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Discussion Starter · #1 · (Edited)
I don’t usually sign-up and post on social websites. Having read the post “…grounds and neutrals connected right...” given the circumstances, I was amazed, impressed, and encouraged by your patience and quality of responses. The more I read, the more I felt, if you could/would help them, I’m sure you could help me.

I have a NEW (no wires pulled) plan to add a 100A sub to a 3-sided pole-barn. The house has a typical 200A service and is full, so tandems will be required. It is ~150’ run total from the house service so vd is an issue. I plan to use 4-wire (of course!) 1/0AL URD but concerned about my ability to bend / pull that stuff. We plan to LB out the back of the service panel (with 1/0, yikes), sweep 90 at the ground (buried 18”), sweep around the driveway and sweep up at the barn. Here I can either LB into the back of the panel (and would that be over-limit now with 5 90’s or are LBs exempt?) or just come up into the bottom of the panel, but that’s a challenge getting the tight angles right through the metal of the side of the barn. Should I switch to direct bury and skip the conduit altogether? Where are GFIs required in this situation? Am I forced to downgrade the whole thing to 60A sub? Of course I’ll separate the gnd and neutral but will I have to drive another ground rod at the barn? Need is for RV plug, a couple lights & outlets, and welder when not using the RV.

Ok, lots of questions. Be gentle, I promise not to shop your answers around. :] oy.
 

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flipping slumlord
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I have a NEW (no wires pulled) plan to add a 100A sub to a 3-sided pole-barn.
I plan to use 4-wire 1/0AL URD...

We plan to LB out the back of the service panel...
(and at other end)
...LB into the back of the (new) panel
Done (well, mostly done.). Stop over thinking it all ;)
Use larger diameter PVC if concerned about wrestling wire...

The house has a typical 200A service and is full...
so tandems will be required.

I hate them and would rather see an additional panel installed at the house...

I plan to use 4-wire 1/0AL URD ...It is ~150’
Am I forced to downgrade the whole thing to 60A sub?
Size the wire based on the load you anticipate having at the barn.
Feed the need.

If 60Amp is all you need there (no machines or tools etc)... you're golden.

Need is for RV plug, a couple lights & outlets, and welder when not using the RV.
You should be fine.

hth

ps: Personally I'd put in as large a conduit (the whole way) as your panels will accommodate using J-boxes if the bends and pulls were really awkward or too many and fill that with the largest wire I could afford to install in it.
 

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We plan to LB out the back of the service panel (with 1/0, yikes), sweep 90 at the ground (buried 18”), sweep around the driveway and sweep up at the barn.
If you switch to copper, the yikes factor would be less. :)



Here I can either LB into the back of the panel (and would that be over-limit now with 5 90’s or are LBs exempt?)
LBs are not 90's. You're allowed 360 degrees of turns between LBs (as you apparently are aware :thumbsup: ) but the LBs are what "breaks up" the 90s nearing that total.



Should I switch to direct bury and skip the conduit altogether?
That's an option, if that's what you want to do.



Where are GFIs required in this situation?
Anywhere that is a wet location. Convenience receptacles are all that is required, AFAIK. So I'm thinking that RV plugs may be exempt from that requirement.



Am I forced to downgrade the whole thing to 60A sub?
That depends on what you have available at the main panel, and what you need in the barn. You're not REQUIRED to, no.



Of course I’ll separate the gnd and neutral but will I have to drive another ground rod at the barn?
Any detached building has to have a seperate (or maybe 2) ground rods driven.
 

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Master Electrician
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I don’t usually sign-up and post on social websites. Having read the post “…grounds and neutrals connected right...” given the circumstances, I was amazed, impressed, and encouraged by your patience and quality of responses. The more I read, the more I felt, if you could/would help them, I’m sure you could help me.

I have a NEW (no wires pulled) plan to add a 100A sub to a 3-sided pole-barn. The house has a typical 200A service and is full, so tandems will be required. It is ~150’ run total from the house service so vd is an issue. I plan to use 4-wire (of course!) 1/0AL URD but concerned about my ability to bend / pull that stuff. We plan to LB out the back of the service panel (with 1/0, yikes), sweep 90 at the ground (buried 18”), sweep around the driveway and sweep up at the barn. Here I can either LB into the back of the panel (and would that be over-limit now with 5 90’s or are LBs exempt?) or just come up into the bottom of the panel, but that’s a challenge getting the tight angles right through the metal of the side of the barn. Should I switch to direct bury and skip the conduit altogether? Where are GFIs required in this situation? Am I forced to downgrade the whole thing to 60A sub? Of course I’ll separate the gnd and neutral but will I have to drive another ground rod at the barn? Need is for RV plug, a couple lights & outlets, and welder when not using the RV.

Ok, lots of questions. Be gentle, I promise not to shop your answers around. :] oy.
URD is direct burial cable. No conduit needed.
 

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GFI protection will be required on the 120 volt 15 and 20 amp receptacle circuits. The RV receptacle will not require GFI protection.

Not all panels can accept or are listed for use with tandems.
 

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Discussion Starter · #6 · (Edited)
Wow, you guys are great, thanks so much!

Yes, “size to load”, but that’s somewhat soft at this point and we are early enough in the design phase that we can shift a bit. In the beginning, this was a case where dad was running a 100’ orange extension cord across his lawn to the barn to run his circular saw, radio and drop light, and sometimes his RV. When I saw that I had to say there’s a better way. I offered to run him a circuit, and I calculated voltage drop on that. #8? Ugh. Not good on a single circuit. I thought we could gain some efficiency by sizing up and adding other capability. Then we started talking about if he ever wanted to get a welder. I said, we should just do-it-right and go with a panel… and next thing you know....well, you know how it grows. Dad’s few hundred $ project to replace his hardware store cord is now launching into the stratosphere, but he’s ok and understands. His SS check is meager, but we are both insistent that we do it right.

So, I haven’t priced cu yet (could that be #2 THHN/THWN?) and it would be easier to work with, but $ was the other yikes in the equation. It’s a balance between convenience/cost. If we went with a 60A sub, my question was of more general nature, could that get us an RV and welder (that were NOT used at the same time, granted) along with a few lights and power saw. I’m fuzzy on rating / derating those types of situations. As for direct bury, I kinda prefer PVC for the comfort of the protection factor. We’ll see how I feel after wrestling the AL, right? I could be swayed to give that up. We are 18” bg after all and who would dig that far down… Yes, was looking at 2” sched 40. What’s this business about “weep-holes”, is that necessary or helpful?

Ok, GFI’s on the recepts since it’s 3-sided-barn, that’s considered wet in my book. Not to mention this is the Northwest, rain, rain, rain! (But hardly enough snow to ski in the Mts, argh!) So no GFI on the RV if that’s right? Save us a little. I don’t know about dad’s main panel regarding tandem limitations. It’s a newer model, 30-position Square-D so I hope were good. 8’ ground rod at the barn – done deal. Under what conditions would I need 2 of them?

Thanks for the great advice.
 

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flipping slumlord
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Yes, “size to load”, but that’s somewhat soft at this point
and we are early enough in the design phase that we can shift a bit.

In the beginning...
Thus the reasoning to go with larger conduit and larger wire.
Go as big as you can afford and remember that even free labor has value.

So, I haven’t priced cu yet ... and it would be easier to work with, but $ was the other yikes in the equation. It’s a balance between convenience/cost.
everything is a balance between convenience/cost..

8’ ground rod at the barn – done deal.
Under what conditions would I need 2 of them?
when you realize the practicality of that approach
vs meeting the installation standard described in current code

hth
 

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Discussion Starter · #9 ·
Yes, (no to 60) 100A for sure, I’m convinced. Go as big as we can reasonably go at this time, while the trench is open so-to-speak. Priced copper today and wow, aluminum it is. I though if it was just a bit more I’d do it, but 200-300% more is definitely out of the question. I see oceans of snot in my future. Good thing I work out. :]

Just did a site visit to get more precise measurements and realized that the existing ground rod is right where we need to run the trench. If I move it, can I re-bury it, or do I need to buy a new one? Ie, I don’t remember if there are any requirements to use a new one. I think I've just about got my drawing and punch list of items.
 

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flipping slumlord
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Just did a site visit to get more precise measurements and realized that the existing ground rod is right where we need to run the trench. If I move it...
Don't move a ground rod.

Turn the LB to a slight angle and then set an angled fitting onto it...
adjust until the end of that angled fitting is square to the ground and past the rod.
 

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Discussion Starter · #11 ·
How far past? If this is the general consensus, it looks like I can, but it could be quite an angle, depending on distances (large dist from LB to angle.) Replacing the rod is a cardinal violation? Obviously I’d prefer not to add another 45 to 3-90’s on this run if I can help it.
 

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flipping slumlord
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How far past?
Far enough... that your shovel can fit (to dig down to the trench).

Obviously I’d prefer not to add another 45 to 3-90’s on this run if I can help it.
What 3 90's? on what run?

With URD... At each end you should only needing/using about 10 feet of PVC including the fittings. That's one 90 from in trench going up the wall to the LB.
Adding a 45 (or 22) into that, to offset the alignment, shouldn't be a big deal.

hrh
 
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