New electrical circuit - requesting assistance

[Jim Joyce]

Hi folks,

I'm planning to run a new electrical circuit out to a storage shed in my back yard and I'd like some help with the details. I'm the homeowner and I'll be doing most of the work myself, but I want it to be safe and up to code.

1. I have called 811 - Call before you dig. They'll be coming out on Thursday of this week to locate and mark all of the underground utilities.

1. I will be using a licensed electrician to connect the new service to the existing service, but other than that final step everything else is on me. I have experience with switches and fixtures, but not with the other aspects of the project.

2. The rest of the 120VAC circuits in my home are 20A circuits, so by default I'm planning to make this new circuit 20A as well. I believe a single 120VAC circuit should be fine for both lights and receptacles out there. The biggest load I can envision is possibly running a miter saw, which is rated at 12A. Just in case I take that saw out there, I think a

15A circuit might be stretching it thin.

Q: Any issues with a single new 20A circuit for both lights and receptacles?

1. Web calculators say I should use 8AWG wire for this circuit because the run is about 120 feet, from the exterior of the house to the exterior of the shed. I'm planning to buy 3 solid copper wires, 8AWG, in colors white (neutral), black (hot), and green (ground). This is instead of a packaged cable such as Romex because I think it will be less expensive to buy individual wires and because it might be easier to pull 3 wires through conduit than to pull Romex.

Q: Any issues so far? I know the black and white wires need to be 8AWG, but does the green (ground) also need to be 8AWG? Am I looking for wire labeled THHN or is it something different? I'm buying everything at the local Home Depot.

1. I'm planning to use conduit versus direct-bury wire. Web calculators seem to indicate that 1/2 inch conduit is fine, but I was thinking about using 1 inch to make pulling the wires easier. I'm also open to using 3/4 inch conduit.

Q: Does code mandate a minimum conduit size? (Conduit fill) Does common sense suggest a different (larger) size? Also, does conduit get assembled as dry press fit, or does it get glued, section by section?

1. The house has a 240VAC breaker box on the exterior wall, with no room for an additional breaker, so I'm planning to buy a small 2-circuit sub-panel that I'd attach to the house, right next to the existing 240VAC panel. I would ask the electrician to connect the sub-panel to the existing

240VAC panel.

Q: I assume the electrician can create a new circuit from the 240VAC panel. Are there any issues with that plan?

1. The conduit will be buried by using a trencher. My understanding is that electrical conduit needs to be buried at least 18 inches deep, whereas if I went with direct bury I'd have to go 24 inches deep.

Q: Any advice on the use of conduit versus direct bury cable?

***

Once I get power to the shed, I'm good with the project after that. I appreciate any help I can get with the questions above or anything I might be overlooking.

[trader_4]

Permit? If you're going to get an electrician out there anyway, might be easier and not much more for you to just dig the trench, let them do the rest.

Having extra capacity isn't a bad idea. Any chance you;d need 240V for anything?

Not that I'm aware of. Make sure it's on a GFCI. Probably best to put a GFCI receptacle as the first point in the shed. That way if it trips, you can reset it there.

8 sounds like over kill to me, don't know what calculator you're using. Generally, 12g is used for 20A. Since it's a 125 ft run, I'd go down to 10g. You can run individual conductors, but you can just use UF cable and it will be easier/cheaper.

THHN is not rated for wet locations. You need THWN. The minimum ground size for 20A is 12g.

Use UF, skip the conduit.

Yes, yes. If you use conduit, I'd go with 3/4". It gets glued together.

Should be OK, depending of course on what other loads are on the existing panel.

That's correct.

If you have to pull a permit and have it inspected, which would be the case in most locations, I would consider doing the trenching and having the electrician do the rest. He has to come out and do a subpanel anyway, installing a couple receptacles and light isn't that much more and you know it will pass. Or at least get it quoted that way before deciding.

[Ralph Mowery]

You might as well put in a red wire and make it a 240 volt circuit. When going to the expense and trouble of running 120 feet underground you may be glad you did at a later date.

There is a minimum size for the conduit and number/guage of wires. I just do not know what it is off the top of my head.

[Ed Pawlowski]

If you blow a breaker at night you will be left in the dark. What are you doing in the shed? Power tools? If so, rethink and bring 240 out there and split it. Even with 120, put a small box for two breakers and split the lights and plug so you can reset right there, not in the house.

Yes, there is a limit to wire size and number. I've not done anything for a long time so I'm rusty on code. I'd get the electrician out there and go over the layout and get his recommendations on what is best. In the long run it will be cheaper.

Best to have him look.

[trader_4]

Rethinking that, you also need a disconnect at the shed. They have GFCI that are just that, no receptacle and I think they can be used as the disconnect. So, you could use one of those. Or a switch, then a GFCI receptacle.

[gfretwell]

Don't let the internet pedantics screw with you too much.

1/2" is probably fine if you run enough wire in there initially (7 legal but maybe not possible). I think 5 is plenty. That gives you 240v capability and an extra switch loop. That will be a tug and use lube. 3/4th is too damned close in price to be worth the hassle. 8 gauge is just silly. What is your load going to be? A weed eater? Some other garden tool? It will just run an imperceptible amount slower .If you had an induction motor load I might worry but don;t get silly. It is a damned shed. If you think it will be a shop some day use 1" and use a #12 to pull in your 4ga.

[gfretwell]

He gets a huge huss in the NEC if this is a 15/20a GFCI protected circuit on dwelling property. (12" burial depth and a break on the disconnect). I would still want a snap switch (but I can be a hard ass :-) )

[Jim Joyce]

A permit is a good idea. I got one for building the shed, so I know the procedure now.

I really doubt it. I've never needed 240V anywhere else in all these years.

Good point.

I used the calculators here:

My inputs were 120v, 120 feet, 3% voltage drop, conduit. Both came up with

8ga wire.

Looking at Home Depot's selection of UF cable from Southwire, it looks like it comes in lengths of 100 and 250 feet. Crap, I'd need the 250 and I'd have a bunch left over.

I only see 2000ft rolls of THWN. I'm not the intended customer for a roll that size, especially since I'd need 3 rolls to get 3 jacket colors.

I see this 150ft roll of 10/2 on Amazon:

Is that what you're recommending?

That panel is dedicated to the kitchen range, the clothes dryer, and the HVAC.

Excellent, thanks. I appreciate the info.

[Jim Joyce]

I like the idea of a disconnect at the shed. Thanks for the suggestions.

[Jim Joyce]

It's all good. :)

Good so far.

Let's see, I'm thinking of a 4ft LED work light, a transistor radio, a weed eater, another light on the exterior of the shed, and worst case, one serious power tool such as a miter saw rated for 12A. 99% of the time that power is being used, it would likely just be the interior work light and the radio. The other stuff would rarely be used, but I want to plan for it.

So 10g and not 8ga, then?

[Dean Hoffman]

I'd sure ask the electrician about buying the wire from him. He has his markup, of course, but you won't be buying stuff to throw in the corner of your shed to gather dust. I'm used to using quad 4 aluminum and larger in my world. Maybe aluminum wire would be a cheaper choice. You boxes would have to be rated for it, though.

[Ed Pawlowski]

I used 10 to my garage and had no problem running a table saw and other tools.

[makolber]

+1 YEP now is the time to look ahead.

Phone wire? Coax cable? Ethernet cable?

or a least a few strings so you can pull cables later

Mark

[Terry Coombs]

  I used 4/0 aluminum for the 50 foot run to the shop ... but then I ran a 220V/100A service . Machine tools and welding machines need a bit more juice than your average table saw .

[Scott Lurndal]

Do not run any of those in the same raceway/conduit that has power conductors. Run a parallel conduit.

[Ralph Mowery]

Isn't it against some code about running power wires and signal wires in the same conduit. I am sure it is in industry,but don't know about home electrical.

I think it is ok to burry them together in the same trench if just the wires were tossed in, but not the same conduit.

It probably would be a good idea to run a phone and coax. Maybe an ethernet cable, but maybe a wireless router would take care of the internet. The cordless phones may have that range, I would check it out to see.

[Jim Joyce]

I won't be running any of those particular cables since we won't be living out there. My wife will occasionally be potting her plants, or transferring them to bigger pots, so I've built her a 10ft workbench along the windowed wall. She plays music and podcasts on her cell phone, so having a radio/stereo is a luxury that might not even get used.

We've had back yard storage sheds at some of our previous houses and never had power run to any of them. There were times when it would have been nice, but frankly I'm wondering why I'm even doing it at all.

[Ed Pawlowski]

At some point you will be glad you did. Do something at night, run a space heater, run a tool. You may want to consider putting a security light on it facing the house. Motion sensor or remote switching would be nice to have.

[Jim Joyce]

If I go with UF-B, it looks like I can use the leftovers for inside wiring to the lights and receptacles, so I could easily use the whole 150ft.

I know AL is still used for some purposes, but I thin I want to stick with CU.

[micky]

If I were putting in electric, I'd also run cat6 internet, coax for tv, and phone line if I had a home phone and the cordless reception in the shed wasn't good. Even if I didnt' connect some of it at either end, I'd have it for the future. Cable internet is more reliable than wifi, and wifi has distance limitations. Phone line is so cheap I'd run it anyhow in case the next owner wanted it.

I'd probably run speaker wires too, so I could listen to the same thing in the house and the shed without turning on two devices, but I suppose most people don't care about that anymore.

And maybe a speaking tube so you could call back to your house, and a pneumatic tube so you could send papers back and forth. ;-)