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Thread: Saw Question

  1. #1
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    Saw Question

    A friend of mine recently got a great deal on a nearly new Hawk scroll saw. $300 for it and it is the bigger model. Looks brand new!

    Anyway, he said he was reading the manual and it stated do not plug the variable speed saw to a GFI circuit. He has made three attempts to contact the company via e-mail to find out why, and is not getting a response. All his shop outlets are GFI protected.

    Anyone know why it should not be plugged into a GFI circuit?
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  2. #2
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    From an article on VS pump motors and GFCI issues :

    Why do variable speed pumps require a different type of GFCI than other pumps that have single-speed induction motors?
    All variable speed motors have switching power supplies which induce line harmonics. Effectively, line harmonics are a distortion of the electrical waveform provided by the utility company. Line harmonics can be generated by any electrical appliance that uses a variable speed motor, such as dishwashers, washing machines, etc. IntelliFloŽ is not unique in this regard; any appliance that uses a variable speed drive/motor may induce some line harmonics. A variable-frequency drive is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. By controlling the speed of a motor attached to a swimming pool pump, users can save energy by allowing the exact volume of water moved to match the requirements of the pool system. Significant efficiency gains can be realized by using variable speed pumps, resulting in large decreases in power consumption. However, the nature of variable speed appliances means that it is impossible to avoid the presence of line harmonics caused by their variable frequency drives.

    I notice GFCI compatible variable speed devices specifically advertised. Unless his GFCI is at the breaker box or the head of the circuit, he could just swap the outlet(?).
    Last edited by glenn bradley; 10-03-2013 at 04:51 PM.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  3. #3
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    My little Jet mini variable speed lathe consistently pops the GFI circuit. Only works on a non-GFI protected circuit. Don't know why, but Glenn's harmonic idea sounds like the culprit.

  4. #4
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    Thanks, Glenn. I forwarded your response to him. If he is lucky, the electrician that wired his nice shop realized there are many VS tools used in a wood shop and used the correct type GFIC. Not sure how he will know but must be something that tells him.
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  5. #5
    That's interesting.

    All the 110 v ac outlets in my shop are GFCI protected.

    My Jet Mini didn't have any problems and my variable speed Excaliber scroll saw works okay too.

    And....yet..... when I was building my shop, I did all the electrical. Something in my home required the services of a licensed electrician. I hired one and asked him to take a quick look at my shop electrical I was currently installing. He looked and he said it was better than he could afford to do and compete with other bids. He also advised me to get it inspected and then remove the GFCI at the head end of my 110 v ac circuits as motors would trip the GFCIs. Nothing...my air compressor, drill press, Jet Mini, scroll saw....nothing has had a problem.

    I would call the company's customer support and ask them to explain the recommendation.
    Ken
    ------



  6. #6
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    I'm wondering if GFIC circuits have become made VS proof over the years. There seem to be more and more VS items available. Maybe that portion of the Hawk's owner manual has just never been updated. And Ted's GFIC is an old one My friend ran his saw and it didn't trip anything.
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  7. #7
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    Quote Originally Posted by Paul Douglass View Post
    And Ted's GFIC is an old one...
    Not quite prehistoric, but getting there

  8. #8
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    Quote Originally Posted by Ted Calver View Post
    Not quite prehistoric, but getting there
    Are you talking about the GFI or yourself?
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  9. #9
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    I should probably add that I have fairly modern GFCI's at the head of my 110v circuit legs and my VS DeWalt scrollsaw has never been a problem .
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

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