Richard Crowley wrote:
"Daniel L. Belton" wrote
I agree that modifying one is much different than repairing
one, but in this case it would still be much safer than
overloading the existing wiring and connectors.
To help you out, here is the very first wire capacity chart from a
Google search: http://www.powerstream.com/Wire_Size.htm
Ok... using that chart, which is for open air wiring, nit bundled
wiring, a typical 22gauge wire can carry 7 amps. put 4 drives like you
say to do with a splitter, and you have overloaded the wiring... look
at the specs for a typical hard drive... here are the specs for the
Seagate ST410014A, 40GB drive...(the 40 - 200 gb are the same specs
powerwise) 2.8 amps @ +12v +/- 10%... 4x2.8 amps comes out ot be more
that the 7 amps that the wire is rated for.
Congratulations... by your advice of using the splitter, you just
caused an overload condition, and a fire hazard...
It shows that an 18-gauge wire (much SMALLER than anything
I have EVER seen in the cheapest and sleaziest PC power supply)
is rated at 16 AMPS. And to quote the description from that web
page: "The Maximum Amps for Power Transmission uses the 700
circular mils per amp rule, which is very very conservative."
look at your drive power wiring again... it's not 18 gauge wire...
most use 22 - 20 guage.
16 amps is enough to "very very conservatively" simultaneously
START eight Hitachi 180GB hard drives (note that they actually
RUN at a fraction of that current). Reference:
http://www.hgst.com/hdd/support/d180gxp/d180gxp.htm
(I used the worst-case startup current of the 12-volt supply
which runs the motor. The 5-volt supply is a fraction of that.)
Any of you running EIGHT 180Gb hard drives in your
computers? Perhaps not. And remember that this is running
all eight hard drives THROUGH A SINGLE "UNDERSIZE"
WIRE but still with a "very very conservative" margin.
Actually, I have 10 running here in my computer at home.
OTOH 14 gauge wire (which I see most commonly in PC
power supplies) is "very very conservatively" rated for
32 amps. That is 16 Hitachi 180Gb drives all starting
simultaneously through a single wire!
14 gauge?? not a chance... 14 gauge is used in the house wiring...
never seen it in the power to a hard drive.
And as for the Molex connectors, the capacity of EACH
PIN is 10 AMPS (or limited by the wire capacity). You
would have to create a daisy-chain of 3 or 4 Y-adaptors
to even approach exceeding the capacity of a single pin
(of the four). Reference:
http://www.molex.com/pdm_docs/ps/b9clpatf_ps.pdf
(bottom of page 2).
I did state that the molex connectors I saw go bad were due to bad
crimps... but you also must factor in that the current carrying
capacity of the wiring actually goes down when you do put a connector
on. you raise the resistance.
I have shown with actual manufacturers' data that under
a combination of completely worst-case conditions,
there is no significant danger of "overloading the existing
wire and connectors". You are virtually guaranteed to
overload the power supply before even approaching
the capacity limits of the wires or connectors.
That chart also states that the capacities are under ideal conditions.
and here's a quote from that same chart... "As you might guess, the
rated ampacities are just a rule of thumb. In careful engineering the
insulation temperature limit, thickness, thermal conductivity, and air
convection and temperature should all be taken into account."