Wiring a shed questions

I am planning on building a large shed in the backyard, and am planning on running electrical to it. I am getting a couple of books in on wiring a house (including one called Wiring a House) but would also be interested in feedback from experienced electricians.
I have a few questions.
First, how is the easiest way to figure out what I have coming into the house. My panel says 120/240AC 200 Amp, and I really have to believe that is what is coming on, but I would like to confirm i have 200A. Does it say on the meter? My bill? Or do I need to call the electric company?
Second, is there an easy, straightforward method of calculating current usage, or load on the main panel? I am guessing the books will go into this, but I wouldnt mind getting some other input on this. I am assuming I will have enough to add a 120V/15A dedicated for an electric wall heater, and then one 15A circuit for the shed, since I recently removed an electric stove in the house (replaced with gas), but I want to confirm.
I was thinking it might be nice to have a sub-panel in the shed, with the two circuits. Is there an advantage to this? I was thinking I could feed the shed with 10g, and then have a 50A panel in the shed, instead of running two separate wires for the circuits. My plan would be to hook the feed wire to a GFCI breaker in the main, and then have two 15A standard breakers in the sub. Is 10g enough for this load on an ~80ft run (underground)? How would I wire it into the main panel? With one single 50A breaker, or 2 25A, or some other way. Using 10g 2 w/g or 10g 3 w/g? I have not looked into how to wire a sub panel, so excuse my ignorance.
Again, just looking for a base before I get my books.
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wrote:

10 Gauge wire is for a maximun of 30 amps. If you want a 50A breaker, and are running 80 feet, you'll need #6 wire. Four strands. One white, one black and one red (or two blacks), plus the bare ground wire. I suggest you bury some 1" pvc (gray) conduit from the house to the shed. That way you can pull anything thru the conduit. If all you want is 2 15A circuits, it would be easier to just run three strands of #12 wire plus the ground from the house. The only disadvantage you have to go in the house if you pop the breaker. But if you have conduit, you can always easily upgrade later if you decide to add a 220V welder or something.
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Just wanted to note something about your comment regarding amperage. Do you have 200A? Huh?
Amperage is a matter of how much you draw, not how much is directed to your house. Your main breaker is probably rated to a max of 200A (and probably so is your panel), nothing more. If you try to pull more than 200A, you'll getit until you pop the breaker or fry something.

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MrC1 wrote:

I have a main panel rated for 200A. However, I am not absolutely certain the house is wired for that, FROM THE STREET. For example, say my house was wired in the 50s for 100A, or 60A maximum. And the main panel, but not the wiring to the house, was changed. I am sure it has happened somewhere by a DIY or bad electrician. I dont want to draw more than what the system can handle, because I dont want to "fry" something.
i.e. So while 200A might not be "directed at my house", I want to make sure that from the street to my house is set to handle 200A of DRAW. I can't belive it isn't, but I want to make sure.
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chester wrote:

The wires between the electric utility and the main breaker (this includes the electric meter) are the only wires than have to handle 200A. These should be very large copper wires or enormous aluminum wires (I don't recall the exact minimum sizes for 200A).
You can only have one circuit going to the shed. If 120V/20A is sufficient, you can directly bury a strand of UF cable and it only has to be covered 12 inches if it is protected by a GFCI at the house. If 120V/20A is not enough, you probably want to run at least a 240V/30A circuit to a small subpanel (it has to be rated for "service equipment", but almost all of them are) and split it into smaller circuits at the shed. This larger circuit would have to be run in conduit and/or be buried a lot deeper, (or run it overhead with UF or triplex or quadplex cable) but it would not need GFCI protection at the house. (You will want GFCI outlets installed in the shed.)
Overhead wiring is more trouble than it sounds like (don't ask me how I know this) so I recommend buried cable if at all possible.
Best regards, Bob
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Yeah they are BIG aluminum wires.

Is that a code thing? I need two circuits, and was planning either to do two 12g wires running from two 15A breakers, or a larger wire (I guess based on above post 10g for a 240V/30A circuit), and doing it like you describe below. At any rate, I am burying them, and was going to run some PVC conduit anyway. It is not that expensive, and looks like it just snaps together. Gonna rent a trench digger, I think. And I will use a GFCI at the house to be on the safe side, and in the shed too, I suppose. But woiuld GFCI in the house not be required if I was running a subpanel and had GFCI in the shed?
Thanks for your help.
If 120V/20A is

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chester ( snipped-for-privacy@hotmeal.com) said...

You can have as many circuits as you wnt in the shed, but do you really want to pay for multiple home runs back to the main panel?
Here are the options I would consider:
Single 120 V circuit: home run to main panel has two 14 ga (for 15 A) or two 12 ga (for 12 A) plus ground
Two 120 V circuits: home run to main panel has three 14 ga (for 15 A) or three 12 ga (for 12 A) plus ground wired to a double pole breaker
One 240 V circuit: home run to main panel with either two (if no neutral is needed) or three (if neutral is needed) 14 ga (for 15 A) or 12 ga (if 20 A) plus ground wired to a double pole breaker
Combinations of more circuits: go with a sub panel in the shed; the home run consisting of three conductors plus ground wired to a double pole breaker, and rated to hande 125% of your worst-case load (i.e.: a 10 ga home run should be protected by a 30 A breaker, but should only be loaded to 80% of this value, or 24 A).
--
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Henry, given electrical codes, you should specify the cable configuration, not (just) "conductor count", otherwise, the person might be tempted to use multiple cables. Which can lead to trouble.
The code frowns on running multiple cables to outbuildings, because they want to minimize the number of things you have to kill to completely kill the building's power. Ie: _one_ breaker (or tied breaker pair).
With that in mind: Regarding grounds: You will _require_ a ground. The wiring nomenclature we use below (eg: "14/2") is wire size/current-carrying-conductor-count. Which does NOT include ground.
In Canada, you ALWAYS have a ground wire. Ie: in Canada a 14/2 will actually have three strands of copper - two insulated (the "/2") and one uninsulated (not mentioned explicitly). In the US, the ground isn't always assumed, so there is such things as 14/2 with only two conductors and no ground. To be sure of things, we're using the Canadian convention, and in the US, tack on "with ground" to the wire designation to be sure.

Using 14/2 or 12/2 respectively.

Using 14/3 or 12/3 respectively.

For 240V, if you need a neutral (120V/240V circuit for four wire devices _only_), 14/3 or 12/3 as above. For 240V _without neutral_ (240V tools _only_) 14/2 or 12/2 respectively.

This will be a single cable "<wiresize>/3". Ie: "10/3" for Henry's 30A example.
Note as well, detached outbuildings with a subpanel USUALLY need their own grounding system (ground rods etc), and do NOT need a ground wire in the panel feed. You will need to consult a local inspector to be sure.
Note: Generally speaking, the third option (A "240V" or "240V/120V" circuit) is rarely useful. Neither of which permit 120V devices (outlets or lighting), they're really only useful if the shed will contain ONLY 240V or 240V/120V devices (can't even mix 240V-only and 240V/120V devices), and usually only one at that (ie: a shed containing only your 240V water pump, and you plan on using flashlights for maintenance... ;-).
[Strictly speaking, while hanging 240V-only or 120V-only devices off a 240V/120V circuit _can_ be made to work, it's almost always a code violation, sometimes potentially hazardous or dangerously confusing, and should be avoided.]
Generally speaking, if the shed only needs lights and a few outlets, a single 120V circuit (first example) is the best approach. This is more-or-less the minimum (and most common) "Garage arrangement". If you plan on anything more substantial, a subpanel (last example) is usually the best approach. Unless you know that you need only two circuits, will never exceed it, and don't need 240V.
--
Chris Lewis, Una confibula non set est
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Well in the US, most wiring is labeled 12/2 with ground. 12/3 witll have 3 insulated wires, with a bare gound, "in my experience". I am sure there are exceptions.

Well, I need two circuits, and that is it I would anticipate. I need one for ruunnning lighting (one over head flourescent, and one other probably incandenscent). Probably also a TV and /or a cumputer. The only big draw I could imagine adding to this circuit is a excercise tredmill. I have no idea what the draw is on those, so I guess I will need to check. The other circuit will be a dedicated circuit to run an in wall electric space heater, set to run at 15A/120V. I have two in the house, in added-on rooms, and they work well. I will look into the 30A subpanel, but would lean on just running two 12/2 w/ground out through some pvc conduit as the easiest option.
Thanks for the input.
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I only mention it because the "with ground" is implicit in Canada (you can't buy wiring suitable for residential wiring without it), and AFAIK, you can still buy wire without it in the US, so the "with ground" should be stated to be absolutely sure you get what you want.

AFAIK, they're usually under 10A.

As a personal preference (and I think preferred by codes), I'd do this with a single 12/3 NMW (or UF) and tie-barred breaker, and just inside the shed I'd split it into two 12/2 branches. You sometimes save a bit of money, and it's a little easier to install.
Buried PVC conduit? You don't have to with NMW (UF), tho, the burial depth requirement is a little deeper. You'll need to check for what the burial requirements are in your area. You shouldn't use ordinary NM/NMD regardless.
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I think I see what your saying. Have two (15A?) tied breakers sharing neutral and ground, with separate hots? That sounds like the best solution. GFCI is code I assume for the breakers. thanks
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moose wrote:

At the shed, you'll split the circuit into two branches. One goes to your electric outlets, and the first one gets a GFCI to protect everything downline from it. The other goes first to the lights (without a GFCI) and then to any specialty outlets you might have (like a freezer that your don't want on a GFCI), and *then* another GFCI outlet and more convenience outlets if you want.
GFCI devices are cheaper than GFCI breakers (especially if you'd need a 2-pole GFCI breaker), and you don't want a GFCI on some things (lights, freezers, maybe a sump pump, etc.)
Check on adding a supplemental grounding electrode at the shed and connecting it to the ground wire at the first J-box.
Bob
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Yup.
I was thinking of saying something about GFCI. You _should_ have it (tho, it might not be explicitly code-required, depending on what the floor is, external outlets etc).
GFCI breakers are expensive. Bob's solution is better:

The above might be a bit confusing. Basically, you put a GFCI in passthru mode on both branches (MUST be downstream of where the neutral splits). You just might want to put a few unprotected outlets _upstream_ of one or both of the GFCIs for things you can't afford to trip (like a freezer).
Note: I believe electrical code can be pretty picky, so you may need to use non-duplex (_single_ outlet) receptacles for them, and they must feed "fixed" equipment (like a freezer). Not general purpose outlets.
[I'd probably GFCI the lights. Depends on whether anything in the shed is going to be "dangerous". I wouldn't GFCI _all_ of the lights in a workshop with power tools, for example.]


You only add supplemental grounding electrodes to outbuildings that have a subpanel. Not necessary for a single circuit (the dual breaker/ multi-wire branch counts as a single).
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OK you have been -very- helpful. One last question:
Is it OK to put that heater, which requires a dedicated 15A/120V circuit (if memory serves), on the tied breakers circuit? I would think not, but I admit I don't know a lot about tied breakers. thx again.
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chester wrote:

Put it on one leg of your 20A circuit, and put almost everything else on the other leg and the heater will be very happy. (this would work with a 15A circuit too, but with a higher chance that you will trip the breaker occasionally if the heater is not the only thing on its leg of the circuit)
Bob
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Most local utility companies will come out and let you know....most will also upgrade the feed to the home in SOME areas at no cost provided proper permits have been pulled and inspections made on the panel box when upgrading by a licenced electrician. Here, all thats required if the service to the home, GOING INTO THE PANEL is not up to the panels capacity, (ex: 60A service to the powerhead going into a 200A box), is a permit and the local utility will upgrade the line at no cost to the homeowner.
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The panel is rated for 200A. Which means you can draw up to 200A safely (subject to limitations of individual circuits) if the main breakers are rated that high.
What is the main breaker rating? It could be less than 200A. That's the true determining factor of how much you can pull from the street.
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