GFI Puzzle

[Doug Hepler]

My Jet DC-1100VX-CK dust collector is connected to power through a remotely switched outlet (PSI Long Ranger). Occasionally, unpredictably, my GFI breaker trips after I have turned off the switched outlet and the dust collector motor has nearly stopped. As the motor slows down, there is an audible click, I suppose a relay operating (starter relay closing?). When the breaker trips, it is always simultaneous with this click, but the breaker tripping does not happen every time.

This is not an overload problem because the BS and DC start and run well together on that branch. When the breaker trips they are both off. Also the lathe and DC run together on that branch. I initially blamed the remote outlet and PSI replaced it. That was not the problem. I consulted an electrician, who said that he thought that it was the GFI not the overload protection

So, how does a motor that has been disconnected from a branch circuit trip the GFI on that branch? I suppose that the remote switch just interrupts the hot side of the supply. How does the relay on the motor cause an imbalance to trip the GFI?

As I said, a puzzle.

Doug

[Arthur Fleming]

Just a guess here, but it's exactly because the relay only breaks one side of the load that's causing the problem. The GFI measures the amps leaving and returning, and opens when there is a ??milliamp discrepancy. It's supposed to open when more current leaves, than returns, as in someone getting a shock, thus protecting them. I'm guessing that as the motor is winding down the coils are inducing a voltage/current, and the GFI is sensing an imbalance from the neutral, and opening. I am an electrician, but not an electrical engineer, so this is just a guess. If you had a remote switch that opened both sides of the circuit, it would be interesting to see if it still occurred. If the remote switch is removed from the circuit does it still occur? Artie

[Bill Orbine]

I would think that the centrifugal start switch (the click noise you hear) might be the culprit. My thinking is the CFS has a pair of contact switches that may close/open at a slightly different time just enough at times to trip the GFI. I'm talking milliseconds difference in time.

[Jeff Fischer]

I had a floor standing fan on the back porch that was plugged in to a GFCI. When the wind blew and the fan blades turned (while the power was off), it would trip the GFCI. Moved the fan to a standard outlet, no more problem. I think it was generating a little current, somehow, I'm just not sure of the theory. I bought a different model fan and it was ok.

[sean meltvedt]

Doug-I would say that Artie is spot on. Try using a double pole relay to break both the hot and the neutral at the same time. I believe you will find that cures your tripping issue.
Happy sawdust
Sean

[Mike Henderson]

Just a guess here, but it's exactly because the relay only breaks one side of the load that's causing the problem. The GFI measures the amps leaving and returning, and opens when there is a ??milliamp discrepancy. It's supposed to open when more current leaves, than returns, as in someone getting a shock, thus protecting them. I'm guessing that as the motor is winding down the coils are inducing a voltage/current, and the GFI is sensing an imbalance from the neutral, and opening. I am an electrician, but not an electrical engineer, so this is just a guess. If you had a remote switch that opened both sides of the circuit, it would be interesting to see if it still occurred. If the remote switch is removed from the circuit does it still occur? Artie

I vote for Artie also. A GFCI measures the total amount of current, which normally sums to zero (two wires - black and white). If you break one wire it should not allow current to flow on the other wire (not a complete circuit) but perhaps the starting capacitor is charged and somehow discharges between ground and the neutral. That would give you current on the white wire and not on the black (ground is not monitored in a GFCI) and would cause it to trip.

Sean's suggestion of a two pole switch should fix that.

Mike

[Doug Hepler]

Ok, guys, thanks for your advice. I think Artie is spot on, also. I was speculating along those lines, but I didn't (don't) know enough to be confident.

So, I have done some preliminary searches on line but have not found anything that looks like what I want. The commonly-available remote switches don't say whether they are DPST. Can you recommend a product or at least a trade designation so I can know what to search for? I'd prefer something that plugs into the wall and that the DC can plug into.

Another approach would be to suspect the GFCI but I replaced the whole entry panel 3 years ago when I moved in. Are there "flavors" of GFCI breakers?

Doug

[Mike Henderson]

Ok, guys, thanks for your advice. I think Artie is spot on, also. I was speculating along those lines, but I didn't (don't) know enough to be confident.

So, I have done some preliminary searches on line but have not found anything that looks like what I want. The commonly-available remote switches don't say whether they are DPST. Can you recommend a product or at least a trade designation so I can know what to search for? I'd prefer something that plugs into the wall and that the DC can plug into.

Another approach would be to suspect the GFCI but I replaced the whole entry panel 3 years ago when I moved in. Are there "flavors" of GFCI breakers?

Doug

Your remote control controls a 120V circuit. Get a 120 volt two pole contactor. Use your remote control stuff to control the contactor and it will engage and disengage both sides of the power that's going to your dust collector. That is, when you use your remote to turn your DC on, what you'll really be doing is causing the contactor to engage, which will turn the power on to your DC.

Artie may even be able to explain it better since he's an electrician. Artie - want to give it a shot?

Mike

[Doug Hepler]

Mike,

Thanks. I understand the problem. I just don't know how to implement the solution. So far I have not found the product I need. I searched for "contactor" but I don't understand how to wire it. Most of them say they have a 24 V coil. What's that about?

Doug

[John K Jordan]

Mike,

Thanks. I understand the problem. I just don't know how to implement the solution. So far I have not found the product I need. I searched for "contactor" but I don't understand how to wire it. Most of them say they have a 24 V coil. What's that about?

Doug

Doug, a contactor is just a relay. The "coil" is the control winding, an electromagnet which hold down the main contact points inside the contactor. 24 volts is a common voltage used for low voltage control applications.

I use a big contactor to switch my cyclone dust collector with a radio controlled remote. The control winding (the "coil") on my contactor is 110v instead of 24v and it switches two legs of 220v power rated for a 5hp motor. That's a bigger contactor than you would need but you could use an oversized one. If you go the contactor route just ask about the wiring and sourcing - I think you can get them from Amazon.

Am I to understand your DC runs on 110v? If so:

The control line is isolated from the switched lines in a contactor. With your setup you could simply wire a cord from the two control terminals of the contactor and plug it into the remotely switched outlet. Then separately, run both the white and black lines of any 110v circuit through both poles of the contactor and on to your dust collector. You could just cut the cord on the DC and put the contactor inline. I would probably keep the original cord and plug it into a new 110v receptacle controled by the contactor with a new piece off 110v cord and plug powering the two poles of the contactor.

I would probably test this first to prove it will work by wiring up a couple of light switches and when shutting down the DC disconnect both the black and neutral wires but leave the ground wire intact. This might eliminate the unlikely possibility of some other issue, such as induction in parallel wiring generating a rogue current from the magnetic field collapse in the motor at shutdown. Unlikely, but conceivable.

JKJ

[Mike Henderson]

Mike,

Thanks. I understand the problem. I just don't know how to implement the solution. So far I have not found the product I need. I searched for "contactor" but I don't understand how to wire it. Most of them say they have a 24 V coil. What's that about?

Doug

Go to eBay and search on "120 volt contactor". The first one that came up when I searched was about $12 - item number 321868591906.

Mike

[Arthur Fleming]

Hi, I made a longwinded explanation of how it works, how to wire it, and apparently hit the wrong button because it isn't here. (I can be very technologically challenged sometimes). So to not try and type all that again, Doug we may have some used parts in the shop, if I made up a (what I believe to be) cure for this problem, would me making it out of used parts bother you? It would be a 4 inch square box with a cord having a male end coming out of one side (this would plug into the remote controlled receptacle) and a cord coming out of the other side of the box. This would have a female end on it, into which your machine would plug into it. Artie

[Doug Hepler]

Artie,

That sounds just like what I need. I will send you a PM.

Doug

[sean meltvedt]

Guys-this is what makes this a great forum! Thanks to all
Sean

[Arthur Fleming]

Well electrical is what I do know about. I work for a public entity (I prefer to leave un-named LOL) and there are lots of used (already paid for) parts available. I guess this could serve as a sorta intro for me. I found this site getting info on cnc machines, a dream that has financially disappeared . I live in a townhouse, and have at most a 13 foot, by 15 foot, work shop foot print available in the basement. My main machine is gonna be a Shopsmith, space will allow for no other real options, and after seeing one, I think they're kinda cool, anyways. I'm hoping to have the shop up and making sawdust by end of February. (My first estimate was June of this year LOL) So I'm sure I will be asking many, many questions here in the near future. I have been reading lots of interesting posts/threads here, and I was impressed by how on most of them the disagreeing opinions were put forth, but politely, and respectfully. I have been on ther various other forums where this not always the case LOL. So I'm hoping/planning on being a more active member here in the future. Hi All. Artie