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Old 10-23-2011, 05:37 PM   #1
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Detached Subpanel help


Hi all,
Looking at finally putting a detached sub-panel in. Sub-panel is 230 feet away from the main panel. This is for a small shed that will house about 20amps (at the most) of pond pumps and some other small resistive loads.

Dug the trench today at 36 inches or so deep. 1.5" conduit is ready to go (not in the trench just here). I am not doing the hookups as I have a electrician doing that part come next spring. Now I know I need two grounds down at the sub-panel as well as 4 wires going down. Both HD and Lowe seem to have the 2-2-2-4 SER (aluminum) for $1.49 per foot, which seems to be the best deal around.

I am told that both the SER would be fine if buried in the PVC. I am also told that 2-2-2-4 would be fine for 40amps at that length.

More or less a double check before I pay a huge amount for this cable. Anybody have any thoughts if this is correct cable to use?

Any thoughts on cheaper sources would be appreciated as well.

Thanks!

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Old 10-23-2011, 06:54 PM   #2
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Detached Subpanel help


You get "voltage drop" with long distances. Plug your numbers into the following voltage drop calculator and it will tell you what you will get at the other end...
http://www.electrician2.com/calculat...r_initial.html

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Old 10-23-2011, 07:01 PM   #3
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Detached Subpanel help


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Originally Posted by ThisIsMe View Post
Hi all,
Looking at finally putting a detached sub-panel in. Sub-panel is 230 feet away from the main panel. This is for a small shed that will house about 20amps (at the most) of pond pumps and some other small resistive loads.

Dug the trench today at 36 inches or so deep. 1.5" conduit is ready to go (not in the trench just here). I am not doing the hookups as I have a electrician doing that part come next spring. Now I know I need two grounds down at the sub-panel as well as 4 wires going down. Both HD and Lowe seem to have the 2-2-2-4 SER (aluminum) for $1.49 per foot, which seems to be the best deal around.

I am told that both the SER would be fine if buried in the PVC. I am also told that 2-2-2-4 would be fine for 40amps at that length.

More or less a double check before I pay a huge amount for this cable. Anybody have any thoughts if this is correct cable to use?

Any thoughts on cheaper sources would be appreciated as well.

Thanks!
SER is NOT rated for burial even in conduit.
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Old 10-23-2011, 07:57 PM   #4
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Detached Subpanel help


If only 20 amp 120vac, #8 would work. You could even get away with 10/2 UF for that outlet. No need for a sub-panel. And that trench only had to be 18 inches deep. Why you went three feet down is beyond belief, unless you are running water also.
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Old 10-23-2011, 08:34 PM   #5
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Detached Subpanel help


You can NOT use type SER cable underground, even in conduit! Do NOT buy it, as you will be wasting your $$$

What kind and how many "pond pumps" are you installing?
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Old 10-23-2011, 09:54 PM   #6
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Detached Subpanel help


#2 aluminum is the correct size, but you can't bury it....period. You could use a #4 copper in conduit for the feeders, and a #6 for the ground (THWN). Individual wires are what I am suggesting. And it's not going to be cheap.
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Old 10-23-2011, 10:23 PM   #7
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Detached Subpanel help


Quote:
Originally Posted by ThisIsMe View Post
Hi all,
Looking at finally putting a detached sub-panel in. Sub-panel is 230 feet away from the main panel. This is for a small shed that will house about 20amps (at the most) of pond pumps and some other small resistive loads.

Dug the trench today at 36 inches or so deep. 1.5" conduit is ready to go (not in the trench just here). I am not doing the hookups as I have a electrician doing that part come next spring. Now I know I need two grounds down at the sub-panel as well as 4 wires going down. Both HD and Lowe seem to have the 2-2-2-4 SER (aluminum) for $1.49 per foot, which seems to be the best deal around.

I am told that both the SER would be fine if buried in the PVC. I am also told that 2-2-2-4 would be fine for 40amps at that length.

More or less a double check before I pay a huge amount for this cable. Anybody have any thoughts if this is correct cable to use?

Any thoughts on cheaper sources would be appreciated as well.

Thanks!
#2 is a little overkill, but it leaves plenty of room for voltage drop. I believe #2 aluminum is good for 90amps. As others have said, ser cable is not rated for wet locations. It is an indoor cable only. What you want is individual conductors.






Quote:
Originally Posted by gregzoll View Post
If only 20 amp 120vac, #8 would work. You could even get away with 10/2 UF for that outlet. No need for a sub-panel. And that trench only had to be 18 inches deep. Why you went three feet down is beyond belief, unless you are running water also.
10/2 for 20+ amps at 200+ feet leaves 0 room for expansion. 10/3 maybe, with a sub panel, or even 8/3. Although pvc conduit would be better.



if i have equipment, i always aim for 3 feet deep especially on my own property. If digging by hand there is no way i would dig that deep. I aim for 2 feet when digging by hand. 18 inches is just not enough for me, especially with UF. I like having that sucker so far down there that even if someone trenches over the top they aren't even going to know it was there.

On a related note. When i was remodeling my house, charter communications came and asked if they could bury a line in my back yard to feed my house. I said sure, but im going to be removing some dirt, so it needs to be very deep. They said sure, we usually do 12" but in this case we will go 24". They ended up doing 12 inches, but somebody couldn't read a tape measure and that 12 inches turned in to about 6 inches in spots. I removed some dirt and suddenly their line was laying on top of the ground. I dug that line down with the backhoe down to about 40inches

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