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My new Oneida bench top dust collector works fine on non protected circuits, but it trips all the GFI as soon as I plug it in (with the fans off). I asked Oneida but they have not heard of this yet. The product has only been out a few months.

I figure there are capacitors in the DC, as it has 6 fans that vary in speeds from stop to high. I am thinking it is the capacitors that cause the imbalance, since it happens on all protected circuits immediately upon plugging in, with the unit off.

My solution is to remove the GFI on one branch and use the unit on that branch. I am looking to confirm my theory and ask is it safe to remove the GFI from one branch?

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    Big motors tend to do that. When I was a carpenter we often had trouble running miter saws on kitchen circuits, for example.
    – isherwood
    Apr 27, 2021 at 18:37
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    This may violate code in your jurisdiction. Since it is new I might try another GFCI circuit and if it still Tripp’s the GFCI return it to the mfg. can the electronics in motor circuits cause a GFCI to trip Yes. My state has legal ways to eliminate the GFCI with equipment known to have problems but since this is the first the company has heard of it it sounds defective, verify with a second circuit test 2 strikes I don’t think I would want a 3rd. Not sure why I could not edit , but seeing Isherwoods comment I have some saws that trip the breaker (not GFCI) on first start and every now and then
    – Ed Beal
    Apr 27, 2021 at 18:43
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    Not clear whether you have GFCI breakers or GFCI receptacles. If you have GFCI receptacles, try replacing with a different brand of GFCI, as the electronics may be ever so slightly different enough to make a difference. Also, check for continuity (or low resistance) between the ground and neutral pins. Apr 27, 2021 at 18:56
  • Thanks Guys! Ok, first off these are GFCI receptacles. I put an ohm meter on the dust collector plug (it is unplugged of course) and read 42 ohms between the ground and one of hot or common pins. Also, I tried plugging it in to all my circuits which have GFCI receptacles and it tripped all of them, without even turning on the unit, just as soon as I plugged it in! Then, I removed one GFCI receptacle and replaced it with a standard receptacle, and of course the unit works great. So now, do I return it to Oneida or just leave my shop outa code? One man says it could kill me!
    – John Rohde
    Apr 28, 2021 at 20:16
  • I heard back from Oneida via email, and even though they have not heard about this new bench top DC tripping GFCI receptacles, they say to use it on non GFCI circuits and it will work fine. They will take it back and refund me, but they don't want to send me another one, because they fear it will do the same thing. Balderdash! I welcome your comments.........
    – John Rohde
    Apr 28, 2021 at 20:42

1 Answer 1

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TLDR: Plug it into a different GFCI. If it doesn't trip, the GFCI is bad. If it still trips, the appliance is bad. It happens.

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That's not how GFCIs work.

GFCI detectors are not connected to the ground wire at all. (Mind you GFCI receptacles are connected to ground, but only for the sockets. A GFCI breaker doesn't even have access to ground.)

Further, UL requires that devices be built intending to have no electrical interaction with the ground wire at all. So the saw should not be interacting with ground. If the saw isn't, then there are only 2 possible current paths: From hot via the machine's internals to neutral.... and from neutral via the machine's internals to hot. And AC power switches between them 120 times a second.

Machines cannot store electrons. (it would take something like the Large Hadron Collider, but even that couldn't store enough electrons to trip a GFCI.) All electrons that come in must come out effectively instantaneously. Therefore, current flows should be equal on hot and neutral on a single-phase circuit.

Since current flows should be equal, the GFCI should not trip. It only trips when currents are imbalanced, meaning electricity is leaking via a third ??? path. The GFCI doesn't care whether the ??? path is to ground, via a human or pet, etc.

In a motor device, especially one where the motor's current is interrupted, this third path can be between the motor windings and the (grounded) motor chassis, due to a defect in the motor windings. A mega-ohm-meter can be used to test for this, after disassembling the machine to avoid putting its test voltage on parts which can't handle it. This isn't your problem on a machine within warranty.

Very often the third (fault) path is via the ground wire. Strictly as a diagnostic, you can try interrupting the ground path, by using a 3/2 prong "cheater" and insulate the little tang so it doesn't contact the receptacle cover plate. If the device stops tripping GFCIs at that point, that confirms an internal ground fault. Don't continue in service a broken appliance with a ground fault. One day you'll use it on a receptacle that is not GFCI, and the appliance will just kill you instead.

Appliance makers who are putting out appliances to be used in garages and sheds, really need to learn to make them not trip GFCIs. Code has required GFCI in those locations for quite some time. Don't let them "try to make this your fault", it's theirs.

But as a last sanity check, plug it into a different circuit protected by a different GFCI. If it does, then yeah, it's the appliance. If it doesn't, I'd examine the original GFCI.

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  • I wish I could upvote this 1000 times. GFCI's were adjusted a number of years ago to raise the trip current so there should NOT EVER BE an appliance that trips them. I have both old and new combo GFCI breakers and the ONLY time I ever had one of them trip it was tripping from a Cisco 12 port switch plugged into a UPS - which literally failed within 9 months of me owning it. And it only tripped it after a power failure when power came back on. And I have many older/antique 110v tools that plug in to these. Apr 28, 2021 at 3:23
  • Ted, please see my comments above about my dust collector. Do you know if a variable speed fan should trip a new GFCI receptacle? All Oneida says is use it only on non GFCI.....
    – John Rohde
    Apr 28, 2021 at 20:46

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