Ground fault

[trickyrick]

Good day
I have a little problem with my ground fault always tripping.

I have an above ground pool with a 1hp pump. I have a wire in a
conduit to the pump. The wire is 14/2 and is about 100 ft from the
panel. The pump will run for about 3 to 4 hours and then the breaker
will trip. I have metered the wire and there are no grounds or
shorts. The only thing that I can think of is maybe the size of the
wire. I did unfortunately run the pump before with out any protection
and the breaker never tripped.
Any suggestions on what might be the problem
Thanks
Rick

 

[Tom Biasi]

Good day
I have a little problem with my ground fault always tripping.

I have an above ground pool with a 1hp pump. I have a wire in a
conduit to the pump. The wire is 14/2 and is about 100 ft from the
panel. The pump will run for about 3 to 4 hours and then the breaker
will trip. I have metered the wire and there are no grounds or
shorts. The only thing that I can think of is maybe the size of the
wire. I did unfortunately run the pump before with out any protection
and the breaker never tripped.
Any suggestions on what might be the problem
Thanks
Rick

There are really only three reasons this breaker will trip.
1. You are overloading the breaker.
2. You have uneven hot/neutral current flow. (ground fault condition.)
3. Its defective or miswired.

Tom

 

[Chuck]

There are really only three reasons this breaker will trip.
1. You are overloading the breaker.
2. You have uneven hot/neutral current flow. (ground fault condition.)
3. Its defective or miswired.

I assume you're in the US.

Overload is unlikely if the only load is
a 1 hp motor. The breaker is at least 15 A?

Defective is always a possibility with
GFCIs, but the circumstances under which
it is tripping don't seem to match the
time constants likely to be found in the
device.

The regularity of the tripping and the
fact that it trips after being under
load for 3 hours strongly suggests heat
as a factor.

Heat inside the GFCI is possible if the
connecting wires don't make good
electrical contact. I would not expect
GFCIs to be very sensitive to heat.

Heat inside the motor could easily cause
expansion of a conductor with consequent
shorting to the motor's case. Measure
resistance from hot wire to case with
the motor cold and it may be hundreds of
megohms. When hot (immediately after
removing ALL power after a trip) it may
drop to 25,000 ohms or less. If so, it
will cause at least 5 mA to be returned
through the ground wire, thus causing
the GFCI to trip. That's what I would
look at first. Let it run till it trips
and then remove all power and measure
leakage resistance.

Good luck.

Chuck

 

[trickyrick]

There are really only three reasons this breaker will trip.
1. You are overloading the breaker.
2. You have uneven hot/neutral current flow. (ground fault condition.)
3. Its defective or miswired.

Tom

Ok thanks
Lets say it was an over load if that was the case would the pump run
for about 3 hours before it triped
If it was a ground fault condition would I not see some kind of ground
on the hot or neutral side ( I see nothing)
If it was misswired would it not trip right away
Thanks

 

[Tom Biasi]

Ok thanks
Lets say it was an over load if that was the case would the pump run
for about 3 hours before it triped
If it was a ground fault condition would I not see some kind of ground
on the hot or neutral side ( I see nothing)
If it was misswired would it not trip right away
Thanks

The overload could take place when the motor is hot.
It would be hard to measure the ground fault since trip will take place with
very little flow.
The miswire probably would trip right away unless you did something weird.

When you say it runs for 3-4 hours, is that after you have been splashing
around in the pool?

Tom

 

[Jasen]

Good day
I have a little problem with my ground fault always tripping.

I have an above ground pool with a 1hp pump. I have a wire in a
conduit to the pump. The wire is 14/2 and is about 100 ft from the
panel. The pump will run for about 3 to 4 hours and then the breaker
will trip. I have metered the wire and there are no grounds or
shorts.

Did you use an insulation tester? a cheap VOM won't find all faults.

The only thing that I can think of is maybe the size of the
wire.
unlikely.

I did unfortunately run the pump before with out any protection
and the breaker never tripped.
Any suggestions on what might be the problem

cable insulation not waterproof?

Bye.
Jasen

 

[trickyrick]

I assume you're in the US.

Overload is unlikely if the only load is
a 1 hp motor. The breaker is at least 15 A?

Defective is always a possibility with
GFCIs, but the circumstances under which
it is tripping don't seem to match the
time constants likely to be found in the
device.

The regularity of the tripping and the
fact that it trips after being under
load for 3 hours strongly suggests heat
as a factor.

Heat inside the GFCI is possible if the
connecting wires don't make good
electrical contact. I would not expect
GFCIs to be very sensitive to heat.

Heat inside the motor could easily cause
expansion of a conductor with consequent
shorting to the motor's case. Measure
resistance from hot wire to case with
the motor cold and it may be hundreds of
megohms. When hot (immediately after
removing ALL power after a trip) it may
drop to 25,000 ohms or less. If so, it
will cause at least 5 mA to be returned
through the ground wire, thus causing
the GFCI to trip. That's what I would
look at first. Let it run till it trips
and then remove all power and measure
leakage resistance.

Good luck.

Chuck

Thanks guys for the input
I will check for grounds today when it trips and let you know what I
find

 

[ehsjr]

Good day
I have a little problem with my ground fault always tripping.

I have an above ground pool with a 1hp pump. I have a wire in a
conduit to the pump. The wire is 14/2 and is about 100 ft from the
panel. The pump will run for about 3 to 4 hours and then the breaker
will trip. I have metered the wire and there are no grounds or
shorts. The only thing that I can think of is maybe the size of the
wire. I did unfortunately run the pump before with out any protection
and the breaker never tripped.
Any suggestions on what might be the problem
Thanks
Rick

Kill power and look for crud/dirt in all involved
junction boxes.

Ed

 

[trickyrick]

Kill power and look for crud/dirt in all involved
junction boxes.

Ed

Ok I waited around for a couple of hours until the pump tripped the
breaker (15 amp ground fault) . I checked both the hot and neutral
side of the plug for a ground and nothing (my meter goes to 3 million
ohms).
There are no junctions between the breaker and the pump. This is a
new pump only 3 weeks old (1 hp). The one from last year sized up
(bearings got wet) I could not get it going this season and even the
old pump did it last year about half way through the season. Any
other suggestions guys
Thanks

 

[Eeyore]

Ok I waited around for a couple of hours until the pump tripped the
breaker (15 amp ground fault) . I checked both the hot and neutral
side of the plug for a ground and nothing (my meter goes to 3 million
ohms).
There are no junctions between the breaker and the pump. This is a
new pump only 3 weeks old (1 hp). The one from last year sized up
(bearings got wet) I could not get it going this season and even the
old pump did it last year about half way through the season. Any
other suggestions guys

Yes.

How much current does it draw ?

Not watts, not hp but AMPS.

Graham

 

[Lord Garth]

Yes.

How much current does it draw ?

Not watts, not hp but AMPS.

Graham

Additionally, the startup surge can be enough to trip a GFI. Another
typical cause is if there is a 3-way on the same circuit.

What does your meter indicate when you probe ground to neutral?

 

[trickyrick]

Additionally, the startup surge can be enough to trip a GFI. Another
typical cause is if there is a 3-way on the same circuit.

What does your meter indicate when you probe ground to neutral?

It' cant be the startup as I said in the original post the pump runs
between 2 and 3 hours before i trips. This is the only thing that is
on the GFI not even a switch.
When I check ground to neutral its over 3 million ohms
Rick

 

[Lord Garth]

It' cant be the startup as I said in the original post the pump runs
between 2 and 3 hours before i trips. This is the only thing that is
on the GFI not even a switch.
When I check ground to neutral its over 3 million ohms
Rick

Read the AC volts between the ground and neutral. It should be very nearly
zero however, I have measured 70 volts here. A new ground solved the
problem.

The 3-way can be ahead of the GFI rather than behind it and cause trouble.

Something is causing an imbalance in the current between the hot and the
neutral.
That is what trips the GFI. Assuming the GFI isn't defective, there must be
a
path to ground somewhere.

 

[Eeyore]

It' cant be the startup as I said in the original post the pump runs
between 2 and 3 hours before i trips. This is the only thing that is
on the GFI not even a switch.
When I check ground to neutral its over 3 million ohms

Can you PLEASE check the current draw when it's contuously running ?

Graham

 

[default]

Ok I waited around for a couple of hours until the pump tripped the
breaker (15 amp ground fault) . I checked both the hot and neutral
side of the plug for a ground and nothing (my meter goes to 3 million
ohms).
There are no junctions between the breaker and the pump. This is a
new pump only 3 weeks old (1 hp). The one from last year sized up
(bearings got wet) I could not get it going this season and even the
old pump did it last year about half way through the season. Any
other suggestions guys
Thanks

Think of the pool as one plate of a capacitor to ground - may be no DC
path to ground but that doesn't mean there isn't some leakage from the
pump to the water - through the water to the pool - across the pool
membrane to ground. AC only circuit.

Check the resistance between hot and neutral to the water.

 

[default]

Another thought on the idea of current flow through the water being
pumped - there may be air voids in the piping that occur when the pump
is off preventing an honest ohm meter reading.

 

[@(none)]

Another thought on the idea of current flow through the water being
pumped - there may be air voids in the piping that occur when the pump
is off preventing an honest ohm meter readi

Remember that three things can trip a GFCI:

leakage currents that bypass the neutral
defective GFCI
excessive current drawn

Too bad the resistance test was negative. Doesn't necessarily mean there
was no leakage. It gets more complicated from this point on. I still
suspect heat because of the time constant. Could be a plugged filter
that reduces water flow thru the pump and causes the motor to overheat.

You can measure the AC current drawn by the motor, by please do be
careful since your test leads will be hot.

You can also measure the AC leakage current in the ground wire. But be
extra careful if you do that, especially if leakage is a real possiblity!

It might be easiest to start by either replacing the GFCI with a known
good one, or routing your pump circuit to a different one.

Use extra caution in all of this.

BTW, did you say if you reset the GFCI it will run for another 2-3 hours?

Chuck

 

[Doug Miller]

Remember that three things can trip a GFCI:

leakage currents that bypass the neutral
defective GFCI
excessive current drawn

Let's clarify, shall we?

Overcurrent will trip a GFCI _circuit_breaker_ -- but that's because it's a
circuit breaker, not because it's a GFCI.

 

[Eeyore]

BTW, did you say if you reset the GFCI it will run for another 2-3 hours?

If it runs for say another 15 mins and trips again, then the fault is likely to be a
small overcurrent on the circuit.

Graham

 

[Eeyore]

There are no junctions between the breaker and the pump. This is a
new pump only 3 weeks old (1 hp). The one from last year sized up
(bearings got wet) I could not get it going this season and even the
old pump did it last year about half way through the season.

Well...... if the bearing getting wet caused the bearing to seize, it's
reasonable to assume that before they seized they became 'tight'.

If they did that, the motor would have to work harder (drawing more current) and
that could cause an overcurrent trip of the breaker, i.e. nothing to do with a
ground fault at all. I see that 1 hp pumps can draw ~ 11A so a modest 'overload'
could indeed do it.

Graham