Electrical tape is better than nothing I suppose. It's never a good idea to jimmy-rig something with electricity running through it. If it means re-designing an entire set up so you can grow herb with no structure fires, just do it. I'm sure you can find UL listed parts to accomplish the same thing you've got going with the solder and tape so look into it. Sometimes it can take quite a while to get even the smallest and most simple of grows up and running.Keep that in mind for the future. The less corners you cut the greater the benefit in the end. This goes double for growing good dope.