I've been trying to figure if the cold wire of a three wire dryer is a neutral or ground. I'd thought it was a ground, but some folks on the list and on the web thought it's a neutral.
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10 years ago
220V dryer sparked on startup (3 wire) What to test?
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10 years ago
Looks fine, on my web browser.
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10 years ago
It may or may not be to code, but I'd sure want to put an external ground on my drier, if it sparked.
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10 years ago
No, it's not. It's one phase.
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10 years ago
It *is* a ground. It's connected to the case of the appliance. Would you connect a neutral to the case?
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10 years ago
It's also connected to the ground bus inside the box, not the neutral bus. Uninsulated, too.
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10 years ago
Oh, now I'm all confused.
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10 years ago
Hi, It's called bi-phase. aka Edison circuit.
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10 years ago
In a 3 wire dryer circuit it is acting as a neutral and as a ground. It is more of just what you want to call it. As most dryers use the 120 volts from one leg to power the control circuits and light , the third wire is acting as a neutral. At the same time it is connected to the frame of the dryer and is acting as a neutral. I am sure if you search the electrical code there will be some name for this wire.
On the 4 wire dryer wiring , you do have a seperate ground and neutral wire, but they both connect to the frame of the breaker box so in effect it is just one wire but they go to two differant places on the dryer. Outside the fact they may be differant sizes and color code differantly to meet the code it would not really mater which wire was hooked to the neutral or ground at the dryer as they both go to the same place in the breaker box.
Having a seperate ground wire for the dryer just gives an extra layer of protection.
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10 years ago
Wrong. It's called "split-phase". ...because that's *exactly* what it is. Two-phase is something entirely different (and quite rare).
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10 years ago
The NEC previously allowed the *neutral* for ranges and dryers to also be used as the ground. It is not allowed now for new circuits, but is explicitly grandfathered for old circuits that were compliant when installed.
There are a number of limitations on using the neutral as both neutral and ground. One of them is the circuit has to originate in the service panel. The neutral and ground are bonded at the service. It has to originate on the neutral bus. In many panels the neutral and ground bus are the same. If there is a separate ground bus that only connected to the enclosure the wire can not be connected there.
Another limitation is uninsulated wires in romex can not be used.
From gfretwell in a recent post: "During WWII they jammed through an exception allowing the neutral to also be used as the ground to save copper. In the 1996 code cycle CMP 5 finally accepted Phil Simmon's assertion that the war was over and they should dump this exemption for new circuits. (existing can stay)"
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10 years ago
That is true. But I have to be careful here. You said that the neutral *always* carries current. I know what you mean, but there are some here who insist on all cases being covered. So, to be correct, it should be said the neutral carries the unbalanced portion of the load in that 240V circuit. Whew. I hope DD feels better now. The ground doesn't carry current unless something is wrong.
correct
Basically correct.
It's tied to the ground system of the house at the panel.
It is for 3 wire appliances that were permitted to be installed that way prior to the 90s when the code was changed. They use one conductor for both the ground and the neutral.
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10 years ago
Assuming that was prior to the mid 90s, then it was code to use a single conductor for both the neutral and the ground. If you did it after that, it's a code violation.
Even if it was an old house, if you were doing new wiring, it has to comply to current code.
Hopefully it's also tied to the ground at your house panel or else it's a major code violation.
It's a more than semantics.
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10 years ago
I agree it is single phase and commonly called "split phase".
I have never heard of bi-phase.
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10 years ago
Wrong. The two hots are out of phase by 180.
Wrong. Any two of a 3 phase system are out of phase by
120. But what comes into your house originates from just one of those via a center tap transformer.
Current from the unbalanced portion of the load flows in the neutral. As others have pointe out, in the case of your dryer that could be things like the timer, the light, etc.
It's both.
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10 years ago
Nonsense. 180 deg out of phase and opposite sign are the same thing. Hook up a scope and you'll see.
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10 years ago
180 degrees out of phase and opposite are the same thing. Look at it on an oscilloscope. What the exact method of generating it is doesn't matter. If you have 3 wires entering a box, the relationship between them is what it is, regardless of how it's generated or what you call it.
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10 years ago
No it's not. I thought you were an engineer.
Wrong. But you're good at that.
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10 years ago
There is however a big difference. The neutral carries current. Unhook a neutral and grab hold of it in a properly functioning circuit and you could be dead. Unhook a ground wire, and unless something is malfunctioning, that can't happen.
.By that standard, the ground on any 3 prong 120V outlet is similarly redundant. Could just as well connect the ground there to neutral.
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10 years ago
Wrong. I thought you were an engineer.