GFCI Circuit protection question-outdoor wiring

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gk wrote:

I'm afraid it does not apply to you because the voltage to ground on both circuits is 120 volts. You can run a multiwire branch circuit that can carry both loads but that would still mean changing the line to three wire plus ground.
If you were trying to avoid the installation of a grounding electrode system at the garage it is a bad idea even were the code permits it. A multiwire branch circuit is a single branch circuit for the purposes of the code so a building supplied by one of those circuits does not require a grounding electrode system at the building supplied. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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I think that this is a mistake. I run some pretty heavy loads in my garage. Sharing the circuitry with god only know what else could cause tripping of the gfci

There are several critical pieces of this puzzle that are not included.
What is the distance to the new loads? My calculations say that your new load (heater) must be less than 145 feet total wire length. Fixed pieces of equipment are not required to be gfci protected. That does not mean that it is not a good idea. Any flammable liquids out in the new area?
Other threads seem to indicate that you already bought the wire. Was the wire UF cable? NM as far as I know is not rated for direct burial.
Not knowing the path of the electrical run and the use of the area. 12 inches could be to shallow. 24 would be fine in all situations.
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SQLit wrote:

Well, the circuitry to the shed running the outlets and lighting is to be a dedicated 20a/120v circuit. the only other outlet outside the shed on this circuit will be the one outside at the house, which will rarely be in use for anything.

kept in the area. finished shed for storage/excercise, TV etc.

I am going for 18-24, with PVC conduit.
Thanks for you input/questions. I was concerned with the two separate circuits, but I found NEC code online, and found there are exceptions to the rule of one circuit (including multi-branch) to an external structure. One exception is when different voltages are supplied with the two lines. This appears to apply to my situation. i feel a whole lot more comfortable with two circuits, than running one multi-brnach circuit with a 240V and 120V running off of it.

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I might be wrong but I do not think your application would permit two feeders under the different voltages provision since the 120 volts is derived as one leg of the 240 volts and thereby CAN be provided from one feeder. Such a provision would apply if you were supplying 480 and 120 volts, where two panels would be required. You might be more comfortable with two feeders but that is not the normal way it's done. I think the primary consideration is that in a fire or other emergency it is possible for emergency personnel to shut off all power to a structure by killing the feed without having to figure out if there might be others. Don Young

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Don Young wrote:

So is it legit to run a multiwire off of dual 20A, and run the outlets off of hot neutral, and run the 240V off of both hots? I mean, I can do that easily, with the current wiring. I just would think two circuits would be better/safer. But obviouosly NEC has its reasons. However, I cant help but wonder why there would be exceptions for higher voltage but not 120 and 240 circuits. For that You would have to turn off two circuits as well. ?
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The multiwire circuit can be shut down with a double pole switch. The thing that makes this legal is using a double pole breaker in the panel. (exception 2) Then you can feed line to line and line to neutral circuiits from the same circuit.
210,4(C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads.
Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device.
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snipped-for-privacy@aol.com wrote:

So I just want to be clear: I can use the two hots from a (20A 3 conductor w/g) multiwire circuit to run the 240V heater, and one of the hots, and the neutral, to run the 120V. True? If this is safe, and legal, I will just do this. I dont expect to be having any high draw devices in the shed, except for an occasional power tool. Thanks for you help and advice.

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You, you can actually split out both of the 120v "hots" to run 2 120v circuits. Maybe put the lights on one and the GFCI receptacle on another. As long as the GFCI string starts after the split it will work OK. You can feed regular receptacles after the GFCI and provide protection if you connect to the "load" side.
As I said way up thread, you will have about 11a to work with if your 240v heat is 2000w. Of course in the summer you would have both circuits at the whole 20a each.. You get a lot of bang for the buck with a multiwire circuit and it even helps your voltage drop problems if the 2 sides are somewhat balanced since the effective load is based on 240v instead of two 120v loads. You don't see the return path voltage drop since the neutral is only carrying the unbalanced load.
A multiwire circuit does only count as a single branch circuit so you can skip most of the rules about sub panels. If you want to be on the safe side you could drive a rod and connect it to the ground wire but it is not required. A double pole disconnect switch is still required and a good idea, just so you can work on the wiring without thinking about someone lighting you up from the house. It can just be the regular wall switch type with 2 poles.
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snipped-for-privacy@aol.com wrote:

multiwire, and I guess it wouldwork fine, but from my perspective, I can't see it as being safer than just two circuits. There are some inherent dangers with multiwire, evidently, and never having wired one, I feel more comfortable with the two separate circuits. Guess I could do a subpanel....
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gk wrote:

The higher voltages cannot be derived from the same circuit without installing a transformer so the code language permits you to avoid that bit of expense and complexity. The code language on which you are relying is meant to allow separate circuits for such purposes as powering a large item of equipment that requires a completely different voltage such as 240 volt delta three phase with one phase grounded to run a large refrigeration unit. You need the 240 / 3 phase power for the refrigeration unit and you need 120 volt power for service receptacles and lighting. Since 240 volt delta is much cheaper to install as corner grounded delta the cost effective way to provide both voltages is to run two circuits. Another example is a guard house for an industrial complex that has 480/277 volt air conditioning and lighting together with 208/120 volt power for receptacles. In short those exceptions are only intended to be applied were a single branch circuit or feeder cannot supply the needed power. -- Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you.
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wrote:

That is not what the code says. In fact the handbook shows a combo NEMA 5-15 and 6-15 device in the example. (a duplex receptacle with a 120 and a 240 outlet)
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snipped-for-privacy@aol.com wrote:

Which example for which section? -- Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you.
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wrote:

210.4(C) ex2 The article I cited when I said the OP could feed his 240v heater and two 120v circuits with a single multiwire circuit.
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snipped-for-privacy@aol.com wrote:

Now I understand what you are saying. The higher voltages I was referring to are the ones that the OP was referring to such as 480/277. Such higher voltages cannot be derived from the same circuit without using a transformer as opposed to may not be derived from the same circuit because the code prohibits it which it does not. My point was that the exception allowing multiple feeders or branch circuits for different voltage characteristics does not apply to situations were the needed voltages can be derived from the same circuit. I do not see any conflict between our two postings. I was urging the OP not to run two circuits to obtain the 240 & 120 volt circuits he needs. I believe you were suggesting that he use a single multi wire branch circuit to accomplish that. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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wrote:

You are right but I would not consider it the most dangerous thing in the world.
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snipped-for-privacy@aol.com wrote:

Yes but it is still a code violation and as one of the guys that crawls into the buidings that all of you sane types have run out of I would ask that you cut us a break and follow the code. That includes providing a single disconnecting means that will deenergize the entire structure as required by the code. If you really want to be nice to us then you could mount the disconecting means outside the building.
"225.31 Disconnecting Means. Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure. 225.32 Location. The disconnecting means shall be installed either inside or outside of the building or structure served or where the conductors pass through the building or structure. The disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors. For the purposes of this section, the requirements in 230.6 shall be permitted to be utilized."
-- Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you.
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wrote:

You were doing OK tom and we love the firemen but if you boys are counting on a single disconnect you might get it trouble. It could be SIX separate switches. They just have to be grouped.
225.33 Maximum Number of Disconnects. (A) General. The disconnecting means for each supply permitted by 225.30 shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be no more than six disconnects per supply grouped in any one location.
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snipped-for-privacy@aol.com wrote:

I am aware of that as my bread work is electrical. I was only asking that if the opportunity presents please put a single disconnect outside. -- Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you.
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