Wiring in conduit

[Unregistered]

I am wiring three seperate circuits in conduit. Can I run all the white wires and all the ground wires to each plug in and just three seperate black wires to each circuit?
I got a screw with my electrical box to bond the negatives and grounds to the box. Do I need this? If so, would this eliminate having to run any ground wires at all?
Please help!!!!!

[Wgoodrich]

The content of your post leads me to believe you are installing a new service and three new circuits, while reading between the lines. Tell us what you are doing as you project totally. Then explain why conduit and not romex.

Short answer you are not allowed to use one white wire to serve three hot wires on a single phase service. Two of those hot wires are like conductors reading zero volts between them. This would cause these two conductors to add load to the white wire instead of subtract load from the white wire such as a true neutral conductor.

If this conduit is metal and properly installed and is a complete conduit system then yes the conduit may serve as an equipment grounidng wire. If you ran an equipment grounding wire in this conduit sized equal to the largest hot wire in the conduit then all circuits may be served by that one grounding conductor.

You cause me some alarm making me think that there are questions you need to ask you don't know you need to ask considering the content of your post.

Just being cautious

Wg

[Unregistered]

The content of your post leads me to believe you are installing a new service and three new circuits, while reading between the lines. Tell us what you are doing as you project totally. Then explain why conduit and not romex.

Short answer you are not allowed to use one white wire to serve three hot wires on a single phase service. Two of those hot wires are like conductors reading zero volts between them. This would cause these two conductors to add load to the white wire instead of subtract load from the white wire such as a true neutral conductor.

If this conduit is metal and properly installed and is a complete conduit system then yes the conduit may serve as an equipment grounidng wire. If you ran an equipment grounding wire in this conduit sized equal to the largest hot wire in the conduit then all circuits may be served by that one grounding conductor.

You cause me some alarm making me think that there are questions you need to ask you don't know you need to ask considering the content of your post.

Just being cautious

Wg
I build a detached shop from my home. I finished the inside with pole barn tin and I running all the wiring in conduit. I have a 100 amp Square D QO service panel.
I have 9 metal electrical boxes with 2 plug-ins in each box. 18 plugs in all. I have 1/2" conduit run between all the boxes running to the circuit breaker box. I figured I would run 3 circuits with 6 plugs on a circuit. (every circuit is 20 amp) I have to run all the wiring and wanted to do it the most efficient way. If I have three 20 amp breakers, and the hot(black wire) going to each circuit, can I elimiate having to run neutrals and grounds to each circuit?
I figured if I run a little ground wire from each plug in then to the box, I would elimate the grould wire back to the breaker box.
If I were to run wires as if it was romex, I would have 9 wires in the couduit. I think this would be to many for 1/2"
Let me know if there are other questions. I really appriciate any help.

[suemarkp]

How many wires feed your panel, 3 or 4? If only 3, then you MUST install that green screw in the neutral bar bonding it to the cabinet. I prefer a 4 wire feeder, in which case you install a separate grounding wire and grounding bar and do NOT install the green screw. But if the wires are already in, it is probably too late. Did you install a ground rod at your building?

Regardless of the green screw, you must run a green or bare grounding wire to all receptacles. I know it seems redundant, since the white wire already goes to the same place, but it must be there and for good reason. Post a separate question if you want to know why white and green must both be installed in your branch circuits.

How many conduits are there going to the panel -- just one, or more than one? If all three circuits must follow one long conduit run, then I recommend you do the following:

Buy a spool of black, red, blue, white, and green #12 copper wire (you need 3 times as much white and green as all of the others). If you are money conscious, you could buy black instead of red and blue, but then buy some red and blue tape.

You must run at least 6 wires in the conduit, but I'd recommend you do a 7th green ground wire even though the conduit is permitted to be a grounding conductor if all conduit connections are made up very tight.

Run a black, red, and blue from the 3 breakers (one color per breaker). Stop the black at the first outlet for circuit 1. Stop the red at the first outlet for circuit 2. Stop the blue at the first outlet for circuit 3.

Run a white to the first outlet with the black wire. Put a label on each end of the white wire that says "1". Run two more whites for circuits 2 and 3 labeling them properly and stopping at the correct box. Ideally the "2" label would be red in color and the "3" label would be blue. THIS IS THE MOST IMPORTANT STEP! You must make sure the circuit 1 neutral wire always only connects to outlets on circuit 1. Criss-crossing to outlets on circuit 2 or 3 can overload the neutral.

Run the green to the first outlet. This is safety ground and is the only wire that can be shared across all of the circuits.

Continue to the next outlets on a given circuit maintaining the wire color and the white neutral wire numbering.

Every outlet must have a black or red or blue wire, a white neutral, and a green ground. I would buy premade wirenut pigtails if you can find them in black, white, and green.

I'd also make the first outlet on each of the 3 circuits a GFCI, especially if that shop has a wood or concrete floor. Finally, you are allowed 7 #12 THHN conductors in 1/2" EMT conduit.

[Unregistered]

At this time I dont have the wiring run to the service box. I have plans to also run a ground rod in the ground.
Can I just run a small ground jumper from each plug in to the box?

[6pack]

Repost exactly what you ran to detached workshop as far as size wire, breaker size,#of wires ran 3 or 4.Is there non current carrying metallic path out there to garage? Did you receive help from this web installing? If so when did you discuss this under what thread.

[Perion]

In the 1/2 in conduit, coming out of the new workshop panel, you would have 5 #12 conductors (3 circuit "hots" plus 2 neutrals) plus 1 #12 equipment ground conductor. That's 6 wires total. You could use the following color scheme for taping the conductors (don't buy separate colored wires unless you know you're going to use it later - just identify your black conductors using colored tape):


************************************

Black - circuit #1 - 6 recepticales
Red - circuit #2 - 6 more receptacles
White #1 - neutral for circuits #1 and #2

Blue - circuit #3 - the last 6 receptacles
White #2 - neutral for circuit #3

Green - equipment ground for all outlets

*************************************

Make sure you put Circuit #1 and Circuit #2 conductors on circuit breakers that are adjacent to each other vertically in the panel. That is, put the red wire on a circuit breaker that is the next breaker directly under (or above) the one you put the black wire on. This will insure that those two circuits are on different phases so that they can share the same neutral (the white #1). You must use that particular neutral for just the receptacle outlets on those two circuits only.

It doesn't matter where you locate the third circuit in the panel (phase A or phase B) since that circuit isn't sharing its neutral wire with any other circuit.

If you're using 1/2 in EMT (metallic conduit vs PVC) you can use the conduit itself as the equipment ground and then you don't need the green ground wire but that opens up some new considerations which I don't have time to explain.

Keep something else in mind. Since your new breaker panel will be what's called a "sub-fed panel", you must make sure your neutral connections and ground connections are isolated from each other. You need separate termination strips for this in the new panel - a neutral bar and a ground bar. The neutral termination strip must be isolated from the grounded metal panel encolsure as well. You will need to feed your new 100 amp panel with 4 wires from your existing panel - two phase conductors, a neutral conductor, and an equipment ground conductor. The neutral and ground must be separate conductors. You may want to get further help from people here on this topic.

Also, it sounds to me like you probably have an application requiring GFCI (ground fault circuit interupter) protection for your receptacle outlets. NEC 210.a.2 requires that all 15 and 20 amp receptacles installed in "garages and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use" require GFCI protection.

I think you have an "accessory building" intended as (at least) a "work area". Anyway, if your application requires GFCI then install a GFCI type receptacle as the first receptacle in each group of 6 - i.e. the first one for each circuit in the group should be a GFCI type. Then sub-feed the remaining 5 receptacle outlets in the group, for that circuit, off of the "Load" terminals of the GFCI receptacle.

Maybe someone has some better ideas....


If you need some more info on the circuits I can probably find time later today to scratch out a simple drawing or maybe someone else would.

Best wishes,
Perion

[suemarkp]

There is an exception to the 4-wire rule for sub panels if the panel is in a detached structure and there are no conductive paths between the serving and served structures. If his wires are already in the ground, it may be too late to change, but he'll need to reallize the limitation of no phone, CATV, or metal pipes between the buildings if only 3 wires were installed.

Here in Washington, the local code mandates 4 wires for all subpanels, even ones in separate structures. So, there may be local rules the original poster needs to be aware of besides the NEC rules. Regardless, I do think the 4 wire feeder is the better approach for all subpanels.

I also didn't mention the shared neutral multiwire circuit approach because of the ramifications of getting the neutrals confused. The conduit should have room for 7 conductors unless its sch 80 PVC. I also think its a better solution for most uses, although the cost is a little higher. Local codes may also require double pole breakers on multiwire circuits.

[Unregistered]

Repost exactly what you ran to detached workshop as far as size wire, breaker size,#of wires ran 3 or 4.Is there non current carrying metallic path out there to garage? Did you receive help from this web installing? If so when did you discuss this under what thread.
I will be running three #2 gauge wires that are direct burial. What do you mean by non current carrying metallic path? I will also be running a cat-5, phone, and cable in pvc conduit to the shop.

[Unregistered]

Thanks everyone for the help. I have asked half a dozen people on how to do the things I am triing to do and they have all gave me different answers. I would like to know why I would need 4 wires going to the shop when there are only 3 going to my house. What would I hook all these wires to when I have only 3 lugs for service wires in my service box?
I have a square D QO box. It sound to me that this is the wrong box. The service box in my shop is a homeline box.
Is this what I should use for my shop.
I dont mean to complain but I am getting to many different answers.
Please Help

[Wgoodrich]

They are actually saying much the same thing only in their own way.

When you said you are running phone and cable between the building this cable is connecting the grouning system [ground rod] at the main house to the accessory building by a grounidng wire inside that phone or cable connection. Look at your phone box outside and you will find a grounding connection from your grounidng system in entering that house to that phone or cable connection. Then that grounding of that house runs to the accessory building. This would be a noncurrent carrying metallic path. This also means you will need to install 4 wire being two hot wires, one neutral wire, one grounidng wire as your feeder between the two structures because of that phone or cable tying the two buildings together.

Even though you are running your grounding system of the house to the accessory building service box you will need to install a ground rod anyway at that accessory building creating a new grounding system in that accessory building. This means the neutral bar in your accessory building must be isolated from the grounding bar in that same panel in your accessory building.

Two key points you are missing.

You house main service is fed by two hots and a neutral from your meter base. Then you are feeding that main service panel in that house with a direct contact with earth [ground rod or other grounding electrode]. This is your fourth wire serving that main panel in your house.

Then the phone system and your cable system is required to be grounded to that house ground rod also. This means when you run that phone or cable system to your accessory building then you are also running the grounding system of your house [ground rod] to that accessory building by way of the grounded conductors of that phone or cable wire ran between the two buildings. This then makes you install a fourth wire [green or bare equipment grounding system of the house] installed with the feeder to that accessory building to ensure all potential is equal between those two structures concerning that grounding systems of the two buildings fed by a common power company service meter.

The second thing you are missing is that the bare or green wire found throughout your home or accesssory building must be kept electrically separate from the white neutral wire in those houses anywhere on the load side of the main panels fed from the meter base. You never want current being carried on that green or bare wire unless lightening strikes or a dead short happens energizing the metal of your appliances that you family touches. This accessory building is being fed from the load side of that main service in that house. Also you are required due to your phone and cable to run a green or bare grounding wire with that feeder. This design makes your accessory structure panel to be located on the load side of your main house panel. Remember the rule mentioned above that any wiring after the main service panel must have the grounding wire connected to every piece of metal your family normally touches to direct a shorted wire current away from your family touching that metal [washer metal case one example] be isolated
from the neutral wires that carries current back to the panel from a hot wire after work is done electrically such as your hair dryer etc.

Breaker trips for two reasons, hot and white wire trips breaker if too much load applied that will over heat the wire. Second reason a breaker trips is if any NONCURRENT CARRYING METALLIC PATH [any green or bare grounding wire connected to any metal shell of any appliance you own that has come into contact with any hot wire. This will trip the breaker for the second reason. This also is that fourth wire you are asking about. grounding !

Hope this sheds some light

Wg

[Unregistered]

In my old shop, I have three wires running from my 200 amp service panel in my basement to my 100 amp service panel in my shop. There are the 2 hot wires that hook to my 100 amp breaker in my house service panel, and the one that goes to ground and the others to my 100 amp service box in my shop. I have a wire going from my ground lug in my shop service box to a copper rod I drove into the ground(dirt outside).
I have a direct burial phone line and cable and all the power wires (2 hots and a ground)all running in the same trench. My entire shop is all wired in romex and I have never had a problem.
Why is running all my wiring in conduit in my new shop(new location) such a problem?
I thought wiring in conduit was supposed to eliminate some of the headaches. Does anyone know of a help line that a person could call for advice? Almost all the electricians I talk to will give me absolutely no advice because they think they will be held responsible if there is a problem.

[suemarkp]

This is the best "help line" I've found... Your local inspection office should be able to answer questions too. There are also a lot of books out there, but I don't believe they get much into this specific issue.

As far as your old shop goes, this used to be legit. However, when you have other metal pathways between the buildings and they are bonded to the neutral, the current in your neutral wire will follow all of these parallel paths -- the CATV shield, the grounded phone line, the neutral wire itself, any pipes, and the ground rods through the earth. This isn't all that bad, but if you break any of those bonded connections it will make a small spark. This could be catastophic on an oil pipe or a metal gas line, or in an area where there may be flamable materials and no one is expecting a spark when something is disconnected.

The current flowing in the earth between ground rods can bother animals. The current is small, because this path is probably the highest resistance of all those parallel paths, but it is still there.

You can avoid all of this by running 4 wires to your shop. I think its only a matter of time before this will be the only option unless the distance involved is quite long.

I think you picked up on a seemingly silly aspect of this, in that your shop is no different than your neighbors houses as far as how it connects via a 3 wire service. This is especially true when your neighbors are fed from the same transformer as you. In this particular case, I think you could argue that the dangers of a 3-wire shop are the same as neighbors on a common transformer, because the CATV and phone are all grounded independent of the transformer but yet your neighbors grounding electrodes are all connected to these wires we all share. Same thing was true in the days of all metal water pipes, as we all connected to the same one.

So perhaps the dangers are overblown, but the code recognizes a danger that can be mitigated by simply running one more wire with your feeder.

[Wgoodrich]

Suemarkup, boy you can bring up some very interesting subjects. Your silly aspects you spoke of has caused hours, days, weeks, and even years of volitale discussions between engineers that have never agreed on the answer to that silly subject. A good solid answer to this silly subject may happen but not sure in this century, ha ha.

Wide open subject that if a post got started with all concerns on the subject touched on it would be a never ending post with a very allusive CORRECT answer.

Think transient voltages, lightening, dead shorts. WOW all unknown territory or not fully understood.

I agree with your thoughts you mentioned.

frustrated

Wg