Wiring a ceiling fan black to white wires

[Jpflex]

back when I was a young lad apprentice for residential wiring, I knew to wire black to feed a black wire of a fan and white to white. However, I always wondered what would happen if this were reversed but never tried it. Would the fan spin in reverse if the branch circuit black hot wire were connected to the fan white neutral wire and white branch circuit neutral wire to fan black lead?

My boss years ago said the house could catch fire if wires were reversed but I told him I did not believe him because AC current inherently reverses direction in a circuit (60 hertz cycles).

I do know that areas of equipment that would normally connect to a neutral would have line voltage if reversed such as a lamp holder bulb threads which may be hazardous to the installer but still would illuminate the bulb

 

[augie47]

Reverse polarity would have no effect on the operation

 

[LarryFine]

Would the fan spin in reverse if the branch circuit black hot wire were connected to the fan white neutral wire and white branch circuit neutral wire to fan black lead?

Absolutely not. If it was one of most types of DC motor, yes.

My boss years ago said the house could catch fire if wires were reversed but I told him I did not believe him because AC current inherently reverses direction in a circuit (60 hertz cycles).

Again, absolutely not. There would be no electrical difference.

I do know that areas of equipment that would normally connect to a neutral would have line voltage if reversed such as a lamp holder bulb threads which may be hazardous to the installer but still would illuminate the bulb.

That's correct. The only thing that makes a conductor hot to ground is grounding another conductor.

 

[Jpflex]

Absolutely not. If it was one of most types of DC motor, yes.


Again, absolutely not. There would be no electrical difference.


That's correct. The only thing that makes a conductor hot to ground is grounding another conductor.

With alternating current I have wandered why a line wire is often regarded more dangerous than a neutral which in some instances is allowed to be non insulated.

I used to wonder if voltage at a neutral would be present or if it would be consumed after the final load in a circuit similar to dc circuits.

However, my current belief is that the neutral only appears less dangerous, allowed to be non insulated and bonded to exposed parts in some situations and touched sometimes without harm only because the entire equipment is placed at the neutral and ground same potential and therefore provided less shock hazard.

The line “hot” wire only appears as “more” dangerous and needs insulation not because it’s more “dangerous” than the neutral but because it is at a different potential than neutral and the two are being separated

This is what I think is hard for new students to understand. The same goes for the confusion as to why the center point xo windings of a transformer can be connected to such a neutral wire and bind to equipment

 

[jim dungar]

The line “hot” wire only appears as “more” dangerous and needs insulation not because it’s more “dangerous” than the neutral but because it is at a different potential than neutral.

Yes.
Line and Neutral are simply two words used as adjectives for conductors, until we create a wiring system.

The NEC basically requires the neutral to be connected/jumpered to ground when the Line-Neutral voltage can be kept to 150V max. This connection creates a reference point for our residential circuits. Reference points are important, for many reasons, so we do the same jumpering even at higher voltages like 277V L-N.

Now once we have the Neutral connected/bonded to metallic surfaces and earth the neutral conductor appears to be safer because touchable surfaces are at the same potential.

 

[LarryFine]

With alternating current I have wandered why a line wire is often regarded more dangerous than a neutral which in some instances is allowed to be non insulated.

Again, the line is dangerous because another conductor is (intentionally) grounded.

I used to wonder if voltage at a neutral would be present or if it would be consumed after the final load in a circuit similar to dc circuits.

It's not "consumed", it's just at (or close to) zero volts to earth because it's grounded.

However, my current belief is that the neutral only appears less dangerous, allowed to be non insulated and bonded to exposed parts in some situations and touched sometimes without harm only because the entire equipment is placed at the neutral and ground same potential and therefore provided less shock hazard.

At the service point, yes; downstream, no, which is why we don't re-bond the neutral.

The line “hot” wire only appears as “more” dangerous and needs insulation not because it’s more “dangerous” than the neutral but because it is at a different potential than neutral and the two are being separated

No. Voltage between conductors is constant. Voltage from line to earth is the "danger."

This is what I think is hard for new students to understand. The same goes for the confusion as to why the center point xo windings of a transformer can be connected to such a neutral wire and bind to equipment

Any one point in a system can be grounded. Corner-grounded delta is an example.

 

[LarryFine]

Check out my "Understanding the Neutral" post again if you need a refresher:

Understanding the Neutral Conductor

Dennis, here's a really basic lesson, and we'll start with direct current, because the fact that we use alternating current is not relevant to the basics: Picture a battery, like you'd find two of in a flashlight. You have a terminal at each end, with a difference in potential of 1.5 volts...

forums.mikeholt.com

 

[Dsg319]

Reverse polarity would have no effect on the operation

The only way to switch the direction of a single phase motor would have to swap around with capacitors correct?

 

[Hv&Lv]

The only way to switch the direction of a single phase motor would have to swap around with capacitors correct?

ok, its a real crude picture I just drew. You would need to swap the main winding and the opposing winding so that the opposing winding now becomes the main winding.
thats all depending on it the ratios of the two coils are the same. Check resistance on the coils.

 

[Dsg319]

View attachment 2571344
ok, its a real crude picture I just drew. You would need to swap the main winding and the opposing winding so that the opposing winding now becomes the main winding.
thats all depending on it the ratios of the two coils are the same. Check resistance on the coils.

Right on. And one is just a start winding?

 

[Jpflex]

Right on. And one is just a start winding?

Possibly yes or no. The capacitor he is showing could be used to create an artificial phase shift impressed on rotor poles in order to initial rotation for a single phase motor

 

[Jpflex]

View attachment 2571344
ok, its a real crude picture I just drew. You would need to swap the main winding and the opposing winding so that the opposing winding now becomes the main winding.
thats all depending on it the ratios of the two coils are the same. Check resistance on the coils.

What you say sounds right since the capacitor along with the 90 degree offset location of primary stator phase windings

 

[Jpflex]

It's not "consumed", it's just at (or close to) zero volts to earth because it's grounded.

I guess this depends on circumstance of the circuit or the reference point of test of test leads.

In a dc circuit specifically you will have a voltage present after a final load if there is resistance in the circuit wire after the final load. This is the concept of focus

Say if we have an ac circuit with the same circuit load and downstream resistance after the final load, will not a voltage be present before the final resistance in the circuit per each frequency cycle that is positive or negative?

 

[LarryFine]

If you mean that voltage drop on the grounded conductor raises it above zero volts to ground, yes.

 

[Jpflex]

If you mean that voltage drop on the grounded conductor raises it above zero volts to ground, yes.

Yes this is what I was getting at

 

[LarryFine]

Yes this is what I was getting at

That's why we treat grounded conductors like ungrounded conductors after the service, other than OCP.