View Full Version : A 220 volt wiring question???

05-07-2007, 08:37 PM
Hey all you lectrick gurus! Got a question for you if you don't mind.
I'm about to hook up a 220V jointer. The previous owner used a dryer plug. I have several of these so I'm going to use them for my woodworking equipment.
Typical...the jointer has three wires coming from it for the 220V. Black, red, green.
The dryer plug/wire has black, red, white, and a bare ground copper wire.
The last guy wired his up using the bare ground wire(on the dryer plug) instead of the white (neutral).
I don't know if he ran the bare wire to the neutral bar or just to a common ground in the breaker box.
When I wire these three wire 220V machines I always run the two hots where they should be and run the white to neutral...there is no bare ground wire of course.
So who is right...or does it matter?

Todd Tolhurst
05-07-2007, 08:44 PM
You need the two hots and the ground, not the neutral. The neutral is only used if there are 120V loads (lights, timers, etc., as in a dryer) in addition to the 240V motor.

05-07-2007, 08:47 PM
I get a little confused in this area, but I'm thinking the jointer doesn't need the neutral. My 220V compressor doesn't. My welder and any laundry type hook up would but only because they also need 110V.

220 is two 110's added around the neutral, but if you don't need 110 for something inside the machine the two outsides, (hots), do the job by themselves.

The 3rd wire on the jointer is probably for an earth ground.


05-07-2007, 08:49 PM
Thanks Tod...Ooops...does this mean I have all my machines wired wrong...
All my 220V stuff, I run the green to neutral...gulp....should be to ground...right?

05-07-2007, 08:51 PM
Red and black of course are hot,you can use green for the neutral and the bare wire from the machine frame to the ground lug in the box if you want a safty ground,but I wouldn't bother.

It's a shame you don't have four wires in the wall,the fourth can be used as a return signal to a relay on your dust collector to switch it on and off with the machine your using.

Todd Tolhurst
05-07-2007, 08:56 PM
Yes, you really want those other machines grounded.

05-07-2007, 08:56 PM
Darin...so the machines I have that have the third (green) wire running to neutral will be ok? (These are all machines with only three wires coming out of them).
Seems to me that the neutral is a ground anyway...right?

Todd Tolhurst
05-07-2007, 09:00 PM
No, neutral and ground are not the same thing. They are connected only at the main panel.

05-07-2007, 09:01 PM
Ooops...ok, I just looked in my breaker panel. The neutral bar doesn't seem to be going to ground.
Dang! I wish I could remember where I got that idea from. Seems to me I copied a wiring setup that an electrician did for me and have been doing it like that ever since.
Oh rats!

05-07-2007, 09:04 PM
Geez...I'm glad I asked this question now. Seems I have a bunch of wiring corrections to make now...like 6 machines worth! Ooops!

Todd Tolhurst
05-07-2007, 09:05 PM
At some point, usually in the main panel, the neutral and ground are bonded. But that doesn't make them interchangable. The neutral is a current-carrying conductor; the ground is not.

05-07-2007, 09:10 PM
Actually Russ it in your situation will depend on the number of wires you have going from the recepticle to the panel box.If it's just three then it's just red,black and green.No need and no use for the bare strand unless you have metalic conduit going from the recepticle to the panel.Even then you would need to check and see if there was a good connection in the conduit run for it to be any use as a ground.

05-07-2007, 09:21 PM
This gets lots of folks confused and sometimes into trouble. Grounding is a difficult animal to get right.

As the previous posts have said, ground and neutral are two different things. The ground and nuetral tie together at the first point of service, which is the first panel from the meter, or if in a commercial building at any transformer. Beyond this point, they remain isolated from each other.

The difference is that a neutral carries current, and the ground does not unless there is a fault. The whole purpose of the gounding conductor (green or bare - ground wire) is to trip the circuit breaker or fuse. The grounded conductor ( white or gray - neutral) is carrying current from a single phase, or the unbalanced from multiple phases.

If the ground and neutral are connected at any point beyond the first point of service, then you take the risk of equipment carrying a current from other circuits. It is also easy to overload a conductor to the point of meltdown in this situation because there is no clear path back to the energy source, and electricity will always follow the path of least resistance.

Hope this doesn't confuse y'all.

05-07-2007, 09:28 PM
In any normal panel, the neutral and the ground are bonded, in other words they go to the same place- same as the panel itself. The ground lead is normally not as heavy as the neutral lead, and partly for that reason should not be used to return current to the neutral at the box. Where the appliance is 220 vac only (not requiring 110 also), then either the green or the bare wire would suffice to act as a ground wire. If the appliance needs to use 110 as well, then the green or white should be used as the neutral, and the bare used as the ground. If the appliance needs 110 as well as 220, there should be four wires- two hots (black and red), a neutral (white) and a ground (bare, or green). You should not use a three wire for this, since you now don't have a safety ground wire.

The whole idea is that the ground wire is not supposed to be conducting any current, unless a fault condition develops. At the panel, if you were to undo one of the ground wires, it shouldn't have any voltage on it. If it were used as the return lead for a 110 v device, then you would most likely be able to get a nasty shock from it since voltage from one of the hot leads would be connected to it through whatever device was plugged in.

Someone might have some piece of equipment hooked up using the ground wire as a neutral, and they may know that because they did the hookup- but then sometime later as memory fades, they might get zapped by it when doing some work in the panel. Best is to stick with convention and use the proper wiring code.

05-07-2007, 09:31 PM
What's being said is that if you have wired your whites (240 only) to the neutral bar of a sub-panel, then it is wrong. You need to change these over to a ground bar. It is a safety issue.

If you are working out of a main panel then it doesn't really matter. However, to avoid confusion, look neat and professional; then the whites (which are really ground and NOT neutrals on a 240 only circuit) may be moved over to a gound bus.

05-07-2007, 09:52 PM

Note that since the neutral and the ground are bonded in the main electrical box, the neutral and the ground buses must not be connected together in the subpanel as this can have ground at 2 different voltages and at least in theory be a safety issue.

I believe it is also true that any color other than green or bare when used as a ground is supposed to have a tape or other attachment on both ends of the wire designating it is ground. I might be hallucinating but I think I also remember seeing NEC recently disallowing the practice of marking conductors and wanting the right color wire used.

Paragraph 1 is definitely correct however.

05-07-2007, 09:57 PM
Thanks you guys...you saved my butt once again! One of these days you'll get me straightened out :D
Another few minutes and I'll be firing up the new (to me) 8" jointer...yippee...wood chips!

05-07-2007, 10:47 PM

Ckell brought up a point.

Mark all those whites that you are using as grounds -yes it is legal and proper.. Use green paint, a green felt tip, or green tape.

Somewhere down the road someone will look into that panel and may want to know why whites are connected to a ground bus.

05-07-2007, 10:48 PM
I believe it is also true that any color other than green or bare when used as a ground is supposed to have a tape or other attachment on both ends of the wire designating it is ground. I might be hallucinating but I think I also remember seeing NEC recently disallowing the practice of marking conductors and wanting the right color wire used.

This is fact. The NEC requires the wire be colored for the intended purpose unless that conductor is a #6 or larger (may not be the exact right size) at which point you must mark it with the appropirate color. The bad thing about the NEC is the regulations are governed by local municipalities, and they make up their own rules and interpret the code as they see fit.

In practice, colored tape is used on conductors of all sizes to mark them as to their purpose. As long as the color codes are kept correct, there shouldn't be an issue (unless your authority having juristiction doesn't like you).

Corners can be cut in many areas, but not on power systems. Doing things properly will greatly reduce the risk of a fire, and will also keep those whom are working on it safe, as well as keeping your equipment safe.

If there is any doubt as to what needs to be done, consult an electrician! And keep in mind that the people working in the home improvement centers are typically not qualified electricians, plumbers, framers, etc., and the advice they give may or may not be correct.

Torker, you are not in bad shape. Just make sure that your grounds are on the ground bar as has been already stated. Remember to turn the power off before doing this! :eek:

Todd Tolhurst
05-07-2007, 10:51 PM
This is fact. The NEC requires the wire be colored for the intended purpose unless that conductor is a #6 or larger (may not be the exact right size)

#6 and smaller needs to be continuously colored (no remarking). Larger than #6 can be remarked, which is fortunate, since wire in those sizes generally only comes in black.

05-07-2007, 10:58 PM
In many areas of the country, the older (pre 1970 or so) houses (and lots of businesses) were wired with 2 - 220 volt wires and 1 neutral - no separate ground. Both neutral and ground were indiscriminately hooked to the neutral leg. Many of these remain and are usually left as is unless major electrical revisions are made.

I have also seen many 110 volt installations where the neutral wire was extended to connect to the ground lug of a grounding type receptacle and many of these still remain in service.

The danger in using a neutral as ground is that an open neutral can (and probably will) put 110 volts on the case of tools and appliances. A properly installed ground will prevent electrically hot cases.

J Tiers
05-07-2007, 11:34 PM
Since you seem to have all 4 wires from the wall (right?), you can connect the jointer using a new style dryer plug, OR convert over to an L14-20 plug and socket (assuming the circuit and jointer are no more than 20A. The latter is better, for less confusion, but not essential.

However, an appropriate fuse or breaker is required for the protection of the lower current jointer and cord. If you use a L14-20 plug, that limits your fuse/breaker to 20A, which is probably much more than your jointer.

Hots to hot, green to equipment grounding conductor, ignore the neutral.

This presumes that the wires go directly back to the service box, as is usual, and that they are correctly hooked up there, with hots to hots, neutral to neutral bar, and ground wire to ground bar. If there are a mess of sub-panels etc, then tehre might be a problem, and I would not presume to guess what was done, nor how to fix it.

For others in the US, at least, with an old style dryer plug on the wall, as a practical matter, the white wire goes ALMOST to the same point in the service box as the green ground. The difference is that the neutral probably goes to a neutral bar (grounded conductor bar) that is "bonded" in turn to the equipment grounding conductor bar (ground bar). Both are grounded.

The old style dryer installation used the neutral both as a neutral and a ground. It was specific to dryers, which were "designed for" that type installation. When done right it was safe.

As a matter of levitical correctness, you should tear everything out and re-do it with 4 wires.

BUT grounding via a wire that has white insulation on it is just as "safe" in the sense of not causing a physical hazard, as any ground wire usage that is "correct", i.e. green insulation or bare. The insulation MARKS the wire, but does not affect how it works..

I would, and have, used THAT sort of neutral as ground, since it goes back unbroken to ground. Yes, it is against the code, and at some future time someone might be confused.....

But, since the plug, when pulled out, removes the "problem", I wouldn't worry about it for now.

Just recall that it isn't what you "should" do.

05-07-2007, 11:45 PM
Go to the College of the Rockies bookstore or some other good book store & order or get a copy of Peter Knight's red book, the Canadian Electrical Code simplified. It will give you the explanations why and "what the code says you shall do"....That's the first step. Trying to explain mickey-mouse wiring to the insurance adjuster or the WCB wouldn't be easy if the "gurl" got fried or the new shop burns down.
Todd and some others have also explained about ground & neutral. If the jointer only has a 240 V. motor and a motor starter, yes a neutral isn't needed because unlike a dryer or range there is no 120 VAC used for controls. (ie between 1 line & neutral.) A ground is still VERY important.
Yes, neutral and ground are almost the same, and the neutral can be followed back to a ground rod at the pole transformer and maybe at the meter base, but neutrals have been known to "float" (common enough) resulting in wildly unbalanced voltages on each hot leg and possibly at connected tools & machines. So ground it...!!! The neutral exists to provide 2 voltages for a single phase service from a centre tap transformer (at the pole) and to provide a return path for unbalanced loads. (120 VAC L-N, 240 VAC L-L....)
Rick (BC Elect Reg. no. 36927)