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Old 04-15-2007, 11:20 AM   #1
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Subpanel to Shed - Check my plan


I'm planning to install a subpanel in a separate workshop, about 100 feet (as the wire flies) from my house's main 100A panel. I'll have a 15A 220 circuit for machinery, a 20A 110V circuit for lighting and outlets, and a 40A 220V breaker that feeds a rotary phase converter, powering a 3HP 3phase 220V jointer. The phase converter is rated for a 10HP total load, so it's to be wired to a 40A circuit, but I'm sure I'm not pulling anywhere it's full capacity since I'm only running the 3hp jointer. The plate on the jointer says it's full load current is 8A at 220V.

So I was planning to run H-H-N THWN #6 Cu in 1" conduit from a 50 breaker on the main panel to a 125A 8-space panel in the shed. That gives me less than 3% voltage drop over the 100' half circuit distance. I'll try to get a length of sch. 80 for the exposed part of the run, going into the shed. Otherwise it's sch. 40 (the only thing HD carries )

I'll put a grounding rod outside the shed, with a #8 conductor to the ground bar in the box. I'm leaning towards bonding the ground and neutral bars in the subpanel box, and only running the three conductors to the main panel, since there are no other metallic connections to the shed, and I can't imagine any in the future (this is a semi-temporary workshop until I build a barn for a permanent one- or two-man woodworking shop).

How does this sound? Is the 50A feeder sufficient for those loads? (I don't know whether to calculate a 3-phase 220V motor plate with a 8A load rating differently than single-phase motor plates.) Is it ok to have the 110V receptacles and lighting on the same branch circuit? (the shed currently has all that wiring run, and fed by a roll of 12-2 romex that the previous owner ran across the yard and plugged into an outlet outside the house. So if I can leave that stuff wired, and tie it into the subpanel as a single circuit that would save a lot of time/money.

Thanks for your input.

Nate

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Old 04-15-2007, 02:57 PM   #2
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Subpanel to Shed - Check my plan


The 50 amp circuit will work, but it doesn't allow much room for future growth.

I would need more information about your future plans before I could offer any recomendations. Such as:
1. What do you mean by this statement?
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Originally Posted by NateHanson View Post
this is a semi-temporary workshop until I build a barn for a permanent one- or two-man woodworking shop
2. Will you incorporate your shed into the new barn/workshop?

I also recommend placing the lighting and receptacles on different circuits. Let's say you are listening to a radio, have the lights on and you start to make a cut with a 110v table saw. When you trip the breaker, will you be able to see your way over to the breaker box to reset the breaker?


Last edited by gilchrist-electric; 04-15-2007 at 03:01 PM.
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Old 04-15-2007, 04:19 PM   #3
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Subpanel to Shed - Check my plan


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I also recommend placing the lighting and receptacles on different circuits. Let's say you are listening to a radio, have the lights on and you start to make a cut with a 110v table saw. When you trip the breaker, will you be able to see your way over to the breaker box to reset the breaker?
I was going to say the same thing. You'll also be able to see your fingers and steer clear of the saw blade until it winds down.
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Old 04-16-2007, 09:42 AM   #4
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Subpanel to Shed - Check my plan


Thanks for the input guys.

All stationary machinery is 220, and will be on the 220V circuits. Only
things like routers, etc will be on the 110V circuits.

I'd certainly set up separate lighting and receptacle circuits if I were starting from scratch, but since this shed already has outlets and lighting wired as a single circuit, I'm considering leaving it that way. Would it pass code that way?

The "temporary" nature of the shed is as follows: It's a 16x16' shed that existed on the property when we bought the house. It's the only place for my machinery right now because the house doesn't have a garage or full basement. We will build a barn/garage/workshop type building in the next couple years, but for the time being I need a place to do some limited work. This shed will not be incorporated into the to-be-built barn. Nor will this electrical service be expanded to the barn. For that I will probably have an electrician add a second tap to my meter, because our meter is on a phone pole 200' from the house, and the barn will be built about 75 feet from the phone pole. It'll make much more sense to run the barn's service from the pole, rather than from the pole to the house and back to the barn. (Also it'll keep the substantial workshop load off of the house's panel).

Basically there's no future expansion that I can imagine for this shed. There's frankly no room even for the equipment I have in there now. The very likely scenario is that in 2 years or so (probably can be read as 4 years), the machinery will all move into a proper workshop, and the shed will become a garden and sports equipment storage shed, with a really overkill electrical service.
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Old 04-16-2007, 06:22 PM   #5
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Subpanel to Shed - Check my plan


Thanks for the tip Silhanek. I'll see if I can get lucky. Heck maybe I've got 100' of sch 80 in the back of my truck right now without knowing it.
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Old 04-17-2007, 03:22 PM   #6
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Subpanel to Shed - Check my plan


Well, no luck on the Sch 80 at HD, but I'll try the local electrical supply.

I'm going to need to get a 50A double-pole Square D Trilliant breaker somewhere anyways. Hopefully they've got it at the electrical supply.

Do you guys generally find that wire is cheaper at HD or at an electrical supply?
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Old 04-17-2007, 03:42 PM   #7
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Subpanel to Shed - Check my plan


Well, my local electrical supply house doesn't sell retail at all, so I'm stuck. I need some Sch 80 1" conduit and a Trilliant feeder breaker.

Anyone have advice on finding these?
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Old 04-17-2007, 09:06 PM   #8
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Subpanel to Shed - Check my plan


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Originally Posted by NateHanson View Post
Well, my local electrical supply house doesn't sell retail at all, so I'm stuck. I need some Sch 80 1" conduit and a Trilliant feeder breaker.

Anyone have advice on finding these?

Maybe try opening an account at your local supply house.
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Old 04-18-2007, 05:48 AM   #9
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Subpanel to Shed - Check my plan


They want me to be a licensed spark.
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Old 04-26-2007, 09:56 PM   #10
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Subpanel to Shed - Check my plan


Well, I'm still looking for an SDT250 breaker, but I'm going to feed the subpanel with a 2 pole/30A circuit that is no longer being used for an electric dryer (we put in gas).

So I dug the trench today, and laid half the conduit. Installed the panel and put in the 220V 20A machinery circuit.

One question for you folks.

What size neutral should I run for this project (assuming it's eventually a 50A service).

I'm running two black #6 hot conductors. The ground is bonded at the subpanel and connected to a grounding rod with #8 green jacket copper THWN.

Thanks, Nate

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