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Old 04-02-2012, 05:35 PM   #1
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120-V outlets and 240-V outlet on same double-pole circuit?


Hello Experts from Los Angeles!
 
I am going to be installing outlets and lighting in a storage shed that currently has no electricity. I want to use the shed as a temporary work-space for a project. After the project is completed, the shed will again be used solely for storage.
 
My Code reference is the 2010 California Electrical Code, which is based on the 2008 NEC (file: ca_2010_title24_03.pdf). I have been reading Article 210, page 67 (and following pages).
 
I want to run (what I think is called) a multi-wire branch circuit to power multiple outlets and lighting in the shed. Basically I would like to have two circuits to divide shed loading and still have one 240-Volt outlet. This is my plan so far (April 2, 2012):
 
(1) Install a double-pole 30A breaker in the main panel [MP] feeding another double-pole 20A breaker in a "Disconnect Panel" [DP] in the shed.
 
(2) The [DP] will be feed via 4x #10 UF cable from the house [MP] to the shed (about 30-40 feet), buried 24" below ground. Conductors feeding the [DP] will be tied together in the [MP] and labeled.
 
(3) The [DP] will have a Ground buss separate from the Neutral buss.
 
(4) Run 4x #12 as one NM cable on a path inside the shed that includes
 
(a) two pairs of grounded duplex outlets (one duplex outlet on each 120-Volt leg in single, two-gang boxes),

(b) one 240-Volt outlet,

(c) and continues from the last box via two 3x #12 runs to two rows of 120-Volt fluorescent lights, one row on each side of the shed.
 
I realize that if any one 120-Volt device blows, all circuitry will be powered off via the double-pole breaker. That's OK.
 
Will this meet Code? All suggestions appreciated.
 
Thanks for your time,
Daneel

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Old 04-02-2012, 05:41 PM   #2
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120-V outlets and 240-V outlet on same double-pole circuit?


Long story short... NO you can't use the same wires for 240 and 120 circuits.
UNLESS you use that wire to feed a SUB PANEL in the garage.

I'll suggest you look into doing this instead and then after the project... to just leave it there.
A 60 amp sub panel is inexpensive and can all be done with #6 wire.

hth

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Old 04-02-2012, 08:40 PM   #3
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120-V outlets and 240-V outlet on same double-pole circuit?


Quote:
Originally Posted by TarheelTerp View Post
Long story short... NO you can't use the same wires for 240 and 120 circuits.
Code reference please.
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Old 04-02-2012, 08:54 PM   #4
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120-V outlets and 240-V outlet on same double-pole circuit?


I just installed a 120V exit/emergency light off a 240V lighting circuit. The first time in 14 years I've jumped off one side of a 240V circuit to feed a 120V outlet. It felt wrong in so many ways, but I couldn't find anything illegal about it, nor could anyone I double checked with.

That being said, it is not normal. Generally, if you are installing a specific 240V recept, you are doing so because something is requiring it. And if the appliance is requiring it, it would be against code for anything else to be on that circuit.

Now, I will also say that the OP needs quite a bit of help on his shed wiring design. No mention of ground rod(s). No reason to run 10-3 UF if the breaker in the shed is only a 2P 20. Likewise, no need for a 2P 30 in the main panel if the shed is protected at 20A.

This makes no sense to me:
Quote:
Conductors feeding the [DP] will be tied together in the [MP] and labeled
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Old 04-02-2012, 09:15 PM   #5
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120-V outlets and 240-V outlet on same double-pole circuit?


An appliance (such as a microwave oven or air compressor) must have the circuit to itself (no receptacles) if it is hard wired in and would use more than half the ampere rating of that circuit. Maximum circuit amperage for ordinary (15 and 20 amp) receptacles is 20 amps.

WHen a subpanel is installed in a detached building it must have both a ground wire going back to the main panel and a ground rod nearby.

There must be a master disconnect switch at the outbuilding. This may be a toggle switch with two poles but otherwise similar to an ordinary light switch provided it has the amperes rating to support the loads to be used at the outbuilding. It is expedient to have a top breaker in the subpanel to be this disconnect switch. At the main panel there must be a double breaker (handles tied together) for the 120/240 volt feed to the outbuilding.
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Last edited by AllanJ; 04-02-2012 at 09:24 PM.
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Old 04-02-2012, 09:22 PM   #6
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120-V outlets and 240-V outlet on same double-pole circuit?


The plan will work with some tweakes. The 30 amp breaker and 10/3 UF to the shed is fine. Install a small sub panel in shed with 2 ground rods. Run circuits for receptacles and lights. Run circuit for 240 volt tool.
Limitation is the 30 amp feed.
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Old 04-02-2012, 09:58 PM   #7
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120-V outlets and 240-V outlet on same double-pole circuit?


One other thing to look out for, depending on what code cycle your state is on, you may or may not be able to even use romex in the shed.

2008=no
2011=yes

Even if your state has adopted the 2011 code, there still may be restrictions on exposed romex due to being subject to physical damage. In garages, it is common that exposed romex must run down parallel to the studs, and you can't run perpendicular to them.
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Old 04-03-2012, 12:54 AM   #8
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120-V outlets and 240-V outlet on same double-pole circuit?


Hi and thanks, k buz.

Re "...tied together in the [MP]..."

Article 210.4 (D) Grouping: "The ungrounded and grounded conductors of each multiwire branch circuit shall be grouped by wire ties ... in at least one location within the ... point of origination."

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Old 04-03-2012, 01:25 AM   #9
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120-V outlets and 240-V outlet on same double-pole circuit?


Hey thanks guys.

Plan additions as of Apr 2:

(5) One or two 1/2" x 8' ground rod(s) in shed.

[Q5.0] Why might I need TWO ground rods?

[Q5.1] Do I need a fourth conductor (safety ground) between house main panel [MP] and disconnect panel [DP] in shed?

[Q5.2] Are Neutral and Ground busses separate in [DP]?

[Q5.3] If YES, ground rod(s) in shed connect to the Ground buss, not the Neutral buss, right?

I will check locally about Romex in out buildings (Is NM the same as Romex?).

[Q6.0] If I use 1/2" EMT, do I still need to run a green ground conductor to devices.

Note: My 240-Volt appliance is not hard wired and will draw less than 50% of the circuit rating.

I would like a Code reference as to why I cannot connect 120-V duplexes off of legs on a 240-Volt circuit.

Thanks for your interest.
Daneel
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Old 04-03-2012, 06:01 AM   #10
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120-V outlets and 240-V outlet on same double-pole circuit?


Quote:
Originally Posted by Daneel View Post
Hey thanks guys.

Plan additions as of Apr 2:

(5) One or two 1/2" x 8' ground rod(s) in shed.

[Q5.0] Why might I need TWO ground rods?
You could install one ground rod, but you have to be able to prove resistance to earth < 25 Ohms. If you don't want to prove the resistance, install a second ground rod.

[Q5.1] Do I need a fourth conductor (safety ground) between house main panel [MP] and disconnect panel [DP] in shed?
yes

[Q5.2] Are Neutral and Ground busses separate in [DP]?
yes

[Q5.3] If YES, ground rod(s) in shed connect to the Ground buss, not the Neutral buss, right?
yes, make sure to remove the bonding jumper in the subpanel [dp]

I will check locally about Romex in out buildings (Is NM the same as Romex?).
yes

[Q6.0] If I use 1/2" EMT, do I still need to run a green ground conductor to devices.
no

Note: My 240-Volt appliance is not hard wired and will draw less than 50% of the circuit rating.

I would like a Code reference as to why I cannot connect 120-V duplexes off of legs on a 240-Volt circuit.
see my answer in post #4, but I am curious what you are going to be plugging in

Thanks for your interest.
Daneel
I should amend the answer to #6
You do not need to run a grounded conductor in the EMT. You do need to ground the device to the metal box though.

Last edited by k_buz; 04-03-2012 at 07:47 AM.
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Old 04-03-2012, 06:13 AM   #11
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120-V outlets and 240-V outlet on same double-pole circuit?


As a semi-unrelated point of information, 240 volt receptacles can be 120/240 volt receptacles with the neutral (and also a 4'th prong hole for the ground).

Semi-unrelated question: Does the grounding electrode(s) at the main building qualify as a second grounding electrode needed to satisfy the 25 ohm requirement for the grounding electrode at the detached building?
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Last edited by AllanJ; 04-03-2012 at 06:32 AM.
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Old 04-03-2012, 06:57 AM   #12
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120-V outlets and 240-V outlet on same double-pole circuit?


Something to consider:
406.4 (F) Noninterchangeable Types. Receptacles connected to circuits that have different voltages, frequencies, or types of current (ac or dc) on the same premises shall be of such design that the attachment plugs used on these circuits are not interchangeable.

What this is saying is that you can change the cord end on your 240V appliance to fit a typical 120V receptacle.

I am a little concerned about your 240V appliance. You say that it will not be over half the load on the circuit. That would indicate to me that this is a 15A (120)/240 V appliance and will have a 15 A 240V cord end on it. If this is the case, I cannot find a code rule that would prohibit you from putting 120V loads on this circuit.

However, if your appliance has anything other than a 15A 240V cord end, such as a 20 A 240V cord end, this appliance needs to be on a separate circuit. There is a reason that appliance is rated 20A, not 15 A. If your circuit is less than half of the rated ampacity, say 9A, it is a good bet that that appliance would have been rated for a 15A circuit, not a 20A circuit.

I guess what I am trying to say is that what you are attempting to do is not typical. There are code rules that could prohibit from doing what you want to do (putting the 120V recepts on the circuit for the 240 V appliance), but the way you have worded it so far, those code rules are not applicable. It would really help if you were to divulge what your 240V receptacle was for.

One last note on the subject. In that shed, your 120V recepts will need to be GFCI protected. Depending on how you wire the 240V recpet into the MWBC, the GFCI devices may not work properly.
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Old 04-03-2012, 07:03 AM   #13
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120-V outlets and 240-V outlet on same double-pole circuit?


Quote:
Originally Posted by AllanJ View Post
As a semi-unrelated point of information, 240 volt receptacles can be 120/240 volt receptacles with the neutral (and also a 4'th prong hole for the ground).

Semi-unrelated question: Does the grounding electrode(s) at the main building qualify as a second grounding electrode needed to satisfy the 25 ohm requirement for the grounding electrode at the detached building?
No, where a sub panel is fed from underground it is now treated as a new service. The same requirements exist for grounding/bonding that exist for a main panel. That means if you run feeders to a sub panel underground to a garage with plumbing, not only must you have ground rods, you must bond the water system as well.

But if for some reason you wanted to bond the new sub panel to the existing ground rods at the house, you could do that by running (minimum #6) from the sub panel continuous to the existing set of ground rods.
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Old 04-03-2012, 09:58 AM   #14
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120-V outlets and 240-V outlet on same double-pole circuit?


Daneel,
I'd suggest checking with your building department regarding whether you need 1 or 2 new ground rods. In some areas the AHJ knows that 1 rod will pass the test and won't require you to drive a second one.
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Old 04-03-2012, 12:54 PM   #15
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120-V outlets and 240-V outlet on same double-pole circuit?


Thanks all of you!

As I try to put this project on a Code-complient footing I have thought of more questions.

Divulge 240V: 240V items are small appliances manufactured for use in Europe. Each uses much less than 15A. These have been stored for several years. I am just testing them. They have round plugs with two hot prongs at 3 o'clock and 9 o'clock and a flat ground contact at 12 o'clock on the side. So they are 240V appliances with no neutral. I will make an adapter cable to connect to the 240V receptacle. Or perhaps I can find an plug-in adapter.

Re GFCI: 1st device on the MWBC "path" would be the 240V outlet. I am thinking to put two GFCI receptacles in the 2nd box along the path, one GFCI on each hot. After that I expect to pair a separate neutral and hot from the LOAD side of each GFCI for all downstream receptacles and switched lights. So this MWBC will bifurcate into two 120V sources for lighting.

[Q6.1] Will GFCI protection work properly all the way downstream for each 120V hot?

[Q6.2] I can RED-tape-strip the ends of the WHITE neutral that is paired with the RED hot -- Code OK?

[Q6.3] www.homelectrical.com makes some inexpensive ($5.79) 20A GFCI receptacles with LEDs for "active" and "replace" (DG20-L-WW-B 20 Amp GFCI White SKU: GP-DG20LWWB). Any experience with the quality of Homelectrical products? Usually it's "cheap, reliable, low maintenance -- pick any TWO!"

[Q6.4] I will bond to the pipe if there is water in the shed (have not looked for this).

[Q6.5] What gauge wire do I need for bonding the ground rod(s)?

[Q6.6] Can the ground wire be bare? -OR- Must it be armored?

I am learning a lot and hope I am not asking too many questions.
Thank you.

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