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Old 05-23-2011, 03:19 PM   #16
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Ground Location and Wire Size


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Originally Posted by SD515 View Post
We are believe the OP is installing the sub-panel in a building separate from the service disconnect, as his serv discon is on a pole. 250.32
Of course, additional grnd rods aren't required if the feeder panel is in/on the same structure the main discon is.

Thanks. I stand corrected.

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Old 05-24-2011, 06:52 AM   #17
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Ground Location and Wire Size


That's cool WarEagle...we're all here to help each other
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Old 05-24-2011, 12:58 PM   #18
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Ground Location and Wire Size


Thanks.

Yes, I'm running a separate ground wire. I got a main lug panel because from other things I've read, I was under the impression that if there were fewer than 6 circuits in the subpanel a separate disconnect wasn't necessary. In the subpanel I'll have a 20A double pole for my well pump and 2 - 15A 120V circuits for light(s) and outlet(s). Do I still need a separate disconnect?

Another 'new' question. How much of that pulling lubricant might I expect to use to pull 1/0-1/0-1/0 + #6 ground 150' through 2" conduit? Long 90 at main and maybe a 45 degree elbow about 1/3 of the way. How about to pull 4/0-4/0-4/0 + #4 ground approximately 200' through 2 1/2'' conduit? Guy at the big box said just dump maybe a quart into the conduit at the start of the pull and then just drag the cable through it. Is that how it's done or do I need to be applying it to the full length of the cable as I'm pulling it through. What test strength rope do you think I'll need to pull?

How clean does the cable need to be at the connection end? I'm assuming the lubricant is non-conductive. Any possibility of adverse reaction with that antioxidant stuff you're supposed to use on Al cable/wire.
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Old 05-24-2011, 01:29 PM   #19
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Ground Location and Wire Size


Lemme see... I bought one of the 1 quart-ish sized bottles years back when I was pulling wire for a pool with a run that was around 100'. I didn't use very much. That was just 1 cable of 10-2 UF. I was generous with the stuff, filled the end of each pipe before I pulled through.

Same bottle, I used it for my 35 foot run of 3 1/0 conductors plus 2 runs of 10/2 UF. I had all the conduit assembled and placed in the trench and pulled everything through from one application of coating the inside of one end of the conduit. The wires were all covered pretty well.

I wouldn't worry about interfering with the conductive grease... You're getting this stuff on the insulation, and you're cutting off the insulation where the conductive grease will go.
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Old 05-24-2011, 06:07 PM   #20
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Ground Location and Wire Size


yes it's called the six handle rule: If less than six throws of the hand then a disconnect is not needed.
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Old 05-25-2011, 06:14 AM   #21
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Oops, sorry LHB Texas, I guess I thought you were going to have more circuits on that panel. Better to error on the side of safety. My bad.
Cowboy is correct, you can have up to 6 breakers be your disconnects.
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Old 05-26-2011, 09:01 PM   #22
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Ground Location and Wire Size


Another question...of course. Actually, two.

I am going to wire an outdoor outlet on the pole where the meter and main are located. At the main, the ground and neutral are bonded of course. Do I ground the outlet to the bonded neutral/ground bus, or for the outlet only, do I need to install a separate ground (say a screw in the cabinet or a small ground bus bar) and then tie that to the ground rod I've driven at the pole?

Next question. I've read several posts here and several articles elsewhere. I tried to do those neutral load calculations, but they're over my head. I've asked an electrician, a couple big box guys, a guy at the electric supply store, and the guy from the rural coop that brought in power to my property, about the size of the neutral I need to have. Can't seem to get a consistent answer. What size neutral do I need? I was going to run 4/0-4/0-4/0 + #4 ground from main to house ~ 170'. I'm figuring 200A load center at the house, but don't expect to ever come close that. My calculations come out to less than 125A. Anyway, I picked up the URD at Elliott Electric thinking I was getting 4/0-4/0-4/0. By the way, I had to hunt around to find that size. Should have looked a little closer before I left, but I ended up with 4/0-4/0-2/0 instead. The reason I'd gone for the bigger neutral was because of the different answers I kept getting about what size it needed to be. I figured too small is bad, so if I go with the big stuff, I couldn't go wrong, but now I have the 2/0 neutral and I'm ready to start pulling cable tomorrow. The Elliott guy said that's what everybody uses. Obviously despite the fact that I said 4/0-4/0-4/0, it didn't register. He heard "4/0" and "URD", and just assumed 4/0-4/0-2/0. The coop guy said 2/0 neutral should be fine. The electrician said 4/0. The big box guys were split. I'm thinking that since the 4/0-4/0-2/0 is so common and the 4/0-4/0-4/0 isn't, the smaller neutral is probably okay and what's usually used around here. So after all that, the question is... will I be okay with the 2/0 neutral? I won't have any atypical loads. I'll be using propane for heat, water heater, stove & oven. I really don't want to have to postpone the work to hunt for different cable if I can avoid it. I've taken time off and rented a mini-excavator to trench.

Thanks.
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Old 05-26-2011, 11:58 PM   #23
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Ground Location and Wire Size


I kinda like a full size neutral, only because I don't have to do the calculation. Now with small sizes it tends not to be a big matter but once you get to large wire it's pricey. The code allows you to down size your neutral, because it only carries the difference between the two legs. which could be quite low. the common size will probably meet all but a few situations. You could do the calc for fun, but it'll be ok.
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Old 05-27-2011, 07:16 AM   #24
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Ground Location and Wire Size


How about grounding the outlet in the main box? Need the separate bus bar? Also, while lying in bed thinking about all this I realized that the ground lug in the main is already connected to the ground rod, so where am I going to connect grounds going to other subpanels? There's only one lug and it's being used. Do I just use the bonded common/ground bus for ground when coming off the main? I don't think it's big enough for my #4 ground wire. Are you allowed to double lug a ground? I'm thinking nothing can ever be double lugged anywhere.

Also, I was going to run the 4/0-4/0-4/0 + #4 ground in 2 1/2" or 3" PVC. Can I get away with running the 4/0-4/0-2/0 +ground in 2" instead. That would sure make life easier.

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Old 05-27-2011, 09:15 AM   #25
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Ground Location and Wire Size


if you know your total calculated wattage,divide that by 240 volts to get neutral load.
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Old 05-27-2011, 09:38 AM   #26
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Ground Location and Wire Size


The receptacle at the main will have the neutral and ground connected to the same bus bar... at that point, they are the same. The ground for the subpanels will also connect to the same bus, and #4 should fit without a problem.

The 2/0 neutral should be just fine. Remember, the neutral carries only the unbalanced current between the two hots, so in a perfectly load balanced panel, neutral current = 0. You will never achieve a balanced load in a residential panel, but as long as the loads are spread as evenly as possible across the two hot legs, you will be fine with the reduced size. If you use the 2.5" conduit, it will be easier to pull through any LB fittings.

In my opinion, the 1/0 run is oversized for the loads you specified. I would do it using 2/2/2/4 mobile home feeder on a 70A breaker.

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