Getting the Ground back to the Rod.

[Mudbone]

UPDATE: Hole drilled in foundation for GEC. See pic below

I am building a small workshop and plan to have 100 Amp service to it. (Mini Split AC, Compressor, 50 Amp welder will be the big draws.) Its around 150 feet from my main service box. The foundation and slab is in with 1.5 inch pvc set in the wall. You can see the build with pics HERE. There are two conduits in the pictures. The right hand one, (from the outside), will be for the panel box. The other conduit is for any low voltage use I may need later: sprinkler, Sat/Cable, etc. They are place so they will come up through the mudsill/floorplate.

The current plan is to run #1 THWN in 1.5 inch pvc. (I believe 4 wires of #1 is the max allowed for 1.5 inch pvc)

The question I have regards running the ground from the panel back out to the buried grounding rod. Can i run it back down the conduit I have now and is there some type of waterproof connection that I can use to run the ground wire out of the conduit to the rod. If I can't do that, what are my other solutions without poking a hole in the side of my building?

TIA

 

[Spudland_Dave]

Timely post...I'm thinkin the same thing. Although my conduit will all be external entrance (Luckily...Since pouring the slab, I've changed the location where I want my panel twice LOL) I'm trying to avoid having an eye sore.

Closest to "slick" I can think of is using my SDS to drill a hole straight down thru the slab between the studs. BUT then I'm leery of drilling a hole that close to the edge for nothing so to speak.

Your idea of a weathertite "Tee" in the main conduit is about as slick/easy as I can think of as well.

 

[Dr.JohnnyFever]

I would go through the wall.

However, I believe it would be code compliant to T the conduit, reduce to 3/4", come up about 8" above ground, attach a PVC FSS box and come back down to ground level.

This would satisfy the physical protection requirements for the GEC while helping to retain the watertightness of the conduit (but it is still considered a wet location).

This drawing is not anywhere near scale, but should give you the general idea:

 

[pattenp]

You don't need to go to all that trouble. Just drill a small hole in the foundation or the wall right above the foundation and pull the ground wire through and strap it to the back side of the conduit and bury it out to the rods (you should have 2 rods). If the ground wire is where you may hit it planting flowers then just sleeve it where it's under ground with a piece of 1/2" rigid metal conduit.

 

[Mudbone]

You don't need to go to all that trouble. Just drill a small hole in the foundation or the wall right above the foundation and pull the ground wire through and strap it to the back side of the conduit and bury it out to the rods (you should have 2 rods). If the ground wire is where you may hit it planting flowers then just sleeve it where it's under ground with a piece of 1/2" rigid metal conduit.

I take it I am not allowed to run it down the other conduit along with my low voltage and communications stuff?

 

[sberry]

The ground doesnt need to be a number 1, a 6 would work I believe, maybe that wire calls for a 4?

 

[Dr.JohnnyFever]

I take it I am not allowed to run it down the other conduit along with my low voltage and communications stuff?

It would not be prohibited. However, I would rather keep electrical stuff and control stuff separate just because.

Let me say again that I would go through the wall.

The ground doesnt need to be a number 1, a 6 would work I believe, maybe that wire calls for a 4?

#6 is adequate if connecting to a ground rod. Unless there are special circumstances regarding physical damage risks.

To quote the NEC: shall not be required to be larger than 6 AWG copper wire

Actually, #8 is permissible if completely protect from physical damage by conduit.

 

[sberry]

Yes, to the rod 8 for up to 100A service, 6 is always better and common, but back to the service panel a 6. 3 number1 which is plenty and then some, even at that distance 2 would suffice but the 4th wire can be substantially smaller, also helps with pipe fill and pull.

 

[Mudbone]

Yes, to the rod 8 for up to 100A service, 6 is always better and common, but back to the service panel a 6. 3 number1 which is plenty and then some, even at that distance 2 would suffice but the 4th wire can be substantially smaller, also helps with pipe fill and pull.

Thanks guys for all the replys.

I want to make sure that I understand this completely. Are you guys saying that both the ground wire running from the building sub panel out to the ground AND the ground wire running the 150 ft from my main panel into this subpanel can be #6? Or are you just talking about just the ground wire from the sub panel to the rod?

If it's both ground wires that I can take down to #6, does that mean that I can up the gauge on the two hots and neutral coming from the main panel? I picked #1 because I needed four wires and that is the max gauge I you can put in a 1.5 inch pvc conduit. (The 1.5 inch was determined by what would comfortably fit in the foundation wall, which was a 4 inch block with a modular brick veneer.) At 150 feet, more or less, can I or should I go to 1/0?

I guess the other option would be to run UF without a conduit. Then it would be a matter of what I could stuff up the short run of conduit into the wall. And the ground rod wire could come back down the same conduit.

Oh BTW, not sure about NEC, but around here in NC everyone seems to get away with only one ground rod. I asked an inspector about this b/c I had seen pics of multiple rods. Apparently around here the dirt composition is such, (lots of clay), that it is always damp enough for a good ground. Even if we have a drought once you get down past 2-3 feet the dirt is damp enough. At least that is the explaination I was given.

 

[Dr.JohnnyFever]

Thanks guys for all the replys.

I want to make sure that I understand this completely. Are you guys saying that both the ground wire running from the building sub panel out to the ground AND the ground wire running the 150 ft from my main panel into this subpanel can be #6? Or are you just talking about just the ground wire from the sub panel to the rod?

The conductor going from panel to ground ground is called a GEC - Grounding Electrode Conductor. It can be a #6.

The conductor going from panel to panel is called an EGC - Equipment Grounding Conductor. It must be sized based on your current carrying conductors.

There is no reason to go to 1/0. #1 is great for this application. If I remember later this evening I will look up the EGC size for #1.

 

[oleguy]

#6 for egc.

 

[pattenp]

All the wire sizes being thrown around without mention of whether it's copper or aluminum.

So what is it?

Edit: I'll add to this, if it's aluminum I think you should up it to 1/0 because you may get more voltage drop at 150' using #1 than you may want. 100A is max for #1 Al.

 

[Mudbone]

All the wire sizes being thrown around without mention of whether it's copper or aluminum.

So what is it?

I was meaning Cu. I first mentioned THWN, forgot that could be Al as well. Seems like around here if you ask for Al you some type of X series insulation. I realize Al would be cheaper, but with my 1.5 inch pvc conduit limit I have issues with the distance and number of conductors in the conduit when it comes to Al. Unless the inspector will do a wink wink nudge nudge on the last four feet of conduit going in the building and up the wall. That piece of conduit is already in place. See the build thread for my workshop.

I can get 4 conductors of THWN at #1 AWG in a 1.5 inch PVC. (NEC2011 Table C.9 page 70-786) That AWG in Al is rated for 100 amps, (NEC2011 310.15(B)(16) ) but that does not account for the 150ft distance.
Unless I am missing something here.....

Edit: Even with running the ground wire, excuse me, the EGC, at #6 I don't think I am allowed three 1/0 with it in 1.5 inch pvc.

 

[pattenp]

If you use Al THHN/THWN you can use the compacted conductor table on pg 70-789 which shows 4 #1/0 in 1 1/2" sch 80 PVC. 4 non-compacted #1/0 will fit sch 40 PVC.

This is XHHW with compacted conductor...

THHN/THWN .....

 

[pattenp]

If you use copper then you can get by with #2 for 100A @ 150'.

 

[matt151617]

Bare copper isn't all that expensive. Make sure you check an electrical supply house though. The one here was $.49/foot for #6, Lowes was $.98/foot.

Also, code requires anything below #6 to be protected ie in conduit.

 

[sberry]

I am with patten here, would likely be number 2 if I was dead set on copper, for the cost to start and its going to be all you are going to do to get 3 of those and a 2 down a 1 1/2 as it is especially at that length. As for 100A, you need to remember that in the rare event you would be close to pulling hi current down this line it would be intermittent at most, I can tell you after wiring a couple dozen or more of these with 2 alum on a 60A breaker over last 25 or 30 yrs never, never not once had a call back because of overloaded main. Got a bud works out of his doing auto, has comp, air cond and way too many lights,,, never an issue. Most 100A service to detached buildings rarely see any real load, they barely figure on a load calc really, biggest issue is air on demand.

 

[wyliesdiesels]

The current plan is to run #1 THWN in 1.5 inch pvc. (I believe 4 wires of #1 is the max allowed for 1.5 inch pvc)

The question I have regards running the ground from the panel back out to the buried grounding rod. Can i run it back down the conduit I have now and is there some type of waterproof connection that I can use to run the ground wire out of the conduit to the rod. If I can't do that, what are my other solutions without poking a hole in the side of my building?

TIA

First off, u do not need a #1 for your EGC! Based on NEC T250.122, and accounting for distance, u can use a bare #6 cu. With your #1 conductors!

And why not just drill a small hole in the side of your building? I have done this many times with no problems! If you're worried about water, seal the hole with some silicone! And u can use a #6 for the gec going to the ground rod without protection as long as its not subject to damage and follows the building contour!

 

[wyliesdiesels]

I want to make sure that I understand this completely. Are you guys saying that both the ground wire running from the building sub panel out to the ground rod AND the ground wire running the 150 ft from my main panel into this subpanel can be #6? Or are you talking about just the ground wire from the subpanel to the rod?

Yes, both the GEC and the EGC can be #6cu! Check NEC tables T250.122 and T250.66. FYI, the ground wire from the subpanel to a ground rod is called a GEC and the ground wire running back to the meter main is called an EGC since this is a feeder/branch circuit!

If it's both ground wires that I can take down to #6, does that mean that I can up the gauge on the two hots and neutral coming from the main panel? I picked #1 because I needed four wires and that is the max gauge you can put in a 1.5 inch pvc conduit. (The 1.5 inch was determined by what would comfortably fit in the foundation wall, which was a 4 inch block with a modular brick veneer.) At 150 feet, more or less, can I or should I go to 1/0?

Why would u go bigger on the hots and neutral cause the EGC can be smaller? 1/0 would be way overkill and a lot of unnecessary pain! U could probably get away with #2 cu with 75deg temp grade. Make sure your breakers are 75deg grade too!(most new breakers are but if u reuse older breakers they might be 60 deg rated which would mean your 75 deg. wire would have to be derated. #2 cu @ 60 deg is 95 ampacity, so this is a moot point! I digress.)

 

[wyliesdiesels]

....Seems like around here if you ask for Al, you're asking for some type of X series insulation. I realize Al would be cheaper, but with my 1.5 inch pvc conduit limit I have issues with the distance and number of conductors in the conduit when it comes to Al....

I can get 4 conductors of THWN at #1 AWG in a 1.5 inch PVC. (NEC2011 Table C.9 page 70-786) That AWG in Al is rated for 100 amps, (NEC2011 310.15(B)(16) ) but that does not account for the 150ft distance.
Unless I am missing something here.....

Edit: Even with running the ground wire, excuse me, the EGC, at #6 I don't think I am allowed three 1/0 with it in 1.5 inch pvc.

In my 2005 NEC based 'Code Check', 75 deg and 90 deg grade al conductors are only listed as xhhw and xhhw-2!

As for conduit and distance issues, go with max #1 cu and u should be more than fine!

 

[Mudbone]

On the original topic, I am going to try to drill the foundation for the EGC. I have already gone to a lot of trouble to hide the main conduit in the wall, a section of conduit coming through the wall and going down the side of the brick is gonna look like a dogs behind.

On the conductor size, the distance is going to be a damn sight farther than I orginally thought. I have to swing out from my house to miss the end of my septic field. Instead of 150ft its more like 220ft. Local electrican said I could go with #1 for the two hots, #6 for the EGC. For the neutral he said I could go smaller than #1, #2 or #3 and still be fine. Any thoughts?

 

[pattenp]

At 100A the #1 Cu will do you fine for the 220'. I'd drop just one size for the neutral to #2. The #6 is okay for the EGC.

 

[wyliesdiesels]

On the original topic, I am going to try to drill the foundation for the EGC. I have already gone to a lot of trouble to hide the main conduit in the wall, a section of conduit coming through the wall and going down the side of the brick is gonna look like a dogs behind.

As stated many times, an egc size #6 cu and larger DOES NOT NEED CONDUIT! You can run it bare, so u don't have to have ugly conduit coming out of the wall and save yourself the trouble of drilling through your slab!

BTW, when u say that you're gonna "drill the foundation for the egc", do u mean you're gonna do a ufer ground instead of a ground rod? If so, the wire gauge is different for UFERs!

 

[Mudbone]

As stated many times, an egc size #6 cu and larger DOES NOT NEED CONDUIT! You can run it bare, so u don't have to have ugly conduit coming out of the wall and save yourself the trouble of drilling through your slab!

BTW, when u say that you're gonna "drill the foundation for the egc", do u mean you're gonna do a ufer ground instead of a ground rod? If so, the wire gauge is different for UFERs!

Personal aesthetics here, but a bare wire poking thru the wall or even coming out from under the siding looks worse than condiut.

I am drilling down through the foundation and coming out the side (below grade), same path as the existing conduit for the main conductors, not through the footer. See pics in the workshop thread, link in my sig.

 

[wyliesdiesels]

Oh ok. Yeah, if aesthetics is an issue then u have a better way!

 

[Mudbone]

Unfortunately, its right on the front of the workshop next to the door going in so..... everyone that walks up is going to see it. Which will mostly be me so everytime I walk out there I will be thinking, "Damn it, if I had only put in a 1/2 conduit through the foundation for the EGC"

OCD is a *****.

And thanks for all the help guys!

 

[Mudbone]

So I got a 1/2 x18 masonry bit and drilled a hole for the GEC along side the conduit. It took me longer to get out all the tools and put them back up than it did to actually drill the hole and chase the pull wire. It turned out to be a lot easier than I thought because I was basically drilling through a few inches of concrete and then down in a space that just had brick mortar in it.

Actually the biggest pain was driving about an hour away to buy the bit. Seems hardly anyone carrys a 18 inch masonry bit for a standard drill chuck. Plenty out there for SDS drills. I have a large hammer drill and didn't really want to buy a $900 SDS drill just for one hole.

So the hole is in and a pull wire is in place, see the pic. I am going to start framing soon.

Thanks for all the advice guys.

View media item 23791

 

[wyliesdiesels]

Looks good! Its gonna be fun driving a ground rod in in that spot!

 

[Mudbone]

Looks good! Its gonna be fun driving a ground rod in in that spot!

You are actually looking at the top of the footer. Just past that is virgin clay. You can see some more pics in the build thread. Link is in my sig for the workshop.

I have a lot of projection due to a last minute change. The original plan was to have a monolithic pour. So the backhoe man showed up with a 24 inch bucket. This would allow for the sides of the mono slab, 12 inches, and working room for the form. After shooting with a transit we realized that there was too much slope for a monolithic slab. Backhoe man didnt have a 16 inch bucket. So we had to dig it with the 24. So instead of having a few inches of projection, its around 6-8 inches. Probably cost me an extra yard of concrete in the footer but that was cheaper than sending the backhoe away and getting one with a 16 inch bucket. Needless to say my little 14 x 20 workshop isn't going anywhere.

 

[wyliesdiesels]

O I c!