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Old 07-04-2012, 02:17 PM   #1
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GFCI on Dock ?


I am helping someone out and trying to get a better idea of whats going on...

GFCI receptical on dock the only trips under load...
The load is 2 3/4hp dock davit motors that are new...

it is wired basically from the GFCI to a motor controller panel with momnetary up or down... If I take the GFCI out and wire in a normal plug the motors work fine up or down...

If I put the GFCI in line... It pops... Which did not happen till recent... it always ran two motors. Under load they both pull 16amp up or down...

If the wires were compromised fromt the house to the GFCI would it hold?

Trying to elimitate one area of possible problem....

Any help is apprecaited

Thanks

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Old 07-04-2012, 04:29 PM   #2
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GFCI on Dock ?


Is wiring from GFCI outlet relatively short and for certain to be dry? Could water be in the connection areas of the motors (ie under a gasketed cover)? What if you power a lamp or some other electrical device from GFCI outlet? Does GFCI trip then? If none of these it could just be breakdown of motor winding insulation causing leakage to ground.

The solution here is NOT to eliminate the GFCI however tempting that may be. You need to find the leakage path to ground.

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Old 07-04-2012, 05:20 PM   #3
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GFCI on Dock ?


Is wiring from GFCI outlet relatively short and for certain to be dry? Yes short... But one of the runs goes underwater though conduit.... just throwing that out there


Could water be in the connection areas of the motors (ie under a gasketed cover)? Motors are new and dry


What if you power a lamp or some other electrical device from GFCI outlet? IF I power them seperatly disconnect one or the other the gfci does not pop...

Does GFCI trip then? If none of these it could just be breakdown of motor winding insulation causing leakage to ground.
The solution here is NOT to eliminate the GFCI however tempting that may be. You need to find the leakage path to ground.
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Old 07-04-2012, 06:15 PM   #4
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GFCI on Dock ?


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Originally Posted by DPSchmidt View Post
Which did not happen till recent... it always ran two motors. Under load they both pull 16amp up or down...
So something has changed.

There may be other current paths but you can check the wire insulation by measuring the current in the cable ground lead.
Multimeter fuses are expensive so use a 7-1/2 w bulb. Measure the bulb cold resistance and then put the bulb in series with the ground lead and measure the voltage across it.
Roughly the bulb should be 150 ohms which means at 5 mA you'd see 0.75V which would be enough to trip the GFCI.
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Old 07-04-2012, 06:46 PM   #5
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GFCI on Dock ?


But why does the GFCI no pop when running each motor seprate?

I guess thats what is more confusing to me than anything...
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Old 07-04-2012, 07:02 PM   #6
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GFCI on Dock ?


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But why does the GFCI no pop when running each motor seprate?
Each motor by itself does not exceed the 5 mA trip limit?

With GFCIs you have a 5 mA budget; some of this is used up by reactive current drawn by cable capacitance, some by motor capacitance to ground, some by insulation resistance, and some by the high transient current that motors draw (which GFCIs are not supposed to respond to).

If you don't want to make measurements, the cheapest fix is probably to replace the GFCI, but just once. Two bad GFCIs in a row are pretty unlikely.
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Old 07-04-2012, 07:05 PM   #7
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GFCI on Dock ?


I have replaced it...

Twice to be sure....
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Old 07-04-2012, 07:08 PM   #8
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GFCI on Dock ?


Am I safe to say thatI am ok upto the GFCI???

I can now see where people loose their mind doing this stuff....

I guess what I keep in the back of my mind is the fact that the conduit for the one motor goes under water so who knows whats going on down there...
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Old 07-04-2012, 07:16 PM   #9
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GFCI on Dock ?


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Originally Posted by DPSchmidt View Post
But why does the GFCI no pop when running each motor seprate?

I guess thats what is more confusing to me than anything...
They probably both have leakage to ground, but not enough individually to trip the GFCI. There's definitely a ground fault somewhere downstream of the motor control switches though. That's the only explanation. The GFCI is doing its job.
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Old 07-04-2012, 07:57 PM   #10
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GFCI on Dock ?


Install 2 GFCI's and plug a motor into each.
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Old 07-04-2012, 07:58 PM   #11
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Can I run a seperate ground and neutral to the switch box just to test?

Is that what we are looking for? I can run a sperate line for each off or an extension cord just to be sure and if it does not trip just replace the wiring...

Thanks
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Old 07-04-2012, 08:00 PM   #12
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BTW these are 5 wire cords...
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Old 07-04-2012, 09:02 PM   #13
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GFCI on Dock ?


Will the GFCI trip if you run the lift motors without the boat on it? As in, could you connect only one motor at a time and test to see which trips the breaker?

You have conduit for the other motor running under the water? Why? It would seem like a phenomenally bad plan to do it that way. Most lifts I've ever seen keep the lift motors on the dock side and use cables and pulleys to do the work. How is your lift setup that it needs wiring that way? Pictures would help, a lot.
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Old 07-04-2012, 09:51 PM   #14
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GFCI on Dock ?


Will the GFCI trip if you run the lift motors without the boat on it? As in, could you connect only one motor at a time and test to see which trips the breaker?

It only has a jet ski on it now... I have run one at a time and does not pop







You have conduit for the other motor running under the water? Why? It would seem like a phenomenally bad plan to do it that way. Most lifts I've ever seen keep the lift motors on the dock side and use cables and pulleys to do the work. How is your lift setup that it needs wiring that way? Pictures would help, a lot.

Dunno if this worked picture wise... But if it did you can look close and see the conduit from one piling to another...




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Old 07-04-2012, 10:56 PM   #15
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GFCI on Dock ?


Most aren't installed the way yours appears to be. Does your lift allow for raising the bow and stern at different angles? Or just the port/starboard sides? If it's just left/right then your lift is installed wrong. Fix that and you eliminate the brain-dead idea of running electrical conduit underwater.

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