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The original was posted on /r/homeassistant by /u/Inevitable-Order4193 on 2026-07-17 12:06:16+00:00.
My Shelly Plug S (Gen1) does not pass through the protective earth connection from input to output. Sharing this so other owners can check theirs.
The issue came to light when my washing machine gave me an electric shock. The Shelly Plug S was connected to it to monitor power consumption. A measurement showed approximately 110V on the metal chassis. This is leakage voltage from the Y-capacitors in the washing machine's EMI filter, which should normally be safely dissipated through the protective earth.
A continuity test on the Shelly Plug S confirmed there was no earth connection from input to output. A second Shelly Plug S showed the exact same result. Smart plugs from other brands in the same wall socket all passed earth through correctly.
After opening one of the plugs, two causes became clear: a plastic ridge inside the housing physically prevents the input-side earth contact from making connection with the output-side earth contact, and the metal tube seems to be a bit short. Removing the plastic burr and some of the plastic pipe covering the metal tube immediately restored the earth connection, confirming these as the cause. That said, this isn't something I'd recommend as a fix as there's no guarantee the connection will hold when the plug is in use.
Shelly support was contacted with photos of the defect and measurements. After some back and forth, they forwarded the findings to their engineering team and will replace my two units with Gen3 models. However, they stated that they have no indications of a wider production issue and have not issued any advisory to other Plug S Gen1 owners. Since the Gen1 has been discontinued, they also said they no longer have production units for comparison testing.
So if you own a Shelly Plug S Gen1, it's probably smart to check yours. Set your multimeter to continuity mode, place one probe on one of the earth contacts on the input side (the pins/clips going into the wall) and the other probe on the corresponding earth contact on the output side (where you plug in your device). You should get a clear beep and near-zero resistance. If you get nothing, your plug is also faulty.
Takes 30 seconds and could prevent a dangerous situation.
Photos as proof: https://imgur.com/a/uASSVPR