main lug panel is in the same structure as the main panel it doesn't need a main disconnect.

 

[nwav8tor]

The six breaker limit only applies to panels that are supplied from a main panel located in a different structure. Since your main lug panel is in the same structure as the main panel it doesn't need a main disconnect.

Thanks, I thought that might be the case because I didn't think I'd miss such an important point on this forum during my planning stages...

Paul