I am having a problem with my GFI breaker tripping when I try to use
my boat lift that was installed last fall.
The lift manufacturer suggested that the voltage could be too low at
the remote control panel. I upgraded the wire from the main panel to
the controller (310 feet) to a combination of 100 feet of #6 AL
feeding 210 feet of #8 cu. The remaining wire from the controller to
the lift motors (two 3/4 hp, 240V) is 50 feet of #12 cu that is run in
PVC pipe along the lake bottom (there are no splices between the
controller and the motors). I measured a loaded voltage (lift running
lifting the boat, 11 amps) at the controller (not the motors) of 242
+/- 13 volts using the 400 volt scale on the meter and 243 +/- 5 volts
using the 200 volt scale (measuring leg to ground and adding. The
meter has a better accuracy on the 200 scale). The unloaded voltage
was 246 volts. Based on this, I am hoping this is not a voltage drop
The remote control manufacturer says it could be 1) a voltage issue or
2) moisture in the motor due to recent heavy rain. The motors are
designed to be exposed. There are drain holes which are plugged
(installer forget to remove them). Not sure how to check this.
After resetting the breaker, the lift will sometimes go up and down.
Other times, it will trip the breaker as soon as I push the button.
The subpanel breaker is 15A which was what the manufacturer
recommends. The main breaker is a 50A GFI.
Any suggestions on how to troubleshoot this problem?
Is this a new problem with an old setup? Has it been used on a regular
basis since the fall? Or is it a problem with a "new" installation that
has not worked right from the start?
The wire and voltages seem to be OK. The fact it sometimes immediately trips
makes me suspect a ground problem. I'd check for moisture, corrosion, bad
connection, that can cause the breaker to trip.
For the OP:
What voltage is measured between the Hot and Neutral AT the motor?
What voltage is measured between Hot and Neutral AT the controll OUPUT to
A gfci does NOT care whether a ground (earth) connection is present or not.
They operate simply by measuring the current in the Hot and Neutral wires
and comparing them. If they are equal, all is OK. If not, then something is
wrong and the gfci trips.
So, somewhere, the Hot lead is feeding power to someplace other than just
the N eutral lead on the setup. THAT is what trips the gfci.
There can be problems with electric motors and gfci's
Now for another possibility: IF the wiring is dry all the to/from the
motor, then some motors create enough phase difference in the current that
it fools the gfci when it sees the lags & leads in current/voltage an
The easiest way to do this is to exchange the motor with something
resistive, like a large light bulb, electric heater, etc., and see if it
still trips it; with a resistive load, it should NOT trip the breaker or
blow the fuse.
This might be where you are.
Check all your junctions for water. A connecton of wires should NEVER be
exposed to the elements. Things like electrical tape etc will NOT keep water
out permanently or at all in many cases; it needs to be treated so no water
can ever touch a bare conductor. I suspect that's your problem with all
those gauge changes you have. How were they done?
If you say that's not the reason, why not?
If you have a 50A GFCI where you only need/is recommended to be, 15A, then
you have a separate, different problem and it could in the right
circumstances be a dangerous one considering what happens to the overall
system. Use a 15A breaker.
Either gfci will still trip at the same mismatch in current in the H & N
lines; but a hard short, well then the gfci will do nothing and leave all
protection up to the fuse/breaker/whatever you have, and if they are a
time-delay as often used ini such places, that fuse doesn't immediately
blow. The real point is, you spent a lot of money on a 50A gfci that wasn't
Okay, orginal poster again. I will try to give more details an answer
some of the questions raised.
This is a 240V circuit with no neutral.
The main panel has a 50A, 240v, GFI. This feeds a subpanel at the
start of a dock. The two are connected with 100ft of #6AL and 100 feet
of #8cu for a total run of 200 feet. The subpanel feeds the dock and
the boat lift. There are 6 breakers. One breaker feeds a 1.5 hp 240V
water pump. That does not trip the GFI. For that reason, I am assuming
that the wires to the subpanel are not an issue.
Except for the 15A, 240V breaker feeding the boat lift, all breakers
at the dock are off. This should isolate any issue to the boat lift
circuit. The voltage measurements noted were taken at the inputs of
the relays in the controller. A quick check today showed that the
voltage on the output of the relays are the same. I have not been able
to open the motors to check the voltage at the motors, These motors
are not that easy to reach. They are 17 feet above the lake bottom on
top of poles driven into the lake bed.
This lift was installed last fall. The wiring to thje subpanel was pre-
existing. All connections are in sealed boxes rated for wet locations.
All wires are individual conductors in conduit. Yesterday, I replaced
the wiring from the subpanel to the controller (upgraded to #8 from
#10) and verify all connections were good. I did not touch the wires
from the controller to the motors. Since the fall, I ran it up and
down a few feet to keep everything lubicated. No issues until
yesterday. Used it about 5 times in the fall to take the boat off and
it worked fine.
*The way I understand the set up is that you have one 50 amp two pole GFI
circuit breaker that provides GFI protection for everything downstream. All
of the circuit breakers in the subpanel are not GFI.
I would replace the 50 amp GFI and install a regular two pole 50 amp
breaker. Then I would install GFI breakers and/or outlets on the circuits
in the sub-panel. Thereby keeping the GFI protection device as close to the
point that needs GFI protection. It may not alleviate the problem, but at
least it will make it more convenient to reset the breaker.
I would also verify that all connections at each end are tight and free of
corrosion. That includes the bus bars inside the circuit breaker panels.
It's too bad you can't access the motors because I would suggest checking
the electrical connections for moisture which I think is your problem.
Even though the motors are rated for wet locations, moisture can still get
inside and that could be enough to trip a GFI. Since the motors are not
used frequently there is no heat being generated to evaporate any
condensation. You may find that when summer comes and the air is warmer the
problem may go away.
I have experienced a situation many years ago with HID lights over an indoor
pool deck. It was a very humid environment. Each day when the lights were
initially turned on the GFI circuit breakers would trip. After the
breakers were reset the lights would come on and stay on for the rest of the
day. Changing breakers, checking connections, replacing ballasts, etc. did
nothing to correct the situation. Eventually everyone accepted the problem
and a maintenance man would turn the lights on each day and then reset the
breakers. The odd thing was that not all breakers tripped each day. Some
would trip one day and others would trip on other days. I always thought
that better ventilation might help the situation, but that was not possible
in this instance.
** John is 100% correct,(as usual) you really don't want to have GFCI
protection on that length of underground cable. Every little nick and crack
in the wires lends itself to GFCI tripping. As he explains, this could
change when summer comes and the ground and the air dry up. Keep the GFCI
protected circuits as short as possible
** Which breaker is the GFCI? If it's the 2/15 I would replace it with a
2/20 standard breaker (for testing purposes), hang an ammeter on one of the
legs and see what the starting current is, and see if it trips . It is
possible to have intermittent grounding through wet windings. It's also
possible that one of the motors has a starting issue. The ammeter should
show exactly what's going on.
Have you run an Earth Ground from the lift/motor assembly that goes back to
the entrance box at the house? You'll have to check your current charts for
the size of the wire, being the largest wire used.
It would seem to me that the motor should be grounded back to the
which in turn should be properly grounded itself.
To the OP, I'd stop focusing on voltages at the motor, which seem
start looking for leakage current from one of the hots to ground,
what the GFCI is looking to trip on. The suggestion of disconnecting
motor and subtituting another load to see what happens is a good one.
also agree with the advice to keep the GFCI localized to the eqpt.
you have one large one, not only are they more expensive, but then
they trip it's harder to determine the source.
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