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Noob needs help water cooling two 7970s.

T

teknic111

Junior Member
I am building my first water cooled system and plan on only applying the water cooling to two 7970s. The case I'm using for this build is a Define R4.

So far I have purchased two XSPC Razor Waterblocks for the 7970s, and plan on buying the following major components to complete the build...


D5 Dual Bay Reservoir/Pump Combo

Black Ice GT Stealth 240 Radiator

What do you guys think? Is that radiator sufficient? Do I need any other components besides tubing, water block fasteners, radiator fans, and hose clamps?
 
teknic111 said:
Black Ice GT Stealth 240 Radiator
Click to expand...

Hmm I wouldn't run 2 GPUs on that small radiator myself, it'll have to be noisy. I aim for a water delta of 10 C normally although without a CPU in the loop that is somewhat less important. 2x 7970 at default clocks push over 420 W of power output so this is what you have to cool.

Simple rule of thumb for thin radiators is about 90 W of dissipation per 120mm fan slot at 800 rpm (near silent). You'll get nearly double that dissipation with a 1600 rpm fan but its still a little lower than ideal but good enough for GPUs. Depends how noisy you like it but I wouldn't put anything below an 1800rpm fan on there.

The stealth isn't exactly a decent thin radiator either, if you can fit it you would get better dissipation at lower speeds from a Swiftech MCR 220. Its a little bit thicker but performs nearly as good as the 6cm thick rads (another 20-30% performance).

teknic111 said:
Do I need any other components besides tubing, water block fasteners, radiator fans, and hose clamps?
Click to expand...

Barbs or pushing fittings to attach the tubing to the radiators, pumps and water blocks.
Maybe a phobya crossfire fitting for joining the two cards together. Nothing else is really necessary to get it working but you may find you need fan control (1800rpm is pretty loud).
 
Ok, thanks for the advice! I'm gonna ditch the thin radiator option and go with a bigger one. To make additional room, I completely removed my hard drive cages. Now I should have enough room to go with a decent sized radiator, while allowing for some nice air flow.

Here's a pic with what I'm working with so far...

NBEF76G.jpg


With the cage removed, I should be able to fit a Swiftech MCR 220 without a problem. Now My question is, is that my best option for a front mount, or is there a better radiator out there that would better suit the larger space?
 
teknic111 said:
With the cage removed, I should be able to fit a Swiftech MCR 220 without a problem. Now My question is, is that my best option for a front mount, or is there a better radiator out there that would better suit the larger space?
Click to expand...

I'd suggest an even thicker rad if your gonna go single 240 to cool them. Another option is to add a 120 at your rear exhaust fan.

Something similar to this 240 would be a better choice than the Swiftech

http://www.jab-tech.com/XSPC-RX240-Dual-120mm-high-performance-radiator-pr-4383.html
 
I am not a fan of the RX series either, they are a reasonable thick radiator but a thermo chill pa will outperform in almost every way.

I second that given the space go with a thick 6cm rad like the RX, the pa or because of the high speed fans a black ice extreme which is better past about 1600rpm.
 
Ok guys, thanks for the advice so far!

I think I'm gonna mount an RX240 in the front and a Black Ice GT Stealth 240 on the top. The Black Ice is gonna be a tight squeeze, but I think I can make it work. That's as much radiator as I can fit in this case.

What do you think?
 
teknic111 said:
What do you think?
Click to expand...
The front radiator has no clearance issues but the mounting could be tricky as the screw holes are not spaced correctly for a radiator. As for the top, there is an obvious clearance issue. I had the same certainty that it will fit in my 400R but the fact is that it didn't; tall VRM heatsinks are to be blamed.

I would suggest using a single Alphacool NexXxoS Monsta 240mm at the front. Dual 240mm radiators will work better and I have mixed reactions about its performance but it should be good provided that you have high static pressure fans to go with it.
 
dma0991 said:
I would suggest using a single Alphacool NexXxoS Monsta 240mm at the front. Dual 240mm radiators will work better and I have mixed reactions about its performance but it should be good provided that you have high static pressure fans to go with it.
Click to expand...
It's to late, I already pulled the trigger on the RX240 and Stealth.

dma0991 said:
The front radiator has no clearance issues but the mounting could be tricky as the screw holes are not spaced correctly for a radiator. As for the top, there is an obvious clearance issue. I had the same certainty that it will fit in my 400R but the fact is that it didn't; tall VRM heatsinks are to be blamed.
Click to expand...
If the Stealth doesn't fit in the top then I will stack the Stealth with the RX240 and mount them both in the front. Then I'll get a RX120 and mount it in the rear if needed.
 
teknic111 said:
If the Stealth doesn't fit in the top then I will stack the Stealth with the RX240 and mount them both in the front. Then I'll get a RX120 and mount it in the rear if needed.
Click to expand...
Radiator sandwiching isn't easy with the radiators you have right now. They have 2 different thread sizes. This could be solved with a fan/shroud in the middle but the screws are often flanged, making it difficult to use a short screw in the middle without grinding off the flanged edge or use a short screw that is only long enough but not long enough that it will impede the insertion of the screw.

Also, the ports will be a problem as the other end of the radiator isn't completely flat, this means sandwiching on opposite ends can be tricky. Read about radiator sandwiching to know which orientation gives you the optimum performance.

If all else fails, go with a single RX240. It should be just enough for a dual HD7970. The Asus Ares II has decent temps even with double thickness 120mm radiator.
 
teknic111 said:
If the Stealth doesn't fit in the top then I will stack the Stealth with the RX240 and mount them both in the front. Then I'll get a RX120 and mount it in the rear if needed.
Click to expand...

All the tests over at xtremesystems with sandwiched radiators showed worse performance than had they not done it at all. Its not an option.
 
It's hard to tell looking at your above image of your rig if the rad will fit up top. Kinda looks like if you position the inlet/outlet at the front of the case it may fit. To me it does look like the rear fan will be in the way but you could just mount it on the outside of the case if needed and put a fan grill on it if so.

Hard to ID your motherboard from the photo so I'm not sure if it'll have any clearance issues or not.

On another note with both rads adding the cpu into the loop should be doable.

GPU's temps on water are gonna most likely drop 50% or so anyways. At least that's what happened when I put a full water block on my 5850.
 
My 2 GTX 680SC's temps is about 24-26C idle with ambient temp of 67-69 roughly. Im using XSPC RX360. I don't know how hot those 7970 gets, but the RX 360 should be enough. But then again, not sure how RX360 would fit in your case.
 
Alright guys, here's a quick update and another question.

I now have all the essential parts and can put this loop together at anytime, but before I do, I'd like to have your thoughts on my plan. Also, what is the best way to construct the loop so I can easily bleed it? Should I add a T-line or add a quick disconnect somewhere in the loop?

Here is a pic of how I plan to construct the loop. I hope this is clear and makes sense...

NvwWLyB.jpg
 
Short is normally best and that looks like the shortest route to me.

Just bare in mind you are currently show a right angle turn in the tubing bottom right to get into the radiator, that isn't going to work. I think you likely have enough space to make a turn down there but if you are at 1/2 that might kink or cause leaks from that barb. If you have a 60 degree connector that would be better. If not then if it seems problematic use some hot water and setup a rig to pit the tubing into the shape you need. Getting the tubing soft then put it into the rig with that turn in it and make sure it doesn't kink. Leave it to cool down and you should be able to make that tight turn where previously when cold it couldn't.

Because the loop is closed you won't need to worry about bleeding too much, the reservoir will collect any bubbles you couldn't remove from the top rad after a little while and you can then just refill what was lost. I don't think a t line is necessary as you have a reservoir. As for quick disconnect you may want those around the GPUs, that way they can be removed along with the machine with the water cooling coming out. Makes upgrading GPU, motherboard etc a lot easier.

Otherwise looks good to me.
 
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Should've added the CPU in the loop. Those radiators should be sufficient with the CPU block. For easy drainage, use a T block with a drain port. Optimal placement should be at the lowest point of your loop, gravity will do the rest.

You might want to lay the RX240 on its side while filling and bleeding. There will be air bubbles stuck in the bottom pan of the radiator. Placing it on its side will allow the bubbles to rise out from the radiator.
 
Would these parts but only one radiator fit in a cooler master elite 430. Which radiator should i use. This would be for a i5-3750k and a 7950
 
Did you have to mod anything to get that RX240 in the front?

Pretty impressive if comes with native radiator support like that.
 
dma0991 said:
Should've added the CPU in the loop. Those radiators should be sufficient with the CPU block. For easy drainage, use a T block with a drain port. Optimal placement should be at the lowest point of your loop, gravity will do the rest.

You might want to lay the RX240 on its side while filling and bleeding. There will be air bubbles stuck in the bottom pan of the radiator. Placing it on its side will allow the bubbles to rise out from the radiator.
Click to expand...

The CPU at default clocks is 95W. The graphics cards are 210W each. 2 x7970's are 420 W of power dissipated into a loop, that is a lot of heat to remove. The CPU at default clocks might be 95W but once overclocked its more like 150W. All in all 570W with the GPUs at default clocks. But lets face it no one runs a 7970 at default clocks, they go up to about 270W overclocked. Total power usage = 270*2 + 150 = 690.

A thin 120mm radiator will cool about 90W quietly, a thick one will cool the same to 120W. Given that you either need very loud fans OR lots of radiators to cool the total system. But GPUs aren't so temperature sensitive, having them in a "hot" loop isn't a problem, it rarely limits their overclocking headroom. Given that this loop is sufficient (at 2x thick radiator (240W), 2x thin radiator(180W)) to cool the GPUs to just about 12C water delta quietly. If you put a CPU in there that delta rises to 16C which means the CPU will be warmer than if you had put a noctua air cooler on it. 10C is the macimum value you really want to use for watercooling, beyond that performance is a bit rubbish. But for a GPU that is enormously better than the default air and more importantly its very quiet.

So no the CPU not should have been added to the loop, it would overload it at full load and would need considerably faster fans to cool it resulting in a poor volume of fan noise.
 
BrightCandle said:
So no the CPU not should have been added to the loop, it would overload it at full load and would need considerably faster fans to cool it resulting in a poor volume of fan noise.
Click to expand...
At the current configuration, the CPU is the final part in the loop hence it wouldn't affect the GPUs much which will get chilled water after passing through the radiators. The temperature delta will increase but not including the CPU in the loop will be a waste as a whole. That Zalman air cooler wouldn't even be comparable to a CPU waterblock in that loop.

Given that the air cooler is run separately, it will be recirculating some of the hot air from the front radiator. Just to make it worse, the top radiator will just have hot air from the air cooler. Given its close proximity to the top 2 radiator fans instead of the rear exhaust, more hot air will pass through the top 2 fans.

Not everyone would want/could achieve the 10C delta if it comes at a cost of noise but the Noctua fans will still be fairly silent at full speed. It is a fair compromise to have a slightly hotter loop.
 
badb0y said:
Did you have to mod anything to get that RX240 in the front?

Pretty impressive if comes with native radiator support like that.
Click to expand...

No, I didn't have to mod anything. The only thing I did was remove the hard drive cages.

I'm more impressed the Black Ice GT fit on top. If it were any larger it would be a problem.
 
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