Thanks for the responses. The garage has a 150A sub panel or I wouldn't have asked the question, frankly. It already has a 20A 240V branch properly breakered to a single outlet. This garage is a part-time wood shop. Currently have two staionary tools capable of operating on 120 or 240 volt. One is wired for each at present because that's how they arrived. Not sure about the logic of 240V devices requiring individual circuits. Nothing magic about the voltage and the big rule is not to exceed the capacity of whatever circuit you might have. I was thinking to install 12 gauge wire and the saw and jointer each have 15a plugs, and draw around 5.5 amps each. I don't envision running both at once. Am I missing something? My intent in putting them on 240 is to add versatility to the shop and impose some automatic discipline in separating medium draw devices from, say, the radio and battery chargers by putting the power tools on the power tool circuit. Then if I had the 120 also available then I would tend toward using those outlets for lower-draw tools also, like grinder, scroll saw. I could see installing a GFCI in each box as they're not that expensive. Seems to come down to price of individual GFCI's versus the wiring effort and the price of wiring. Since the garage itself is a work in progress I think I'll 1. Think it over for now 2. Add outlets to the existing 120V circuits where appropriate 3. Extend the 240V circuit to a couple convenient spots, and if there is not already a 120V outlet nearby, add a 120V GFCI receptacle 4. Make up a 240V extension cord for the time being. How's that sound?

Are any of the receptacles GFCIs? I found a similar situation in a restaurant where the new owner had decided he needed GFCIs everywhere in the kitchen and had to do it himself. Some of the original receptacles were split-wired on two circuits. He ended up hooking one circuit to LINE and the other to LOAD. You could have a similar situation. Unrelated to your case, but fairly humorous (to me): the duplex he replaced was 240V 2wire+G for large toasters. He replaced it with a regular 120V GFCI, and the two hots were in opposite directions. The results were: 1- (original complaint) "everything I plug into that outlet blows up" 2- GFCI was very hot (and non-functioning) 3- Turning on one breaker caused the other (which was in another panel) to trip. That place was (and probably still is) a disaster. I'm sure terribletom has seen it.

Greg, it does sounded like I have a switch loop here which is switching on the hot side. I did not include this possibility initialy. But the problem is not a switch connection. The problem is I have no best way to know which wire is connected to which switches or outlet, especialy there are muilti-circuits tighted together ( another word, I try to figure out how the circuits are connected) . My initially thought was only one circuit which make sense to me for it is in the basement, not much power needed there. I doubt the condition is dangerous. Well, it is dangerouse when you walk when you trip and fall... or you can conside eating is dangerous,you can choke to death... I would say it needs to be cautious when you deal with voltage and current. But as long as you know what you are doing, and know what you need to look out for, any househood wiring is not as dangerouse as you think. Understand the circuits is important as well as having solid grounded wires. My attemp is to find the best way to understand how my circuits are connected together so I can track down if there is open/short somewhere. Once I know where is the problem at , I can fix it. Also, I can go on to add my ceiling light. ronnatalie, The ceiling box have 5 conduit ( which means 15 wires) in and out. I have no best way to tell which are feed lines from breakers which are not. I suppose I can untight the black wires and test the voltage presents. If the ones has voltage are the current "in" , and the onee doea not have the voltage are the current "out". At this moment, I hate to un-tight the wirenuts of red and black connection at the box. If I do, the box will be looking like a Medusa's hair, a mass. Is there a simply way to sort this out?

bigbird, I hate to be the one to inform you of this, but "immigrant" is hardly a racial slur. Ah, an illegal immigrant special! EXTREMELY "non-NEC-compliant"... Ole'!! Please tell us who the builder is, so we can all add to our "gotcha" database. ;') ... Just say NO to illegal UNlicensed immigrant electricians... yes, I've seen their fine fire hazards first-hand, when I lived in NV and AZ. I am not going to go to Germany and start working as an electrician. Why? Because I don't know German codes, standards, equipment, etc. Likewise, someone from another country should NOT just randomly move here (as ILLEGAL immigrants often do) and decide to pick up a skilled trade, for that same reason. I personally have no hatred for illegal immigrants - I just don't want them doing my electrical work - nor do I have an issue with immigrant electricians who have the proper education or experience. Education and/or experience would tend to imply some higher level of planning and organization than the concept of an illegal immigrant would seem consistent with. I am in 100% agreement with fixizin that ILLEGAL IMMIGRANT ELECTRICIANS are a bad idea. As far as his other posts: 12 AWG is the wrong wire to use for an electric water heater, as a 20A circuit cannot supply a continuous load of 4500W. I personally am an african/portugese mix, and my friend next to me is... well we haven't figured out what he is. I think I am quite qualified to be offended when it comes to true racism, which fixizin's posts do not contain. Search for forum for his name. He asks plenty of valid questions. His assumption that the original poster had two red wires in a conduit may (or may not!) have been inaccurate, but, based on his asking many questions, I do believe he realizes that he doesn't know everything, and I suspect he merely made the assumption that everyone's water heater was hooked up the same way as his. I have often made such assumptions about other devices and arrangements, in addition to drawing electronics theory into electrical wiring. I am thankful when people correct my assumptions, but not when they get pissed off at me for making them. In no case have I ever seen one of these hate-filled threads where only one party is at fault. RELAX, MOVE ON.