10-2 w/ Ground for dryer 220v?

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  #1  
Old 06-22-04, 02:38 PM
Iceman
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Question 10-2 w/ Ground for dryer 220v?

Ok - I've read through many threads relating to my particular question but nothing hitting it straight on.

The situation: Three years ago the service was upgraded in the house I moved into. The existing setup was inspected at that time and apparently considered ok. At that time the dryer was wired with an existing outer cloth-insulated 10-3 wire (inside plastic insulated red, black and white conductors). Now, I wish to move the dryer about 10 feet. In the house, there is a length of 10-2 with (paper insulated) ground tacked up in the joists which would be long enough to reach the new dryer location from the breaker box. Presumably, this 10-2 with (paper insulated) ground was used for the dryer in days gone by, though I am just speculating.

Now, the questions: Will the 10-2 with (paper insulated) ground wire be as safe as the 10-3 wire (insulated red, black and white wires) if used with my 220 volt 3-prong dryer outlet? Can the (paper insulated) ground conductor be connected similar to the insulated white neutral in the existing setup?

I understand that code would require switching to a four wire installation. But my question remains: Is the paper insulated ground conductor as safe as the plastic insulated white conductor when connected to the neutral bar in the described situation?

That's it. Thanks in advance for your advice...Iceman
 
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Old 06-22-04, 02:50 PM
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A strict interpretation of the code would say that you cannot extend this at all. You need to replace the wiring all the way back to the panel with 10/3 with ground. You'd have to check with your inspector to see if he/she is going to interpret the code this way.

Even if the inspector allows the extension, you absolutely may not use the 10/2. The reason is that the paper is not an insulator (no matter how many times you use the term "paper insulated"), and you cannot use an uninsulated wire as a neutral conductor. You need to go buy ten feet of 10/3. If at all remotely possible, buy enough to reach all the way back to the panel. Now is a good time to upgrade to modern codes and improve safety.
 

Last edited by John Nelson; 06-22-04 at 03:02 PM.
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Old 06-22-04, 02:54 PM
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IMHO the installation that you propose (using an existing 10-2 with bare ground rather than the existing 10-3 without ground, in both cases using the same conductor as both the ground and the neutral) would be approximately as unsafe as the current installation. I base this on the assumption that you would use a plastic box, that this cable goes back to your main panel, and that there are no other cables or junction boxes connected to the ground in this cable.

I should note, however, that the NEC permits the 10-3 with the _insulated_ white wire to be grand-fathered for this sort of installation, but does _not_ permit 10-2 with bare ground to be grand-fathered for this installation. Thus what you propose would clearly violate the NEC. Additionally, if there isn't already a dryer outlet on this 10-2, then grand-fathering wouldn't apply, this is a new installation.

If your dryer does not require the neutral, and is a pure 220V appliance, than you can use the 10-2 and be code compliant. The only issue is sharing the neutral and the ground.

IMHO you are in a basement with exposed studs, and you are doing the work to install and outlet and move the dryer. Don't waste your time doing a half assed job. Buy and install the correct cable. The life you save may be your own.

Finally, have you confirmed that 30A is sufficient for your current dryer? Many require more.

-Jon
 
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Old 06-22-04, 02:57 PM
doingitmyself
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Originally Posted by John Nelson
A strict interpretation of the code would say that you cannot extend this at all. You need to replace the wiring all the way back to the panel with 10/3 with ground. You'd have to check with your inspector to see if he/she is going to interpret the code this way.

Even if the inspector allows the extension, you absolutely may use the 10/2. The reason is that the paper is not an insulator (no matter how many times you use the term "paper insulated"), and you cannot use an uninsulated wire as a neutral conductor. You need to go buy ten feet of 10/3. If at all remotely possible, buy enough to reach all the way back to the panel. Now is a good time to upgrade to modern codes and improve safety.
John, did you mean to say that he "absolutely may not use 10/2?

I think what Iceman's missing is that he needs two hots (for the 220-v) and a neutral (for the 120-v parts of the fryer), plus a ground for this 220V Dryer. Therefore, 10/2 won't work, since there's no 120-v return?
 
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Old 06-22-04, 03:03 PM
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Thanks. I did indeed leave out the word "not". I have since edited it into my original reply. Good catch.
 
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Old 06-22-04, 03:05 PM
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Finally, have you confirmed that 30A is sufficient for your current dryer? Many require more.
I have yet to see a residential dryer that requires more than 30 amps. Is this a new trend? Can you cite us a make and model? I'd like to check this out.
 
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Old 06-22-04, 03:13 PM
doingitmyself
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ah, I see - he wanted to use the "paper insulated" ground as the neutral. Of course, the paper comes off very very easily, so even if paper was an insulator, it wouldn't be a good one in this case.
 
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Old 06-22-04, 04:59 PM
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Regarding dryers >30A...my error. I took 4800W and 240V, and got 30A and a requirement for >30A OCPD and conductors. Stupid maths error Further, I think that I cross read the NEC section on ovens for the section on dryers. Bad cold today. I hate summer colds.

-Jon
 
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