AC Fan use in PC??

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Splork

Other than having to wire a separate external circuit for them, are there any
reasons for not using 120v fans in a PC?? I have a bunch as well as the tools
to mount and wire them. Quiet and powerful relatively speaking.

Any drawbacks via radiated EMF noise??
 
Splork said:
Other than having to wire a separate external circuit for them, are there any
reasons for not using 120v fans in a PC?? I have a bunch as well as the tools
to mount and wire them. Quiet and powerful relatively speaking.

Any drawbacks via radiated EMF noise??
Click to expand...

I can't imagine any problems, except possibly with sound cables that
run close to the fan or its AC cord, but I had no noticeable noise
pickup with old Roton and Sanyo AC fans.

Assuming this is a 120VAC fan, be absolutely certain to cover all
exposed high voltage, such as at the connectors. Use connectors with
hard plastic shells on them, and cover their wire connections with 2
layers of heatshrink, even if they're enclosed in hard plastic. Use
proper strain reliefs that also provide electrical insulation.
 
Other than having to wire a separate external circuit for them, are there any
reasons for not using 120v fans in a PC?? I have a bunch as well as the tools
to mount and wire them. Quiet and powerful relatively speaking.

Any drawbacks via radiated EMF noise??
Click to expand...

Yes, I think so. It is another path for EMI to couple to the AC line.
The AC line is a radiating antenna, so the power supply manufacturer
tries to keep high frequency off of the AC line. You will have wires
to the fan running around the case, closer to the high frequency
stuff, and those wires will be tied directly to the AC line without
any filtering (unless you install some).

This is also another way for 60 Hz to couple into the computer. It
would be easy to introduce 60 Hz hum into the audio system, for
example.

I'd be surprised if the resulting case meets EMI standards. But this
may not be an issue for you, as it's your own computer and if you have
EMI problems you can address them yourself.

I think a more important disadvantage is safety. If anyone other than
you ends up opening the case, they are not going to expect 120 V AC to
be going to the fans.

DC fans are pretty inexpensive, are the AC fans worth the effort?

Terry
 
The magnetic field from the 120v unshielded AC fan will do wonders for
garbling your data in the computer.
 
The magnetic field from the 120v unshielded AC fan will do wonders for
garbling your data in the computer.
Click to expand...

I'm pretty skeptical of this.

First, DC motors have changing magnetic fields too. So why don't they
cause problems?

Second, the only thing the motor's magnetic field could affect would
be the hard drive (and I suppose a floppy disk). You'd have to have a
pretty big motor, much bigger than the small fans used in computer
cases, and loaded (ie, drawing a lot of current) to cause problems.
And you'd have to mount the fan right on top of the hard drive.

Terry
 
Splork said:
Other than having to wire a separate external circuit for them,
are there any reasons for not using 120v fans in a PC?? I have a
bunch as well as the tools to mount and wire them. Quiet and
powerful relatively speaking.

Any drawbacks via radiated EMF noise??
Click to expand...

I don't know, but I thought of that today while in Target. They had
some 4 inch steel AC fans. Just like regular type but tiny. Of course
made in China.
 
I don't know, but I thought of that today while in Target. They had
some 4 inch steel AC fans. Just like regular type but tiny. Of course
made in China.
Click to expand...
Thanks all for your input.

Have a bunch ot these in the 3 & 4 inch versions, similar to their DC
counterparts but heavier construction and greater power.
Might give it a go. I need a lot of airflow.
I Am wondering about proximity to hard drives though. Just an inch away. Guess
some more research is needed.
 
I think a little 12v power supply to run all your 12v fans
would be a good way to go. I'd pass on 120 volts.

Too much juju.
 
I think a little 12v power supply to run all your 12v fans
would be a good way to go. I'd pass on 120 volts.

Too much juju.
Click to expand...
I do not have a bunch of 12V fans but I do have a bunch of great, powerful,
quiet 120V fans.
 
Splork rattled our cages with this on Friday 4/7/2006

Other than having to wire a separate external circuit for them, are there any
reasons for not using 120v fans in a PC?? I have a bunch as well as the
tools to mount and wire them. Quiet and powerful relatively speaking.

Any drawbacks via radiated EMF noise??
Click to expand...

I wouldn't do it because of the possible hazards and probable
interference with computer operation. However, if you think it's
viable, give it a try. Remember *safety* though. You'll be pumping a
120V line through your box instead of 12V. If something goes wrong and
the hot side gets loose (physically) you can do an awful lot of damage
to the MB and surrounding equipment as well as possibly to yourself.
If you experience intermittent problems after installation then you
know you're experiencing interference and it will either have to be
addressed of the fan(s) will have to be removed.

--
_____________________________________________________________

That's all,


"Just because you're not paranoid doesn't mean they're not out to get
you"

< Colin Sautar >
 
Splork rattled our cages with this on Friday 4/7/2006



I wouldn't do it because of the possible hazards and probable
interference with computer operation. However, if you think it's
viable, give it a try. Remember *safety* though. You'll be pumping a
120V line through your box instead of 12V. If something goes wrong and
the hot side gets loose (physically) you can do an awful lot of damage
to the MB and surrounding equipment as well as possibly to yourself.
If you experience intermittent problems after installation then you
know you're experiencing interference and it will either have to be
addressed of the fan(s) will have to be removed.
Click to expand...

Thanks for your comments.

I have no problems with the ac harness and its installation and there will be no
ac hazard whatsoever. There are mini plugs that attach to the fans solder
terminals and a simple distribution point to join wiring to an inlet. May even
tap into the Power Supply ac before the Circuit breaker to give me a one plug
connection to the outside world.

My case is large and I would use 2 4" fans in front for intake and perhaps one
smaller fan above the power supply for out take if required. Drill and saw
will be required to open things up a bit as well as adding a second drive bay.

Intent is a positive case pressure and a high QUIET airflow. High airflow dc
fans make a racket.

I am concerned about the radiated 60hz AC field and wondered if there were any
information sources regarding this or someone who had direct experience.

Thanks again!
 
Splork said:
I have no problems with the ac harness and its installation and there will be no
ac hazard whatsoever. There are mini plugs that attach to the fans solder
terminals and a simple distribution point to join wiring to an inlet.
Click to expand...

Unlike sockets, when plugs come loose they can expose high voltage.
May even tap into the Power Supply ac before the Circuit breaker
Click to expand...

What circuit breaker? I haven't seen one in a PC power supply in
decades.
I am concerned about the radiated 60hz AC field and wondered if there were any
information sources regarding this or someone who had direct experience.
Click to expand...

The electric field is easy to shield against with any metal covering,
although I doubt you'll need any because of the low impedance of all
the audio signals, except possibly the microphone input. The magnetic
field should be even less of a problem since the 10x higher voltage
will make the current 10x weaker than for an equivalent DC version of
each fan.
 
Jeepers, one way to get speed up.... and get wind...

Note the fan doesn't 'have' to be a 120V, it could be some othe
voltage but obviously would need the use of a transformer, gee a 1
watt fan will do some blowin' and on a 120V system will only tak
around 80 mA or 0.08 A, a circuit breaker need not be elaborate, a
in-line fuse holder would be enough, but what about th
noise level..

Do avoid those that uses carbon brushes and use a brushless, don'
think the magnetic field will create havoc but obviously need's to b
kept away from the audio circuitry in case of induced hum a
mentioned, keeping all magnetic fields away from the hard drive

Surprising how effective a fan is on the side of the case, these ar
the cases I will get next time

Dav
 
Unlike sockets, when plugs come loose they can expose high voltage.
Click to expand...
The plugs are made for this purpose, and when detached do not expose anything.
I have the plugs as well. If you were looking at them you would have no
concern.
What circuit breaker? I haven't seen one in a PC power supply in
decades.
Click to expand...
Whatever circuit protection device might be used for the PS line input, not an
external device, meaning I would be tapping off the AC Line socket before any
other internal PS connection.
The electric field is easy to shield against with any metal covering,
although I doubt you'll need any because of the low impedance of all
the audio signals, except possibly the microphone input. The magnetic
field should be even less of a problem since the 10x higher voltage
will make the current 10x weaker than for an equivalent DC version of
each fan.
Click to expand...
Metal coverings would obstruct airflow, no.

If the fans were equal in power consumption, would not the same power yield the
same magnetic field??
Besides, I am using AC fans because they (the ones I have in my hand) are of
greater air moving power and consume more power. I am expecting WIND. I really
need to keep the case cool.
 
Splork said:
On 18 Apr 2006 02:56:32 -0700, (e-mail address removed) wrote:
Click to expand...
I am concerned about the radiated 60hz AC field and wondered if there were any
information sources regarding this or someone who had direct experience.
Click to expand...
Metal coverings would obstruct airflow, no.
Click to expand...

I'm including the shielding foil or braid found on some cables. I'm
sorry I didn't make this clear.
If the fans were equal in power consumption, would not the same power yield the
same magnetic field??
Click to expand...

The strength of a magnetic field is related to the current, not the
power, so for the same air flow your 120VAC fans should generate a
magnetic field 90% weaker than that of 12VDC fans.
 
Besides, I am using AC fans because they (the ones I have in my hand) are of
greater air moving power and consume more power. I am expecting WIND. I really
need to keep the case cool.
Click to expand...

I used a fan for a long time with no problems. I also
wanted more force and liked to idea of not loading
more onto the power supply that I had. So I bought
an AC fan at Radio Shack, cut a hole in the side
of the case, mounted the fan, and plugged it in
separately. I never had any trouble. It pulls a lot more air,
though. To cut down on dust deposits I mounted it
to blow inward and I bought a blanket-type furnace filter.
With that I fashioned a large
filter on the outside to stop dust without creating air
resistance. It looked like a 7-year-old's model of a
nuclear power plant stuck to the side of my PC, but it
worked well.
 
mayayana said:
I used a fan for a long time with no problems. I also
wanted more force and liked to idea of not loading
more onto the power supply that I had. So I bought
an AC fan at Radio Shack, cut a hole in the side
of the case, mounted the fan, and plugged it in
separately. I never had any trouble. It pulls a lot more air,
though. To cut down on dust deposits I mounted it
to blow inward and I bought a blanket-type furnace filter.
With that I fashioned a large
filter on the outside to stop dust without creating air
resistance. It looked like a 7-year-old's model of a
nuclear power plant stuck to the side of my PC, but it
worked well.
Click to expand...

Far more dust will be blocked by a car air filter, and either the round
or rectangular type can be used. Even the worst one will clean the air
much better than the best blanket-type furnace filter, and some are
available for as little as $1-3. They also have so much surface area
that they'll last a long time before clogging.
 
Other than having to wire a separate external circuit for them, are there any
I've done that to one case long ago: nibbled a hole in the power supply
and ran a zip cord to the internal 120 volt fan.
Like you, I had a selection of fans: quiet vs. louder
but moving much more air.

If anything, I'd suspect that the 60Hz fans have much more metal
so they're better shielded that today's mostly-plastic 12 volt fans.
Remember, the DC fans are turning their magnets on and off
to spin the blades but seem to create no interference.
I wouldn't do it because of the possible hazards and probable
interference with computer operation. However, if you think it's
viable, give it a try. Remember *safety* though. You'll be pumping a
120V line through your box instead of 12V.
Click to expand...

AAAAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHH!

I just can't stop screaming enough from that statement.
- there's 120 - 240 volts in the power supply.
Why is /that/ safe?
- mainframe and midi computers used 120v Boxer Fans all over.
I've never seen them 'zapping' anything, mostly because
they used higher quality wiring and connectors than today's 12v fans.
Use a pre-molded fan connector and there are no exposed connections anywhere.


On the other hand, only low voltage fans offer the
yellow tachometer wire to monitor them,
not that you're running any program that'll monitor and report that anyway.
 
Jeff said:
I just can't stop screaming enough from that statement.
- there's 120 - 240 volts in the power supply.
Why is /that/ safe?
Click to expand...

Because it is isolated inside a metal box, and without prying the box
open it's hard to electrocute yourself.
- mainframe and midi computers used 120v Boxer Fans all over.
I've never seen them 'zapping' anything, mostly because
they used higher quality wiring and connectors than today's 12v fans.
Use a pre-molded fan connector and there are no exposed connections anywhere.
Click to expand...

They were also opened only by people who knew what they were doing.

(There are exceptions, like the one I know of who laid a metal tool
across some low-voltage rails on the backplane--in the days when these
rails really were rails--and fused the tool to the rails before the
power supply blew.)
On the other hand, only low voltage fans offer the
yellow tachometer wire to monitor them,
not that you're running any program that'll monitor and report that anyway.
Click to expand...

It's hard to find software that will successfully find and monitor
fans and temperatures.
 
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