No ground wire on dryer plug

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jghrist said:
250.140 does not allow this if there is a grounding conductor present in the outlet.
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That is correct. The dryer can be used on either type of existing ciruit. You would match the cord to the circuit. Of course if you are installing a new circuit it would have to include both a grounded and grounding conductor.
 
PhaseShift said:
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Maybe this is my problem I am thinking of it as a voltage divider. But in essence wont the voltage across your body be determined by a voltage divider setup by impedances, with the intentional bond to ground creating a parallel low impedacne with body? ...
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It is a parallel circuit...the voltage is the same across the impedances that are in parallel. If the frame of the equipment is energized and in contact with the earth, the person is in parallel with the frame of the equipment.
 
PhaseShift said:
Yes but what if you intentionally bond the dryer frame to ground. Wont the low impedance of this intnetional bond create a parallel low impedance with the body thus dropping the majority of the voltage elsewhere?
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Yes, which is exactly why they decided to require a separate grounding conductor. If a neutral opens, the load side of that open conductor will no longer be at, or close to the supply's neutral voltage, which should be at, or close to zero volts.

If the neutral is being used as the grounding conductor, everything that is expected to be at zero volts will becone energized, unless a separate EGC is used. With a separate EGC, the appliance cabinet will not become energized even if the neutral opens.

Maybe this is my problem I am thinking of it as a voltage divider. But in essence wont the voltage across your body be determined by a voltage divider setup by impedances, with the intentional bond to ground creating a parallel low impedacne with body?
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Yes, that is correct. They stopped the allowance for the neutral to double as the EGC is to prevent the hazard of energized surfaces when the supply neutral is lost.

That internal bond jumps the now-energized load neutral to the now-energized appliance cabinet. With a separate EGC, an open neutral cannot energize the appliance.

Am I right in understanding your explanation as to what happens when you loose a neutral on the line side of the main bonding jumper?
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I believe so. When that happens, only the earthen pathway between the source's electrode and the load's electrode remains, and is generally very bad at it. In cities with a metal water supply, one house's neutral is tied to the neighbors' neutrals, so they seem to function okay, at least until a water meter is removed.

Then, the open-neutral syndrome occurs, and what is normally at zero volts to earth is suddenly energized, and is now a hazard around any still-grounded surfaces. See my description of the shocked customer a few posts ago. His range's cabinet was hot, and had been for a while, and one day, he happened to bridge the voltage.

Often, people will receive a shock when touching an appliance, and while it's likely the appliance is indeed the offender, it could also be the 'reference' that is hot. A shock is a current caused by a potential difference between two points. It matters not which of the points is grounded, unless one of them really is grounded.

I usually use a solenoid-type tester (to present a real load) with an extension cord that is plugged into a known-properly-wired receptacle, giving me 3 references. If a whole house is behaving strangely, and non-electrical surfaces that should be grounded are shocking, I'll plug that cord into a neighbor's house if possible.

As often mentioned here, an entire house is supplied as a 3-wire circuit, with the neutral being used as the EGC. The main reason we don't get shocked by a whole house with an open neutral is because the entire house becomes the energized cabinet, and the bonding minimizes the voltage between various should-be-grounded items.

With plastic water supply and no other metallic connections between the house and the outside world (which includes the utility neutral), the house's bonded systems all become energized like a giant appliance, and the only symptoms are burned cable-TV shields (or sparks at the TV) and shocks from outside water spigots.

So, the extent of energization of normally-grounded surfaces depends on where in the system the break in the normally-low-impedance pathway occurs. The closer to the source, the greater the magnitude of the affected area in terms of the circuits involved. All of this info is important in troubleshooting.
 
Larry, are you saying if the dryer's frame is grounded thru the neutral conductor, and you loose that neutral anywhere, the frame automatically becomes energized?
 
zappy said:
Larry, are you saying if the dryer's frame is grounded thru the neutral conductor, and you loose that neutral anywhere, the frame automatically becomes energized?
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If you loose the neutral anywhere between the dryer and the source then yes the frame can become 120 VAC to ground.
 
zappy said:
Larry, are you saying if the dryer's frame is grounded thru the neutral conductor, and you loose that neutral anywhere, the frame automatically becomes energized?
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To expand on Bob's response, anything on the load side of the break can become energized, because of a combination of the equipment enclosure being tied to the neutral and current through any line-to-neutral part of the load.

It's the exact same thing as an open neutral to a service. Unless the two opposing line-to-neutral loads happen to match, the voltage on the normally-zero-volts-to-earth neutral rises. In the house, we see it as a voltage imbalance.

However, to the outside world, the entrire house's "ground plane" becomes energized. We don't notice that because we're inside the "box", but outside, the normally-grounded surfaces, such as the meter base and water taps, are hot.

So, whether the dryer's cabinet is a shock hazard depends on whether you're inside the box (or the house), where you're safe, or outside the box (or the dryer), standing on a concrete floor. Remember, it's not voltage that zaps, it's current.

So, the literal answer to your questions is "Yes, any time the dryer is on, so there is a path between an energized conductor and the now-energized appliance cabinet through part of the load."
 
LarryFine said:
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So, the literal answer to your questions is "Yes, any time the dryer is on, so there is a path between an energized conductor and the now-energized appliance cabinet through part of the load."
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Actually the dryer wouldn't even have to be on to energize the frame if the neutral were lost line-side. It would be enough to open the door and send power to the light bulb.
 
PetrosA said:
Actually the dryer wouldn't even have to be on to energize the frame if the neutral were lost line-side. It would be enough to open the door and send power to the light bulb.
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True, although our dryer has no bulb, so I didn't think about it.

For this conversation, the light is included as the dryer being on.
 
zappy said:
Why after so many years of it being OK for the neutral to be connected to the frame, it's now a violation? Where people getting shocked?
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I thought that older dryers didn't have a need for a neutral. That both the heating element and the motor were 220V. Now they have electronics and timers and other stuff that uses the neutral.

I could be wrong, it just seems logical.
 
jaylectricity said:
I thought that older dryers didn't have a need for a neutral. That both the heating element and the motor were 220V. Now they have electronics and timers and other stuff that uses the neutral.
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RETRAINDAILY said:
when was a kid we ran 3 wire dryers then some time in the 90's in changed to 4 wire
Same with the range, it was 2 hots and a ground, ran timer, light, ect.
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In response to both of these posts, it was always two hots and the neutral, which was permitted to do bonding tasks in the past.

The separate EGC is what was added, not the neutral. You were permitted to use either an NM cable without EGC or an SE cable.
 
LarryFine said:
To expand on Bob's response, anything on the load side of the break can become energized, because of a combination of the equipment enclosure being tied to the neutral and current through any line-to-neutral part of the load.

It's the exact same thing as an open neutral to a service. Unless the two opposing line-to-neutral loads happen to match, the voltage on the normally-zero-volts-to-earth neutral rises. In the house, we see it as a voltage imbalance.

However, to the outside world, the entrire house's "ground plane" becomes energized. We don't notice that because we're inside the "box", but outside, the normally-grounded surfaces, such as the meter base and water taps, are hot.

So, whether the dryer's cabinet is a shock hazard depends on whether you're inside the box (or the house), where you're safe, or outside the box (or the dryer), standing on a concrete floor. Remember, it's not voltage that zaps, it's current.

So, the literal answer to your questions is "Yes, any time the dryer is on, so there is a path between an energized conductor and the now-energized appliance cabinet through part of the load."
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Just so I understand, The frame has no EGC connected to it. It has the neutral connected to it. You lose that neutral connection, so now you have nothing grounding the frame. Why would there be any electricity on the frame? Is it like a car, where the frame is being used as a conductor for neutral current? Where not talking about some loose hot wire that just happens to be touching the frame are we? Bare with me, I'm not the sharpest tool in the shed.:D
 
zappy said:
Just so I understand, The frame has no EGC connected to it. It has the neutral connected to it. You lose that neutral connection, so now you have nothing grounding the frame. Why would there be any electricity on the frame? Is it like a car, where the frame is being used as a conductor for neutral current? Where not talking about some loose hot wire that just happens to be touching the frame are we? Bare with me, I'm not the sharpest tool in the shed.:D
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On MY dryer, the drum lamp is 120V connected, I ASSUME, from phase to neutral. If neutral is also frame ground, the frame will have 120 to (cold water pipe or washer frame?) through the lamp filament.
 
zappy said:
Just so I understand, The frame has no EGC connected to it. It has the neutral connected to it. You lose that neutral connection, so now you have nothing grounding the frame. Why would there be any electricity on the frame?
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Because the dryer has line-to-neutral loads within it. Every dryer I've seen only powers the heating element from line-to-line; everything else is powered line-to-neutral.

The timer motor or electronics, the drum motor, any lights, etc., are all 120v components. This way, the dryer functions on either 120/240v or 120/208v, just at 3/4 the heating power.

Is it like a car, where the frame is being used as a conductor for neutral current? Where not talking about some loose hot wire that just happens to be touching the frame are we?
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No, although that would be a hazard with an open neutral/EGC as well, because the loss of the neutral menas the loss of grounding. The cabinet is energized wither way.

In a car, the frame functions as the grounded circuit conductor. In a 3-wire-supplied dryer (or range), the frame is bonded to the grounded circuit conductor.
 
Note in this pic that the only thing connected to L2 is the heater element (through the drum-rotation switch):

CC57668.jpg
 
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