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What gauge wire size would you recommend on a sub panel to my 10 x 20 shed 300' away?

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13K views 47 replies 23 participants last post by  12dbsinad  
#1 ·
I know that this is not an electrical forum but I also know that there are a good number of you who know what you are doing when wiring your sheds/barns etc. I want to put electricity into my metal shed which is 200' feet from the house. I have already dug a trench and am using 1.25" black PVC well pipe for the conduit. I would like to put a subpanel in it. I am thinking something like a 30 amp subpanel or maybe a 40 amp. I would like to have lights in it and also have some outlets as well so I can see at night and be able to have electricity to use tools to work on things there as well.

The guy that put my new pump into my well gave me the idea of using the black plastic pipe for running the electrical wire through as a conduit. They do it all the time. I have almost finished digging the trench through some pretty rocky soil and had plenty of large rocks to move out of the way. The 990 with the 8B BH has been a great rig for doing stuff like this. I am always amazed what the thing can do. I have 2, 100 foot lengths of pipe already lade and I will have to run the wire through from the main panel which would be another 50 feet and I probably have another 40 feet to go to where it will come up through the conduit I put in when the 6" floor was poured for the shed. So that is where I come up with the 300'. I know Cu wire is not cheep now a days. I kind of wished I would have bought the wire back when I put the shed in!

My question is do you think that I am crazy doing this. I of course have started the project so I am already in the midst of it. I didn't think about the length of the run and the current I was looking for. I believe it is doable but I know I will need a pretty heavy gauge wire and that is why I was thinking just a 30 amp sub panel. A 40 amp would be better in my mind but maybe the 30 amp would be plenty for lights and having a 20 amp outlet.

I pulled this off of one site giving input on putting in a sub panel:

The wire gauge of the cable you use to connect the subpanel to the main panel depends on the size of this breaker as well as the distance between the panels. In general, you need 10-gauge wire for a 30-amp subpanel, 8-gauge for a 40-amp one and 6-gauge for a 50-amp subpanel. If you need a 100-amp subpanel, you'll be running beefy 3- or 4-gauge cable with a 6-gauge ground wire.

Voltage drop becomes an issue over distances in excess of 100 to 150 feet depending on cable size. If you have to run cable for a longer distance, it's recommended to upgrade to the next wire gauge.

From this I would guess I should be using 8 gauge for the 30 amp and 6 gauge for the 40 amp.

I am also thinking about putting in a CAT6 cable so I can have internet access there as well. We have our garden there and my wife spends a good amount of time there. It would be good to have internet access when needed.

Any comments would be much appreciated even if they are about me not doing all the thinking before I started acting..

Thanks
 
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Discussion starter · #6 ·
EmmtBot said:
(I am NOT an electrician!)

For that kind of distance I'd forget copper and be looking at aluminum. Maybe some 2-2-2-4 or 4-4-4-4 MHF (probably cheaper online) or individual XHHW-2. If your power needs were really minimal there's UF but that really limits you. You definitely need something wet rated, any other ratings may depend on whether it needs to make any runs indoors beyond just coming up to a panel. PVC well pipe is not a rated conduit - personally I'd use the right thing but I get that not everybody everywhere is worried about codes. I guess maybe that's OK if it's a direct burial rated wire? Detached building subpanel should have its own ground rods.
Click to expand...
Yes I will go with wet rated wires. I have 2' depth and deeper for the whole run. I wasn't thinking of using Al wire but that is an interesting thought.
 
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Discussion starter · #25 ·
I really appreciate all the input. I knew, even though this is a green tractor forum, from my years of being a member, that people who are knowledgeable about many things reside here.

Yes I dug it with my 8B BH with an 18" bucket width and in some places it is even wider due to the rocks I had to move. I will attach some pictures for you to see. One of the things I am a bit concerned is the inner diameter of the pipe and it being big enough for the gauge of wire needed for a sub panel in the metal shed. It is a little over 1". It is one of those scenarios where I did not do all the homework I should have done in the first place. A long story but not worth giving all the details. My well guy was the one that sold me on using the black pipe. They use it all the time for their wiring as a conduit and I liked the idea because I have wanted to get electricity to the shed. So while redoing the pipes from the well with a new submersible I put the black pipe through the foundation which is about ~50' from the main breaker box. From the place where it comes into the cellar it is already buried out a hundred feet and at ~4' depth. It runs close to a water line that I have put in with a freeze proof water hydrant . So I really do not want to have to dig that all back up again to change the conduit out even though I hear what many of you have said. The black water pipe is 200 psi rated and of course the gray sched 40 or 80 conduit is I am sure even more highly rated if it was rated at PSI.

I like what one said about maybe just running the 10/3 but I fully understand the voltage drop so what if I ran 8/3 and ran two of those and did not put in a sub panel . I am wondering if I put a sub panel in the house where the conduit comes into the house. The run in the house from the main panel to the sub panel would be a good ~ 50' as I have already said. That drops my distance from that sub panel to the metal shed to ~250' or maybe a little less. Could that be an option? Then I run 2, 8/3 waterproof bury-able wires through the black pipe to the shed and hook up a couple of LED lights and have myself a 20 amp outlet. could that work? And if I put myself a POE ethernet switch in the same place as the sub panel and then run a 250' length CAT6A would that work. I have a Micro Center not too far from me and I have bought 250' spools from them before. I did all the terminations in our office we setup back in 2020. I have the tools to handle that without a problem. I was looking at the fiber cable that the link was given to and if I am reading it correctly it seems as though you are not to bury it but I could be reading it incorrectly.

thanks again for the input. See some pics below. I threw one in with some bears. We have more than we know what to do with in northern NJ never mind the amount of deer and not the green ones either! We have two mothers, one with a set of older ones and another with 3 younger ones and then we have others as well. The one's in the picture laid down just above my metal shed and took a nap for a little over an hour while I was digging in the pictures with the water hydrant. That was back in Aug-Sep. My projects tend to be real lengthy when you work 10 hour days.



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Discussion starter · #35 ·
OK I have been looking at the wire and the circuit. If I go with a 20 amp subpanel instead of a 30 amp (This would give me 2, 20 amp circuits in the shed to use) at the 300' using Al wire which is for direct ground burial using the referenced calculator linked earlier Voltage Drop Calculator | Southwire it comes up with 2 gauge on the wire. I could go with 4 gauge if I use Cu. I can get this from Lowe's 2-2-2-4 3E AL USE-2 RHH RHW-2 MOBILE HOME FEEDER 500 FT | Southwire which is 2-2-2-4 @ $3.87/ft. There is also this at Lowe's 2-2-4-6 3E AL USE-2 RHH RHW-2 MOBILE HOME FEEDER 500 FT | Southwire which is 2-2-4-6 at $3.50/ft and they have it in stock. Would that work. It would give me 2 gauge on the 120 V lines and then 4 gauge for the neutral and 6 gauge for the ground. I would put in the ground rod at the shed as others have recommended for code. Or should I stick with the 2 gauge for the neutral and 4 gauge for the ground? Thanks for the input.
 
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Discussion starter · #36 ·
Also looking at these two Eaton panels. I am not sure what the difference really is in both of them accept the price. I like the Eaton because that is what my panels are in my house. Always nice to be able to use the same breakers.
There is this one also with a little more space but I do not think I would need so many spaces but you never know and it is not a whole lot more money for it either.
With any of these I could add a couple of extra circuits like a 15 amp for the lights and have 2, 20 amp circuits etc. Obviously knowing I can go max 40 amps.
 
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Discussion starter · #37 ·
robpm said:
I can get this from Lowe's 2-2-2-4 3E AL USE-2 RHH RHW-2 MOBILE HOME FEEDER 500 FT | Southwire which is 2-2-2-4 @ $3.87/ft. There is also this at Lowe's 2-2-4-6 3E AL USE-2 RHH RHW-2 MOBILE HOME FEEDER 500 FT | Southwire which is 2-2-4-6 at $3.50/ft and they have it in stock. Would that work. It would give me 2 gauge on the 120 V lines and then 4 gauge for the neutral and 6 gauge for the ground. I would put in the ground rod at the shed as others have recommended for code. Or should I stick with the 2 gauge for the neutral and 4 gauge for the ground? Thanks for the input.
Click to expand...
I have thought about this more and I do not think that I should be concerned with a voltage drop on the return so why wouldn't the 4 gauge on the neutral work OK. Obviously the neutral and ground will not be bonded in the subpanel and I will also be driving a ground rod for the sub panel because it is detached from the main building and a long ways away with no other connections. Feel free to let me konw if you think my thinking is wrong.
 
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