Heatsink/fan config on new build

[ursa9_NCX]

First time builder. My question is: I installed an Arctic Cooling 7 Pro heat sink/fan on an Abit IP35 Pro motherboard. Following the manufacturer's recommendation I oriented the fan so it blows hot air towards the rear. So the fan faces the front of the case, and the heat sink faces toward the rear. The case has two 120mm fans, one intake at lower front, one exhaust at upper rear. This configuration places the heat sink about 2mm away from the the northbridge heat sink. The fan housing (plastic) is actually touching the northbridge heat sink. I'm not comfortable with this set up, but the only other option is to rotate the heatsink/fan 90 degrees so that the fan is pulling air from below the PSU (not a lot of head space here either), and exhausting hot air across the northbrige heat sink. What's the best compromise in this situation? If I rotate 90 degrees, will the PSU limit air intake, and is it OK to exhaust hot air onto the northbridge? Is my current configuration OK, or asking for problems down the road?

[Cricket]

What about orienting the fan towards the bottom of the case and the warm air exhausting up towards the PSU? If you can't do this for some reason then just leave the heatsink in it's current orientation. If the fan touching the northbridge heatsink bothers you, you could either notch the northbridge heatsink of the CPU heatsink fan housing.

Cricket

[ursa9_NCX]

Basically there are only two positions this thing will fit in. Exhaust to rear or across NB heat sink. Actually, would like to keep the hs/fan in its present position as it was
a bit of a pain to install in the first place. So your saying it doesn't matter if the two components touch? Not sure if blowing hot air on the NB heat sink is a good idea either, or maybe would actually help?

[Cricket]

In it's present orientation it's blowing warmed air towards the rear of the case, right? I would leave it like that (if that's the way you have it installed). Having the two components touch each other isn't ideal but I don't think anything really bad will come of it. Unless the fan is putting pressure on the northbridge heatsink...that might cause the pins (or whatever is holding the heatsink down) to weaken and come loose, and the northbridge may overheat. But if the two components are just barely touching each other I wouldn't worry about it.

Cricket

[ursa9_NCX]

Yes, the fan is facing toward the front of the case, and the fan casing is attached directly behind, and to, the heat sink. If this thing works as I think it does, the fan is sucking air in from the front and exhausting through the heat sink, dissapating heat to the rear then out via the 120mm fan mounted in the rear of the case. The HS fan and case exhaust fan are both mounted at about the same elevation. I removed the plastic fan & housing from the heat sink during installation, and when I put it back on it butted up against the northbridge heat sink. I bent one of the copper fins a little doing this, but seems easy to fix with a pair of needle nose pliers. At that point I realized it was really really tight, maybe there shouldn't be any contact at all between these two. There isn't any physical contact between the processor and NB heat sinks but the distance separating the two iis only about 2mm-very close. Other than that, the fan can operate but I'm worried that this configuration may impair the NB heat sink in some way I may be ignorant of.
No, I don't think there's any pressure on the NB heat sink now because the case is laying on its side but may be different later when the case is standing upright. In other words, I don't know if the weight of this unit will have any tendency to apply pressure against the NB when turned upright. In theory, it shouldn't if the pins are installed correctly on the motherboard. But I'm skeptical of theory, it's come back to haunt me before!

[Krazeee]

Maybe I just read too fast, but is it the plastic Fan casing that's touching the NB Heatsink? Or is it the CPU Heatsink that's touching...or is this the part that's just close, but not touching? If the plastic is touching the NB Heatsink, I'd just shave a bit off the plastic casing...doesn't do much...it's just plastic. If on the other hand its the CPU Heatsink that's touching the NB heatsink, I'd do like Cricket said and shave off a bit of the NB Heatsink so they don't touch. That's just my opinion though based on the situation as I understand it.

[Cricket]

Do you have a digital camera? If you do, take a picture of the problem area and we'll let you know what we think.

Cricket

[ursa9_NCX]

No, the processor and NB heat sink are not touching. There's about 2mm space between them.
It's the plastic fan casing that butts against the NB heat sink. As Cricket and Krazeee both suggested, I think shaving the plastic fan casing is probably the easiest solution, short of repositioning. By the way Krazeee, how would one go about shaving a piece off the NB heatsink? It's metal, and wouldn't this impair the heat sink? Anyway, I don't think I need to do that! Sorry, don't have a digital camera on hand at the moment. By the way, what do you think about the idea of rotating the processor fan/heat sink 90 degrees such that it exhausts across the NB heat sink? I'm not familiar enough with the thermal properties/ behavior of motherboard heat sinks to say if this would be good, bad, or indifferent as far as the NB is concerned.

Sorry if I'm making a mountain out of a molehill here but I'm sort of obsessive when it comes to design and engineering details and I feel pretty ignorant at this point!

[Cricket]

Originally Posted by ursa9_NCX By the way, what do you think about the idea of rotating the processor fan/heat sink 90 degrees such that it exhausts across the NB heat sink? I'm not familiar enough with the thermal properties/ behavior of motherboard heat sinks to say if this would be good, bad, or indifferent as far as the NB is concerned.

No, don't turn the assembly around, just leave it as it is...you want the warmed air from the heatsink to blow out of the case, not into it.

Cricket