Shed - cannot figure out wire type

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Old 06-17-19, 06:22 AM
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Shed - cannot figure out wire type

Hi everyone,

This is my first post to this forum. I'm having some issue figuring out exactly what type of wire to use to run a 30A circuit to my shed. I'm planning on running a grinder and smaller power tools, a sensor light for the driveway and some music. On occasion, I'll run some big saws, but 30A I think would suffice. I'm running mostly lights inside. Since the run from the house to the shed is about 110ft, for 30A, I established that I need 8 gauge wire. I am digging a trench (18-24 inches) and using 1 inch schedule 80 conduit (I'm going under my driveway, which is currently crushed gravel). I've been trying to figure out what type of 8G wire I need. I believe I need 8-3 wire because of the voltage drop? Would that be UF (underground feed) wire? If so, is my only option to buy by the foot or are there rolls of this stuff? The UF by the foot looks way beefer than I thought and I'm not even sure if I can pull that through a 1 inch conduit. Any help is appreciated.

Thank you.
 
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Old 06-17-19, 08:00 AM
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If you have conduit you don't need to use UF. You can use individual conductors of type THWN.
 
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Old 06-17-19, 08:40 AM
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If you run 30A you will need to install a subpanel in the shed, ground rods, and split off various circuits once in the building. General-purpose circuits cannot exceed 20A.

Another option you might not have considered is to install a 20A multiwire circuit which gives you two 20A circuits using a shared neutral, without the subpanel or grounding requirements.
 
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Old 06-18-19, 05:58 AM
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If I'm running off a panel in the house, which already has a ground rod, do I need another grounding rod for the shed? I've decided to go 8-3 UF to have the option to run 240 on a double 30A breaker on the main panel. I am putting a subpanel in the shed with it's own shutoff switch (required by code in my town). I was looking to save some money maybe run well pump wire? I found 380ft for 250$, but I believe those are twisted and not a solid wire? Inside the shed, I will have 4 15A circuits, 1 for lights (switched), 1 for motion light (always hot), 1 for the grinder/stereo/outlets (x2) and 1 for external outlet for the shopvac.

Do I need to go bigger?
 
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Old 06-18-19, 07:37 AM
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Yes you need a ground rod at the shed -- one is required at each detached structure with a panel.

You have to use UF direct buried or THWN in conduit. Is it actually 380 feet? You would definitely need to upsize for that run.

A 30A feeder would be adequate for the loads you listed.
 
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Old 06-18-19, 07:40 AM
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If you are installing conduit why use UF? If the conduit is going from panel to panel use individual conductors of THWN as suggested earlier. Also Sch 80 conduit is not needed for the portion underground and only above ground if subject to damage, so use Sch 40. Also you do need ground rods at the shed if the feed is large enough to need a subpanel. A more economical wire to use is aluminum XHHW-2, you can use three #4 and one #8 and still use 1" conduit and have up to 60A and cost less than the 8/3 UF.

In first post you say run was about 110ft. Correct?
Voltage drop should not be an issue for your use.
 

Last edited by pattenp; 06-18-19 at 08:00 AM.
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Old 06-18-19, 09:51 AM
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In first post you say run was about 110ft. Correct?
Voltage drop should not be an issue for your use.
I agree. Unless you have specific needs for the entire 30A, I would stick with 10ga wire (either UF or THWN in conduit). Voltage drop is calculated based on actual usage, not the max, so the chance of you actually using 30A is slim to none.
Some lights and a one-person shop, I think 30A @240v with 10ga wiring will do you just fine.
 
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Old 06-18-19, 10:24 AM
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The shed is 110ft from the main house. The wire to go under is going under driveway, which my town requires the use of sch80 conduit. We are in NH, so our frost line requirements are strange. I have no idea why I have to go down 18-24 inches with my conduit trench. The inspector said I "could" go 10-3 and get away with it, but he recommended dishing out the extra $ for the 8-3. And I'm having a tough time finding either 10-3 or 8-3 in the 125ft length, other than off the reel. Never done a grounding rod before, so that will be interesting, but I'll save that topic for another thread.

So, running 110ft from the main panel to a subpanel, which will have it's own goundring rod and a terminating switch, what is most economical from a box store perspective? 10/3 or 8/3? There is some other wire, (8/3 Stranded Romex SIMpull CU NM-B W/G Wire) which comes in my needed length, but it says indoor? Since I'm going inside conduit (wish I didn't have to dig), can this be used?
 
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Old 06-18-19, 12:00 PM
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Nm-b is not allowed in wet/damp areas which includes in conduit outside. Larger sizes of wire will be stranded. Go to electrical supply and get the wire you need.
 
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Old 06-18-19, 04:08 PM
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Never done a grounding rod before, so that will be interesting, but I'll save that topic for another thread
The ground rod is easy. Just beat it in with a large hammer or sledgehammer.

and a terminating switch
Since you will need a sub panel in the shed you do not need a separate switch. You can use a main breaker on the panel or backfeed a plugin breaker for your disconnect.
 
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