I bought a small ceiling spotlight fixture that I meant to convert into an outlet-powered desk lamp. It has three wires (brown, blue, yellow-green) coming from it, e.g. it has a grounding wire because the fixture is of a metallic material. I'm in Finland, the lamp is from Germany.
Because I plan to use it for a smart LED bulb that is commanded by software (electricity to device always on), I thought that I probably wouldn't need to get an on-off switch to the wire; Also, I found it very difficult to find desk lamp switches with three instead of two wire terminals. So I bought a regular mains cable that has exactly the same color coded three wires in it. I connected them to the lamp's wires by fastening them to the kind of screw terminal that you usually use for ceiling fixture installations. A very simple installation, and technically not one that I hadn't done many times before. But because I had tampered with the wire myself and I was about to switch this fixture on for the first time ever, I hesitated to do so by having to be so near; So instead of plugging the device directly to the mains outlet, between them I put a remote controlled plug adapter so I could switch it on from a remote control. I use them all the time, to switch on/off some of the hard to reach devices around the house. But when I switched it on, this new lamp blew the fuse in that part of the house! At the moment when that happened, the fixture base lied on heavy wooden material, no contact with metals. The bulb that was connected to the fixture has not been damaged, it lights up when tested with another fixture. It's a GU10.
I re-checked my connections and detached the fixture's socket to investigate. I found no visible flaws or imperfections. I got a multimeter but the instructions are of absolutely no help to someone who doesn't already know everything. But I think that I have now ruled out that the main circuit doesn't short: By setting the meter dial to Ω2000➜├ and touching each prong with the measuring pins, the meter reads "1". I have not measured ground.
As a complete amateur I can only come to think of a few things:
- Should I have just skipped the remote controlled plug adapter and plugged the device directly to the outlet? On the other hand, I don't understand how the adapter could've been the problem: I use them all the time, also on devices with a grounded wire, and the adapter has metallic contacts for receiving the ground signal from the plug.
- Or is it the actual mains outlet's fault? I live in an old house with outlets so old that they don't have the ground contacts, outlets with ground contacts are only found in the kitchen and the bathroom, likely a more recent addition. But then again, I'm using devices with grounded plugs here all the time and I've heard that it shouldn't be a problem.
- Or did I just happen to have too many devices on at the same time and that was the last straw? It does seem a bit odd though, after all, we're talking about switching on a single LED bulb – hardly a heavy strain.
I haven't attempted to plug the device in since. Did I create something dangerous, is some part of the system malfunctioning, or was this a one-off to ignore and simply retry? What should I test or attempt to do next?