GRM elec-chickens - 120V GFCI breaker trippin', yo (when it's excessively wet out).

So I have a circuit that I recently ran for my outdoor pool patio.  This is a fresh installation that I did from the ground (heh) up just this past August or September, so I know the wires and such are good.  It passed the local inspection (which I know doesn't really mean anything).  I'm running a 10ga THWN wire inside of a conduit from my panel to the pump house where I have a junction box.  From there, the connection is "broken" and connected out to a daisy-chain of outlets in those weatherproof boxes.  It also goes up to my shed which has a light switch and a few outlets.

Now, because this is right at the perimeter of a pool patio, and outdoor outlets, I put a GFCI breaker in instead of using a GFCI outlet.   I'm starting to regret that decision and I want to know if it was something I did wrong.

Basically, occasionally when it rains really hard the GFCI breaker will trip if there's any load at all on the circuit.   The last time it was Thursday when it warmed up from 3° earlier in the week to 55° with 2" of rain.     I noticed that it had tripped because I'm using an outlet in the shed to drive a poultry water heater which left my chickens pecking at ice over the weekend.  The heater claims that it's 125W, which means it should be ~1 Amp on 120V if my math is right.  By my numbers, I should be able to support about 30 Amp after voltage drop due to distance with 10Ga wire?

tl;dr:  Should I rip it out and replace it with a GFCI outlet somewhere on the chain?

Thanks!

You probably need to try to get everything water tight again. If you wait until it trips again you will probably find water in one of the exterior boxes causing the short to ground.

Why do you suspect the GFCI breaker?

What amperage is the breaker?

Is the junction box weatherproof?

Is anything near the ground?

Are the outlet covers also weatherproof?

The link you provided is not to a weatherproof box. It’s to a weatherproof box cover. 

Did you also use weatherproof boxes?

I wouldn’t be quick to blame the breaker. It sounds like it’s doing it’s job. 

gfci also means that if any of the appliances you use are 'leaking' any current to ground and not back to neutral it will trip. 

So for example, the heater gets wet, and then it has some small momentary short to something else that is wet and nearby, the gfci SHOULD trip. 

SVreX said:

Why do you suspect the GFCI breaker?

What amperage is the breaker?

Is the junction box weatherproof?

Is anything near the ground?

Are the outlet covers also weatherproof?

Thanks for chiming in.

The break is 20Amp

The junction are these plastic jobbies with a gasketed top.

Good call on the boxes since I only linked to the lids, these are the boxes I used.

The main reason I suspect the GFCI breaker is that I also wired up a 240V GFCI breaker to run the pump/chlorinator at the same (same wire gauge and pulled at the same time).  It doesn't seem to be anywhere near as sensitive as this one.  But, it also doesn't have the same conditions as there's only two 240v outlets, "inside" the pump house.  It's not daisy-chained out through the yard.

Basically, I'm asking about it because I've never used a GFCI breaker before and I wanted to know that I wasn't using it "wrong" somehow.

RossD said:

You probably need to try to get everything water tight again. If you wait until it trips again you will probably find water in one of the exterior boxes causing the short to ground.

Probably not a good idea to spray 'em down with a hose, eh?

So the big take away that I'm reading is that I probably didn't screw anything up too badly, but there's likely water intrusion somewhere which is causing a momentary short to ground instead of neutral?  Reseal all boxes and try again?

In reply to WonkoTheSane :

Ok. Good info. I figured you knew, but it’s always good to start diagnostics with the basics. 

Is the poultry water heater the only load?  I would be suspicious of it first.   I’d also check the heater’s thermostat. 

Can you see if you get the same results with a load that does not include a heating element?

I’d also go back through those boxes and check that all of your connections are tight. 

SVreX said:

In reply to WonkoTheSane :

Ok. Good info. I figured you knew, but it’s always good to start diagnostics with the basics. 

Is the poultry water heater the only load?  I would be suspicious of it first.   I’d also check the heater’s thermostat. 

Can you see if you get the same results with a load that does not include a heating element?

I’d also go back through those boxes and check that all of your connections are tight. 

You guys are right.. I don't actually have good data.  I jumped on the unknown and just assumed I screwed something up :)

The only other tripping I've had with it tripping is a known-flakey little submersible pump that I've drained the top cover with earlier this year.   I say known flakey because it's the kinda thing you have to pull out of the water and tap a few times to get it to spin up before it'll pump.   I need to get a new one.  The pool lights (submerged) are on the same circuit as were some power tools I used while I was installing the fence with no problems.

I'll take a closer look at what the heater is pulling, and as I use the pool more this spring I'll pay close attention to see if there's anything else that trips it up.   I can also experiment by disconnecting half of the outlets to isolate if it's one box only when it's not freezing.

Thanks!

Is the GFCI necessary in this application; that is, is it necessary to have the extra protection beyond what a normal breaker provides?

Our ambient air monitoring stations at work are fitted with GFCI breakers for the outside, roof-top equipment and they do exactly what you're describing all the time; even when it's hasn't rained.  I've written the contract specs for the electrical service and built the systems myself, so at least in some cases, I know the components are quality, commercial-grade parts.  Still they trip.  I went so far as to build a piece of test equipment to see if I could make the breakers trip in our lab.  I couldn't make them trip in controlled conditions.  We tracked this behavior for years and I determined that basically ambient humidity is the likely culprit for us.  Our applications don't expose the site operators to standing water and the electrical code doesn't apply, so if a circuit continues to trip, I just put in a regular breaker.  If you're not bound to have a GFCI breaker, maybe just use a regular breaker?

In reply to Apis Mellifera :

Why wouldn’t the electrical code apply to an exterior outlet in a residence?

As far as I know, they are required. AND a good idea. 

If you're referring to my experience,  our usage is commercial not residential and not accessible to the public.  We're also the government, but I don't think that's relevant because the local/city governments inspect us from the pole to the panel, but it could be. 

GFCI breakers might be a good idea for interior use where there is a reasonable risk of serious electric shock, such as near water (pool, tub, sink, etc) and protection is necessary.  However, in my experience, the breakers, when used for exterior outlets servicing sensitive, sophisticated, scientific equipment, they stink.  We've used GFCI outlets as an alternative and they seem to be less prone to random tripping, but they do get sensitive after 5-10 years.

For ALL outdoor receptacle applications NEC (national electric code) requires GFCI protection.  A breaker or plug should provide the same protection.  Based on your description,  it appears that the unit is working g properly.  If I read your original post this happens when or after ir rains, correct? If so something is getting wet and the GFCi is detecting the problem and shutting off before some one gets shocked. They trip at 5 mA which is very little current. They also do have issues with some loads. A submersion heater may mess with it's sensors. They are designed to "see" if there is a difference in potential between the neutral and the ground and if the difference is too big it trips. The immersion heater is basically a controlled short circuit, the GFCI and heater may not play nicely with each other. Try testing the heater on another GFCI circuit and see if it trips that one. Your bathroom or kitchen outlets should have GFCI receptacles.  As for the load overall, #10 is good for carrying up to 30 amps. Your breaker is a 20 Amp and it will typically carry about 80% of that (16A) continuously but only 100% for a short time.  So if the breaker is tripping on other than wet weather you may need to check to see if it is tripping on over current or ground fault.  If the heater is truly only 125 watts that shouldn't be enough to overload the circuit, but if it is 1250 watts you are about 10 Amps so if you have other loads.o. the circuit it may just be too much on the circuit. It seems like.you did everything properly and where it has worked for a while I think all your components are probably good. I would start by checking all the boxes for moisture/water,  lose wiring, proper grounding and that all the gaskets and covers are good. If everything checks out, it may be as simple as the wild temperature swings you are having. It is likely condensation is building up inside the boxes and dripping on something and that would cause a ground fault. 

imgon said:

 If everything checks out, it may be as simple as the wild temperature swings you are having. It is likely condensation is building up inside the boxes and dripping on something and that would cause a ground fault. 

 

Looks like he beat me to it. My guess is condensation too.

Please provide clarification on where your chicken water heater is living. The not-weatherproof Heyco bushing in the side of it tells me it's not designed to get wet. Some of the reviews echo this thought. 

You might have water intrusion and once a GFI trips, it seems to do it just that little bit easier the next time. I have a GFI outlet on the back of the house that used to trip once in a while in the rain (because it has a semipermanently attached extension cord on it to the boat) and now it trips every time it rains.

Gearheadotaku said:

imgon said:

 If everything checks out, it may be as simple as the wild temperature swings you are having. It is likely condensation is building up inside the boxes and dripping on something and that would cause a ground fault. 

 

Looks like he beat me to it. My guess is condensation too.

That's true..  I didn't think of it but that's a great theory.

TenToeTurbo - the heated base for the water heater is inside the chicken coop.  There won't be any direct contact with water except the little bit that I spill when I refill it and that hasn't been bad enough to get near the cord/hole.

Apis Mellifera said: We've used GFCI outlets as an alternative and they seem to be less prone to random tripping, but they do get sensitive after 5-10 years.

This is exactly what I was asking.

I think I'll keep a log of when it trips and what the weather was near that time.  If it's a continuous problem, then I'll swap out the breaker to a normal one and put a GFCI outlet in.  I have one of those laying around anyway, so it's a free test.