Need some other brain matters on this fault ...

I'm about ready to pull my hair on this one. I built a service 4 years back for landscape equipment only. It has a 125a panel with two 15a circuits. Each circuit feeds one gfi mounted directly below the panel. One circuit is for lighting and one for sprinklers, and one gfi has been replaced at some point so light is cooper and sprinkler is P&S.

The sprinkler gfi trips for no reason I can find. When owner first found it, simply plugged sprinkler into light gfi. When I was called I went and looked at it and I could see nothing wrong. Cycled the sprinkler and held fine. Called the owner and he said it only did it when lights turned on. Well, that's unlikely since they are on separate circuits, but ok ill cycle them. Worked fine, so I left them separate.

Texts me me the next day, tripped, and owner combined again. This time I swap out the gfi, and cycle everything, works fine.

Texts me the next day, tripped. That's really odd. Maybe the tolerances between cooper and P&S aren't the same? So, I go and get a cooper, cycle everything and works fine. I even change pigtail which has a 90 degree end on it, in case the molded plug has a intermittent short.

Get another text ... This time I completely rewire whole thing from breaker to gfi. This was last Friday. He checked over the weekend and worked.

Got another text today ...

I'm at a loss. I thought maybe a bad control, but he said it is brand new. It only runs two stations, and I've ran then for 5 mins with no problem. It would work fine with both light and sprinkler on same circuit, but that's not the issue.

Any thoughts?
 

kwired

Electron manager
Location
NE Nebraska
Are the sprinklers wetting the devices or equipment?
Been down that road before with agricultural irrigation equipment. Trying to find out what why we had problems with a generator driven center pivot. After many attempts to fix some high resistance faults (that I didn't really think were a problem to start with) and even have a motor shop check out the generator because I was out of ideas of what was wrong. I even hooked up a 10 kw electric heater and ran it from the generator for 30 minutes and nothing unexpected happened. Owner called me back within 15 minutes after I left and it failed again. Then it finally hit me - all the testing I had done was always when running the system with no water. Turns out as soon as we were pumping water, a water leak happened to be spraying on the drive belt for the generator causing it to slip:slaphead: Of course this would have been a little more noticeable sooner had the center pivot (which is where the symptoms were appearing so the focus was more there) not been something like 800 feet away from the generator.
 
ptonsparky
Are the sprinklers wetting the devices or equipment?​


The only thing that get's wet when I cycle the sprinklers is me. :ashamed1:

The way this is set up is like an H frame, built out of unistrut. The meter and panel are about 4' high, and connected with an offset nipple. The two GFI's are coming out of the bottom of the panel, and facing to the back of the panel. Both GFI's are in weatherproof single gangs, and both have good in use covers on them.


1793
Have you tried to move the sprinkler to the light GFCI and unplug the lights to see if it trips?

When the sprinkler GFI trips, the owner swaps it over to the light GFI and it holds. Now, since you asked me that question, I realize I have never just swapped both out, one to the other. However, if it held then, I really would be at a loss. When I first went out there a few weeks ago, I found that some of the connections for the power supply inside the sprinkler were loose, from the factory. I explained that this might possibly have caused the tripping due to the noise in the signal. I tightened them up and it worked for a short while.

[disclaimer]
Now, my understanding of how a GFI monitors the line, is that it basically has a CT over both sides of the line and if one side's current changes by a set amount, it trips. I'm guessing noise in the signal will skew that up. I know I have seen firsthand small, cheap fans trip GFI's when you changed speed and I associated that with how noisy the signal must look. I didn't actually scope it. [/disclaimer]

In reality, as small of a load that the lighting circuit is and the sprinkler circuit is, they could share the one GFI that holds. However, it's not about that anymore! I'm a man on a mission! :) I really hate not being able to figure this out. The dang thing worked for a few years with no problems.
 

growler

Senior Member
Location
Atlanta,GA
One circuit is for lighting and one for sprinklers, and one gfi has been replaced at some point so light is cooper and sprinkler is P&S.

The sprinkler gfi trips for no reason I can find. When owner first found it, simply plugged sprinkler into light gfi.
In reality, as small of a load that the lighting circuit is and the sprinkler circuit is, they could share the one GFI that holds.

Trying changing out that lighting GFCI to a new one and see if it still holds with both lights and sprinkler plugged in.

I'm thinking there really may be a fault ( sprinkler) but for some reason the lighting GFCI is just not tripping as it should.
 
What's your lighting load? What technology, watts per fixture and how many fixtures?
It's either a 300 or 600 watt transformer, (I didn't install it), and there are three LED fixtures on the tx. Mind you, this on a totally separate circuit and it never trips out the GFI, even when sprinkler system is plugged in. Sprinkler is a Hunter controller, with two zones, maybe 6 station heads.

Trying changing out that lighting GFCI to a new one and see if it still holds with both lights and sprinkler plugged in.

I'm thinking there really may be a fault ( sprinkler) but for some reason the lighting GFCI is just not tripping as it should.
That is my next option, only think I can think of.
 

GoldDigger

Moderator
Staff member
FWIW, the nominal spec for different GFCIs in terms of the 60Hz current mismatch should keep all units comparable in behavior. But there can be more variation in how they react to current differences at harmonic frequencies (filtering).

Tapatalk...
 

busman

Senior Member
I have seen cases of branch circuit neutral-to-ground faults that would trip a GFCI breaker based on load being placed on other circuits in the same panel. The best reason I could come up with was that the neutral current was taking all parallel paths. I have seen this in action using a AC Leakage Clamp meter that is sensitive enough to read a microamp of leakage. If the GFCI trips when loads on other circuits are used, I would look for a neutral-to-ground connection on the load side of the GFCI.

Mark
 

kwired

Electron manager
Location
NE Nebraska
I have seen a wall switch type occupancy sensor that would cause an a GFCI on same circuit trip although the sensor and its load were not protected by the GFCI. This trip must have been because of some kind of inductive kick back as it tripped when the load turned off. Same load without the occupancy sensor and just a standard switch never tripped the GFCI though. I never did figure out exactly why it did that.
 

1793

Senior Member
I have... This trip must have been because of some kind of inductive kick back as it tripped when the load turned off. ... I never did figure out exactly why it did that.
This was my thinking and why I asked if the lights were on, if they were maybe they could have absorbed some of the inductive kick back.
 
When the sprinkler is moved to the lighting GFCI and "holds", are the lights on when the sprinkler is on?
Well, it get's swapped over to the other GFI and stays there for days, working. (I assume, as I don't get back for a few days, so I would think everything is cycling as it should.)

Why not hard wire the irrigation controller and eliminate the GFCI?
Because I hadn't thought of that. :D This is just how I do all of this developer's stations: service, panel, and two GFI's. Mainly done that way as nothing is installed when I build the service and they plug in whatever they want later. However, I just may go hard wire the damn thing in and be done with it. It just bugs me to not be able to determine a definite answer to this puzzlement.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
I have seen a wall switch type occupancy sensor that would cause an a GFCI on same circuit trip although the sensor and its load were not protected by the GFCI. This trip must have been because of some kind of inductive kick back as it tripped when the load turned off. Same load without the occupancy sensor and just a standard switch never tripped the GFCI though. I never did figure out exactly why it did that.
I've seen it when on different circuits.
 

kwired

Electron manager
Location
NE Nebraska
I've seen it when on different circuits.
I guess I have too.

When we were without power one time, I was powering the house from a portable generator, the generator ran out of fuel, right at the time the lights were going out, I heard several pops around the house - just about every GFCI in the house tripped, my guess is because of inductive kickback.
 
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