Conduits, circuits, and outlets.

[Rick Moyer]

Which way would you do this?
I plan to install about 8-12 duplex 110 outlets and about 4 or so 220 single outlets in the new shop. All wiring run in 3/4" EMT, surface mounted, and along two adjoining walls. I know that I can run up to three circuits in the conduit (12 ga. /20a.).
A. If I run all the wiring from three circuits (110 and 220) I can run one line of EMT plus j-boxes for drops. This however would only allow me to have 2 110 circuits and all four or so 220 would be on one circuit.
B. But if I choose to split receptacles or to seperate boxes into more circuits, I will have to run twice as much conduit in order to have more circuits.
I am leaning toward more circuits as I have a >1/2-empty 100a. panel box, but am concerned about the EMT clutter, especially having to leapfrog the conduit in places (I don't want to buy a bender and learn to use it if I don't have to), and also the extra expense. I suspect I would run three 110's in one conduit and 2 or 3 220's in another conduit. Would you go to the trouble of running extra circuits or would you save the trouble and expense and run 2-110's and one 220 in one run of conduit?


I should note that the DC will have it's own circuit and breaker. I am a one-man shop so nothing running simultaneously except with the DC. Lighting is already installed on two seperate breakers, so that's not a factor. Only 220 tool right now is the jointer (besides the DC), but would like to have 220 TS and maybe 220 BS in the future, but again only one runing at one time.

Another question: If I were to run all three circuits in one run, can I use any color wire for the 220 hots? I would like to use blk/wht for the 110's, then maybe red/blue for the 220 hots, along with green for the ground. If I use only one ground for all three, will 12ga. be OK or does it have to be larger wire?

[Scott T Smith]

If it were me, I'd either run two conduits or upsize my single conduit to adequately carry the extra circuits.

[Rod Sheridan]

Rick, if you're a one man shop where only one machine is running at one time, you only need one circuit.

You can use a 2 pole 15 or 2 pole 20 Ampere breaker to feed all your 120V and 240V receptacles.

The 120 V receptacles can be wired as an Edison or split circuit to yield 2 circuits for 120V and 1 circuit for 240V.

You would only need 3 conductors plus ground, so 1/2" EMT may fit the bill.

Regards, Rod.

[Rob Russell]

Rick,

One factor that will impact how you can wire the shop is WHERE the shop is located.

Is your shop in either a garage, unfinished basement or grade level standalone shop?

If the answer is "Yes", then your 120v circuits must be GFCI-protected.
If your shop is an "accessory" building and the floor is "at or below grade level" and its use is as a "work area", then the 120v circuits must be GFCI-protected.

[Von Bickley]

Rick,

One factor that will impact how you can wire the shop is WHERE the shop is located.

Is your shop in either a garage, unfinished basement or grade level standalone shop?

If the answer is "Yes", then your 120v circuits must be GFCI-protected.
If your shop is an "accessory" building and the floor is "at or below grade level" and its use is as a "work area", then the 120v circuits must be GFCI-protected.


Again this depends on where you live and the local inspection department. In my area, the receptacles DO NOT have to be GFCI if that area is designated for woodworking and woodworking equipment. Talk with your local inspector.

[Craig Moulton]

I'm sure you know some of this stuff, but better too much info...

You can double the number of circuits by running the 3/4" EMT both ways from your P-Panel to the loads, two branches of pipe each containing half your circuits, rather than one big loop. If needed, you can use flex cable between junction boxes. Easier than learning to bend conduit, trust me. Just make sure that any wire-nutted connections you have to make have a good mechanical and electrical connection. Twist the wires together well before putting the wire nut on them. The wire nut's job is insurance and insulation, not your main connection.

By code, 12 GA or larger for 20A service (regardless of voltage), 14GA for 15A (Lights etc) string. The overcurrent protection amperage size is to prevent the wires from overheating due to resistive heating based on current draw.

Use individual wires (not romex) inside EMT. Heat dissipation is the concern here, from extra layers of insulation between the copper and the air. Stranded wire is easier to pull than solid copper, but harder to push. Use pulling elbows at some corners to make your job easier. I use pieces of masking tape at the end of wires to indicate circuits when pulling them. You could also use one piece of black tape for ckt 1, two pieces for ckt 2, etc.

Typically for 110V service, wires are black / white / green or bare.

Typically for 220V service, wires are black / red (or black) / white / green (or bare) if a neutral is used, Black / red (or black) / green (or bare) if no neutral is used. Using non-standard colors may create confusion later.

Black wires have 110V to ground and neutral (white). So do red, or the other leg of 220V service, whatever you color it. The only real problem as far as wire colors, is when people use white wire for one leg of 220V and don't mark it at the ends, and later someone tries to use it for a 110V circuit. This causes fires, shocks, burnt out equipment, other badness. If you have to use white wire for some reason, mark the wire at every connection point with a piece of red electrical tape wrapped around the wire.

Your number of circuits depends on their loading, and how often they will be running. If you have your table saw, planer and jointer on one circuit, but only ever use one machine at a time, this works well. Air conditioners draw large starting currents, and start their compressors at irregular intervals, so shouldn't be on shared circuits. I try to think about all the things that will never be running simultaneously and tie them together to free up other circuit choices, then go from there.

Put a GFCI on any circuit that you will have a portable tool plugged into. Or might ever plug one into. Or might ever think of plugging one into. This includes vacuum cleaners, etc. I recommend a GFCI breaker rather than individual outlets, much cheaper. OSHA requires use of a GFCI with portable tools, and is the best practice for a shop even if not required by local codes.

Size ground wire the same as the rest of the wires in the circuit. It doesn't normally carry current, that's the purpose of the neutral wire. Neutral and ground wires are the same electrically, except that neutral is the return path in 110V circuits (or the 110V portion of 220V circuits) and ground is there to prevent you from getting shocked in the event of an electrical ground fault.

[Rick Moyer]

If it were me, I'd either run two conduits or upsize my single conduit to adequately carry the extra circuits.
Thank you for answering my question

Rick, if you're a one man shop where only one machine is running at one time, you only need one circuit.

You can use a 2 pole 15 or 2 pole 20 Ampere breaker to feed all your 120V and 240V receptacles.

The 120 V receptacles can be wired as an Edison or split circuit to yield 2 circuits for 120V and 1 circuit for 240V.

You would only need 3 conductors plus ground, so 1/2" EMT may fit the bill.

Regards, Rod.

I understand that. I was thinking it may be better to add more circuits "just in case" things change. Maybe I am overdoing it however. I will consider your idea.


I'm sure you know some of this stuff, but better too much info...

Typically for 110V service, wires are black / white / green or bare.

Typically for 220V service, wires are black / red (or black) / white / green (or bare) if a neutral is used, Black / red (or black) / green (or bare) if no neutral is used. Using non-standard colors may create confusion later.


Your number of circuits depends on their loading, and how often they will be running. If you have your table saw, planer and jointer on one circuit, but only ever use one machine at a time, this works well. Air conditioners draw large starting currents, and start their compressors at irregular intervals, so shouldn't be on shared circuits. I try to think about all the things that will never be running simultaneously and tie them together to free up other circuit choices, then go from there.

Size ground wire the same as the rest of the wires in the circuit.

Thanks Craig. I DO know must of what you posted but as you said, better too much than...
"Using non-standard colors may create confusion later". I know the typical colors, but I figured having several blacks would be more confusing than having for instance, a red and blue for the 220 hots, and the black(s) be for 110 only. Would you think this would be a bad idea?

"I try to think about all the things that will never be running simultaneously and tie them together to free up other circuit choices, then go from there." That's easy for now as I said I am a one-man situation. I was thinking that if something changed down-the-road, which would be best. I have a lot of spaces in a 100a panel box, just not sure how much wire and conduit I want to run.

"Size ground wire the same as the rest of the wires in the circuit"
Thank You. This was something I was not sure about.


To All; I guess I was asking if it would be a good or bad idea to run red/blue for the 220 hots or keep the one hot always black along with the 110's, and whether YOU would add several circuits or go minimal for the sake of ease and expense. I'm leaning toward extra circuits I think but would like others opinions as well.

[Joe Jensen]

I used to have one 220 circuit as I am a one man shop. Then I got an air compressor that will come on when it wants (need 2nd circuit). Then came a 2HP dust collector (need 3rd circuit). Then I added a mini split AC (now need 4 circuits).

If I were starting again, I'd spend the extra and do additional circuits for future flexibility. I also had to rewire when I upgraded from a 3HP to a 5HP table saw. I didn't think of that detail until I was unpacking the saw. Needed to run larger wire and a new breaker.

[Scott T Smith]

Rick, you pose some good questions, and I'll toss out some extra thoughts for consideration.

First, I like your idea regarding the color separation for your 120 versus 240 circuits. By all means use red and blue for your two hots on your 240, and black for the hot on your 120.

Something that I do in my boxes and at my load center is - where the wires enter the box - to put a cable tie or piece of tape around wires that are associated together. Thus, if I'm using multiple black wires for my various circuits, one of them will have red tape around it denoting the second leg, and both will be taped together indicating that they are a paired circuit. Same thing with a black and white - makes it easier to troubleshoot long term.

I recently built a new shop, and wanted to install an electrical infrastructure that would be flexible enough so that I could run additional circuits in the future without having to redo everything. Sure, I know what equipment that I have today, but who knows what cool thing I may stumble across in the future?

I opted to install several runs of 3" conduit infrastructure through my slab, and terminate these into 6" junction boxes in various locations along my walls. From the junction boxes, I run either 1" or 1-1/4" conduit to 4" electrical boxes spaced along the walls.

Each 4" box has two 120V receptacles in it, fed from two different breakers (and two different legs of the service). So, at any time, if I need a 20A 240 circuit in the shop, I only have to do two things: First - replace the two 120V receptacles with a 240 receptacle (I use NEMA L6-20's), and second - swap out the appropriate single pole breakers in the load center for a dual pole 240 breaker. Voila - 240 availability with no rewiring.

In the event that I don't need 240, I still have two separate 20A 120 circuits available at every receptacle location, so I can operate two larger pieces of equipment simultaneously if needed.

If I need a 30A 240 service, then I'll pull two new 10 ga wires for the larger service. I typically leave a pull string in place in my conduits for ease of future wiring.

All of the 6" junction boxes have #8 green ground wire pulled to them, which I can branch off of for individual grounds in the appropriate receptacles along that wall.

So I think that the most important thing for you to consider is to install a conduit infrastructure that will allow you flexibility longer term, because if you need a larger 240V circuit you will need to pull larger wiring. Conduit is fairly cheap - wiring is not, so by investing in the conduit up front you are providing yourself with a lot of long term flexibility without dedicating $ to wiring that you might not need?

If you do any ceiling drops, then consider using NEMA L14-20 and L14-30 twist-loc receptacles. The nice thing about these is that you can use them for either 120 or 240 wiring, so a single receptacle can serve both purposes.

One other thing - stranded wire is usually the best option through conduit, as opposed to solid. It pulls easier and carries more current.

Hope this helps - good luck with your project.

Scott

[Dennis Ford]

You can avoid leapfrogging the conduit by using J-boxes that have two openings in each side and a single opening in the bottom. This will allow two parallel runs of 3/4" conduit that share J-boxes.

[Bruce Wrenn]

If you are use EMT, you shouldn't have to pull a separate ground wire. But you will need to bond recpts. with a ground wire to boxes. Here, inspectors generally only require GFCI closest to outside doors. So I use multiwire branch circuits.

[Rick Moyer]

Scott, again thanks for the info. Very insightful.

Dennis, that sounds great, but I am wondering about the allowable current carrying wires in a given j-box for multiple circuits. I know I am allowed 6 current carrying wires in the 3/4 conduit but not sure if this correlates directly with the boxes? If I went with two conduit runs into a j-box, each conduit containing two circuits (4 current carrying wires ea.) would this be allowable or too much? I suspect the j-box would only be allowed the same as a given conduit (i.e. 6ccw's).

[Bill Stoffels]

As previous stated have more circuts than less. I built my first shop and added circuts, then here at my second shop just doubled the plans and to date 5 years later its working well.
Just a suggestion?
Bill

[Rick Moyer]

OK, here's what I think I will do:

Run two separate conduit runs; one for 240, one for 120.
Each conduit run will contain three circuits

This will accomplish several things:
1. allow me to have plenty of circuits
2. separate the 120 and 240 lines to avoid confusion
3. make it a little easier to add-on later if needed

I could run it all in one conduit (three circuits) and be fine but that will limit me to only one circuit of either 120 or 240. Since the DC should have it's own 240, I would only be able to have one 120 circuit then (plus one for the DC and one for the other 240 outlets).

Questions? Will it be better to use GFCI breakers in the panel box , or use GFCI receptacles in the first position of the circuits? Also, will I need to pull a ground wire throught the EMT or can I just attach a "bond" wire from the boxes to the recepts?

[David Parker]

Hi Rick,

A lot of great advice on this thread. Having recently wired my basement shop, I found that box size was a limiting factor in the number of circuits I could run. I didn't want huge surface mounted boxes on my cement walls. I limited them to 4x4 1 1/2" deep drawn metal boxes (as apposed to welded boxes). Fill capacity calculations limited the number of wires I could bring into or through any box. You can get a little extra capacity using the raised Garvin style box covers. I wanted to use a separate horizontal run of 3/4 conduit with interspersed boxes on each of my two adjacent cement walls about 52" above the floor (sub-panel near the corner). This let me keep the bottom of the boxes above 48" and also kept the walls above the boxes clear of any conduit drops. This gives a nice clean appearance and keeps the upper wall space clear for future cabinets/shelves/whatever.

I placed a 20amp 240V twist-lock outlet in the first box (using 10g wire so I could easily upgrade breaker and outlet to 30 amp if needed in the future). An adjacent box has a duplex 20amp GFCI outlet on a separate 12g circuit that then feeds two other outlet boxes further down the horizontal conduit run. The GFCI outlets are a lot cheaper than GFCI breakers. My adjacent wall is similarly configured but with separate circuits. My thinking is that if I have two heavy amp devices running at the same time, I'll just make sure they are on different walls. I do have a separate circuit for my 120V dust collecter. I also have outlets on my other two stud walls that are fed via additional circuits run with Romex through overhead joists.

Also, I would definitely run a separate ground wire and not rely on the metal conduit for your ground. Although the metal conduit ground is within code, all the electricians posts I've read on the electrical forums recommend running a separate ground wire. It's easy and inexpensive.

[Chris Padilla]

You should check with the AHJ (authority having jurisdiction) about messing with the colors of your wiring. I really wouldn't use anything but black, red, white, and green/bare for any residential wiring.

I know zilch about 3-phase systems but that is likely a place where colors other than the ones I mentioned come into play.

I also agree to run a separate ground/ECG (bare cooper or green wire) and to not rely on the conduit. The AHJ can tell you if conduit is acceptible or not but I would use wire regardless. The EGC is no less important than any other wire and in fact, could be the most important one to safeguard YOU.

I went with 4 11/16" x 4 11/16" x 2 1/8" boxes in my garage rewire. Finding mudrings for them was a bit more challenging than visiting the BORG...I had to go to an electrical warehouse.

[Rick Moyer]

David, most of my boxes will be on a wall with two windows that will preclude me from running horizontally as you did since the windows would be in the way. I will run along the top of the wall and drop on either sides of the windows. this will still give me 7'-8' of unobstructed wall space between the windows with the 4-plug recept boxes about that far apart. That should give me enough places to plug into with having to go more than three to four feet max. I wll also run across the middle of the ceiling with conduit, placing a ceiling box for the two garage door openers to plug into and and an additional outlet for future use. This will continue across and down the opposite wall to a box. I don't really even need outlets over there as that is where the wood racks are, but thought I would put some there anyway. you never know.

Chris, since I decided to run seperate conduit I don't feel the need to use other colors as previously suggested. I'll stick to the usual blk-red-wht-grn. I also don't need mud rings as this will all be surface mounted. The AHJ doesn't know me nor I him and we'll probably keep it that way;).

I believe I will use the GFCI outlets as stated and will pull a ground wire throughout the conduit. Shouldn't be any problems that way. I plan on using the larger boxes as well for the extra space.

[Rick Moyer]

Here are the three walls for reference. the fourth is two OH garage doors.

I plan to run from the panel box, up the wall , then across the top of the wall to the crnr behind the DC, across the wall to beyond the second window. there wil be drops to the right of the entry door, next to the blue board at the DC, on the right side of the left wdw, and both sides of the right wdw. Also will come across the ceiling between the wdws and put a box in the ceiling then over and down the wall between the lumber racks.

Anybody have any thoughts as to how many outlets at each of these drop locations? Or if you would do anything differently (before I get started)?

[Rick Moyer]

You can avoid leapfrogging the conduit by using J-boxes that have two openings in each side and a single opening in the bottom. This will allow two parallel runs of 3/4" conduit that share J-boxes.

Using this idea, how many ccw's can I have in a j-box?

The conduits could contain 6 ccw (three circuits)each, but when I pass thru the j-boxes and also tie into the drops I would have a lot of wires in there. For example: if there were 3 circuits in each conduit (6 ccw)coming into the box, four of which would just pass thru, and two would drop to the first outlets, that would be 12 ccw in the first box. I suspect this is not good.
I'm still struggling with being able to do this as I'd like. If I run all the 120's and all the 240's in their own conduits, I think I'd have to have them in their own j-boxes as well, but then I'm back to leapfrogging around the drops. (picture two j-boxes staggered such that there are two conduits coming in from the left and two going out to the right of each, with each box having a drop conduit. somewhere one conduit will have to jump over another). The only way around this that I can see is if I am allowed the 12 ccw's in the j-box. Any ideas???
If I have to leapfrog, would you suggest flex cable in a short span to leapfrog? Sounds like I keep making this more complicated.

[Rod Sheridan]

Rick, this is getting far more complicated and more expensive than needed.

If you are only running one machine at a time, use a 20 ampere multiwire feed, which requires a single 2 pole 20 ampere breaker.

Run a feed from the panel around the room at the ceiling, use 4 inch junction boxes at the ceiling to drop a piece of 1/2" EMT to a 4" junction box for your machines.

Put a 240V 20A receptacle, and a 120V 20A GFCI receptacle in the box. This gives you a receptacle for any machine or portable tool.

This requires qty 3 #12 AWG conductors plus a #14AWG ground wire. I never count on the conduit as a ground, the wire's cheap, and ground is the only wire that has to work.

Regards, Rod.

P.S. A seperate circuit for your dust collector and you're in business for any machine of 3 HP or less with only two circuits.

[Rick Moyer]

Rod, I appreciate your suggestion and your sensibility. I know I really only NEED what you propose. I have a tendency to over-engineer stuff. When I look into costs I MAY decide to go the route you propose. I will think on it some more. I just don't want to put it in and later regret not having more circuits.

[Rod Sheridan]

Rod, I appreciate your suggestion and your sensibility. I know I really only NEED what you propose. I have a tendency to over-engineer stuff. When I look into costs I MAY decide to go the route you propose. I will think on it some more. I just don't want to put it in and later regret not having more circuits.

Far be it from me to ever suggest that I never over do anything.:D

Regards, Rod.

[Dennis Ford]

I don't see a problem with 12 ccw in a "large" J-box, most of them would pass straight through with no connection. If you drop to the outlet and come back from the outlet, there would be no connections in the J-box and then it is just a pull box. You can get into trouble trying to make too many connections in a J-box and I can not promise that your inspector (if any) will be happy with your installation.


Using this idea, how many ccw's can I have in a j-box?

The conduits could contain 6 ccw (three circuits)each, but when I pass thru the j-boxes and also tie into the drops I would have a lot of wires in there. For example: if there were 3 circuits in each conduit (6 ccw)coming into the box, four of which would just pass thru, and two would drop to the first outlets, that would be 12 ccw in the first box. I suspect this is not good.
I'm still struggling with being able to do this as I'd like. If I run all the 120's and all the 240's in their own conduits, I think I'd have to have them in their own j-boxes as well, but then I'm back to leapfrogging around the drops. (picture two j-boxes staggered such that there are two conduits coming in from the left and two going out to the right of each, with each box having a drop conduit. somewhere one conduit will have to jump over another). The only way around this that I can see is if I am allowed the 12 ccw's in the j-box. Any ideas???
If I have to leapfrog, would you suggest flex cable in a short span to leapfrog? Sounds like I keep making this more complicated.

[Rick Moyer]

Dennis, I spoke with the local electrical supply place and they said basically the same thing; that all the pass-thru wires would be no problem. If I use a 4 11/16" box I could run two runs of 3/4" emt in and out and still drop from that box, with plenty of room in the box for any connections I would need. I now just have to decide if I want to go to the extra trouble and expense of that arrangement or go more simple.

Thanks to everyone for their help.

[David Parker]

From your pictures, it look like your windows are high enough to allow a horizontal conduit run beneath them. I attached a quick sketch of a possible wiring scheme in PDF format. This would consist of 4 circuits; two 120V 20amp circuits and two 240V 20amp circuits. One of the 240V circuits would be dedicated to the dust collector. I included box fill calculations on or adjacent to each of the boxes. For 12 gauge wire, you need 2.25 cubic inches for each volume unit (based on NEC 314.16). The largest count is 21, which would require 47.25 cubic inches. A 4 11/16 inch square 2 1/8 deep box with a raised Garvin type lid would accommodate this.

If you use one duplex 120V outlet in each box, you can split apart the top and bottom plugs electrically and wire a separate circuit into the top and bottom portions. Alternatively, if you use two duplex outlets in each box, you can wire each up to a different circuit. (You can use different colored outlets to indicate which circuit is which). 3/4 inch conduit will carry up to 16 12 gauge wires, so that's not a problem. On the 120V outlets closest to the door, just use two GFCI outlets and run the protected outfeeds from these back up the drop so they can continue downstream to the rest of the 120V outlets. (that actually will bump the volume units up to 11 for this box -13 if you use two duplex outlets). For about $50 more, you could instead use two GFCI circuit breakers in the panel.

You can either continue your ceiling conduit across to the wood storage wall for an outlet there, or you can run a conduit directly from the breaker panel, whichever you think would be simpler. A direct run from the panel will give you another circuit.

Good luck with your project.

[Rick Moyer]

David, the bottom of the windows is exactly 48" of the floor. I could do as you suggest but would have to tilt any 4x8 sheets, although they really wouldn't be over there anyway. I'll consider this option.
The only real problem I see is even though the 3/4 EMT would hold that many wires, I am only allowed 6 current carrying wires and still be ok with 20a. Therefore only 3 circuits, not 4.
I appreciate the suggestions and will consider some more.

[David Parker]

I agree with you. If the window bottoms are at 48 inches, I'd also do separate drops for each location just to keep the outlets above any carts, etc. The other advantage of separate drops is that you can then use smaller boxes for the outlets. I calculate 9 fill units for each box. A standard 4x4 by 1 1/4 box has a volume of 18 cubic inches. If you use a Garvin raised box cover (typically 5 to 7 cubic inches), you meet the 20.25 cubic inch volume requirements (9 x 2.25). I'd use drawn boxes rather than welded boxes. They look nicer and don't have the sharp corners. The junction boxes up high will still have to be the large 4 11/16, 2 1/8 deep ones.

I'm not sure if you're limited to 6 current carrying conductors in the EMT. According to Table 310.15(B)(2)(a), the adjustment factor goes from 80% (4-6 conductors) to 70% (7-9 conductors). Since 12 gauge THWN 90 degree wire is rated to carry 30 amps (Table 310.16), if you use the 70% adjustment factor, this still keeps you above 20 amps. Therefore, you should be able to run 9 current carrying conductors in the EMT. Maybe someone more knowledgeable could set me straight on this.

[Michael Lutz]

When I ran my outlets, I ran two 120V outlets in one conduit and 2 - 240V Outlets in another (one for DC/Air Comp., one for tools) in both directions to power three walls. If needed I can just plug into an outlet on the opposite wall to run more than one tool at a time. It was just a few more breakers since I was running the conduit to both locations anyway. I just ran the conduit between duplex boxes without putting in any extra junction boxes. In each 120V duplex box I had two outlets (1 white, 1 grey) so I could tell which circuit I had something tied into.

Mike

[bill gervais]

Hi Rick,
First my recomendation, hire a licensed qualified electrician. I have been reading many postings in regard to electrical wiring here and elseware scary stuff!!!!
I know we all mean well and want to help each other out and save a buck. So i honestly don't think anybody on this site will intentionaly give you the wrong information but there are just to many variables.

Think of this;
1. In my state we have adopted the National Electrical Code not all states or citys do.
2. Some have their on code.
3. My state requires 6 years of work experience and 576 hour of classroom instruction as well as a current 45 hour code class to qualify to sit for the Master Electrician exam. Not finished yet. Once you get to this point slightly above 50% will pass the written exam the firt time!
4. You screw up a water system sweatted joint , pipe leaks. You screw up a wiring project you loose your house and heaven forbid your family or at a minimum try explaining your loss to an insurance adjuster..

By the way i am a Master Electrican with nearly 30 years experience and also an Electrical Instructor of both high school students as well as adults for over a decade.

Wow! Sorry for being so long winded on my first post.

Bill

[Terry Brogan]

Not trying to hijack this very useful thread but I have a simpler question that's always nagged me: none of my 3 or 5 HP 1-Phase machines gets a neutral wire. They all double up two 110 conductors at the outlet to make up the 220. Why no neutral to return current? Is it the motor design? (Never mind the ground.)

[David G Baker]

Terry,
In 220 circuits the two 110 legs complete the circuit. The only reason you would need a neutral leg is if there was something on your machine that required 110 volts, for example if your machine has a lamp or another device that needs a 110 volt supply. Someone else can explain the technical side of 220 better than I can.

[John Coloccia]

Not trying to hijack this very useful thread but I have a simpler question that's always nagged me: none of my 3 or 5 HP 1-Phase machines gets a neutral wire. They all double up two 110 conductors at the outlet to make up the 220. Why no neutral to return current? Is it the motor design? (Never mind the ground.)

first: I'm not an electrician...but I did just rewire my whole shop. I'm just telling you what I ended up doing, and it seems to work well (and passes inspection)

The two "hot" legs are the returns, so to speak. There are 2 phases going into your house, 180 out of phase with eash other. To make it as simple as possible, when one is "pulling" the other is "pushing" and vice versa. That's how you get 220V when each phase is only 110V to earth....they're always 220 to each other.

re: everything else

There are simple calculations you can do to determine box fill based on the size of the conductor...it has to do with how many wires and connectors you can reasonably fit in the box and still be able to tuck it all back in. Be careful...I had to install a two gang outlet box along a run JUST for box fill.

Conduit fill has to do with how much wire you can reasonably pull through the conduit. The size of the conduit has nothing to do with the derating....in conduit, all the wires will be laying on top of each other at the bottom of the conduit regardless how big it is, so the conduit size is irrelevant for heat generation.

I just rewired my shop with conduit, and would strongly suggest wiring a 110 outlet everywhere you run a 220. You'll use it for lights and other things. You may also want to consider running everything as 10AWG. If you run 10AWG, you'll be good for 30 amps on some runs, and 20 amps on runs where you really pack the conduit (depends on the derating). I can take practically any 110V outlet in my shop and convert it to a 220V-20A (3HP) by changing the plug and the breaker. Some of them I can convert to 220V-30A (5HP). Makes for a flexible layout.

I also ran stranded wire. Solid wire is a royal PITA to pull, especially the longer runs.

Anyhow, good luck. You'll be expert at pigtailing and pulling by the time you're done!

[Terry Brogan]

I'm dense, and I'm still not getting it. I do understand the two sine waves being out of phase with each other by 180, so, in your terminology, one is pushing one pulling, so to speak, but in 110 circuits you could get half of that with one black conductor. A push or a pull or whatever. My question is about the white. A 220 delivers twice the current, but nothing goes back, whereas, if I understand Electricity and The Universe right, on the 110 side a wire is needed to go back. Why is that.

[John Coloccia]

I'm dense, and I'm still not getting it. I do understand the two sine waves being out of phase with each other by 180, so, in your terminology, one is pushing one pulling, so to speak, but in 110 circuits you could get half of that with one black conductor. A push or a pull or whatever. My question is about the white. A 220 delivers twice the current, but nothing goes back, whereas, if I understand Electricity and The Universe right, on the 110 side a wire is needed to go back. Why is that.

There is current going back on the 220V....back and forth, actually, at 60Hz.

110V with a neutral is like having a water pump on one end of a hose, and a pool of water on the other end (the neutral is the pool). The pump alternately sucks water out of the pool and pumps water back into the pool 60 times a second (hence the name "Alternating Current").

A 220V system is exactly the same but there's a pump on BOTH ends. You can see that having a pump on both ends gives you twice the power for the same amount of water.

This is why a 220V system will typically draw less current than the equivalent 110V system. Ultimately, they use approximately the same amount of power, but the analogy is that the 110V uses more water at lower pressure, and the 220V system uses less water at higher pressure. The practical benefit of this is that you can run a 5HP motor with 220V@30AMPs and use reasonably sized wire, as opposed to 60amps@110V with ridiculous wire. There's lots of other problems with the 110V system to0, but it will all boil down to wire size, wire length, effeciency, packaging, etc.

In an AC system, there's no net movement of charge through the wire (not exactly true, but any movement is incidental and can be ignored). The electrons don't actually have to "flow" anywhere to be useful. They jiggle back and forth, and you can get work out of that, just like you can get work out of moving a hand saw back and forth, even though the net effect of all that motion is that the saw doesn't actually go anywhere....it just moves back and forth, more or less around the same point.

edit: What most folks don't realize is that there are 2 pumps coming into your house, and it's setup so that they're always doing the opposite thing (sucking or pumping). For 110V you randomly choose one side or the other, and hookup a neutral. Panels are designed so that when you plug in a ganged 220V breaker (it doesn't matter where you plug it in), it always selects 2 phases that are exactly opposite. That's why the 220V breaker is exactly twice the size of the 110 breaker. It's literally doing exactly what 2 seperate breakers would do. In fact, you could use 2 seperate breakers and it would still work. It wouldn't pass an inspection anywhere on the planet, and it's not at all safe (NOT SAFE!) but in terms of getting power from point A to point B, it works just dandy.

[David Parker]

I'm dense, and I'm still not getting it. I do understand the two sine waves being out of phase with each other by 180, so, in your terminology, one is pushing one pulling, so to speak, but in 110 circuits you could get half of that with one black conductor. A push or a pull or whatever. My question is about the white. A 220 delivers twice the current, but nothing goes back, whereas, if I understand Electricity and The Universe right, on the 110 side a wire is needed to go back. Why is that.

Hi Terry,

Actually, John beat me to this answer and did a better job at it anyway. I'll post mine anyway so you can read the same thing in different words.

In 120 volt AC circuits, the current is first pushed from the black wire, through the load, and into the white ("neutral") wire. 1/120 sec. later, the current is pulled from the white wire, through the load, and into the black wire. The force of this push or pull averages out to 120 volts (also known as the effective voltage or "rms" voltage. Actually the peak voltage is about 170 volts).

In 240 volt AC circuits, the current is first pushed from black wire #1, through the load, and into black wire #2. Black wire #1 is pushing with 120 volts of effective force and at the same time black wire #2 is pulling with 120 volts of force. This results in a combined 240 volts of effective force moving the current through the load. 1/120 sec later things are reversed, black wire #1 is pulling the current and at the same time, black wire #2 is pushing the current.

[Terry Brogan]

So, now, two more questions.

1. W=AV. Since the utility company charges us for Watts, and since doubling the voltage allows half the amperage (whicfh makes thoe 220 circuits so efficient), and since, in your helpful examples, the electrons are merely jumping back and forth, as opposed to being pushed through in one direction only like a water hose, can I then assume that the net minus of all that jumping is equivalent to the wattage consumed?

2. What's unsafe about taking the 220 off two separate breakers, i.e. two separate circuits? Let's assume they're both on the same side of the main bus.

[Tom Veatch]

...
2. What's unsafe about taking the 220 off two separate breakers, i.e. two separate circuits? Let's assume they're both on the same side of the main bus.

First, if both breakers are on the same side of the bus (same leg of the incoming service) you won't get 240v at the outlet, you'll get 0 volts. At a given instant of time, one leg of the service is 120v above ground potential while the other leg is 120v below ground potential. That gives you a potential difference (voltage) of 240v between the legs. The potential difference between 120v above ground and 120v above ground, which is what you'd have if your breakers were both on the same leg, is zero (0) volts. The two breakers have to be on opposite legs.

CLARIFICATION: You'd have zero voltage between the "hot" wires of the circuit if both breakers were on the same leg. That does NOT mean there's no voltage on the wires. You would still have 120v between each hot wire and ground or neutral. So you could still get zapped by the hot wires, but you couldn't run a 240v load off the circuit.

Why is it dangerous to use two separate single pole breakers? Because if one leg developed a short to ground, the breaker on that leg would trip and break the circuit. However, with two separate breakers, the breaker on the other leg would not be tripped and that particular wire at the load would still be hot.

A 240v, 2 pole breaker is actually two separate breakers in the same body. The two breakers are interconnected so that if one breaker sees an overcurrent for whatever reason and trips, it forces the other breaker to trip also. That cuts power in both legs so that both legs are "cold" at the outlet/load/etc.

[David Parker]

So, now, two more questions.

1. W=AV. Since the utility company charges us for Watts, and since doubling the voltage allows half the amperage (whicfh makes thoe 220 circuits so efficient), and since, in your helpful examples, the electrons are merely jumping back and forth, as opposed to being pushed through in one direction only like a water hose, can I then assume that the net minus of all that jumping is equivalent to the wattage consumed?

That is correct. As long as there is a load (motor, light, etc.) connecting the black ('hot') wire and white ('neutral') wire, or the two black wires in the case of 240 volts, there is current flowing back and forth in the wires. It takes power measured in Watts to produce that current movement. That is what your electric company charges you for.