ᐅ Troubleshooting Short Circuit During Rain

Hello, every time it rains, the RCD trips. This means that the garage door, the gate, and the washing machine stop working. You can only "fix" the latter problems by switching off the circuit breaker for the outdoor lighting. We have numerous outdoor lights. Is there a way to narrow down the problem so that you don’t have to dig up the connections for each individual lamp, as the electrician suggests, but can approach it more selectively? Thanks in advance.

Do the outdoor lighting fixtures have only fixed wiring connections, or do they also include socket outlets? Do any of the outdoor lights have their own dedicated circuit breakers?

In case of rain, I would gradually disconnect everything from the power supply that can be disconnected WITHOUT digging, and check if the fault disappears on a specific circuit.

Troubleshooting should proceed from simple to complex, not the other way around.

Rain -> Corrosion/Resistance Value -> Ground/Moisture…
Smells a lot like outdoor lighting.
The RCD monitors Line and Neutral.
If the outdoor lights are connected separately, you can isolate the fault current flow by disconnecting the neutral conductor at the terminal strip.

Warning: Working with electricity is and remains life-threatening!
If the professional already suspects a defective outdoor light, I wouldn’t recommend experimenting.

Remove the bulbs and see if the situation improves.

For the brave: Artificially sprinkle individual lights with a watering can until the RCD trips.

That already sounds very much like damaged insulation in the ground.

We had exactly the same issue. We also tried to narrow down the problem by process of elimination, but without success. The conclusion: no more outdoor lighting during rain. By coincidence, after two years, a cable fault was being investigated by Bayernwerk AG just around the corner, in an underground cable beneath the street. Long story short: an electrician found the fault at our place using a similar device. The cable was located directly under the paving of the driveway. The underground cable was damaged, most likely either already damaged during installation or from years of stress caused by vehicles.

Often a lamp is also "flooded." I would try to locate the problem area by pouring water, even using a watering can.

It is best to seal everything outdoors with Aquasit or a similar product. This is reversible and provides peace of mind. Of course, only after a successful test run.