To all the brewers who provided great information, thank you.
I start writing answers to some of these questions and then have to re-edit my responses because I need to get more detailed. I want to try (as I’m sure others do) and cover as many bases as possible so no one gets hurt or killed. Respect The Volts! (I know it’s current, but it doesn’t sound as good…
SAFETY FIRST. As has been mentioned in this thread, electricity will kill you fast. Yes, it’s sometimes a PITA to go to the panel and shut off a breaker, but you’ll still be alive. (From my point of view, it’s probably the most exercise I’ll get all day.)
An inexpensive multimeter is a worthwhile investment. Flexible leads will also make your life easier. Some cheap azz meters/cord combos have cords that are too stiff and can wind up pulling the meter off a table or shelf, causing you to become distracted. The meter should also have slot at the top of the meter to put one of the probes in. This way you can put the meter/probe on the neutral bus and use the other lead to measure power at the breaker or hot terminal.
Don’t assume that the person who did the wiring before you did it correctly. If you have to assume anything, assume that the previous homeowner or landlord was the stupidest person on earth. Check first and be sure! Some houses have had more than one owner, which means more opportunities to have something done wrong. Homeowner #1, “Wiring For Dummies” in one hand, screwdriver in the other, “I don’t have the time to run to get the right parts, I’ll just take a short cut.”
The National Electric Code (NEC) is NOT law by itself. Municipalities, governments, etc. usually use a current version of the NEC (Most current is the 2011.) For example, here on Long Island, some towns use the ’05 code, others use the ’08 code. They take the NEC and make it law and usually amend it to make it more stringent. If you need to consult the NEC, I would suggest using the NEC code handbook. It’s the same code, but has explanations of some of the Fine Print Notes and diagrams, etc.
BrewBeemer, I like when people quote the NEC here, it gives me the chance to look up the citation and learn more.
Also, no matter what we say here, the final word lies with the Authority Having Jurisdiction (AHJ). Some places use an independent inspection company, others use an inspector from the Building Dept., or Power Company (POCO). Be nice to the inspector. They can make your life hell. If you have a question, ask it. Most inspectors will be happy to answer your questions or provide an explanation.
SUB PANELS. Like Pickles said, keep ground and neutral buses isolated from each other. Ground bus bonded to the panel itself, not the neutral. The neutral doesn’t get bonded to anything in the panel. Grounds to the ground bus and neutrals to the neutral bus, no mixing and matching.
Hermit. “Check from the third wire, whether it is neutral or ground, and see if you get voltage. Sinks, wall plugs if they have the third wire, copper plumbing, etc. If you get voltage between the two then you have problems. Chances are you won't see anything. Check from a hot to the test ground to make sure it is in fact grounded. But yes, in a properly wired environment neutral and ground are virtually the same. The earth ground is used to have a common reference. If you are pretty far from the transformer or have some other unusual circumstance, then they may not be the same.” With the advent of more and more plastic in our lives, using plumbing as a ground reference may not always work. At one time panels were grounded to the water main. Then we had to add a jumper to bridge the meter to the “street” side of the meter (rubber gaskets/Teflon tape may isolate the meter from the rest of the plumbing). Now some areas are using plastic pipe to deliver water to your house. Goodbye nice grounding point.