GFCI and Exterior Rain at House Outlet

Good Morning to All and Merry Christmas! 
Lots of rain coming down here and I have a wee doubt about a gfci issue. Dedicated 30 amp house breaker in house panel for a fifth wheel. Properly wired 30 amp cord running to 5th from house outlet. I installed a grow light (small 2 bulb modern T5) using an outlet same side wall and close proximity to the gfci reset outlet in the 5th wheel bathroom. Grow light on timer was working fine for 3 days until the the rain storm came, then gfci tripped. Grow light outlet is downstream from the gfci deduced from checking all other outlets, never lost house power, no tripping RV breaker on house panel, battery fine, inverter fine, fuses fine. All good. However, the protective covering I had put over the exterior house outlet for the 30 amp going to the 5th had blown off in the wind and rain and was wet around the power cord, and on the face of it after unplugging and checking it. I could not find any apparent leaks inside the trailer to account for a short. After I had replaced the exterior protective cover and several hours had passed, the gfci reset button held and I got power back in those interior gfci 5th outlets (and it was still raining and blowing).
Is it possible that the short was right at the hot box on the house from the get go (from water) and this is what caused the gfci to trip, and the subsequent cold outlet connected to that gfci? The draw for the light is minimal and basically nothing else is running inside. The rest of the trailer was in perfect working order. Everything is working now. I thought these exterior cords are able to withstand hell and high water but maybe not.

Sounds like normal GFCI behavior.  It trips when there's any kind of leakage to ground, even a miniscule amount. It's purpose is to open the circuit whenever it detects the tiny amount of leakage current it takes to shock a human.

It has no way of knowing if the leakage to ground is caused by a human getting shocked or something else.  Even a little moisture between the hot pin and the ground pin at an outlet can create enough leakage to trip a GFCI.

Lou Schneider said:

Sounds like normal GFCI behavior.  It doesn't take much to trip a GFCI breaker ... it's purpose is to open the circuit whenever it detects the tiny amount of leakage current it takes to shock a human.

It has no way of knowing if the leakage is caused by a human getting shocked or something else.  Just a little moisture on some dust will create enough leakage to trip the GFCI.

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Wow, that was fast lol! But does it make sense that "the circuit" would be from the house box to the 5th, or is "the circuit" supposed to be contained within the 5th - i.e., can I trust that the exterior 30 amp hot box taking rain is the most likely culprit? It has a metal box and lid but due to the plug it doesn't shut all the way and got wet though I'd tried to staub in a good sized covering to sheet rain off it. I guess there could be two scenarios - one being the circuit from the exterior, another being a circuit short from within the 5th having zero to do with the exterior source of power. Just trying to be logical here and track this down, don't want to fry myself from ignorance lol.

tinkie said:

Wow, that was fast lol! But does it make sense that "the circuit" would be from the house box to the 5th, or is "the circuit" supposed to be contained within the 5th - i.e., can I trust that the exterior 30 amp hot box taking rain is the most likely culprit?

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It depends on where the GFCI that tripped is located.  Everything downstream from it is suspect.

If the GFCI is inside the RV, only outlets and wiring downstream from it will make it trip.

If the GFCI is at the power source (house panel or campground power post) everything is suspect, including the shore power socket, plug and cord.  And everything in the RV.

So yes, the wet 30 amp outlet is a prime suspect if the house panel GFCI tripped.  Remember, it only takes a very slight leakage to ground to trip a GFCI,  not a full blown short.  Although it will also trip if a full blown short makes the citcuit draw more current than the breaker's rating.

Ahhhh ok. So that changes things as the gfci is in the 5th wheel bathroom, meaning it would have to be either a water leak onto old exposed wiring on that downstream or that my grow light pulls too much (which I doubt). House panel breaker never tripped, no gfci on exterior plugin unit. Just odd that after hours of  "drying out" the exterior plugin, the gfci worked while it was still pouring rain, which would theoretically be the source of the short inside the 5th (barring too much draw from the light). Grow light is working perfectly fine NOW, will just have to keep my eye on things and look for wetness behind wall panels and elsewhere and check if the grow light timer kicking on is possibly creating an issue. Thank you for answering, trying to narrow this down.

...or that my grow light pulls too much

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It is not that the grow light "pulls too much". That's not what a GFCI does.  It only detects leakage of current (amps) from the hot or neutral wire to ground. It doesn't care whether that amperage is high or low and will totally ignore even a direct short from hot to neutral wires.  The circuit breaker that supplies the GFCI outlet is responsible for detecting and stopping excessive amp draw.

Gary RV_Wizard said:

It is not that the grow light "pulls too much". That's not what a GFCI does.  It only detects leakage of current (amps) from the hot or neutral wire to ground. It doesn't care whether that amperage is high or low and will totally ignore even a direct short from hot to neutral wires.  The circuit breaker that supplies the GFCI outlet is responsible for detecting and stopping excessive amp draw.

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Thanks for explaining that to me. Hunh...well it's only 100 watt, that shouldn't cause a problem. I just had it trip again after zero problems running the grow light all day yesterday and switching off via timer in the evening. Then timer and light switching on fine this morning running for 4 hours +-, when I went to check on it and opened the door the lights went off and gfci was tripped. No breaker thrown in the house panel, no breaker thrown in the RV panel, flipped the appliance circuit breaker and general purpose breaker and the gfci reset fine and lights are back on.
Is it possible a breaker is "bad", besides there could be a worn wire taking water somewhere in my wall?  Don't know how water could get past my eternabond seal on the roof seams but as we know...have water, will travel. I see zero indication of moisture in the walls but I guess all it takes is a tiny infiltration from somewhere to possibly screw this up. Next time it happens am gonna slow down and flip RV breakers one by one and check each time if the gfci resets, find out which one (if any) might be acting up. If it all points to a water leak somewhere, I gots some work cut out for me lol

It doesn't have to be an actual water leak that makes a GFCI trip. Even condensation from a shower or boiling tea kettle can do it under some circumstances. Is your grow light in a high humidity location?

NY_Dutch said:

It doesn't have to be an actual water leak that makes a GFCI trip. Even condensation from a shower or boiling tea kettle can do it under some circumstances. Is your grow light in a high humidity location?

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Hmmm now that's an interesting twist. I AM growing orchids and other tropicals in there and do run a humidifier but it's on the other side of the wall where the gfci outlet is at, using an outlet downstream. I just put the hygrometer right next to the gfci and get a read of 44% - too low for blooming orchids and doesn't seem high enough to trip anything. I try to keep it above 50% around the orchids under the light.

I put 3M plastic window seal on the tiny bathroom window and noticed it was gathering lots of condensation on the bottom edge of the plastic hanging a bit below the cold metal window frame. And that's roughly 2" to center of the gfci outlet,  but at present there is no water there since I wiped it a few days ago. I keep the furnace at an ambient temperature for the orchids of about 68-70 and that dries out any "weepiness" but I guess not around that particular window.

This is a bit bedeviling. I can't imagine that a random drop of water traveling in from some tiny leak would be responsible for an intermittent tripping that resolves itself quickly. One tiny drop falling on just the right wire in the right place sounds plausible but not if I can flip breakers that aren't tripping and get the gfci right back on. Logic says if there was a leak shorting it, that if it continues to rain - as it usually does here - then the conditions for shorting should remain pretty constant and/or a "wet wire" wouldn't just allow the gfci to be reset quickly. Since neither breaker - house or RV - is tripping, it's either gotta be a leak, possibly a worn out gfci outlet, or this high humidity you suggested.
Gary the RV Wizard clarified that it wouldn't be how much draw the light is pulling that would trip a gfci, so there goes my theory about the 3 prong plugin strip I've got the lights and timer unit plugged into instead of direct. Gosh darn it, so far its RV 1 vs. ME 0 !

Further checking!! You might be on to something Dutch! I still have some sleuthing to do but just noticed my fountain wasn't running where I keep the bulk of the orchids, and it's on a timer unit plugged into the same side of wall as the grow light but separate outlet. The timer unit had fallen a bit out but still plugged in though not running the fountain, and this is where I run a humidifier also. If I can test that outlet as also a downstream to the gfci, that could be the culprit getting mist on it and leaking. Have since switched it to the top plugin where it fits snug, but was watching the mist arch up in the air then fall down right in that area of the outlet with the timer unit prongs exposed a bit. It's possible!

An easy way to think of a GFCI is like a teeter totter.. Perfectly balanced neither end touches the ground but if one wire (Black or white) is carrying more weight.. (Current) then the thing tips or rather trips.

John From Detroit said:

An easy way to think of a GFCI is like a teeter totter.. Perfectly balanced neither end touches the ground but if one wire (Black or white) is carrying more weight.. (Current) then the thing tips or rather trips.

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And it only takes a 4-6 milliamp "weight" difference to throw it off balance...

The location of the GFCI outlet itself is not important - it could be many yards away.  Anything plugged into it or wired downstream of it can have the ground fault and cause the GFCI outlet to trip. That's its job - to remove power if any attached device is causing a safety issue.  So it's likley the lighs are the wiring to them that is causing the problem.  Some of the possibilities are physical damage to a wire, excessive moisture around connections or in a fixture/light/device, dirt or corrosion at a plug or wire connection, etc

It could be the power strip. How old is it?
The ?surge suppressor ? that is in many power strips has a failure mode that leaks current from the hot to safety ground. If the amount gets to the trip level, the cgfi trips. It could be that the strip leaks a little, the timer leaks s little and something else plugged in somewhere (like another power strip) also leaks a little. Doesn?t take much to get to 5ma.

Others are doing a good job of covering the electrical situation.

I'm just glad to learn that it's orchids you are growing.

Merry Christmas,

MERRY CHRISTMAS EVERYONE!!!

@Heli_av8tor

I'm just glad to learn that it's orchids you are growing.

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BWAHAHAHAH! Yeah, I guess someone could think otherwise. Thank you everyone for winnowing this down and teaching me. I think I got a handle on it - maybe.

@Lynx0849 The power strip is brand new and NOW only has the timer plugged into it with the grow light power cord into that timer (before it had one of those cordless house phones that rings from the house base phone) . The other downstream outlet has the other directly plugged timer for the fountain around my other stash of orchids, the plug that was half hanging plugged in when the gfci tripped last time.

So far today my conditions are exactly the same in terms of what's plugged in and where since trouble shooting after plugging the other orchid timer into the top snug position - and it's still raining the same as when it first tripped.  So far grow lights on timer popped off no trouble last night, then popped on perfectly this a.m., no tripping.

Only other thing I noticed was that in the gfci outlet itself, the bottom 3 prong plugin would not take a power cord. I was walking around plugging 2 and 3 prong things into all the outlets and thought hmmm lemme try both positions on the gfci. I wasn't going to jam something in while feeling resistance, so think am going to have that gfci outlet replaced.

The fact it's not tripping now since I put the other orchid timer power cord into the snug receptacle downstream (still not sure it IS downstream but would make sense considering where it is) makes me think that's the culprit. The humidifier there makes a very wet plume of moisture, and it's only about 5" away on the wall from the bulk of where my orchids live. I might not be the brightest bulb when it comes to electricity, but I knew enough to disregard the advice from my bil who said to tape the gfci in the "in" position. Ummmm no, doesn't work like that, but thanks.

As long as this holds under rainy conditions with no more tripping, am pretty positive it was the orchid timer downstream wobbling around over halfway out the socket and taking moisture. The inability of the gfci outlet to accept a standard plugin in the bottom socket also tells me it's probably titz up and time to replace. You have all been great in explaining what it does and doesn't do, I've learned something. The timers are definitely weak points to be watched. I'm pretty confident y'all got this solved for me! Thank you!

Stop fretting over WATER! GFI's trip for many reasons. Not just water!! It is a high possibility that you have a very cheap timer motor causing your problem. It's all about electric leakage to ground. Cheap motor winding will do it. A cheap transformer for lighting will also do it.