Running power supply with just fans

[parker.trevor]

Would it be safe to run a 500W power supply with the only load being 4
12V fans (and a few LED lights) or would this not be sufficient load to
operate safely? If not, about how much load should I put on it?

 

[Eric]

I don't know why you would want to do that, but a Google search such
as: minimum + load + power + supply - as is, should find links to the
information.

Eric,
PC Buyer Beware!
http://www.pcbuyerbeware.co.uk/

 

[Conor]

Would it be safe to run a 500W power supply with the only load being 4
12V fans (and a few LED lights) or would this not be sufficient load to
operate safely? If not, about how much load should I put on it?

AFAIR you need a load on the +5V rail as it is a Switch Mode PSU.

 

[Guest]

Would it be safe to run a 500W power supply with the only load being 4
12V fans (and a few LED lights) or would this not be sufficient load to
operate safely? If not, about how much load should I put on it?

If you go to the power supply manufacturer's specification, you will see
that it has minimum loads specified on outputs, as well as maximum
loads. Here's an example:

http://www.antec.com/specs/NeoHE380_spe.html

In practice, some supply manufacturers build in loads that meet the
minimum power requirement. Others only require that one output is loaded
- but it may be the 12v, 5v or 3.3v.

In general, a load of a few watts (say 5-10) is enough. So one hard disk
will be fine as a minumum load. Doesn't even have to be connected to an
IDE cable...

If your fans are rated at .25A, 4 of them will take around 12W, which
should be fine. If they are rated at 0.1A or less, then that is pushing
the limit. But they need to be running at full speed, so no speed
controller!

 

[Guest]

Would it be safe to run a 500W power supply with the only load being 4
12V fans (and a few LED lights) or would this not be sufficient load to
operate safely? If not, about how much load should I put on it?

It's a good idea to load each of the positive voltages with at least
1-2 amps, such as with resistors, to prevent the duty cycle of any
output from going to an extreme, which you can often notice since the
supply whistles audibly or makes a screeching noise.

Resistance = volts/amps, meaning a 2A load on the +5V output will
require 2.5 ohms, either with a single 2.5 ohm resistor (hard to find)
or 4 separate 10 ohm resistors. Also very important is the power
rating of the load. Power = volts x amps, or in this case, 5W.
However a resistor run at its maximum rating will be hot enough to
cause burns in flesh or start fires when contacted by wood, fabric, or
plastic, so the power rating should be at least 2-3 times the
calculated power. If you use multiple resistors of the same resistance
rating, the power will be divided evenly among them, meaning in the
example above, with a total power of 5W, each of the four 10 ohm
resistors will dissipate 1.25W, and resistors rated for 3W, 5W, or 10W
are commonly available from sources like Radio Shack.