Synching PSU and rear case fans?

halfpower · Post by **halfpower** » Sun Feb 06, 2005 12:06 pm

For the best air flow one should probably turn on the PSU fan when the PSU gets hot and also when the rear case fan comes on. If this is not done, then potentialy semi-hot air surrounding the PSU will get backwashed into the PC case and upset ideal airflow patterns.

Is my thinking correct? Does the PSU fan always rotate at a slow speed? Is the amount of warm air small? Will my motherboard likely take care of this?

- - h a l f p o w e r - -

Pjotor · Post by **Pjotor** » Sun Feb 06, 2005 9:31 pm

I can't think of any PSU where the fan controller isn't built-in (PSUs with manually controlled fans exempted).

PSU fans are controlled either by temperature (which is the most common solution) or PSU load.

I don't know if this answers your question, since I didn't quite figure it out. Please rephrase for a dumb Swede if you need more info and I'll try to help you.

lenny · Post by **lenny** » Sun Feb 06, 2005 10:51 pm

Pjotor wrote:I don't know if this answers your question, since I didn't quite figure it out.

I've tried to read his questions several ways and can't quite figure it out too. Sounds like he's trying to build his own fan control circuit for the PSU, but I'm not sure.

halfpower, not sure if this helps, since it's not what you asked about, but you can try searching for "psu duct" in the forums.

Kaizer · Post by **Kaizer** » Sun Feb 13, 2005 1:37 am

I think he's talking about synchronizing the speed of the rear case fans with that of the psu fan(s) so the two units don't work against each other. This can be a pretty big issue if your rear case fans are pulling more air out of the case than your psu exhaust fan(s) - there is a tendency for the hot air inside the psu to "back wash" into the case. I have this problem as my enermax psu has a considerable amount of opening on the panel opposing the rear exhaust fan. Heat has a tendency to "back wash" into the area between the psu and the upper 5.25 inch bays, despite the dual fan set up of my psu. In my case, a blow hole may help venting out the heat but a control strategy for the fans, (ie building a fan controller that balances the air flow of the fans) may work better.

StarfishChris · Post by **StarfishChris** » Sun Feb 13, 2005 11:50 am

I think the best way to do that is to have a PSU with leads for other fans, giving them the same voltage as the PSU fan (e.g. Antec). Of course, if you have a 120mm case fan and 80mm PSU, you'll probably want to reduce the voltage further to keep CFM the same - but then why not use the same fan for both?