Here is a picture of the incoming wires to my main circuit breaker:
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If we follow those three wires *back* to the nearest transformer, what do they look like (in terms of phase relationship to each other)?
If we follow those three wires *forward* to the first circuit breaker, what do they look like (in terms of connection to the literal earth of the ground)?
Note: This question is an offshoot of a 220v dryer question; but this question is asked to get to the root of *what* it is that is entering the house in the first place.
Hmmm, Your question has been answered more than once throughout this thread. If still did not get it. You really ought to follow the wires upto the main breaker panel. One note: Gnd and Neutral is connected together but they are not same in functionality in the circuit.
Hi, How is your house electric system grounded? I still think your dryer is not grounded well. Measure between the dryer chassis(body) and ground point in Ohm scale on your meter. Do you read zero Ohm or fraction of Ohm? Also you should read zero Ohm between gnd(dryer body) and neutral on your dryer.
If it is all OK, some one else mentioned heating element sagging when hot rubbing on the dryer chassis not enough to kick the breaker but give spark and shock specially when hand is moist(doing washing)
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Danny:
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If you can e-mail me, I'll send you a write-up that answers your question on what goes on both upstream and downstream of your electrical panel.
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So far as an electrical spark inside the dryer goes, I would look for any wires inside the dryer that are rubbing against the rotating dryer drum. In time, the drum will rub it's way through the insulation, and contact the copper conductor. Then, depending on WHICH wire is rubbing against the drum, you can get a shock from the dryer by touching the drum while it's running, or only when the heating element is heating, or only during the Permanent Press cool down cycle, or whatever. I'd at least make sure that no wires are touching the rotating drum.
I hate to display ignorance, and I know I should know this.
But maybe somebody can explain.
The power lines are 3 phase, meaning they're 120 degrees out of phase to ea ch other allowing 3 wires to carry what 6 wires should (since they're gener ated by 3 sets of coils at the power plant).
The house is fed by just one of these wires, through a center tap transform er. That transformer sends 3 wires to the house: Neutral, +120 volts, -12
0 volts. Connect the two hots and you get 240, connect either hot to the n eutral and you get 120. Your safety ground is bonded to the neutral and so you should also have 120 from any hot wire to the ground. Neutral is the center tap.
Here's what I'm not getting at the moment. What are the connections to tha t transformer? If it is 3 phase leg to neutral on the primary side, then t he center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I'm pret ty sure it is.
each other allowing 3 wires to carry what 6 wires should (since they're gen erated by 3 sets of coils at the power plant).
The 6 vs three makes no sense.
rmer. That transformer sends 3 wires to the house: Neutral, +120 volts, -
120 volts. Connect the two hots and you get 240, connect either hot to the neutral and you get 120. Your safety ground is bonded to the neutral and so you should also have 120 from any hot wire to the ground. Neutral is th e center tap.
hat transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, righ t? Which would mean that house neutral is NOT at ground level. But I'm pr etty sure it is.
All the neutrals are tied to ground. Why would you expect the neutral on the secondary to not be at ground level? In the strictist sense, if you take a center tap transformer, the secondary side doesn't have to have any relationship to the potential on the primary side. It's can be completely seperate, it's a seperate winding not connected to the primary. What and how you hook it up determines what level anything is referenced to. In the power transformer case, the center tap (neutral) is tied to ground.
that transformer? If it is 3 phase leg to neutral on the primary side, th en the center tap should be above neutral on the secondary (house) side, ri ght? Which would mean that house neutral is NOT at ground level. But I'm pretty sure it is.
Well, you're not seeing the problem. I wish I could draw here.
Your transformer has two wires going in, and three going out.
I don't know what primary is in my neighbor hood, let's say 2400 vac for an example. Which two wires do we use? You only have the choice of leg to l eg, or leg to neutral.
Choose leg to neutral: use a 10 to 1 turns ratio, your secondary will be 2
40 volts line to line. Then center tap it, and you get 120 from each line to center.
BUT: why would center tap be anywhere near neutral?
Choose leg to leg: does the same problem exist?
Once it gets into the house I understand how it works, but on the pole I'm hazy.
By the way you are dead wrong on the 6 wires thing. That part I do remembe r.
The secondary centertap is the "neutral" because it carries the imballance of the current in the secondary hot wires - the ends of the
240V winding. That is a common definition of a "neutral".
The secondary has no relationship to the primary, it is isolated from the primary.
The secondary relationship to earth depends on how the secondary is connected. The "neutral" (centertap) is earthed at the transformer. The neutral is then also earthed at the building. That limits the maximum voltage in the building with respect to the earth.
Anywhere from 11,000 to 30,000 VAC, single-phase + transmission neutral, enters the transformer which has a primary winding and a secondary winding used to drop the distribution voltage to the service voltage. The secondary winding is 'center-tapped' and connected to GND. L1 and L2 are connected to the main breaker in your service entrance panel. The N conductor from the pole pig is connected to the grounded (neutral) bus-bar in the service entrance. The grounding bus-bar in your service entrance is connected to a service ground associated with the premises and that bus-bar is bonded to the grounded bus-bar in your service entrance (and _only_ in your service entrance, not downstream subpanels).
Note that the primary side of the pole pig is single phase for most residential applications. The secondary side splits that single phase.
to that transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I' m pretty sure it is.
an example. Which two wires do we use? You only have the choice of leg to leg, or leg to neutral.
It's one of the 3 primary phases to primary neutral.
240 volts line to line. Then center tap it, and you get 120 from each lin e to center.
The center tap has no relation in terms of potential difference to anything other than the two ends of the secondary, until you connect it to something. The center is called the neutral and as part of the installation, it's run to the house and also tied to ground. Now the neutral of the transformer is at the same potential as ground.
You would go from 6 wires to 3 wires in a distributions system if and only if you were to consider the 6 wire system as the only other alternative to deliver power. That is that you have fixed in stone that you're to have a generator with 3 windings, delivering
3 phases via 6 wires to the load. Of course if you start with that, then a balanced 3 phase load reduces the wires in half.
But that isn't the real world. No one would do it that way to begin with. There are other alternatives and even a single phase system can deliver the same power without 2X the wires. 3 phase does use less copper and is better for other reasons as well. But it's not a miracle. The current carrying capability of the conductors is what it is and
3 wires can't suddenly carry the same current as 6. As i recall, the reduction in copper you get with 3 phase is around 25%.
Well... There are two AC wires that are opposite, yes. If you said they were +120wt and -120wt, you would have a point (w being the angular frequency, or 2*Pi*f and t=time).
Yes.
Assuming no faults and ideal wires, sure.
Yes. ...which is grounded.
Yes. Almost always, though it really doesn't matter.
No. The center tap is grounded at both the transformer and the entrance panel. It *is* ground.
It is. I don't see your problem. You described things pretty well.
Because that's how it's wired. You *DEFINED* it as being 0V and connected it to ground.
No. There is no problem. Remember that transformers isolate. The secondary can be at any voltage you desire it to be, regardless of the primary (within the breakdown limits of the transformer, obviously). You connected one of it's secondary terminals to ground, defining that as 0V. Everything else falls out from there. You could have connected it to 1000V, but that wouldn't be smart. ;-)
There isn't any difference how it's connected there. You may have heard of "Delta" or "Wye" connections. Delta, connects the primary of the transformer between phases. A "Wye" connection would be from phase to ground. In the US, almost all loads are connected as "Wyes" and generators as "Deltas". I'm sure there are exceptions but that's what you'll find on your pole.
And if you said they were 180 different in phase from each other, relative to the neutral, you would also be correct.
KRW only understands opposites, not phase.
Yes because the two hots are 180 deg out of phase with each other. If they weren't you wouldn't get 240V
The center tap is by definition the neutral. Connecting it to ground ties it to ground potential. It's like if you had a battery in your hand, and someone saying the negative terminal is above earth/ground potential. It makes no sense. It has no realtion to anything when it's not hooked up to anything. Hook the neg end of the battery to ground and now that end is at ground potential.
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