How many pumps needed for a MORA3 420

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[H]ard|Gawd
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Jun 25, 2007
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So after many many years of watercooling and many different builds, I’ve decided to switch to an external radiator setup and be done with switching radiators, fans, etc…. It starts to get expensive lol.

I’m currently cooling the following parts.

5900X and RTX 3090

The Mora radiator will be under my desk and case will be on top of my desk. There would be a total 8ft of soft tubing connecting the 2.

Do I need 1 or 2 D5 pumps?

Thanks in advance!
 
It's really tough to predict, and I'd defer to someone who has used that specific radiator, but given its size I would make an educated guess you'd probably get OK, but not spectacular flow with one D5. Probably in the just below 1GMP range. 0.8 to 0.9 somewhere.

This is certainly a usable flow, but your temps would likely benefit a little bit by bringing that up to 1 to 1.25 somewhere, and for that you'd probably need a second pump in series.

This will also depend on restrictiveness of the water blocks you use, and how many tight bends are in the loop.

Your water blocks and radiators would be operating slightly more effectively at those higher flow rates, BUT you'd also be dumping more heat into the loop from the second pump (~20 to 25W) so I'd probably use PWM controlled pumps so you can speed them up when needed, and slow them down when not.

The difference in temps would likely be no more than 1C at full load though, so you'd have to decide if the expense of another pump is worth it.
 
Sry, I missed your thread :(

Wise choice!
I definitely agree with going with a pair of d5s for a few reasons.
First is to make filling your loop easier. I'll explain. With my loop which consists of a hwlabs sr2 420, gtx 360, gts 360( a little less volume than your mora), cpu and gpu blocks and a 200mm res. Trying to fill and purge with one d5 can be a huge pita. Particularly getting the coolant up to the top rad for me. With both pumps running at roughly 60 to 70% its sooo much faster and easier. I use an old sunbeam rheostat style fan controller to adjust the pumps due to their defaulting to 100% (until I can connect the pwm cable and set it up). Running them both at full blast is just a little bit hairy because its so easy to run them dry.
Second, like Zarathustra mentioned you may not be able to hit 1-1.5gph with that combination of rad, blocks and length of tubing with a single pump. With two pumps you can easily adjust your pumps and flow once you're loop is filled at your leisure. So finding that sweetspot will be gravy.
Finally, it's never a bad thing to have some redundancy. I have had several DDCs die on me over the years. Needless to say, I do not tempt fate if I can help it! 😆
GL with the build, it sounds like a fun one!
 
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