120v Off of 240v Circuit?

[Russ Filtz]

I'm extending an existing 240v circuit (unused for an old dryer) for my TS. The existing circuit is 10-3 romex (4-wires). I've cut the romex in the middle and installing a new pull box there for the new 240v circuit to branch out.

Question is, can I tap one or both of the hot legs for some extra 120v circuits? For this I'd employ the unused neutral wire that I don't need for my TS (plus the ground of course!).

The circuit is 30A and I've only got a contractor saw (1.5hp I think). Does the TS care if the 120v legs are not equally loaded. Doesn't seem like it would, only the wire would see any extra amps from the 120 circuit and then only on the part from the panel to my new pull box?

[Jim Becker]

I'm not going to attempt to answer the "can you" part...I'll let others with more knowledge do that, but will comment that if you are tapping into that existing 240v dryer circuit, make sure that the existing outlet is disabled/removed from the point of your new box. Cap off the un-used side of the feed to the "dryer" location and remove the outlet there, capping the wires and putting a blank panel on the box. A future owner can then remove your shop extension at the pull-box and re-engage the dryer purpose if necessary, but in the mean time, there is no question about where the 30 amp circuit is actually going.

[glenn bradley]

I've asked a similar question and always gotten the same answer (from electricians); 220v - one breaker, one outlet, no options. I've been told it CAN be done in some situations but have always been advised against it. I'm no electrician, that's just what I've been told.

[Bruce Wrenn]

Get a copy of the NEC and look up multiwire branch circuits. Popular Woodworking featured an article a couple years ago on this. Titled "Efficent Shop Wiring". You would wind up with two 110 circuits, or one 220 circuit. A 220 circuit can have more than one recpt. on it. You can buy duplex 220 rects., but they aren't cheap. Generally, though, they are considered dedicated circuits with only one recpt. Currently in rewire project for my shop, I'm using multiwire branch circuit. At each location, I get two 110's and a 220. Because one leg of 220 is through DC control loop in box, this means one of the 110's in addition to the 220, will operate DC. This is handy when using jointer, router table, or portable planer, which operate on 110. Other 110 won't operate DC. Get up with Rick C. and he can explain all the mumbo jumbo in codes.

[Rick Christopherson]

I've asked a similar question and always gotten the same answer (from electricians); 220v - one breaker, one outlet, no options. I've been told it CAN be done in some situations but have always been advised against it. I'm no electrician, that's just what I've been told.Glenn, If this is the answer you are getting from electricians, you need to question their credentials. There is nothing in the NEC preventing multiple outlets on 240 volt circuits.

Russ, Technically you could do this, but the 30-amp breaker causes a problem. You can't install a 15 or 20 amp outlet on a 30-amp circuit. You can do this if you drop the circuit to 20 amps, but I get the feeling this defeats what you are going after.

[Al Garay]

Why not replace the 220V circuit at the panel with two 110V circuits? I did that in my last house and ran new romex to the desired outlets.

[David G Baker]

What I have done is to install a breaker box sub panel. From my main breaker panel I ran 30 feet of #8 three with ground copper wire from a 220volt 40amp breaker to a sub panel breaker box with 4 positions for breakers. The center two positions are 220 volts for my well pump (2 ea 20 amp breakers pined together at the factory), the outer two breakers are two 110 volt 20 amp circuits, one used to power my refrigerator and the other to power a couple kitchen wall plugs. My neutral wire and ground wire are not tied together in my sub panel. Don't know if this helps. My circuits do not have any real heavy current draw, the pump is 1/2 HP, not sure about the fridge and the plugs have a toaster on one and a small microwave on the other.
The TS having a 1.5 HP motor may have a heavy starting current. I would not put any heavy draw equipment on your set up, for instance a 5 HP air compressor that will be operating while you are using the saw and I would use a sub panel with correctly sized breakers. If you are not comfortable doing the work your self please hire an electrician just to be safe.
Hope I don't get into trouble on this site for telling folks what I have done.
David B

[Paul Simmel]

>>> Question is, can I tap one or both of the hot legs for some extra 120v circuits? For this I'd employ the unused neutral wire that I don't need for my TS (plus the ground of course!).

You are asking about extending your 30a 220v circuit to feed your TS (fine to do), but you also want (have done already?) to tap one of the legs to make another 110v circuit (not ok to do).

Not ok because your desired 110v (max 20a outlets) wont be breakered properly at 30a.

Either extend the 220v dryer circuit for your 220v TS, or extend the dryer circuit for two more 110v circuits but CHANGE the 30a double-poll breaker to a 20a. If you opt for running two 110v circuits you will be sharing the neutral between the two phases, so you will need a double-poll breaker to turn off both neutral-sharing legs.

>>> Does the TS care if the 120v legs are not equally loaded. Doesn't seem like it would, only the wire would see any extra amps from the 120 circuit and then only on the part from the panel to my new pull box?

If you are running other stuff off one of the hot legs while the TS is running, yes, the TS will care. FYI: New 220v dryer/washer/range/oven circuits have neutrals (4 wires) because these appliances frequently have 110v timers/lights, and pinch a bit from one or both legs... a few watts… not another circuit… hence your white wire at the dryer receptacle.

[Lynn Hanks]

Hey Russ. Can this be done?, sure, I've seen it done many times over the years by jack-leg electricians. Not saying this is you, but most guys think well if I've got a 30amp breaker, let's load 'er up. Or, even worst, well if that 20 amp is tripping, let's put in a 30. Other factors must be considered. Bare with me on this as it may get long.

On any dedicated circuit, the breaker should be sized to protect the end device that will be operating on it. The norm is a RLA/FLA (Run Load Amps/Full Load Amps) of no more than 80% of protection rating. In other words; 12 amps on 15 amp breaker; 16 amps on 20 amp breaker, etc. Some large in-rush (starting) motors can be more like 70-75%.

Once breaker size is determined, you "shall" use wire with a maximum amp rating of =/> breaker size. #10 or 10 awg wire is rated at 33 amps, so the maximum breaker that can be used is a 30 amp. And this is for a 100' run; if the run is over 100', you need to increase to the next wire size and again for every 100' after that. (Example: Run is 165' on a 30amp circuit; wire must be #8/8 awg.) This is because of the resistance that wire has and with increased resistance, you get a decrease in voltage(remember this for later). Got to http://xtronics.com/reference/wire_gauge-ampacity.htm for wire rating chart. Use last column "CU Max enclosed amps for Romex or wire in conduit. It does not matter if the circuit is 120v, 240 or 480, single phase or 3 phase; the rated ampacity of the wire size should not be exceeded.

As previously stated, to properly protect your saw (I'm guessing that amp draw at 240v is gonna be approx. 6.4 amps +/-), you need to remove the 30 amp breaker and install a 15 amp which is the smallest double pole breaker you will find. Starting amps on this motor will probably be approx. 18 amps, but since it is only for a second or two, the breaker does not trip and all is good. (Starting amps are usually 3 times running amps)

One of your questions was "Does the TS care if the 120v legs are not equally loaded?"; if you are gonna plug in a 100w light bulb to it, the answer is no. On the other hand, what are your plans for this other circuit? If it's for a 120v DC, CS, CMS, etc., then I would say, NO WAY.

You're pulling 6+amps on a 15 amp circuit. Any of the above devices at 120v will probably pull approx. 8-12 amps and now we've just tripped your breaker. BUT, let's say that the breaker did not trip. Now we've got a 6 amp load on one side of the breaker and a 14 amp load on the other side. Yes, I remember that we're using #10 wire, but let's say that we've got a slightly loose connection on the loaded side. Now we've got increased resistance (remember above), we've already got high amps and if the breaker still hasn't tripped,,, guess what, now we have lower voltage on one leg of our motor. So, "Does the TS care... MAYBE-E-E!!

Hope this helps Russ, maybe not what you wanted to hear, but I'd sure hate to hear you burned up your TS motor or worst, your home. Good luck. Lynn:D

[Rob Will]

What I have done is to install a breaker box sub panel..... My neutral wire and ground wire are not tied together in my sub panel......The TS having a 1.5 HP motor may have a heavy starting current. I would not put any heavy draw equipment on your set up, for instance a 5 HP air compressor that will be operating while you are using the saw and I would use a sub panel with correctly sized breakers. David B

Well said. A small sub panel is the best way to deal with this.
The limitation here is that the feeder is only a 10-3. As David pointed out, you probably should not run multiple heavy draw items. IMHO, many homes and home shops would be better off with sub panels. I am in the process of installing a 100 amp 3ph sub panel in my own shop.

Rob

[Russ Filtz]

Thanks all! I thought this was a dubious idea, but would have been easy if it worked! I'll just run the 240 and be done with it.

Now on the subject of multiple 240 outlets on a single breaker. Seems there were some differing opinions! If I do have multiple outlets on a single breaker, can they be used simultaneously? As in a TS and DC at the same time as long as total amps are less then 30?

The circuit would be branched off like a "Y", not a loop so each outlet would only seem to draw what it needs and not "see" the other branch loads?

My main panel is in the garage which seems like it would be ripe for a subpanel (I actually bought one to put in). However after further inspection, it would require some demolition to get at since the walls are finished. Don't think I'm going to be in the house long enough to warrant this level of commitment! Hence the cobbling of the unused 240v outlet which I can get at in the attic space.

[Jim Becker]

Now on the subject of multiple 240 outlets on a single breaker. Seems there were some differing opinions! If I do have multiple outlets on a single breaker, can they be used simultaneously? As in a TS and DC at the same time as long as total amps are less then 30?

Russ, I do have multiple outlets on a couple of my 240v circuits...in the shop and purely for "positional" convenience...but they are still for single tool use at one time and only one tool is ever plugged into a given circuit. The "branching" is done in a j-box, not at the outlet. The only reason I did this was for flexibility when I occasionally need to reconfigure tool position for some reason or another. Using the j-boxes also makes more "permanent" changes easier into the future...I've used that ability a few times, including last weekend when I relocated my jointer/planer.

Anything that needs to run simultaneously in my shop has its own circuit. (Compressor or DC in this case)

[Russ Filtz]

Thanks! I am branching in a j-box, so it will be permanent, not just taped together! I was planning on just leaving the old dryer outlet for convenience. Not planning on using it myself. However if I could run both the TS and DC it would have been convenient!

I'm comfortable doing electrical work such as this as I ran my own subpanel and circuits in my last house (it also had multiple 240v outlets for convenience, but at the time I only had a TS on 240). Fully inspected/permitted work too! I'm just not up on the codes and such, so I don't know all that is technically feasible (I'm a mechanical engineer, not a EE!)

[Jim Becker]

Russ, sometimes it's not just code you need to think about...it's practicality and also "human nature". Leaving the dryer outlet "live" makes for a potentially dangerious situation in the future, IMHO. If you want to re-purpose the circuit, I don't see an issue with that, but re-purpose it, don't add on since that dryer outlet sounds like it's not in the shop, but elsewhere in your home. That's why I was clear that the multiple outlet accomodation I made was "in the shop"...

[Ted Miller]

I just recently took my two pull 15 amp breaker for my dryer, disconnected in the panel and wire nut both red and black wires, since this is using north and south polarity. Then I tapped into the panel and with 3/4" conduit and ran this downstairs to my garage with 3 each #10s and 4 each #12s so I could have two 20 amp dedicated circuits for added outlets plus the 220 outlets. I did notice for my service I am getting 244 volts which is a little over but I do not run my jointer, TS or RAS all day long...

[Mike Seals]

I just recently took my two pull 15 amp breaker for my dryer, disconnected in the panel and wire nut both red and black wires, since this is using north and south polarity. Then I tapped into the panel and with 3/4" conduit and ran this downstairs to my garage with 3 each #10s and 4 each #12s so I could have two 20 amp dedicated circuits for added outlets plus the 220 outlets. I did notice for my service I am getting 244 volts which is a little over but I do not run my jointer, TS or RAS all day long...

I'm taking this as you added more breakers and not fed all of these of the retired double polls.

244 is good and nothing to worry about, I wish mine was but the drop the utility company gave is a long way away. A higher voltage is a good thing for most appliances. Two types of load, inductive and resistive. On an inductive load, motors and such, a higher voltage means less current draw. On a resistive load, heaters and such the higher voltage will cause a higher current draw.

The voltage levels our homes is not set in stone, it will vary up and down. The power company tries to keep it level, but the changing loads through out the day can make it tough.

[Jim Becker]

I did notice for my service I am getting 244 volts which is a little over but I do not run my jointer, TS or RAS all day long...

240v AC is normal in most locations, so 244v AC really isn't an issue. We tend to call these "220v" circuits, but they are really 240v AC circuits. In the same vein, many folks refer to single pole circuits as "110v" AC, but they are 120v AC in most locations.

[Rob Will]

I just recently took my two pull 15 amp breaker for my dryer, disconnected in the panel and wire nut both red and black wires, since this is using north and south polarity. Then I tapped into the panel and with 3/4" conduit and ran this downstairs to my garage with 3 each #10s and 4 each #12s so I could have two 20 amp dedicated circuits for added outlets plus the 220 outlets. I did notice for my service I am getting 244 volts which is a little over but I do not run my jointer, TS or RAS all day long...

Ted,
Did you use the existing 30 amp(?) two pole breaker to feed the 10ga. wires? Did you install additional 20 amp breakers to feed the 12ga. wires?
Since the wires share a conduit, did you use a common 10ga. wire for a ground? Not sure what you mean by North and South polarity.

Perhaps an easier way to do this would have been to replace the dryer breaker with a 50 - 100 amp two pole breaker and use that to feed (with correct wire sizes) a sub panel in the basement. Remember that this requires 4 wires and the neutral and ground stay separate. Do not bond the two together in a sub panel.

Rob

[Rick Christopherson]

I don’t understand why this thread had to get so convoluted over night, but you need to understand that there is some misinformation written to sound like it came from knowledgeable people. :confused:
Thanks all! I thought this was a dubious idea, but would have been easy if it worked! I'll just run the 240 and be done with it.

Now on the subject of multiple 240 outlets on a single breaker. Seems there were some differing opinions! If I do have multiple outlets on a single breaker, can they be used simultaneously? As in a TS and DC at the same time as long as total amps are less then 30? Yes, this is perfectly acceptable. Even if the DC was 120 volts, then you would just need to use 30-amp plug and outlet for the DC. (And no, the breaker is not there to protect the device. This is a cord and plug application.) (see more below)
The circuit would be branched off like a "Y", not a loop so each outlet would only seem to draw what it needs and not "see" the other branch loads?This is not necessary unless it is more convenient for you. The outlets are wired in parallel, not series, so it makes little difference if they are in-line with each other as long as everything is #10 wire. Note that you cannot use the outlet as a feed-through device. You must make your connections in the junction box and pigtail to the outlet (NEC 300-13). In other words, removing the outlet does not break the circuit, especially the ground and neutral wires.

I agree with Jim’s comments that you probably should not leave the dryer outlet connected for the reasons he gave.

As for the comments about imbalancing the legs to the motor, the motor wouldn’t have a clue. It only sees the 240 volts. The only thing the motor might notice is a slight voltage drop, and I stress the word “slight”.


However if I could run both the TS and DC it would have been convenient!This is something that you can do, and it is specified in NEC 210-4.c, exception #2. As long as you are using 2-pole breakers, it is permitted to have both a 240-volt and a 120-volt device on the same miltiwire branch circuit. Going back to my first posting, you couldn’t install standard 20-amp outlets on this circuit, but you can install 30-amp outlets on it (NEMA 5-30 or L5-30 twist-lock). It would be pointless to do this with portable tools because you would have to install new plugs on them, but for a specific tool like the DC, then this is a viable option.

Note that you do not need to install #10 wire for the cord on the DC. According to NEC 240-4 exception #2, this cord can be as small as 14-gauge. I’m not sure if exception #1 is applicable, but this would even permit the use of 16-gauge cord. (Just make sure there is no confusion, I am referring to the power cord from the tool to the outlet.)

[Craig Coney]

Russ,
you would not want to pull 120V off one leg & just cap the other side, as your 220V breaker is likely a 2 pole breaker tied together, and of one side tries to trip, the other side without a load may not allow it to trip.

You could try to put in a load center at the 220V outlet, then you could put appropriate circuits for what you want with the proper breakers. Then you wouldn't have to change anything out in your existing panel.

[Rick Christopherson]

Russ,
you would not want to pull 120V off one leg & just cap the other side, as your 220V breaker is likely a 2 pole breaker tied together, and of one side tries to trip, the other side without a load may not allow it to trip.

You could try to put in a load center at the 220V outlet, then you could put appropriate circuits for what you want with the proper breakers. Then you wouldn't have to change anything out in your existing panel.That's not how breakers work. 2-pole breakers are required because an overload on one leg will cut power to both legs. Yes, this is true even if one wire was unused.

[David G Baker]

That's not how breakers work. 2-pole breakers are required because an overload on one leg will cut power to both legs. Yes, this is true even if one wire was unused.
Rick,
I was going to post pretty much what you wrote with one exception, the 2-pole breakers should be factory joined. Some folks make their own joining mechanism using nails, etc. This is where the danger comes in, sometimes if the two breakers are not joined correctly one side will will cut power while the other will remain hot. I have had this happen to me back in my quick and dirty days.
David B

[Craig Coney]

That's not how breakers work. 2-pole breakers are required because an overload on one leg will cut power to both legs. Yes, this is true even if one wire was unused.

There is the 'Way it is designed to work' and the real world the way it happens. I have been to many repairs where only one leg is used off an existing 220V circuit creating problems without correcting deficiencys to ensure proper circuit design. Most of the occurances have been done by someone who is not electrically savy and done in a pinch to get equipment working. Are people supposed to do this per the NEC? I beleive the answer is NO!. This could be based on which revision of the NEC you are referencing and ones own interpretation.

Real world experience here, not just what I read somewhere or experienced in a controlled lab environment. If I need to reference the NEC, I pick up the book and look for what I need. That is why they make reference materials.

[Mike Seals]

Real world vs ideal world. The NEC is a guide line and a good one to follow, but you'll see so much abuse of it by card carrying electricians that some times it makes you wonder. Knowing how to pull and land wire is great, but understanding what happens when you turn on and off the switch is even better.

I work in a rather large chemical plant and have work in these plants for the last 31 years. The plants do not have to follow the NEC, they are on their own, BUT! they will follow it as much as possible just to stay away from any litigation.

Then you have the city, county and state rules, they tend to follow the NEC but will sometimes go overboard. As a home owner, many cities will allow you to do your own electrical work in your primary residence, but not in something such as a rental property.

I myself am an over kill artist and go by the rule that the breaker is there for protection of the wire, nothing more. So if I have a 20 amp breaker, it will have a #12 throught the system and 20 amp receptacles. No #14 branches and no 15 amp receptacles. Having been in these plants, I've seen the results of everything from a 230KV insulator blown to a simple receptacle fire and every thing in between. Had some friends killed in a 5KV breaker explosion, and have seen several folks burned as a result of not fully knowing what they were measuring.

This said, most folks have no clue as to what they are doing when it comes to electricity and the potential effects from improper wiring, most importantly grounding. Not only will they see damage to their selves or others, but also damage to equipment in thier homes.

So if you are in doubt, ask, and for a good reference use the NEC, but nothing beats experience and nothing will kill you quicker than electricity trying to find a path to flow and you becoming part of the circuit.

[Travis Lavallee]

I just wanted too add a little something to the 244/240 comment earlier. I work for the utility company up here (as a student engineer) and specifically work in the distribution planning area. We always do our studies in a 110/120 base and our limits for voltages at the entrance to the customer are a max of 124V and a minimum of 110V. So calling it 240/120 or 220/110 are both correct, it is not specifcally confined to one of the two. Also it is impossible for the utility to keep the voltage constant at the service entrance. Just think about how many things you turn off and on in a day, and that there are on average 150-200 homes on a rural feeder, there is no way to compensate for all those changes.

[Paul Simmel]

>>> This said, most folks have no clue as to what they are doing when it comes to electricity and the potential effects from improper wiring, most importantly grounding. Not only will they see damage to their selves or others, but also damage to equipment in thier homes.

Mike is absolutely correct on all accounts throughout his entire post.

I’m one of those wiring my entire shop/home (new construction). I am not an electrician, but have two of them on call, plus the local Electrical Inspector.

In existing construction, there are many temptations to “work around” an electrical issue because certain wiring exists already, and there is no Inspector looking over your work. In new construction, you must design from scratch and get it right with no excuses.

IMO, all electrical issues should be considered from a new construction point of view.

Russ,

Run 3 #4 conductors from your main to the new sub with an 85a breaker at the main. If you are not using EMT, run another #4 for ground. Do not bond the sub panel in either case.

Now, wire from the sub till you are content. Run dedicated circuits to each machine/DC. Run dedicated circuits for your outlets, lighting, etc.

(You can certainly have multiple 220v outlets along the same circuit run, but just like any other circuit, you should not exceed the breaker’s amperage draw.)

Don’t mess around with this. For the few extra pennies, you will have it right with room to spare and peace at night.

For a sub-panel, #10 is good for nothing. Pull the 30a breaker from the main, and use the space for the 85a breaker. Tie off and label the #10 dryer conductors on both sides, “Dyer, not in use”.

[Ted Miller]

Mike, Yes I added 2 each 20 amp breakers for the 2 lines of 120v.

Rob, Yes I used #10s for the 30 amp run and yes I used a #10 ground, no need for a sub panel for just two extra circuits, its a one man shop so 70 amps are more than enough for me right now...

[Ted Miller]

I should have mentioned that all I did was, wired outlets, 70' of 1/2" and 60' of 3/4" runs, pulling the wire but I did nothing in the panel, this I had a friend who has been doing sparky work for 35 years and is a class 1 inspector, I would never touch panels since there is no disconnect in my unit and I know just enough about electrical to get in trouble.

This panel is a 125 amp panel in condo unit of 8 condos in 1 building.

Not only did he teach me a ton about the panel but know I know how to do dead end three ways, this gave me headaches for days til he came by and sketched it out on paper for me...

[Ted Miller]

Paul, I was under the impression that you had to have dedicated circuits for each 220 outlet, by my buddy the inspector said as you did as long as the amp pull does not exceed the breaker you will have no problem and you can have multiple outlets on one run.

I visited one guys wood shop and the inspector in that city had him use GFIs on every single outlet, 120v...

[Cliff Rohrabacher]

If I were going to do that I'd run a little sub panel where I could breaker the lines down.