shop wiring question

[andre mallegol]

Is it acceptable to put multiple outlets on a 240V circuitk, the same as we do on 120V circuits. Seems to me I read on the pond that it was not allowed. Someone give me some help before I close up the walls and ceiling. Thanks, Andre

[Phil Phelps]

I wouldn't wire two outlets on a 110 circuit unless the city code allowed it. Please check with local code first.

[Dr. Zack Jennings]

I have read it before & I had my licensed electrician in Saturday to run my first 220V Circuit. He put it on a 20amp breaker and said it was matched to the machine. He said he could run other drops out of the same junction box so long as I don't intend to use 2 of the machines at the same time. <p>
He suggested a dedicated circuit for the DC (I don't have yet) since it will run at the same time as other machines. <p>
So...... My answer is yEs Do it my man. Go forth and make sawdust.

Disclaimer: I know absolutely nothing about electricity/ I'm reporting my experience with a licensed, experienced, repected bonafide Professional.

[Ben Mathews]

I agree with the Dr. When I wired my shop, I ran 3 circuits (small shop) for 110 outlets, and alternated which outlet was on which circuit. I also ran 1 30 amp 220 circuit for my bandsaw/tablesaw/future welder. I made sure that my compressor was not on the same circuit as my most commonly used outlets. I have had zero problems to date (about 2 years) so I am glad I didn't spend more money on more circuits.

[andre mallegol]

Phil, Zack,Ben,

Thanks for your advice. It help clear up the confusion, which seems to occur more frequently as time passes. I'm going to go with the bandsaw and jointer on the same 240V circuit.

Andre

[Rob Russell]

I'm not aware of anything in the NEC that would preclude you from having multiple outlets on a 240v circuit.

A couple of thoughts for you with your wiring.

<ol>
<li>Run a 4-wire cable, not 3-wire. Your 240v machinery only needs the 2 hots + ground to run. If you ever want to add a worklight to a 240v bandsaw or router table into your 240 tablesaw's outfeed table - you'll need a neutral. It's easier to run the neutral now and never need it than it is to want it later and have to rewire. The cost difference between 12/2 and 12/3 or 10/2 and 10/3 isn't that great.</li>
<li>Standardize on a twistlock plug configuration and use that for all of your machines. You want a "3-pole, 4-wire, grounding" - either L14-20 or L14-30 series. It's a one-time expense for the higher cost plugs and receptacles, but they are designed to take the abuse of connecting and disconnecting in a commercial environment. I also like the fact that they can't just "pull out" prematurely when you're in the middle of your glory (ex. ripping down a 12/4 oak board).</li>
<li>Consider running 10-gauge wire and 30 amp circuit breakers. You can run lower draw machines on those circuits safely (the motors should have overloads to protect them) and it gives you the ability to grow into bigger machinery if you ever so desire.</li>
<li>Consider running (2) machinery circuits plus separate dedicated ones for your DC and compressor.</li>
<li>An easy way to get a lot of 120v circuit capacity for your workshop is to run a "multiwire" circuit. You use a standard 2-pole, 240v breaker and run 12/3. This gives you (2) hot leads for (2) separate 120v circuits. The only thing is you need to either splitwire the outlets or put in 2-gang outlets. To me, the 2-gang idea is best - use (2) different color outlets for the circuits - ivory for one, brown for the other.</li></ol>

One last comment - some of the above may seem like overkill now. It sounds like your shop will be a finished space (<i>"before I close up the walls and ceiling"</i>) and the extra expense now may save you tearing apart your walls/ceiling later.

Just my opinions. Wire and work safely.

Addy protocol: unlicensed homeowner electrician, tool nut, woodworker.

Rob

[Ken Salisbury]

<p align="center">
JUST BE CAREFUL
<p align="center">
<IMG src="http://www.klsal.com/electricshock.gif">

[Scott Greaves]

This is a reply to Rob Russell's comment above. You suggest the use of NEMA L14-30 to get the four wire. Is this just for the future convenience of having a worklight or some other 115v item connected to that circuit, or is there a reason beyond that to have the L14?

I asked a bit at the Pond, and came up with a standard for my shop of using NEMA L6-30 plugs and receptacles, which is a three prong plug. Is there anything I lose by using this other than the future capability of adding a worklight?

Another question I came up with - what about GFCI protection on the 30 amp 240v circuits for the machines - is it necessary? I'm protecting all my 115v circuits for GFI, but haven't seen any GFI receptacles for 240v. What do you think?

Thanks!

Scott.

[Bob Lasley]

Scott,

I am not aware of any 240 GFCI recepatacles available, however there are 2 pole GFI circuit breakers available. As far as these being necessary, they are not required by code except in wet areas, ie. kitchens, baths and outdoor receptacles. Some areas require them in garages as the receptacles are used for outdoor equipment such as weed eaters, hedge trimmers, etc. I personally do not want them in my shop as they are subject to nuisance trips from motor starting, but if they make you feel safer and you don't mind resetting them once in awhile, by all means go for it.

Bob

Addy protocol: Electricial trades since 1974.

[Jason Roehl]

Originally posted by Rob Russell

<li>An easy way to get a lot of 120v circuit capacity for your workshop is to run a "multiwire" circuit. You use a standard 2-pole, 240v breaker and run 12/3. This gives you (2) hot leads for (2) separate 120v circuits. The only thing is you need to either splitwire the outlets or put in 2-gang outlets. To me, the 2-gang idea is best - use (2) different color outlets for the circuits - ivory for one, brown for the other.</li></ol>

Addy protocol: unlicensed homeowner electrician, tool nut, woodworker.

Rob

Rob,

Now I'm not a licensed sparky, either, but there is something in there that bothers my former EE training. In a 120V circuits, any current that runs through a hot returns through the neutral. So, if you have two hots, a ground and a neutral to attempt two 120V circuits, both hots would be using the same neutral, doubling its potential amp load if two machines were using the two 120V circuits.

I.E., a 15A router on one leg of the 240/120 circuit and a 12A shop vac on the other means that neither of the hots would be exceeding the 15 or 20A rating of the wire, but the neutral would be carrying 27A. Not a problem on 10/3 rated for 30A, but 12/3 is only 20A.

I think some of our resident electricians who know the code need to weigh in on this!!!

Jason

[Dennis McDonaugh]

Andre, its okay to run put multiple outlets on each 220 circuit. This is common in one man shops where only one tool will be used at once. Be careful if you use 220V 30 amp breakers, don't install 20 amp plugs on a circuit capable of providing 30 amps of current. You may know its a 30 amp circuit, but the person who comes along behind you might not know. I have two dedicated circuits in my shop--one for the compressor and one for the dust collector. I actually ended up with the bandsaw, table saw and jointer on the same circuit because thier location didn't work out as I had originally planned. It works fine because I only use on tool at a time.

[Mac McAtee]

In Europe most homes are wired for 240V AC. Like even your can opener is a 240V machine. Multiple outlets on the same circut all over the house.

As long as all the devices pluged into the circut do not exceed the amp rating for the breaker you can run mulit machines on the same circut, no problem. The breaker should be sized for the wire gage and length of the run of wire, not to the amp rating of the machine you are plugging into it. So, if your electrician did a proper job, you can plug up to 20 amps worth of full load amperage (see data tag on motors) in the circut and run them all until you get to 20 amps total plugged in.

[Rob Russell]

These are answers to some questions that were asked in this thread.

<b>Scott Greaves</b>

<i>"You suggest the use of NEMA L14-30 to get the four wire. Is this just for the future convenience of having a worklight or some other 115v item connected to that circuit, or is there a reason beyond that to have the L14?"</i>

You are correct. The additional (neutral) conductor is purely for the convenience of being able to run a 120v load off of that circuit. If that circuit will only, forever, be used for pure 240v loads, there is no need for the neutral.

<b>Bob Lasley</b>

As far as GFI requirements, I believe that code now requires GFI protection for basement circuits too, at least for the 120v circuits. I agree with your statement that GFI isn't required for 240v circuits.

<b>Jason Roehl</b>

<i>"So, if you have two hots, a ground and a neutral to attempt two 120V circuits, both hots would be using the same neutral, doubling its potential amp load if two machines were using the two 120V circuits. "</i>

The 2 legs of that 240v circuit are 180&#176 out of phase from each other. The current that will flow back through the neutral leg is the <i>difference</i> between the current flowing through each of the (2) hot legs.

If you had 15 amp loads running on each of those (2) hot legs (say a shop vac drawing 15 amps on 2 leg and a router drawing 15 amps on the other), they would exactly cancel each other out and the current flowing back through the neutral leg would be 0 amps.

If you had a 15 amp shop vac running on 1 leg and a 10 amp drill press runing on the other leg, you'd have 5 amps flowing back through the neutral conductor.


Addy protocol: unlicensed homeowner electrician, tool nut, woodworker.

Rob

[Scott Greaves]

This was the information I needed. I have already stocked up on Hubbell brand L6-30 receptacles, plugs, etc. I was hoping I hadn't done it wrong. There will be nothing but shop machinery on these 240v circuits, and there are other 115v outlets close enough to use for anything like worklights. Thanks for the info!

Scott.

[Jim Amundson]

A point to remember - if you are running two 120 circuits with two hot wires and one neutral you need to put GFI 's on each outlet. Use a seperate neutral for each circuit and you need only one GFI at the beginning of each circuit and the following receptacles can feed off the first one. Sometimes wire is cheap.

Regarding GFI's on 240, I ordered a GFI breaker from my eledtrician and it cost $125. I ran my 2 hp lathe with the inverter and adjustable speed off that circuit and kept throwing the GFI breaker. THEN I found out that it is common for that to happen. The electrician was nice enough to give me my money back.

[Dave Hammelef]

Wow an electircal thread that appeared not to have any disagreement in it. Amazing.

By the way I am in agreement with all that was said also.

Dave

[Jason Roehl]

Rob Russell,

I got it now. I should have drawn it out on paper to begin with. The load on the neutral wire cancels out at the node (connection). Good answer!

Jason

[John Sanford]

Originally posted by Jim Amundson
A point to remember - if you are running two 120 circuits with two hot wires and one neutral you need to put GFI 's on each outlet. Use a seperate neutral for each circuit and you need only one GFI at the beginning of each circuit and the following receptacles can feed off the first one. Sometimes wire is cheap.

Wire is cheap, but the time to pull it etc, isn't. Even when you're doing it yourself. An important point about using GFI receptacles (as opposed to breakers) is that the receptacles can only protect a limited number of devices downstream, AND the receptacles are not nearly as long lived as GFI breakers. (some would say "notoriously short lived")

The separate neutrals is important, as I, to my dismay, have discovered. Unfortunately, none of the reference books that I had consulted bothered to mention this, but if/when one takes the time to explore the subject of GFIs, it becomes obvious. A GFI works by comparing the "outgoing flow" to the "returning flow", and any discrepancies outside of design parameters results in a tripped breaker. A shared neutral means that the power may goes out on one circuit and returns through "another", snick goes the breaker. I really, really wish someone had explained this to me before I pulled all my wire, wired my devices, etc.

I now have two 9 receptacle circuits wired up on two GFIs, with a shared neutral. They don't work... :( grrrrr....


Regarding GFI's on 240, I ordered a GFI breaker from my eledtrician and it cost $125. I ran my 2 hp lathe with the inverter and adjustable speed off that circuit and kept throwing the GFI breaker. THEN I found out that it is common for that to happen. The electrician was nice enough to give me my money back.

[Ben Mathews]

I would like to add something that is pretty anal and problably doesn't mean much, but I think that it deserves some mention. When you get amps going through a wire, you get some measurable voltage loss. If you have a 240 circuit, you have two hot wires at, say, 115 and -115 volts. Since you are pulling a "balanced" load from an AC motor, the current drop in each wire is the same and the voltage of the two legs is equal (and opposite). If you add a 100 Watt light bulb to one of the legs, you have added nearly one amp of current to one of the legs, and have lost a little bit of voltage on that leg. You have maybe 115 and 114 volts. Is this important? Probably not. Do I have lights on my 240 machines? Nope.

The argument can be made that a single phase motor sees the difference of the two voltages, and doesn't care about the individual voltages. Maybe that is correct, but as I said in line one, the point is kinda anal.

[Jim Amundson]

John, don't feel alone. Before I knew I needed two neutrals I dug a 30' trench 2' deep, placed conduit and wire with ONE neutral, covered it up and wired my garage with 6 double receptacles. NO room to pull another neutral, so I, too, have a bunch of GFI's I wouldn't have needed.

[John Sanford]

The question of 3 vs 4 wire 240v circuits is answered in the most recent NEC.

4 wire.

From a FUNCTIONAL perspective, the neutral is not necessary for a pure forever 240 circuit. However, according to all I've read, it is required by the NEC, those arbiters of electrical good taste who may be operating on the assumption of "let's leave room for flexibility in the future."

For garage/basement circuits, dedicated to a single device (i.e. one breaker, one receptacle, one device 120v circuits do not require GFI. All other 120v receptacles do require GFI.

[Rob Russell]

John S.

What section of the NEC says 240v needs 4 wires? I'd like to read that section, because I don't find it in my '99 copy of the code. There are some circumstances where, what used to be a 3-wire 240v circuit now requires 4 wires. Examples are dryers and ranges, but that's because the NEC is requiring separate neutral and grounds where it didn't before.

Your point about dedicated circuits not needing the GFI is a good one too. An example of such a circuit, and one where you don't want the GFCI, is a freezer. If the GFI pops, you end up with a big pile of melted ice cream. Yuck.

The point was made about GFI's and needing separate neutrals which is true and a good point. Also - there has been a recent change in the requirements for GFCI receptacles and at what levels they trip. I don't remember the specifics, will try to find it somewhere. The new Arc Fault requirement for bedrooms is a whole 'nother story.

Rob

[Dave Hammelef]

Originally posted by Rob Russell
John S.

.... The new Arc Fault requirement for bedrooms is a whole 'nother story.

Rob

What is this I have not heard about this one? What code change is that in? Just courious? To me Arc Fault solves a much more common problem. GFI is a good idea in a wet area, BATHROOM, and around sinks but beyond that does not do much.

Dave

[John Sanford]

Originally posted by Rob Russell
John S.

What section of the NEC says 240v needs 4 wires? I'd like to read that section, because I don't find it in my '99 copy of the code.
Rob

My understanding is its something the NEC looked at for the '99 but hadn't approved, but it is part of the 2002, like Arc Fault. However, I'm not an electrician, nor do I have a copy of the codes, so my information is "referential heresay", i.e. I'm going based by stuff that I've read that is published by "reputable authorities" (as opposed to heard in the diner or read at somebody's website). All of which is a long-winded way of saying "I could be wrong." (My apologies for overstating the certainty.)

If anybody can check the 2002 NEC to put the 3 vs. 4 wire 240v 2-pole circuit question to rest, it would be appreciated. :)

[John Sanford]

Originally posted by Dave Hammelef
What is this I have not heard about this one? What code change is that in? Just courious? To me Arc Fault solves a much more common problem. GFI is a good idea in a wet area, BATHROOM, and around sinks but beyond that does not do much.

Dave

uhhh, because you haven't been into Home Depot or Lowe's over where the circuit breakers lurk? Seriously, they have the info there, I suspect in part to educate the irate customer who now has to pay 10 times as much for a breaker for the new bedroom addition than they do for the new game room addition. An unexpected 35 bucks for a breaker as opposed to 3.50 may be just enough to send the frazzled remodeler over to the axe display... :D

It is new to the 2002 NEC.

http://www.arcfault.org/ResidentialArcF.htm

[steve banks]

NEC states that all 220v appliances in the house shall have a separate neutral and common. This only makes sense because if one of the returns is lost, there is NO path back.

[Bob Lasley]

If you have an appliance that is strictly 240 volt, what do you connect the neutral to? If there is no place to connect a neutral, what good is it?

Bob

[Rob Russell]

I'm gonna take a swag at this 4-wire 240v requirement and say that it's a "preventative measure" if it's really in the 2002 version of the code. We all know that dryer circuits now have to be 4-wire. We also know that motors only need the 2 hots + ground and will <u>never</u> need that neutral. However, the code-makers may have decided to make the neutral a requirement as a preventative measure for future uses of a 240v circuit for a 120v load.

For example. my old 240v bandsaw has a worklight on it. I know that worklight has to be wired between a hot and the ground because the saw has no neutral (I haven't gotten around to rewiring it yet).

It makes sense to me that the code folks would say "240v circuits need a neutral so future 120v loads that use one of the 2 hot legs have a neutral available to use so people don't just use the grounding conductor" or something similar.

Again - this post is not based on reading the 2002 code, I've never seen the 2002 code update, I'm not a licensed electrician and this is simply a guess at why the code might have been written that way if indeed it has and I could be all wet and dead wrong on this (count the words in them thar run-on sentence!)

Rob

[Kevin Gerstenecker]

There is an application that uses 220V with a neutral wire pulled along with the feeders for the high voltage, and it slipped my mind yersterday. A Central Air unit sometimes uses this method of wiring. The Compressor for your Central Air unit is 220V, but the fan is usually 120V. Most installers will pull a neutral wire with the 2 feeders, usually #10 wire, and the ground. Once outside at the unit, they will use one leg of the hot for a hot leg for the 120V fan, and then use the neutral they pulled for the 120V neutral back to the panel. They then share the ground. This connection is usually accomplished at a Terminal Block on the Condensing Unit. It works well for this application, but I still think using a leg with a neutral and ground from a 220V machine to power a light, or 120V recepticle, is a bad idea. For one thing, the wire size would have to be rated for the voltage rating of the breaker in the panel that is controlling the 220V. It just makes better sense, and is safer, to wire a 120V load from a 120V source, and not mix the voltages. If you do this, you may know what you have, but the next guy that comes along may not, and he may get a not so pleasant surprise!

[Dave Hammelef]

Originally posted by John S.
uhhh, because you haven't been into Home Depot or Lowe's over where the circuit breakers lurk? Seriously, they have the info there, I suspect in part to educate the irate customer who now has to pay 10 times as much for a breaker for the new bedroom addition than they do for the new game room addition. An unexpected 35 bucks for a breaker as opposed to 3.50 may be just enough to send the frazzled remodeler over to the axe display... :D

It is new to the 2002 NEC.

http://www.arcfault.org/ResidentialArcF.htm

Thanks for the link there was some great info there especially this link http://www.zlan.com/

Well I geuss I need to be hanging out at my local HD electrical dept. more often. May also need to start replacing some old Circuit breakers.

Dave

[Ed Weiser]

My understanding of the 2002 NEC code is that the separate ground and neutral for 240v appliances is based upon the dual voltage of many household appliances. For example, electric stoves use 120v for their timers and lights, electric dryers use 120 v for their timers and lights, and so on. The previous practice of using the ground to return the 120v leg is now forbidden. In the case of 240v motors (as in woodworking machinery) there is no 120v leg (unless one wires a 120v light using the same circuit) and a separate neutral is not required. And, by the way, on a 240v induction motor the ground carries NO CURRENT unless there is a frame or motor short circuit. If the ground wire were disconnected the motor would still run but become highly dangerous.
My opinion only. Not an electrician but an informed consumer. Hope this helps.