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 <[email protected]> On Behalf Of Adam Moffett
Sent: Wednesday, April 10, 2019 3:08 PM
To: [email protected]
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.
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