SSR, grounded frame, and GFCI

Context: I took the frame and part of the Z stage from the piece-of-junk Tronxy X5S I bought a few years ago, and started over for almost everything else. After getting sidetracked for a long time with other projects, I’m back to finishing it. I’m using an SSR to switch a 750W keenovo heater. I put TCOs on the heater and the SSR heat sink to catch the two likely failure cases. I bolted the SSR heat sink to the frame as a secondary heat sink.

When I switched on the SSR, the GFCI tripped. (This is how I discovered that the room is behind a GFCI. I think a lazy electrician 15 years ago messed that up.) The frame is grounded. It appears that the SSR is leaking sufficient current to the frame to trip the GFCI.

Does anyone know whether this is a normal characteristic of SSRs or an indication that I have a dodgy SSR? I can isolate it and make sure that it doesn’t leak dangerously if it’s normal; if it’s a sign that the SSR is faulty I can replace the SSR.


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When you have eliminated the impossible and the improbable, it’s often a good idea to check out the probable as well. :roll_eyes:

One of the possible reasons for a GFCI to trip is if you actually connect load to ground and — I had a stray connection to ground. So yay, lazy electrician who picked a convenient place to wire in the new outlets instead of going all the way back to the breaker panel!

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