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Old 08-25-2011, 08:06 PM   #1
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Hi All,
You guys helped me out about 2 years ago so here I am again.

I'm trying to get electrical out to horse pastures for a huge charity event that I am having for the horse rescue.

I have 4 size 2 wires running through (pvc ....idiots,) that go from a 30 amp breaker in our well house, out 900 feet to an unused well at the rear of our property.

I want to use the 4 wires, from that 30 amp breaker at about the 500 foot mark in the center of the property. The wires have been exposed at that location and I want to put in an outdoor panel, and then run wiring out to service 8 duplex outlets that will have lighting and in the winter each outlet would have a 1250-1500 watt horse trough . The wiring will no longer service that well. What size panel can I put out there, what size wiring to the outlets. The furthest outlet would be approx 600 feet from the sub-panel.

Thanks for your help.
Cyndi

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Old 08-25-2011, 08:32 PM   #2
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Total distance 2200 feet round trip. No. 2 copper wire has a resistance of 0.16 ohm per 1000 feet.

Assuming that the existing wires are copper and you run #2 copper the additional 600 feet to the receptacles, your total current draw can be just 20 amps for 3% voltage drop (loss). Note that using the existing wires as-is and running smaller wires from the 500 foot mark to the new usage locations will result in significant additional voltage drop.

This also assumes using the 4 wires as hot-hot-neutral-ground in a 120/240 volt circuit.

For 20 amps you would not need a subpanel but you would have to use a 20 amp (double wide 240 volt rated) breaker back at the main panel. You could run no more than two 120 volt horse troughs or three 240 volt horse troughs.

Plan 2: Use 30 to 35 amps (30 or 40 amp breaker at the main panel) and suffer the additional voltage drop. You will need to run two sets of wires (hot hot neutral ground+) beyond the subpanel at the 500' mark, #2 for the furthest group of receptacles and perhaps #4 for the not so far group of receptacles. Common 120 volt receptacles and appliances with common 120 volt plugs can be breakered at no more than 20 amps (branch circuits in the subpanel). If you tried to draw all 30 amps* at the furthest point you would have a 4-1/2% voltage drop which may be okay for heated horse troughs but might not be okay for motorized equipment. (Drawing lesser amounts more or less evenly distributed among the receptacles also distributed along the outer 600 foot run for a total of 30 amps will result in a little under 4-1/2% drop)

I am guessing that you can run at most six of the horse troughs altogether with no other usage. THis would have a voltage drop in the 5 to 6% range; if it does not work well you would have to cut back to four horse troughs altogether.

How inexpensive (small) a subpanel you can use depends on whether the subpanel accepts #2 wires. You need 4 branch circuits.

*If the load is not more or less balanced between the two hot-neutral combinations then the voltage drop can exceed 5%.

+The ground can be #10 copper for the amperage used here (under 60 amps)

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Last edited by AllanJ; 08-25-2011 at 09:06 PM.
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Old 08-25-2011, 09:06 PM   #3
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The main panel is 200 amp. From that panel is a sub-panel down in a control pit for the well.

In that sub-panel is a 30 amp breaker for the old well. The four wires are exposed about 500 feet from the sub-panel in the pit. This is where I want the second sub-panel out by all the horse pastures. So the main 4 #2 wires are 500 feet from the original sub-panel in the pit. At that 500 mark is where I want to put another subpanel. (total of 500 feet from original sub-panel in pit)

Then from that sub-panel the first outlets are 20 feet away, 70 feet away, 120 feet away, 170 feet away etc. With the farthest being approximately 400 feet away.

What size sub-panel should I buy for the pasture area? (the new second sub-panel)

If I run number 10 wire, will that make it all work better together for my purpose. I can't go down to less troughs than 8 because there are 16 mini-pastures, each two of them share a trough. So that totals 8 heaters.

Again, my main questions are
What size sub-panel should I get to come off of the first sub-panel.....(500 feet from original sub-panel)..the original sub-panel is 10 feet from the main 200 amp panel.

What size wires should I use to make it all work well. Is there a way to add a drawing to this forum so you can see what I mean?

Thanks

Last edited by cherokeestar; 08-25-2011 at 09:12 PM.
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Old 08-25-2011, 09:25 PM   #4
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Allan, how did you get the VD distance of 2200'? The OP says the subpanel would be at 500'. This would make the circuit distance 1000'. This will greatly change the VD calculation.
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Old 08-25-2011, 09:26 PM   #5
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Here is a chicken-scratch diagram of what I want to do. Hope it makes sense.
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Old 08-25-2011, 09:33 PM   #6
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I have a guy...retired contractor that says he made a call to an electrician and was told to use a 30 amp sub-panel for the new panel and to abandon 2 of the 4 wires, only using the two that are left. That doesn't make sense to me because where would the ground be?

Right now my husband is heading to HD to buy an exterior sub-panel....please advise me on what size to get.

Thanks
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Old 08-25-2011, 09:50 PM   #7
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Using only 2 conductors would only give you either 240 without a ground or a 120 panel with half the breaker spot dead and no ground. You would also have greater voltage drop with the 120.

I think you guy needs to check the latest code that requires a 4 wire feeder. Even under the old rules a 3 wire feeder was allowed, not 2.
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Old 08-25-2011, 09:53 PM   #8
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It didn't make sense to me but I'm not an electrician and neither is he. I don't know his friend but regardless, I want to do it right. That's why I'm coming to this forum.

Noone has answered my question yet.

WHAT SIZE SUB-PANEL do I need to have my husband pick up. He will be at home depot in the next half hour and I need to know what size, please.

He is buying the one for out in the pasture, 500 feet from the original sub-panel.
Thanks
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Old 08-25-2011, 10:06 PM   #9
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Most of the subpanels will be rated at 100 amps. You can run less.
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Old 08-25-2011, 10:10 PM   #10
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If it were me doing this, I'd have a 60 amp breaker at the source. Hence, a 60 amp panel would be the minimum. You'll likely find 100 amp ones though. You can have a larger panel than the breaker that feeds it, but not smaller.

If the panel has a main breaker in it, it too can be larger than the breaker that feeds it. It can also be smaller.

You could put a 100 at the source if you wanted to. The breaker size protects the wire and panel, voltage drop doesn't enter the picture until load is calculated.
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Old 08-25-2011, 10:10 PM   #11
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Jim, if the new panel is going to be connected to a 30 amp breaker in the original sub-panel, can I use bigger than a 30 amp panel for the new panel?
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Old 08-25-2011, 10:11 PM   #12
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Quote:
Originally Posted by cherokeestar View Post
Jim, if the new panel is going to be connected to a 30 amp breaker in the original sub-panel, can I use bigger than a 30 amp panel for the new panel?
Yes. you could feed a 2000 amp panel with a 30 if you want to.
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Old 08-25-2011, 10:48 PM   #13
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Okay, so I had him pick up a 100 amp exterior panel for out in the pasture.
Thanks for the info. I'm sure I will have more questions about the first sub-panel down in the pit. It's pretty small with only two breakers in it I believe. I'll check tomorrow and go from there.

Good night for now.
Cyndi

By the way, does Stubby ever get on this forum anymore? He was the one that helped me with my huge project two years ago.
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Old 08-26-2011, 06:27 AM   #14
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Quote:
Originally Posted by Jim Port View Post
Allan, how did you get the VD distance of 2200'? The OP says the subpanel would be at 500'. This would make the circuit distance 1000'. This will greatly change the VD calculation.
Subpanel at 500' then extending the line 600' more. 1100' one way 2200' round trip.

If you use just 2 wires at 120 volts you will get the same number of volts dropped for a given number of amperes, 7 to 11 volts cdepending on load which is twice the percentages I gave you.
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Last edited by AllanJ; 08-26-2011 at 06:30 AM.
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Old 08-26-2011, 08:09 AM   #15
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Thanks, missed the part about the 600' to the last receptacle.

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