Advice on DIY electrical work

First and foremost electrical work done wrong can cause fires and death. Second, most jurisdictions in the U.S. require electrical inspection and permits to prevent the first item. Third, anybody who is handy can and will do some un-inspected electrical work. Please do not be offended, but from the questions you are asking, you are not knowledgeable enough to be doing these things. I suggest that you hire a licensed electrician to do the first few tasks you need done and watch what he does. Ask questions. If he is willing, let him show you such things as what color the wires are that carry the live current and which are "common" wires. Let him get you familiar with the very basics. Next, look for a class in basic electrical wiring and home repair either at your local community college, extension or Big Box home improvement store. You need the basics before you start touching wires. As to your specific questions, I am interested in how you determined that the pipe supplying the furnace is copper. There should not be copper in the wall or ceiling carrying gas. Could it be a water line? I would not want a copper gas line in a wall where there is electrical. If the wall is open (you mention it is a garage) electrical can pass through the same area, but you should never close up this wall until the gas is in black pipe. The kitchen floor issue is strictly the province of a licensed electrician. There are commercial boxes that are intended for installation in commercial kitchens and are meant to protect against mopping and such, but you don't want to do this kind of work. No, I do not believe there is a book that will tell what you need yet. Get some instruction or befriend a good neighbor, but learning to do electrical work from a book is about as safe as learning to fly a plane from a book. Start with a mentor or instructor. Being self-sufficient is a great goal. Just do it the right way.

..another good reason to hire and chat up a tradesman is that there's nothing in this world as relaxing as watching somebody else work.

Be careful with wiring, there are a lot of mistakes that can be made that will burn you house down. Look for savings elsewhere. Just to be sure, when you, "tied off the wire ends with electrical tape and a wire nut." -you separated the wires and used 2 nuts, right? It you're going to tie off an outlet, it should be inside a junction box and behind a panel for access. Otherwise you need to disconnect it back at the next nearest junction box. Don't bury a live connection under the floor. What you really should do is hire an electrician and watch him and ask questions while he's working. If you don't interrupt the workflow too badly, tradespeople are often really happy to chat and explain what they're doing. You''ll learn a lot and they'll often offer advice on other jobs (like the conduit you wan to run in the garage. You add this to your knowledge base for next time you need to do something similar.

"Practical Electrical Wiring" (for US wiring) is a great primer. https://www.amazon.com/s/ref=nb_sb_ss_c_1_20?url=search-alias%3Dstripbooks&field-keywords=practical+electrical+wiring&sprefix=practical+electrical. It taught me a great deal about house wiring. I am Not An Electrical Engineer, but common sense and caution will take you a long way. You need a neon tester and turn off everything before you start modifying anything. I repeat, IANAEE! Any doubts, don't do it!

Old Geezer http://ask.metafilter.com/151850/Advice-on-DIY-electrical-work#2175696 "As to your specific questions, I am interested in how you determined that the pipe supplying the furnace is copper. There should not be copper in the wall or ceiling carrying gas. " Copper gas line is legal and common in Canada, even when covered. Practically any new residential install that can't be done with a single length of black iron uses copper instead. And one isn't restricted from running electrical in the same cavity. I missed that you intended to use conduit for the new wire run. EMT or Electrical PVC don't have to be protected at all, you can surface mount it where ever you want or bury it in the wall at any depth. However metal conduit should not touch copper pipe as there is a chance of galvanic corrosion.

Just to be sure, when you, "tied off the wire ends with electrical tape and a wire nut." -you separated the wires and used 2 nuts, right? I separated the wires and used two strands of tape and two nuts, and then pushed the tied-off wires back into the junction box that held the light fixture. As to your specific questions, I am interested in how you determined that the pipe supplying the furnace is copper. There should not be copper in the wall or ceiling carrying gas. It's a very dark, vaguely greenish pipe that looks like oxidized copper, and it runs across the garage ceiling and through the wall to the furnace and water heater in the basement. So knowing about galvanic corrosion (thanks, Mitheral) or other issues from metal touching metal (or being near metal) would be useful.