GFCI Tripping by Z-Wave Switches Controlling Christmas Lights

Hi. I’m having a GFCI tripping problem - my outdoor Christmas lights are going off when the GFCI trips.

I have a GFCI-protected outlet in the garage which is wired to two downstream outdoor outlets. A Honeywell Z-Wave Plus Plug-in Outdoor Smart Switch (39346) is plugged into each outdoor outlet. This is a Jasco switch and is identical to the GE outdoor smart switch and to the one Jasco itself sells. The Christmas lights are plugged into the Z-Wave Outdoor Switch.

I put up our Christmas lights last Weds 11/21. They worked fine with the Z-Wave automation for two days, then the switches went offline Friday 11/23 3:20 PM. They both went offline at the same time. Turns out the GFCI tripped killing power to both switches.

I reset the GFCI yesterday and the switches were immediately available again to the network. The SmartThings controller turned them on at sunset yesterday and then off at 11 PM. This morning both switches are offline again.

It was raining on 11/23 when the GFCI first tripped and it was raining again all last night, so maybe the tripping is weather-related.

I bought the house earlier this year. It is about 25 years old, but I think the GFCI outlet was installed about 10 years ago during a major landscaping project.

What to do here? On my earlier thread about this same circuit, GFCI, and a fountain pump (link below), some people were mentioning potential problems of Z-Wave switches tripping upstream GFCIs. On other we searches, people were mentioning the possibility of a slight current leakage during rainy weather that could trip the GFCI. I’ve also read that more modern GFCIs are less susceptible to nuisance trips.

Does anybody have any ideas on how to make these Honeywell Z-Wave Outdoor switches work reliably with upstream GFCIs in rainy weather? I sure would hate having to revert to old-fashioned dumb timers.

Z-Wave Control + GFCI: Will This Work?

If they are unprotected, make sure they are pointing down. That should be in the user instructions.

But really the simplest thing is just to get an enclosure box:

Your local Home Depot should have several to choose from.

If you get a double gang enclosure, it should be large enough for two of the outdoor switches.

Avoid metal enclosures and blue plastic enclosures. For whatever reasons, the blue plastic frequently interferes with signal more than clear or gray.

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It may not be your Z-wave switches, more likely you are getting water into somewhere.

I’ve used those Jasco’s - I have 4 but they invariably drop off my network and need to be removed and re-enabled. When I used them they never tripped a GFCI.

I have currently have GE switches in outdoor boxes and never tripped a GFCI. I know some say not to use outdoors, but 1 has been in use for 20+ months and 2 winters. It’s outside on an unheated shed. 2 are 1 1/2 old and mounted low on the house. 1 is on the outside of an unheated garage.

All are GFCI protected. I use a GFCI receptacle with these mounted downstream.

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I have had the same exact issue for years and prior to my journey into HA. The issue is most outdoor lights are cheap and not built to hold out water. Some are better than others but I have started using electrical tape to cover open ends of string lights, put around connections, etc. Even with this effort, heavy rain still trip my GFIC in my garage and I have just learned to live with it because the point of the GFIC is to protect your house, plus code requires that all outdoor outlets be on GFIC.

It’s not your Jasco plug causing this. You can read many posts online of other struggling with the same issue and ideas to solve here:

As you will see in some posts, you can try to narrow which light is causing the problem and then analyze it to see where the issue is or just remove it.

@Paul_Haskins @JDRoberts @ritchierich. Thanks for the input and ideas. After I posted this, I did a lot of Google searching and indeed found this is a common problem.

As a first shot at solving it, yesterday I changed the Z-Wave switches out for some simple timers that have photo cells and an on time delay of 2, 4, 6 and 8 hours. I selected 6 hours, so the lights will go on at sunset (about 4:30 pm late November) and off 10:30 pm. This will help narrow down whether it’s the Honeywell / Jasco Z-Wave switch or a more general fault of water ingress to the lights or cord connections between light strands. They worked fine yesterday, but it was a dry day. Rain and snow are in the forecast for Friday this week – that will be the big test.

I just talked to an electrician and he says GFCIs have gotten a lot better in the past five years and even improved a lot the past two years. The new ones are much less susceptible to nuisance trips like I’m having. He likes Leviton. Next week, I’ll swap out the old GFCI for a new one to see if that helps.

If I continue to have troubles with the Honeywell Z-Wave switches tripping the new GFCI (and assuming the new timer with solar cell works), I’ll install a power monitor on the GFCI outlet in the garage to send me notifications when the power goes out on that outlet (i.e., when the GFCI trips). Unfortunately, the Z-Wave Power Outage Sensor by seven7express is no longer sold. But its simple to use a 5V solid state relay hooked to the dry contact of a Fibaro window/door sensor. The 5V will hold the NC connection open when power is present. When power fails, the NC will go closed and I’ll get a push or SMS message that power has failed. See “Power Loss Alerts.”


@Paul_Haskins @JDRoberts @ritchierich
I just found the following item at Solid state/remotely resetable GFCI circuit.

My neighbours and I had one hell of a time trying to figure out why the hottub breaker was tripping…It’s a new GFI breaker that has an extra pigtail wire which goes to box ground.Now ever so often it would trip like a pig but we could never figure out why…Well we figured it out this way…Wire guage was over kill to handle the amount of draw…It was the only thing on the circuit so it wasn’t an overload issue…Proper outdoor outlet with cover etc…It was really driving us nuts till I remembered I had a huge problem with 1 spark plug wire on my old van do the same shorting thing…I simply used a dielectric grease on the inside of the wire (the boot) to block out all moisture and it worked…So we coated the plug wires on the outlet and no more moisture tripping which is what I think the problem is…Your GFI’S are tripping cause of moisture in the air reacting with the copper inside the receptical…So my point is try using dielectric grease on the plug to seal out moisture and outlet plugs with grease on them for your open outlets…You can get dielectric grease for like $7.00 at any auto parts place.Worth a try as it worked for me all winter as I also use a GFI breaker for my lights as it was easier to wire up then a full GFI circuit.Both are really sensitive to moisture…It also reminds me of when I was in high school and how they tested them with a spray bottle of water spraied directly into the outlet…Once it tripped it was reset and that is how they knew it was working…Keep it inmind when you think of GFI…The grease doesn’t take away from it tripping incase fo a short.It simply displaces moisture that is seen at the outlet itself…Outside is a damp place…All my cords were coated in this stuff…No trips at all.

Dielectric grease is not conductive. One incorrect logic is the “dielectric” in “dielectric grease” means the grease should only be used to insulate. All greases work by the low viscosity allowing the grease to completely push out of areas with metal-to-metal contact. Dielectric grease is just better at holding off high voltages over long paths.

Noalox Anti-Oxidant IS conductive and can be used on mating parts (pins, sockets, blades, etc). The problem is that it can cause a short between hot and neutral if it gets smeared in the wrong place.

Others have recommended Deoxit F5 on contact surfaces.

Good information here on “Dielectric Grease vs Conductive Grease.”

In my case it was a particular strand of lights that was the issue and not the plug and receptacle. I found many open ended wires on this particular light strand and ended up replacing it.