Wiring a workshop...is it correct?

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rpdwyer

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I finished the wiring to my shed/workshop this weekend. The connection between the two is 225 feet of direct burial 8/3 cable with ground. Where it exits/enters the house and shed it does so via 2" electrical conduit. The shed panel is mounted to plywood and the electrical coming in stays in 2" conduit recessed in the wall behind the panel except at the top where it has a service entrance cap that allows the direct burial cable to leave the conduit and enter into the subpanel. The diagram below is how it's wired. I'd appreciate it if I could get feedback to confirm what I have below is safe. Thanks!

*Note the "ground/gound" at the house panel should read "ground/neutral" and blue dotted wire is the neutral wire.
Screen Shot 2021-11-15 at 9.14.42 AM.png
 

wwhitney

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The grounding/bonding you show complies with the NEC. The ground rods should have 8' in contact with the earth, i.e. fully buried for an 8' rod.

The direct burial cable should be under 24" of earth, and at each end should be sleeved with conduit from that depth to above grade.

With 225' of #8 AWG copper, you'll only be able to draw about 10A for a 120V load, or 20A for a 240V load, while staying within the guideline of 3% voltage drop. Of course, a lot of loads will work with a higher voltage drop.

Cheers, Wayne
 

rpdwyer

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"With 225' of #8 AWG copper, you'll only be able to draw about 10A for a 120V load, or 20A for a 240V load, while staying within the guideline of 3% voltage drop."

Hmmm....I don't know why I was thinking it would be higher. 10 Amps won't be enough to run my 15 Amp/110V compressor. 20's available at 240V...but that won't help my compressor.
 

wwhitney

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Hmmm....I don't know why I was thinking it would be higher. 10 Amps won't be enough to run my 15 Amp/110V compressor. 20's available at 240V...but that won't help my compressor.
Some loads may tolerate a higher voltage drop, 3% is just a guideline. And if your house supply is running above nominal, that would help. So really the only way to know is to try the compressor and see if it works, I think there's a good chance it will.

In the future, consider running a complete conduit system with bigger aluminum wires in it. Aluminum is also available direct bury, but I hear it degrades rapidly underground if there's any insulation damage.

Cheers, Wayne
 
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