SLK3000B, Phantom and negative airpressure?

Cros · Post by **Cros** » Fri Apr 22, 2005 12:14 am

Hi!

I am considering buying a SLK3000B case to complement my system. In this system I would have my Antec Phantom. I am one of the people who already has had one Phantom die on them, so as you can understand I'm a bit wary of not having enough airflow around the Phantom.

My plan for the case is to have two Nexus 120mm fans in it (back and front) and to have both of them sucking out air from the case. The front fan would be undervolted to probably 5v or so. Would this be helpful in keeping the HDs cool, or would it not help at all? Would it be better to have the front fan blowing in outside air over the HDs and would this make for higher PSU temps?

I'm just not very versed in airflow and airpressure matters. My thinking around this setup is that the negative airpressure of the case will pull some air through the Phantom as well as blowing it out across the bottom of it keeping it cool.

Thoughts please

sthayashi · Post by **sthayashi** » Fri Apr 22, 2005 6:27 am

It's not my place to say whether it would be better or not for the Phantom (perhaps AntecRep can answer that question), but having a Nexus in the back as well as a Nexus in the front will give you a pressure-neutral case (neither negative pressure nor positive pressure).

By only having one Nexus in the back you would create a negative pressure case.
By only having one Nexus in the front, you would create a positive pressure case.

~El~Jefe~ · Post by **~El~Jefe~** » Fri Apr 22, 2005 6:29 am

sthayashi wrote:It's not my place to say whether it would be better or not for the Phantom (perhaps AntecRep can answer that question), but having a Nexus in the back as well as a Nexus in the front will give you a pressure-neutral case (neither negative pressure nor positive pressure).

By only having one Nexus in the back you would create a negative pressure case.
By only having one Nexus in the front, you would create a positive pressure case.

positive pressure is where its at. Too many years of negative pressure cases to clearly show me how many illogical sorts of problems arise from that situation.

Cros · Post by **Cros** » Fri Apr 22, 2005 6:40 am

Thanks for reaplying!

Maybe I wasn't clear enough: My first plan is to have both of the fans blowing out of the case, i.e. the front fan would be sucking warm air from the system across the HDs and out of the case, increasing the negative pressure of the case (I think I'm using negative pressure correctly here).

~El~Jefe~:
So what you are saying is that you think that maybe I should have both fans blowing into the case? That would of course mean that there is room temp air blowing across the bottom of the Phantom, and only case-warm air ventilating out through it if any, so that might be a good idea.

The reason for thinking about negative pressure, I guess, is mostly for the dust situation.

StarfishChris · Post by **StarfishChris** » Fri Apr 22, 2005 6:49 am

He was talking about (doubly?) negative pressure:

Cros wrote:My plan for the case is to have two Nexus 120mm fans in it (back and front) and to have both of them sucking out air from the case. The front fan would be undervolted to probably 5v or so.

Since that is what most systems use as a matter of course - except with PSU and case fan exhausting at rear - it shouldn't bring any more dust, however I do see a situation where (if I am correct that the Phantom has fins and lets air through the bottom) you could easily create an 'air short circuit' with the rear exhaust unless you put some kind of partition; see the Silentium T2 review here, it's the same principle.

With both sucking you will have higher HD temps, since this air is coming from the PSU or the front of the case (depending on how well you cover the bay holes). I think you would be better off switching those fans around for positive pressure, which will give you the option of filtering the intakes if dust is a big problem.

ultraboy · Post by **ultraboy** » Fri Apr 22, 2005 7:20 am

If you have both fan blowing out, I think they will be fighting each other rather than helping each other in generating airflow for your Phantom.

My 2 cents.

sthayashi · Post by **sthayashi** » Fri Apr 22, 2005 7:48 am

Cros, do you have all the parts for this yet?

This sounds like an instance where just trying it out would be a lot easier than discussing it. You may want a thermal probe or thermometer to monitor the Phantom's temperatures.

I'd be inclined to agree with Ultraboy, except for the fact that the 3000B has a lot of holes that could theoretically be used for intake. In theory, it could actually work. In practice, the intake could still be quite restricted.

If you're really concerned about the Phantom, though, you COULD use the top 5.25" bays of your case, ghetto-mount a nexus fan up there and then create a fresh air duct from the fan to the Phantom. I think this would be a more effective way of ensuring that your phantom remains cool.

vertigo · Post by **vertigo** » Fri Apr 22, 2005 10:56 am

The problem I see with having a fanless PSU is that it is forced to become an intake in a negative pressure case and an exhaust in a positive pressure case, and when you have an intake near an exhaust the exhaust air goes straight into the intake again.

What happens is the air goes past the CPU, out the exhaust then in through the PSU and back to the CPU again, a baking hot cycle of air. The result is the PSU and CPU overheat typically and the PSU fries first because it can stand less heat.

The task is to not have an exhaust near the fanless PSU. A front exhaust and a side-panel exhaust might work, but usually a front exhaust is quite noisy. Usually you buy the fanless PSU because you want more silence, so this approach probably won't work.

The other idea is to use positive pressure so that even with a slow back exhaust ducted from the CPU the PSU is still an exhaust. This requires a high-rpm intake in the front, or multiple intakes. This can be done by having an intake at the bottom front in the usual spot but then also an intake in the 5.25" bay. These two intakes would give more pressure than the ducted exhaust fan at the back, and the air through the PSU would be relatively cold.

The problem with this approach is that you still have 3 fans, so the fanless PSU has not reduced your number of fans, but only resulted in them being in different locations. I think this is the best way to deploy a fanless PSU though because the air through it is cold.

Having 2 fans in the front and 1 at the back is surely more noisy than having 2 at the back and a slow intake in the front, so I am not convinced that fanless PSU's actually enable you to run a quieter PC. I would think you are better enabled with a fanned PSU.

~El~Jefe~ · Post by **~El~Jefe~** » Fri Apr 22, 2005 5:29 pm

Eh, well, if i had to make one with case fans and a phantom (my phantom is in its box I just bought it)

... I would put one 120 in front and one in back. I would get 2 nexus fans. I would put the back one at like 5-6 volts and the front one at a more obvious push. This would create a lot of air flow that would put more pressure in the case, but only slightly. I think neutral pressure is best with flow for a system, slightly positive is good, massive 2 in positive would be kinda crazy and I picture not enough exhaust ports in most silent cases, so logically (untested though this is just my thoughts!) it would cause a bit of stillness/not so great situation.

SLK3000B, Phantom and negative airpressure?

SLK3000B, Phantom and negative airpressure?

Re: SLK3000B, Phantom and negative airpressure?