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Old 06-29-2020, 11:10 PM   #1
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Default Advice: Fitting 350mcm into short 2” conduit run

Before I order the cable I wanted to see what you guys think of making this fit!

200A service, 270ft from meter to load center, yet I have 2” conduit at the last 15ft under the slab. The rest is 2.5” conduit.

For voltage drop reasons I want to run 350mcm for the hots, 4/0 for the neutral and #1 for EGC. That is a 39% fill on 2” conduit.

As a fall back I will go 250mcm for hots, 4/0 for neutral and #3 EGC and deal with around a 5% VD if I ever hit above 150A.

So, will the 350mcm make it through the 2” with a bell sweep 90? Lots a lube?
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Old 06-29-2020, 11:21 PM   #2
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Quote:
Originally Posted by Keaton85 View Post
Before I order the cable I wanted to see what you guys think of making this fit!

200A service, 270ft from meter to load center, yet I have 2” conduit at the last 15ft under the slab. The rest is 2.5” conduit.

For voltage drop reasons I want to run 350mcm for the hots, 4/0 for the neutral and #1 for EGC. That is a 39% fill on 2” conduit.

As a fall back I will go 250mcm for hots, 4/0 for neutral and #3 EGC and deal with around a 5% VD if I ever hit above 150A.

So, will the 350mcm make it through the 2” with a bell sweep 90? Lots a lube?
I think it will go especially since it is just 15 feet, but I think it will still be a mother. I pulled three 250s and a #4 into a 2" a while back at about 37% fill and it sucked.
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Old 06-29-2020, 11:35 PM   #3
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If this is for a house, I would go:

(2) 250's
(1) 2/0
(1) #4
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Old 06-29-2020, 11:45 PM   #4
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With the a descend end made in the cable and someone pushing it should go. (pushing as important as pulling)
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Old 06-30-2020, 12:54 AM   #5
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I know this might sound weird but I use a C02 tank to blow out old conduits that are underground. The amount of rocks/sand that come out will surprise you. I am sure most of it was from initial install from dragging the conduit. It makes a HUGE difference on lowering the drag when pulling new conductors. Just make sure the other end of the conduit is funneled away from live panels and directed in a safe direction. It literally looks like a sand blaster, and the small pebbles/rocks can cause damage if you don't think ahead. Oh yeah and sometimes a lot of water/mud comes out.
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Old 06-30-2020, 03:16 PM   #6
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Thanks everyone! The other option is going to copper which increases the cost a lot. The conduit is already pretty clean since I vacuumed through foam inserts to get the mousing line in.

Wouldn’t 2/0 be way to small for a 200A service at 270ft? Since voltage drop would be a bit even with a low unbalanced current.

Does having grid-tie solar positively or negatively impact the voltage drop? Since I will be putting in a 7KW array later.
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Old 06-30-2020, 04:51 PM   #7
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Quote:
Originally Posted by keaton85 View Post
thanks everyone! The other option is going to copper which increases the cost a lot. The conduit is already pretty clean since i vacuumed through foam inserts to get the mousing line in.

Wouldn’t 2/0 be way to small for a 200a service at 270ft? Since voltage drop would be a bit even with a low unbalanced current.

Does having grid-tie solar positively or negatively impact the voltage drop? Since i will be putting in a 7kw array later.
Advice: Fitting 350mcm into short 2” conduit run-fc37209e-0c81-4013-93d1-793821befcb9.jpg
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Old 06-30-2020, 08:20 PM   #8
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Quote:
Originally Posted by Keaton85 View Post
Wouldn’t 2/0 be way to small for a 200A service at 270ft? Since voltage drop would be a bit even with a low unbalanced current.
I think you need to sit down with a voltage drop calculator and figure out exactly what you need, if you're skeptical. I know what I posted would work for the typical house, but if you're skeptical, take a crack at it! Do the calc! That's how you learn!

I did a feeder to a house about that same distance, maybe 240-250', with 4/0 4/0 2/0 #4 a year ago. There just isn't that much running load in the typical house for it to be an issue.

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Old 06-30-2020, 09:03 PM   #9
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Quote:
Originally Posted by Cow View Post
I think you need to sit down with a voltage drop calculator and figure out exactly what you need, if you're skeptical. I know what I posted would work for the typical house, but if you're skeptical, take a crack at it! Do the calc! That's how you learn!

I did a feeder to a house about that same distance, maybe 240-250', with 4/0 4/0 2/0 #4 a year ago. There just isn't that much running load in the typical house for it to be an issue.
Very true. I've got a big house with natural gas and I rarely see 80 amps with most all loads on. Like you say, he needs to do a load calculation.

Here's the calculation with 100 amps.

Advice: Fitting 350mcm into short 2” conduit run-e65c176c-f9df-45fb-8e29-f326901c5b17.jpg
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Old 06-30-2020, 09:06 PM   #10
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Just a thought. If you're that worried about voltage drop you could parallel smaller conductors. 4(2/0) for the hots, it would drop your fill down from 39% to 35% and the smaller wires would be much easier to pull and cheaper than 350 kcmil

Edit: also due to higher number of conductors the adjustment would be 80%. Wires would still be rated for 215 amps.

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Old 06-30-2020, 09:20 PM   #11
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Are these service feeders or feeders? Service feeders do not require an EGC. PVC or RMC? PVC has a lot more gripsion, if that is a word. Also if you oversize the feeders for voltage drop, then you also have to increase the neutral and EGC proportionally. How is the transition from 2 1/2" to 2" made?
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Old 06-30-2020, 09:24 PM   #12
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Also do the load calculation for the building. As Cow alluded to above, many times the actual load is not that high. You might only have a 75 amp load.
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Old 07-01-2020, 07:33 PM   #13
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Thanks guys! lots of information to take in.

I have been through many VD & fill calculations on this as I want to increase my potential for expansion later with car chargers and a garage/barn down the line. This would feed off the 200amp subpanel in the house.

OK! so responds to questions.

This is from pole to customer (mine) owned pole to a meter disconnect, run 270ft to the panel in the house which is now considered a subpanel. NEC requires from my understanding to run a EGC for this installation, unless I remove the disconnect and run 3 conductor approx 3ft into the house. This is cheaper and easier but not as safe and I cant feed off the meter to an outbuilding.

This is 2" PVC down into the slab, to outside the house with a reducer bushing and 250 or so feet down to the pole with 2.5" PVC. all downhill to the poll.

Kb1jb1: My understating the neutral can be downsized as there are very few unbalanced 120vac loads that would require the upsize. I have upsized the EGC in accordance with NEC to match the hots.

Motogp1199: I do like the parallel conductor sizing idea as that comes out with good VD & Fill numbers.

At the end of the day, 5% VD at 200A is not the end of the world as this would only really be for surge current and probably never make it past 150%. Which brings up another point. Does the feeder still have to go by the 80% rule of a circuit load?
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Old 07-01-2020, 09:25 PM   #14
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Are these service feeders or feeders? Service feeders do not require an EGC. PVC or RMC? PVC has a lot more gripsion, if that is a word. Also if you oversize the feeders for voltage drop, then you also have to increase the neutral and EGC proportionally. How is the transition from 2 1/2" to 2" made?

I was wondering the same thing? Especially U/G.
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Old 07-01-2020, 09:27 PM   #15
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[/B]
I was wondering the same thing? Especially U/G.
It's with a bushing that inserts into the bell of the 2.5" PVC and makes a clean fit for the 2". I'm going to start the cable on the inside of the house and run it downhill so the 15ft of 2" will be the start and have a clean transition to the 2.5".
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Old 07-01-2020, 09:36 PM   #16
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Originally Posted by Keaton85 View Post
It's with a bushing that inserts into the bell of the 2.5" PVC and makes a clean fit for the 2". I'm going to start the cable on the inside of the house and run it downhill so the 15ft of 2" will be the start and have a clean transition to the 2.5".
Do you mean like a plumbing reducer? What would happen if you, or someone else, fished it from the other way? 2-1/2" to 2"? Why the reduction in the first place, seems strange.
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Old 07-01-2020, 09:43 PM   #17
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The original plan was a pole less than 150ft from the house, meaning much smaller required wire, thus 2" was installed not even considering anything else. Yes, it was an oversight as even 2" is just not great for service entrance.

The neighbor went back on their word of an easement to go over 20ft of property to have the pole. So, I ended up having to go 270ft down the whole length of my property.

I used the 2.5" the rest of the way to make it at least a little easier.

hence, why I'm in this pickle now
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Old 07-01-2020, 10:59 PM   #18
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Be sure to check with someone who has solar experience. We did an install awhile back. fortunately we had the local inspector and rep look the job over ahead of time and the stat e rep warned us about VD between the inverters and the service. It was a 400 ft run so we upsized for less than 1% vd. I do not remember the size details. Only everyting had to be watched careful.
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Old 07-01-2020, 11:45 PM   #19
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Are you an electrician or just the home owner?
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Old 07-02-2020, 12:34 AM   #20
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Do you mean like a plumbing reducer? What would happen if you, or someone else, fished it from the other way? 2-1/2" to 2"? Why the reduction in the first place, seems strange.
He should be using something like this:
https://www.menards.com/main/electri...4444962280.htm

Usually they are tapered inside to guide a string or fishtape into the smaller conduit.
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