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220v grounding question

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  • 220v grounding question

    I am converting a 220v 30amp dryer connection to use for my 220v 25amp tablesaw (I know it is a little overkill). The dryer plug has (red, white, black). It is capped as we have a gas dryer, the red and black are hot (110 each). The white on the other hand is the old neutral. I have capped the dryer plug and run the circuit to the garage to use with a 5hp 220v tablesaw. Right now the tablesaw is wired, black and white are hot with green being ground. The green(ground) from the tablesaw is hooked to the old white(neutral) from the dryer. The black(hot) from the tablesaw is hooked to the old black(hot) from the dryer. The white(hot) from the tablesaw is hooked to the old red(hot) from the dryer. I am using a locking 250v 30amp plug (NEMA-L6 i believe). In any case, the tablesaw runs (should I say purrs), but I am leary of the ground. Here is the question...

    Can the neutral from the old dryer plug be used a ground for the new plug since it is run to the ground bar in breaker box? To qualify my reasoning, this is a dedicated circuit and the old dryer plug is gone. Logic would tell me yes, but for some reason I have a bad feeling. I understand I might not be 100% in code, but I definitely want to be safe. Any help would be appreciated. Thanks in advance.

  • #2
    NOTE: I am not a electrician or do I play one of TV,

    I would say your probably safe, but what I understand your not code,

    the neutral is not ground and ground is not neutral even if they do connect together at one point in the system, (bonded), and depending on age of the original box there may or may not be a independent ground bar, but if you pull the "neutral" off the neutral bar and put it on to the ground bar, and tape both ends with green tape to indicate it is the ground then I think you would meet code, if both neutrals and grounds are on the same bar, in the main box then there is little to change,

    but if that dryer was wired to day it would be a 4 wire black (hot), red (hot), white (neutral) , and green, (ground). Hot to hot would read about 240, hot to neutral would be 120, and if you would check hot to ground you would also get a 120 volt reading from a hot, and you should get 0 volts, ground to neutral,

    but in your saw you do not need a neutral as your not using any 120 in your saw, if your saw was using some thing in the 120 voltage you would need to run a new ground wire,

    and since the neutral can have a voltage in it if the two different legs are not carrying the same load it is possible to have the neutral to have a different voltage potential than the ground has, and since the concrete floor in your shop is a ground there is a possibility of carrying a voltage potential back on the neutral, to the saw, so it is better to have the ground to a true ground wire and not a neutral wire,

    I will probably get blasted here for saying this but for years the neutral was considered enough for safety, (your dryer was wired that way, setting right besides the washer that was hooked to water pipes that were a true ground, arc welders were wired that way and even ran the fans off the "grounds", ranges, and other appliances, all wired the same, but the code has changed, and some of it is for the proper working of ground fault plugs, and so on, but there is a logical reason to have the ground to the ground,
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    • #3
      I am an electrician. What you're doing is legal, just tape the white wire ends green. You are correct that the ground and common bar are one and the same, as long as it is the main panel, not a sub panel.

      This will work just fine, though I must wonder what you are ripping that needs so much motor.


      • #4
        The price difference between the 3hp motor and the 5hp motor was $100 and this might be the last tablesaw I ever buy. I didn't go totally hog wild, I did get the best bang for the buck in a Grizzly G1023SLWX so I could spend a little more on the motor and accessories and still come out 30%-50% cheaper than the competition. This was a 30th birthday present from my wife and I guess the testoterone was flowing when I put the order in. Besides I would rather overbuy a little just in case than regret it later.

        I do have an awesome blade on it so the smaller motor would have been fine. Hell, I spent more on the blade than my last tablesaw. I was nervous the 5hp motor was going to be loud, but it is actually quieter than most of the sub 2hp tabletop models. The saw is so smooth you can stand a nickel on end and it will not roll or fall when the motor is turned on or off. Of course I had to try it and confirmed it to be true.

        Thanks so much for putting me at ease with the electric info. I have run a lot of 110, but this is the first 220 I have ever run. Time to make sawdust......
        Last edited by RME29; 08-07-2006, 10:45 PM.