No ground wire on dryer plug

[PhaseShift]

A friend of mine recently bought a new dryer, and noticed that the cord on the dryer only had the (2) hot wires and a neutral wire and did not include a ground wire or ground prong on the plug. He was asking me where the ground was and why it was missing.

After thinking about this, the only thing I could come up with, is that he neutral terminal of the dryer must be bonded to the dryer frame inside the dryer. Is this usually how this setup works.

If he finds that this is indeed the case, would it be safer to remove this jumper and buy a new 4-wire/prong cord and connect the ground directly to the frame of the dryer since his outlet has a ground (EGC) coming from the panel?

I didn't think newer dryers would have this 3-wire setup with the frame bonded to the neutral. I guess for a L-G fault, the fault current will return on the neutral? Is there a chance that during normal operation L-N current can flow on the dryer frame since it is bonded to the neutral thus setting up a shock potential.

If he looks at the dryer and sees that it is not bonded inside the this would present a dangerous situation because for a L-G fault there would be no path to ground to clear fault current and this could set up a dangerous potential on the dryer frame and may cause shock or electricution?

 

[jaylectricity]

A friend of mine recently bought a new dryer, and noticed that the cord on the dryer only had the (2) hot wires and a neutral wire and did not include a ground wire or ground prong on the plug. He was asking me where the ground was and why it was missing.

After thinking about this, the only thing I could come up with, is that he neutral terminal of the dryer must be bonded to the dryer frame inside the dryer. Is this usually how this setup works.

If he finds that this is indeed the case, would it be safer to remove this jumper and buy a new 4-wire/prong cord and connect the ground directly to the frame of the dryer since his outlet has a ground (EGC) coming from the panel?

I didn't think newer dryers would have this 3-wire setup with the frame bonded to the neutral. I guess for a L-G fault, the fault current will return on the neutral? Is there a chance that during normal operation L-N current can flow on the dryer frame since it is bonded to the neutral thus setting up a shock potential.

If he looks at the dryer and sees that it is not bonded inside the this would present a dangerous situation because for a L-G fault there would be no path to ground to clear fault current and this could set up a dangerous potential on the dryer frame and may cause shock or electricution?

If it is a brand new dryer, it should have 4 wires unless everything in the dryer runs on 220-240 volts. That's not usually the case. If it were the case you would find no neutral terminal and no bonding strap where the cord connects to the dryer.

Open the dryer panel, if there are 4 terminals, replace the cord with a 4 wire and wire it properly.

If not...well, I don't know what you would do. Maybe change the receptacle to a 3 prong, and leave the neutral wire floating inside the box, taped off.

 

[Buck Parrish]

Some dryers have a little green wire jumper from the frame that you can move to the W or the G terminal. Pull it off the W and move it to the green and buy a 4-wire cord. Some times the delivery persons install the cord and they have been known to do it wrong.
If it's older like jay said. You can wire nut the green jumper to the equipment ground from the cord.

 

[nakulak]

250.142 b (2005)

 

[SG-1]

With the last dryer I purchased I had a choice of plugs so I could match it to my receptacle. Of course none matched, because I had a 4-wire receptacle. That was 20 years ago...

 

[Sierrasparky]

Some dryers are 240v not 120/240. No white just a ground!

 

[PhaseShift]

Some dryers are 240v not 120/240. No white just a ground!

How would the lights and controls work, with no 120V source?

With the dryer frame bonded to the neutral, is there a potential for neutral current flowing through the ground during normal operation and thus causing a shock?

 

[don_resqcapt19]

Most dryers are sold without cords and are internally set up to permit the use of either 3 wire or 4 wire codes. There is no requirement that a new dryer have a 4 wire cord. There is a requirement that if you install a new circuit for the dryer that you must install a 4 wire circuit.

 

[don_resqcapt19]

How would the lights and controls work, with no 120V source?

With the dryer frame bonded to the neutral, is there a potential for neutral current flowing through the ground during normal operation and thus causing a shock?

Under normal conditions there is little potential for shock as the only voltage to drive a shock would be the voltage drop on the neutral conductor. In the case of an open neutral there is serious danger.

 

[Dennis Alwon]

I f this is a standard 120/240 dryer then yes it needs a neutral and a ground. I have installed a few Bosch dryers that used straight 240 volts and was only 20 amps.

There are all kinds of configurations out there. Here is an odd duck. It is 2 separate units- w/d but the washer plugs into the recep. seen inside the dryer access point. There are 2 fuses, etc.

 

[PhaseShift]

Under normal conditions there is little potential for shock as the only voltage to drive a shock would be the voltage drop on the neutral conductor. In the case of an open neutral there is serious danger.

O.K. so during normal operation I guess there would be no current flowing on the dryer frame since it is only bonded at 1 point. If it was bonded at 2 points would this maybe be an issue?

I think I see what you are saying with the voltage drop in the neutral. With the neutral connected and the dryer frame bonded to neutral then when you touch the dryer you are essentially touching a neutral point on the circuits neutral return. The amount of voltage that will drop across your body is equal to the amount of voltage dropped on the neutral since both your body and the neutral will be connected to the panel ground. under normal operation this voltage drop on the neutral should be small and not cause any issues.

However if the neutral broke like you said, then when you touched the dryer you would create a path to ground, and since your body's impedance is much greater than the dryers load impedance, all of the voltage would drop across your body thus causing a shock.

Is the dryer sitting on the ground considered to be grounded and thus will help reduce the voltage dropped across the body in a case where neutral is lost?

If you the dryer frame has a seperate EGC and is not bonded to the netural then you dont have to worry about a broken neutral and there is only a hazard when one of the lines faults to the frame which in that case should clear the fault.

 

[nakulak]

there is always the possibility of a failure causing a touch hazard, which is why on new installation the ground is required. However, the code makes it clear that all the dryers installed before (87 ?) can remain.

so, yes, the best practice is wiring it with the ground.

 

[SegDog]

burned-up

burned-up

On the Saturday after Thanksgiving, I got a call from a lady and she said that she finally got a new electric dryer, and during the first use it started to smell bad. After questioning her I knew she wasn't telling the whole story, but my concern was her safety. I arrived on Monday and she said the installers had to make some changes to the wiring. Since it still had an old 3-wire and I didn't know what they possibly could have changed, I just told her that I'm putting in a new 4-wire circuit from the panel. When I took the cover off the old disconnect, I saw what was smelling; the charred insulation and melted plastic. The dryer had a white pigtail coming off of the white wire that was part of the assembly going to the terminals. That white and the green EGC were connected to the frame. I separated and capped the pigtail.

It used to be that the number one cause of residential fires was the clothes dryer. Although it was a lint problem rather than wiring, I have paid quite a few bills telling the home owner about upgrading their dryers. I now carry an extra vent kit, 6 foot 4-wire plug/receptacle, and learned how to properly install and repair sheet metal. Now everyone is happy!

 

[don_resqcapt19]

O.K. so during normal operation I guess there would be no current flowing on the dryer frame since it is only bonded at 1 point. If it was bonded at 2 points would this maybe be an issue?

Still only a voltage drop issue, assuming that there are no problems with the neutral.

I think I see what you are saying with the voltage drop in the neutral. With the neutral connected and the dryer frame bonded to neutral then when you touch the dryer you are essentially touching a neutral point on the circuits neutral return. The amount of voltage that will drop across your body is equal to the amount of voltage dropped on the neutral since both your body and the neutral will be connected to the panel ground. under normal operation this voltage drop on the neutral should be small and not cause any issues.

Exactly.

However if the neutral broke like you said, then when you touched the dryer you would create a path to ground, and since your body's impedance is much greater than the dryers load impedance, all of the voltage would drop across your body thus causing a shock.

Correct.

Is the dryer sitting on the ground considered to be grounded and thus will help reduce the voltage dropped across the body in a case where neutral is lost?

This will not really change the voltage across the persons body.

If you the dryer frame has a seperate EGC and is not bonded to the netural then you dont have to worry about a broken neutral and there is only a hazard when one of the lines faults to the frame which in that case should clear the fault.

That is correct only if the open neutral is on the load side of the main bonding jumper. If the open is on the line side of the main bonding jumper there is a shock hazard to anyone that is touching any conductive object that is connected to the EGC and touching earth or some grounded conductive object that is not bonded to the electrical grounding system.

 

[don_resqcapt19]

I f this is a standard 120/240 dryer then yes it needs a neutral and a ground. ...

Dennis, I am not aware of any residential use 120/240 volt dryer that cannot be used with a 3 wire cord.

 

[PhaseShift]

This will not really change the voltage across the persons body.

Why wouldn't it? If the dryer frame was bonded to ground either intentionally or by nature of the ground it was sitting on, then wouldn't this be a small resistance to ground in parallel with the larger resistance of the human body touching the dryer frame? Becuase this would lower the resistance then the greater resistance would most likely be the remote earth connection from the ground surface to remote ground on the dryer end, and the resistance from remote earth to the gound rod on the source end. Wouldn't then most of the voltage drop across these two seires resistances and not across the now small resistance created across your body due to the low resistance parallel bonding.

During normal operation if the dryer is sitting on the ground, then wont some of this current flow though the ground to earth back to the source?

That is correct only if the open neutral is on the load side of the main bonding jumper. If the open is on the line side of the main bonding jumper there is a shock hazard to anyone that is touching any conductive object that is connected to the EGC and touching earth or some grounded conductive object that is not bonded to the electrical grounding system.

So as an example if the main bonding jumper is in the panel and the neutral is cut between the panel and transformer, then when you touch an EGC you are creating the path for the neutral current to flow though ground back to the transformer and thus can result in shock. Esentially since the neutral is lost and the neutral is bonded to EGC then neutral current will use your body and ground as path back to source?

 

[LarryFine]

Why wouldn't it?

Simply, because the 120v portion of the dryer's internal circuitry (drum motor, timer, light(s), everything but the element) will have a much lower impedance than the dryer-feet-concrete-earth-electrode-GEC-neutral pathway, and thus the dryer-to-earth voltage will still be almost 120v.

When you parallel that convoluted pathway, you will be subject to that almost-120v potential. A customer of mine got caught between the range and the kitchen sink. I found that the neutral conductor of the 3-wire flat cord pulled right out of its crimped-on lug inside the wiring compartment.

Upon further investigation, we discovered that the range had been relocated. I found the plug end of the range cord under the house, with the original SE cable conductors pared down to three strands each and fed through the plug prongs and wrapped around them, then wrapped in tape.

The shocked customer (pun intended) mentioned that the range clock and lights had not worked for a few months. That's how long the range cabinet had been energized, and they somehow hadn't happened to span the range to the sink in all that time. Luckily, it wasn't one of their kids.

 

[zappy]

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?

 

[don_resqcapt19]

Why wouldn't it? If the dryer frame was bonded to ground either intentionally or by nature of the ground it was sitting on, then wouldn't this be a small resistance to ground in parallel with the larger resistance of the human body touching the dryer frame? Becuase this would lower the resistance then the greater resistance would most likely be the remote earth connection from the ground surface to remote ground on the dryer end, and the resistance from remote earth to the gound rod on the source end. Wouldn't then most of the voltage drop across these two seires resistances and not across the now small resistance created across your body due to the low resistance parallel bonding. ...

The connection to earth does not make the voltage "go away"...it is just another path. We are not making a voltage divider here, we are making a current divider. The only way a connection to earth makes the voltage "go away" is when it causes the OCPD to open the circuit.

 

[PhaseShift]

Simply, because the 120v portion of the dryer's internal circuitry (drum motor, timer, light(s), everything but the element) will have a much lower impedance than the dryer-feet-concrete-earth-electrode-GEC-neutral pathway, and thus the dryer-to-earth voltage will still be almost 120v.

When you parallel that convoluted pathway, you will be subject to that almost-120v potential.

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?

The connection to earth does not make the voltage "go away"...it is just another path. We are not making a voltage divider here, we are making a current divider. The only way a connection to earth makes the voltage "go away" is when it causes the OCPD to open the circuit.

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?

Current will be determined by the ipmedance between frame and ground return?

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?