Ganging 220V outlets into conduit..HELP

[Pavement SuX]

I am currently wiring up my shop and using EMT conduit, I have a question for an electrician.

I have run 1" EMT all the way around the peremiter and have starting pulling wires for both the 220 and 110 outlets. Can I "share" the nuetral for all 5 220 volt outlets (30 amp welders) like I can with the ground and neutral for the 110?

 

[MrMark]

There is no neutral to share on a 240 volt circuit. Just two phase legs.

You also don't share the neutral between ground and neutral on 120 volt circuits. You share the neutral between two circuits, each of which use one phase leg. The neutral must only be shared between opposing phases and the two circuits must be installed on a double pole (or handle tied) breaker back at the panel.

Seriously, based on your question, and please don't take offense, you shouldn't be using any shared neutral circuits. You should run individual 120 volt circuits. There is too much opportunity to screw something up and I doubt you are going to go broke buying an extra white wire.

 

[MrMark]

You do get credit for using the correct past participle "run" rather than the incorrect "ran" that everyone else uses on this forum.

 

[Pavement SuX]

There is no neutral to share on a 240 volt circuit. Just two phase legs.

You also don't share the neutral between ground and neutral on 120 volt circuits. You share the neutral between two circuits, each of which use one phase leg. The neutral must only be shared between opposing phases and the two circuits must be installed on a double pole (or handle tied) breaker back at the panel.

Seriously, based on your question, and please don't take offense, you shouldn't be using any shared neutral circuits. You should run individual 120 volt circuits. There is too much opportunity to screw something up and I doubt you are going to go broke buying an extra white wire.

OK, let me expand on this just ot be clear, and I appreciatte your help. I have run 100' of 1" EMT, and have installed 18 4" boxes into the run. I am going install 6 110v circuits with multiple plugs in each, and 5, 220V "welder" outlets. I guess my question is this.

For the entire run I have pulled a sinlge TNN stranded 12 guage "green" ground wire. Can I do the same for the welders? Pull a single 10 guage "white" for the ground on the three wire 220V outlets. Or does each 220V outlet need a dedicated ground?

If I understand you corectly, I cannot "share" the nuetral for multiple circuits? So does that mean I can run a single 12 gauge white "neutral" for each "circuit"

My neighbor is an electrician and I am going to have him look at it tomorrow, just trying to wrap my head around it tonight.

 

[MrMark]

You only share one neutral per two 120 volt circuits if you go that route. I advise against it. I think you should pull a white wire for each 120 volt circuit that you have.

On the 240, you can use one 10 gauge GREEN wire for your ground. That green wire can go box to box and serve the whole run of 240 volt outlets.

 

[Charles (in GA)]

It sounds like a lot of wires. You will need to calculate the fill of the conduit to make sure you are legal. In additon, if you exceed three conductor (not counting grounds) wires in a conduit, you will need to start looking at derating of the circuits, after 9 wires, the derating becomes serious enough to warrant lower amperage breakers, or more conduit runs to get out of the situation.

Even with deep 4" boxes, the box fill will need to be calculated also. If a wire comes into the box, connects at a wirenut and then the wire continues out, it is two wires for the count, if the wire passes thru the box without interruption, it is one wire. Again, you will have to sit down and calculate square inches of area of the wires based on NEC tables and fill based on cubic size of the box and the cu size of the cover (they should be marked) and you have to count devices in the box also (receptacles) and each device equals a certain number of the largest size of wire in the box (its two wires equivalent I think, its late and I don't feel like looking it up right now).

If you run all of this stuff together, you can share the green ground, but it has to be properly sized for the largest circuit.

You CANNOT use a white wire for a earth ground, it must be green or green/yellow striped only, or a bare wire. You CANNOT remark the ends of the wire used in conduit for any reason, until you get up to 1/0 (I forget the exact size cutoff, where, above that size you can remark a black wire as a neutral. In any case, it is well above any sizes you are installing).

Trying to put everything in one conduit is a BAD plan. You have to pull all the wires at one time, or you get a tangled mess.

Charles

 

[Stuart in MN]

There are also limits for how many currrent carrying conductors you can put inside a single conduit, without derating their current carrying capacity. There are enough variables here that it's probably best to wait until your neighbor has a chance to look at things in person.

 

[Pure Oil]

Food for thought - I used 1/2 inch conduit and ran my 15 amp circuit / 14 gauge wire black (hot) green (ground) white (neutral) & for my 40 amp 220/230 circuit 8 gauge wire red (hot) black (hot) green (ground) you don't need a neutral for the compressor (ie; 80 gallon 4.5 hp) or the welder NEXT; from your post it sounds like you want to run everything in the same 1" conduit - you can't get to many wires into a conduit, think of heat - I don't have the spec handy - I'm sure your electrician will be able to advise you. PS Have Fun!!

 

[mrb]

you can use the same ground wire for all the circuits. You dont need more than one ground in the pipe.

you have a bigger problem though -you have too many current carrying conductors in the conduit, derating is going to cause you to have to use larger wire (if you are doing the work to code)

 

[Pavement SuX]

OK, yes I do want to run everything "to code" for sure. When I originally talked with my electrician he speced the 1" EMT due to the amount of wire I would be installing.

The actual amount of wire I believe was enough for 3/4" but he suggested the 1" to make sure I had "extra" room to make the pull easier.

To make things crystal clear I have 10 boxes for 110V with two 20amp duplexes in each (split) at the box into 3 circuits.

I also have 5 220V plugs in the same run of conduit. So what am I looking at doing in this scenario?

Common Ground for all?

or

Ground for all the 110, and ground for the 220?

 

[mrb]

are all 5 240v receptacles on seperate circuits or all on one?

 

[Steevo]

are all 5 240v receptacles on seperate circuits or all on one?

There's the question I was waiting for.
You'd have fun pulling 5 pairs of 10Ga (for the 240v receptacles), plus the three pairs of 12Ga (for the 20A receptacles),plus the associated grounds, through a 1" conduit, so I was wondering about that myself.

 

[mrb]

There's the question I was waiting for.
You'd have fun pulling 5 pairs of 10Ga (for the 240v receptacles), plus the three pairs of 12Ga (for the 20A receptacles),plus the associated grounds, through a 1" conduit, so I was wondering about that myself.

yeah. and with 50% derating (from table 310.16 ampacities) you end up having to use #10 for the 20 amp circuits and #6 for the 30 amp circuits (not considering being able to use smaller wire for welders and i dont know how that comes into play with derating for more than 3 CCC)

 

[oleguy]

stop right there!!!do your self a favor,you can run three #4 thwn-2 and 1#8thwn-2.put a sub panel in your shop with a 70 amp breaker in your main panel.cost wise not much different and a lot more useable...the #4 are two hots and neutral.the #8 is ground.

 

[mrb]

stop right there!!!do your self a favor,you can run three #4 thwn-2 and 1#8thwn-2.put a sub panel in your shop with a 70 amp breaker in your main panel.cost wise not much different and a lot more useable...the #4 are two hots and neutral.the #8 is ground.

he has this conduit run around the perimiter of his shop for distribution when he should have had 2 or 3 seperate conduit runs. A subpanel isnt going to fix this.

 

[Aceman]

This is a pretty common mistake you made. A lot of people think the best way is to oversize your conduit and run all the way around a building. Then just pull every circuit you need into it. A lot of people don't realize derating starts to affect wire sizing usually after 6-9+ wires. What I usually do when I wire shops is when I run out of the panel, I'll run two conduits(one going each direction) and meet in the middle on the other side of the shop, rather than running one conduit in a complete circle around the entire building. Make sense? This way your circuits are split in half in each conduit which helps tremendously with the number of wires and usually will leave you with extra room if you decide you want an extra circuit or two in each conduit later on.

Do I think you'd ever have a problem with your install? Probably not. You'd have to have a crew of people all working at the same time in there to melt all those wires down.

But, is it legal? No.

 

[oleguy]

OK missread.took it he ran 1" conduit from main panel.

 

[MrMark]

You could probably stick with your current design if you scale back and go with 4 120 V. circuits (if you do the shared neutral thing, 6 conductors total - 4 blacks and 2 whites) and 1 240 Volt circuit (2 10 gauge conductors). That's 8 conductors total. Derating that you need to worry about begins at more than 9 conductors. For this issue, you count hots and neutrals because each is a circuit conductor.

I imagine you only intend 1 240 volt circuit anyway. So you would be able to keep all your work intact if you drop down to 4 120 volt circuits.

Here's what your pipe filling would look like:

4 black (or 2 black and 2 red) 12 gauge THHN (4 circuits)
2 white 12 gauge THHN (two neutrals to be shared appropriately)
2 black 10 gauge THHN
1 green 10 gauge ??? THHN. (I think it's 10 gauge not 100 percent)

Total of 9 wires.

 

[Pavement SuX]

Thanks Guys,

I have made a couple changes, and I think I have the perfect plan for what I plan to do....

 

[Pavement SuX]

This is a pretty common mistake you made. A lot of people think the best way is to oversize your conduit and run all the way around a building. Then just pull every circuit you need into it. A lot of people don't realize derating starts to affect wire sizing usually after 6-9+ wires. What I usually do when I wire shops is when I run out of the panel, I'll run two conduits(one going each direction) and meet in the middle on the other side of the shop, rather than running one conduit in a complete circle around the entire building. Make sense? This way your circuits are split in half in each conduit which helps tremendously with the number of wires and usually will leave you with extra room if you decide you want an extra circuit or two in each conduit later on.

Do I think you'd ever have a problem with your install? Probably not. You'd have to have a crew of people all working at the same time in there to melt all those wires down.

But, is it legal? No.

I can add another leg to the run, which is what I plan to do, it is just a pain because I have to go over the garage door, that is a pain.

My plan is to add another leg to the conduit for two seperate 220V plugs on one wall, and run the other three on the same circuit. Then divide the shop into 4 110 circuits total with split "duplex" at each plug.

This gives me a total of 9 wires in the EMT for the first half of the run, and 6 for opposite half.

Then a seperate 1" EMT with 6 #10's for two dedicated 220V plugs.

Everything I look at says that is legal......yes?

 

[mrb]

I can add another leg to the run, which is what I plan to do, it is just a pain because I have to go over the garage door, that is a pain.

My plan is to add another leg to the conduit for two seperate 220V plugs on one wall, and run the other three on the same circuit. Then divide the shop into 4 110 circuits total with split "duplex" at each plug.

This gives me a total of 9 wires in the EMT for the first half of the run, and 6 for opposite half.

Then a seperate 1" EMT with 6 #10's for two dedicated 220V plugs.

Everything I look at says that is legal......yes?

that sounds good. Remember, you dont need a seperate ground wire for each circuit -you can use one. So for your conduit for the two 240v circuits (its 240v in the usa, not 220v) you dont need 6 wires, 5 is ok (four hots and one green EGC)

 

[ishiboo]

You only share one neutral per two 120 volt circuits if you go that route. I advise against it. I think you should pull a white wire for each 120 volt circuit that you have.

Important caveat here is that the shared neutral only applies if the two circuits phases are offset. Since you have 3 120 circuits, you wouldn't want to accidentally share the neutral of the two on the same phase, or the neutral would be potentially overloaded.

I'd put a little tag on the neutral in the breaker box saying "shared neutral" if you do this. 2008 may also require a double breaker for this, not necessarily a bad idea.

Looks like due to derating from all those wires you have bigger problems to deal with though. This is because even the little resistance in a length of wire causes a voltage drop, which means the wire "heats up." In normal usage, you wouldn't have any issues, however if you loaded multiple circuits very heavily, you could see an appreciable voltage rise cause potential future issues.