My rule for -48 plants is we label the - side -48 and the + side RET. Then I get a hammer and beat "positive is positive and negative is negative" into my techs heads. I also like to do Black for RET and white for -48.
On Wed, Apr 10, 2019 at 3:49 PM Adam Moffett <dmmoff...@gmail.com> wrote: > There's an IEC standard where you use +blue and -gray for a -V DC system. > I'm sure we can find a document somewhere saying -Red for a -V DC system. > I read a book when I was around 10 or 11 that said red was positive, and > that stuck with me forever. > Then I learned about AC where red was a second hot when you need 2 > phases or a 3-way circuit. > > When you get multiple DC circuits in one box it seems more dangerous to > follow "standard" colors than not to. > > So I'm not gonna bag on anybody for preferring one way or another as > long as they're self consistent. Some future generation might thank you > for putting a label somewhere that says "+" or "-". > When you get into someone else's box, Red is just a color, and you > better get your multimeter out and check. Assume makes an ass out of u > and me. Mostly me. It also blows up your equipment and trips > breakers. I guess if someone labeled a wire as "+" I'd be more likely > to believe it, but you never know who came after and thought it was > wrong and decided to "fix" it. > > I'm not trying to lecture the EE about electricity. Just shouting at > the wind I guess. > > > On 4/10/2019 4:16 PM, Ken Hohhof wrote: > > I have a couple sites where I used purple or blue for -48, but I have > spools > > of red/black zipcord that I use a lot, and I assign red to voltage > > independent of polarity, so that black is ground. Then even if I use > single > > wires, I make red voltage and black return in order to be consistent. > > > > I think it would be even more confusing to have red be ground and black > > be-48V. Especially at mixed voltage sites that also have +24V. > > > > > > -----Original Message----- > > From: AF <af-boun...@af.afmug.com> On Behalf Of Adam Moffett > > Sent: Wednesday, April 10, 2019 3:08 PM > > To: af@af.afmug.com > > Subject: Re: [AFMUG] DC/DC converter question > > > > Some people use red for negative on -48V systems. > > I've got a -48V Alvarion Wimax thingamabob with a red and black pigtail > > coming out the back and the red is clearly labeled negative. > > > > So yeah, can't go by color unless you put that color there. > > > > > > On 4/8/2019 3:31 PM, Christopher Tyler wrote: > >> Turns out the whole shelter's bus was wired backwards when we got it. > Red > > is negative and black is positive. Not sure what the ground is relative > to, > > not sure it really matters at this point but I'll check that out when I > go > > out there later myself. > > > > -- > > AF mailing list > > AF@af.afmug.com > > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > > > > > > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- Carl Peterson *PORT NETWORKS* 401 E Pratt St, Ste 2553 Baltimore, MD 21202 (410) 637-3707
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