Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!agate!usenet.ins.cwru.edu!gatech!mcnc!borg!oscar!tell From: tell@oscar.cs.unc.edu (Stephen Tell) Newsgroups: sci.electronics Subject: Re: RMS versus pk-pk (was Re: polarity) Message-ID: <3868@borg.cs.unc.edu> Date: 15 May 91 00:57:54 GMT References: <2399@cluster.cs.su.oz.au> <1991May10.202150.6785@rand.org> <2953@odin.cs.hw.ac.uk> Sender: news@cs.unc.edu Organization: University of North Carolina, Chapel Hill Lines: 71 In article <2953@odin.cs.hw.ac.uk> adrian@cs.hw.ac.uk (Adrian Hurt) writes: >In article <1991May10.202150.6785@rand.org> edhall@rand.org (Ed Hall) writes: >>In article <2399@cluster.cs.su.oz.au> rex@cluster.cs.su.oz (Rex Di Bona) writes: >>>The three wires in an AC General Purpose Outlet (those wall sockets) >>>are the active (red or brown), neutral (light blue or black), and >>>earth (green/yellow). >> >>Careful! Although the ground wire is generally green in the US, the hot >>wire is frequently black, *not* the neutral, which is generally white. >>Needless to say, what is standard in Australia (or the US) may not be >>elsewhere. >Here's the table I was given by our safety office: [Nice table deleted for brevity] >U.S.A. and Black* White | Black White Green or >Canada or Grey | or Grey Green and Yellow > >*Black for live in 2-core cords is now being replaced by Brown. > >My notes: >1. If you see green, yellow or a combination thereof, it's almost certainly >earth. >2. If you see blue, it's almost certainly neutral. Carefull!! In larger buildings in the US, 120/208 volt 3-phase service uses Black, Red, and Blue for the three hot wires, with the standard white for neutral and green for brown. I've seen such an installation (build less than two years ago, passed inspection) that kept the hot wire in its original color to identify which phase it was associated with even when there were no other hot wires in that conduit. So, an outlet could be fed by blue (hot), white (neutral), and green (ground). In the same building, yellow, brown, and orange are the three hot wires for 277/480 volt 3-phase. I don't think 277/480 is ever supposed to share a conduit with 120/208, though. I have seen it advised to "re-code" the white wire to blue with electrical tape when using both wires in two-conductor cable as hots, like to a switch. >3. If you see brown, it's almost certainly live. >4. What the black wire does, depends on what other colours are present. If >there's a white or grey wire present, then black is live, and white is >neutral. If there are two wires (black and red) or three wires (black, red >and green) then black is neutral. If there are three wires (black, red and >white) then black is live, white is neutral and red is earth! In the US, red/black/green could be 240 volts with ground and no neutral (two hots). Red/black/white could be 120/140 (or 120/208), although there really should be a neutral in there). >5. The jokers in the pack are Japan (red earth), and Greece and Switzerland.... Thanks for the useful info, but I think the real lesson should be: If you're planning to mess around with AC power, know what you're doing, have a voltmeter, know how to use it, and be extremly careful. Especially in another country or in an old building. > Adrian Hurt | JANET: adrian@uk.ac.hw.cs > UUCP: ..!ukc!cs.hw.ac.uk!adrian | ARPA: adrian@cs.hw.ac.uk -- Steve Tell tell@cs.unc.edu H: +1 919 968 1792 #5L Estes Park apts CS Grad Student, UNC Chapel Hill. W: +1 919 962 1845 Carrboro NC 27510 Duke Blue Devils: 1991 NCAA Basketball National Champions! We're Number 1 !! UNLV 90-91 record: "34 and DUKE."