230V 'polarity'?

A little OT but I need help with 1 phase..

I recently wired up a 230V heater it says connect white wire in this terminal and black wire in other, sure I did that at the appliance side, but I cannot figure out which wire goes were in the breaker, I took a guess and it seems to work.. the element heated up and fan blows forward.

So now something more critical, I need to wire up a 230V compressor, how do I know which leg on the breaker is the white or the black, will the compressor/motor spin in wrong direction if I mixed it up?


Reply to
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If the breaker is on your main panel, there is no white or black on it until you connect the wires that the breaker would feed.

It does not matter which color hot wires you connect to motor terminals, the motor will spin the same ay regardless. What does matter is that the grounding wire should be connected to the grounding terminal on your machine, and hots are connected to hot terminals.

It would be worthwhile to call around and look for an electrician.

i i

Reply to

you are going to get someone killed if you aren't careful - the electrical code says: green = safety ground white = neutral, tied to ground at one point (in most jurisdictions) black, red, blue, any other color - hot, voltage not specified.

all your breakers are treated as "black" the neutral (white) wire is connected to a junction block in the breaker box, and a wire from there goes to the neutral ground the green safety ground is connected to a local ground and to all metal boxes, etc

for your 220 air compressor, you MUST use black (or some color other than green) for the hot wires, and green for the safety ground.

The reason messing up is dangerous is that someone working on the wiring will naturally assume that the white is neutral (not hot) - and if it's hot they can get hurt/killed

you also need to understand that there is no "polarity" on AC power, only DC - but there is the notion, explained above, of hot and neutral

Reply to
William Noble

No, but it may affect the electrical safety.

Reply to

I am sorry if I seem clueless but I am familiar the color codes. at least 110V. But generally I buy the Romex 10Gw-2 for example which has a black and white and bare copper, the bare wire should easily be understood as ground. So are you saying I should not use this romex for 230V wiring because the white wire is really a HOT wire? It will be wired from the breaker directly to compressor so one would have to be carelessly touching the wires at the compressor end without shutting off the breaker/mains in order to get electricuted.

Reply to

Tape the white wire red at both ends and it should be okay.

Wes S

Reply to

Cute answer.

Reply to

It may or may not be cute, but I know that 25 years ago this was allowed by the National Electrical Code. I suspect it is still a valid method today. What I wonder about is that the heater instructions mentioned a white wire. I wonder if it had a 230V heat element and a 110 fan and was intended to be wired with 2 hots, a neutral and a ground.


Reply to
Carl Boyd

That was my concern: if the instructions called for a white wire, the instructions SHOULD be calling for a neutral and thus cannot be calling for a standard US style hookup. Probably some sort of Chinglish instructions. Not good.

For the >

Reply to

As far as I know (all my electric exp is in the US) in order to get 230-240V to an applaince with 3 wire romex (2 conductor 1 bare ground) both the black and the white wires will go to the breaker so they tap both hot legs. In this type of use there is no "netural". As long as both wires go to an appropretialy sized breaker you will get the 240 you need.

You would benefit from hiring a licensed electrician and watching him work and get a book on basic wiring. That's what I did long ago and over the years I have done some extensive wiring (new service panel/several sub panels, outlets and machines) and I don't ever feel like I'm "guessing" about any of it. If I do have any question about some electric work I get a sparky to do it and learn from the process, the piece of mind is well worth the few bucks.


Reply to

If you are in the United States, the only thing that's critical is to get the two hot wires for 240V on the power terminals, and the green/bare safety ground wire to the chassis ground.

There really is no "Polarity" per se, because both power lines are above ground potential, the ground point is the center-tap of the transformer secondary. In Europe it might make a difference, because they're using 240V where one line is at ground potential.

On 120V gear, you want to hook the hot wire to the side that is fused and switched in the equipment, and the grounded side is the white wire for current return.

When using Romex cable that is factory made with a White and Black, you only need to tag the white at both ends (circuit breaker end and equipment end) with colored tape (anything other than white or green) to remind the next person that it is NOT a neutral, and is being used as a power conductor.

This is also applicable when setting up switchlegs on house lighting circuits that have power and neutral to the light, and the 2-wire cable down to the switch is power and switchleg - you don't absolutely have to do it, but the reminder sure helps when troubleshooting later.

Same thing, just get the two hots to the two hot connectors in the motor end bell. The rotation direction on a single-phase motor is determined by the internal construction of the motor, not on the external power connections.

On reversible motors you have to switch a few wires going to the windings inside the motor connection box to get it rotating the other way. Switching the power wires to utility power won't change a thing.


Reply to
Bruce L. Bergman

let me add this - I would be EXTREMELY reluctant to use romex to wire a compressor - it has solid wire, the vibration will cause it to harden and fatigue - will it happen in your lifetime? I don't know, but why risk it - run flex with stranded wire. For permanently installed wiring, run EMT (conduit) and then pull two black wires through

Reply to
William Noble

In North America you use 3 wire (NMD3 or NMW3) for 220. The "line" connections are red and black (one goes to each breaker) and the white is neutral. Ground is the bare wire, on the green or bare terminal. Voltage from either "line" to neutral is 110. "line" to "line" is 220.

Reply to
clare at snyder.on.ca

Taped or painted meets code in Ontario, but most inspectors prefer you use 3 wire.

Reply to
clare at snyder.on.ca

The very vast majority of stationary compressors are wired with solid copper. Industry wide.

Reply to
clare at snyder.on.ca

For items that are straight 240V and do not have any 120V parasitic loads like pilot lights, controls, etc., you do NOT need to provide a neutral wire that will never be used. This would be electric water heaters, AC Condensing Units (compressor load), and the like.

Large air compressors are a straight 240V fixed motor load and fall under that rule, and if they have a combination motor starter it more than likely has a 240V coil and controls.

You are free to provide a neutral if you want, but most homes will not have them where they are not required - they're bid too tight.

For items where there will be 120V loads connected for interior lights timers and controls, you have to provide 3-wire cable with a white neutral back to the power panel - Clothes Dryers, Cooktops, Ovens, Ranges (UKtrans: combination cooktop & oven).

Old houses are Grandfathered from that rule, you can put those parasitic loads on the safety ground for the clothes dryer or range. But all new installs must have a proper neutral and 4-wire service cord.

Neutral is bonded to safety ground at the main service panel, but they want two separate wires going out to the appliances to ensure that the Ground is only being used as a safety ground.


Reply to
Bruce L. Bergman

If you are using Romex...or non-metalic sheathed, to be more accurate...for

220v wiring, you should be using THREE conductor w/groud, not TWO. You'll have a bare ground wire, a white neutral wire and a black hot wire AND a (usually) red hot wire. In the breaker box, you'd connect the ground AND the white to the gound buss, the red to one side of the breaker and the black to the other side of the breaker. Use a single, two pole breaker for this...that way if you your breaker trips on ONE line, it'll trip and protect both.

Unless you WANT to work on a hot wire, do NOT use two single pole breakers as a trip will only kill half the power.


Reply to
The Davenport's

That is not correct. A compressor typically has no 110 volt loads so a neutral is not called for. There would be nothing to connect the neutral to at the equipment end.

Reply to

So how is it normally wired in a home for a pure 220 volt circuit instead of the split 110/220 circuits that are more common with home appliances (which is all I currently have in my home). I might be wiring a socket for a welder soon so I'm interested in learning. I've done a lot with 110 volt circuits but I've never had to wire a 220 circuit before.

So far in the thread, we have seen the idea of using the normal black/white romex wire and mark the white wire with red tape.

And we have seen the suggestion of using conduit and pulling two black wires and a green safety ground.

Do they make romex with black red and bare ground? Or black/red/green?

I'm looking at an #8 AWG (or maybe #10) run. What form does 8 or 10 gauge wire come in typically? (I've only worked with the normal #12 and #14 gauge wire in the past).

Basically, what I'm asking, is if I were to hire an electrician to run a 60 amp 220 volt circuit to my garage, how would he most likely do it (what is the cheapest solution that meets typical code)? Or, what do people think a typical inspector would be most comfortable with?

Ultimately, I know I just have to find out what my local codes are, but I thought it would be interesting to hear more ideas from the group. I understand all the theory - I just don't know the codes and standard practice for 220v circuits.

Reply to
Curt Welch

As mentioned variously:

1) There is no polarity as such, 2) You will have 240 between the two legs, and 120 from either leg to 'neutral 3) You do not need a neutral in this case, and probably have nowhere to connect it 4) If you are using two wire black and white romex, you must clearly identify the white as being hot (usually with colored tape), lest it be mistaken for neutral 5) You must absolutely use a dual breaker so that a fault in either leg will disconnect both legs.

Additionally :

1) When I wired my last shop (and entire house, with new panel) the electrical inspector was happy to let me use 'heater' wire for the 240 volt outlets. Baseboard heaters are also typically 240 volt, with no neutral. 'Heater wire' is also a 2-conductor romex, but instead of black, white and bare ground, it has black, red and bare ground (and typically a red jacket). I would think this would be the safest and most fool proof.

2) You may not be able to arbitrarily connect to two adjacent breakers to get phase opposed 240 volts! It depends on the design of your panel. In certain makes of breaker panel (Federal Pioneer, for one) you may have to shift existing breakers to guarantee that you get the connection you intend. Otherwise you will just get two parrallel 120 volt lines. This will give you zero volts across your device, but you'll still have 120 volts between the device and ground. Not Good!

3) I'm surprised no one has mentioned guage. Have you determined that the wire you intend to use is adequate for the load?

4) With all respect, you are clearly not very experienced in what you're undertaking. There is a huge gap between 'hook it up like this and it works' and 'hook it up like this and it will not only work, but be safe'. I suggest you at the very least do some studying before you undertake this. If you're in a hurry, hire a licensed electriction so that it is done to code.

Wiring to code means that:

1) When you or someone else works on the circuits years later they won't get any unpleasant (possibly fatal) surprises, and

2) When your house burns down, the insurance company won't have that particular excuse to withhold payment.

Not directly relevant to your situation, but "Old Electrical Wiring Maintenance And Retrofit" by David E. Shapiro gives some interesting insights into how things can be wired so that they 'work', but are far from safe.

Good luck.

Reply to
Mickey Feldman

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