Question AlphaCool D5 pump not strong enough?

turok_tt

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Hi everyone, I just got a Singularity Computers Protium D5 reservoir and an alphacool VP655 D5 PWM pump. I?m testing them out of my system to make sure that the pump works fine before installing it in my build. Water travels from the radiator up to the inlet of the pump/reservoir and then it leaves the pump into the green tube (testing only) going back into the radiator. My question is this, there is a huge air bubble in the green tube close to the outlet of the pump and it looks like the pump isn?t able to pump the water strong enough causing the massive air bubble. It looks like water is just trickling down the green tube. Is this normal? I made a video and posted it in the link below.

At first, I thought this might be caused by the 90 degree inlet bend restricting the water flow into the pump. But then again, the pump is gravity fed by the reservoir so there is plenty of water feeding the pump and this shouldn?t be a feeding/intake problem.

I tried using a different D5 pump (Laing D5T Vario) and I get the same result. I also tried a different PSU (EVGA 850W) and get the same result.
So is that massive air bubble normal when water is leaving the pump? Or do I have to wait for it to naturally bleed itself out of the loop? I?m worried that my pump isn?t strong enough, but then again, I know D5 pumps can push through a lot.

Any comments/suggestions would be helpful, thanks.



View: https://youtu.be/HQ9Lx82aqIw
 

rubix_1011

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Open the vent cap on the reservoir. There is most likely air which cannot be displaced and removed and by the system being pressurized, it will remain in this state until the airlock is cleared.

Always leave the reservoir or loop vented until priming and filling is complete. This allows the pump to displace air by allowing the bubbles a way to escape.

Also make 100% the flow direction is correct based on the pump housing markings.
 

turok_tt

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Alright, I think I fixed it after some testing today. Yes, the flow is indeed correct based on the manual. I've checked 100 times.

Here is a video of the pump spinning, notice how its spinning quite fast and generating a lot of air bubbles? The air bubbles are then fed back out from the pump into the water loop. Also, notice how loud the pump is? With all the pumps I used in the past, it never sounded this loud.

View: https://youtu.be/ojIQlHWkOr4


After connecting it to a separate computer, this is how my pump sound like now. It’s completely inaudible (the background noise you hear is from the computer at the back). There are minimal air bubbles in the reservoir and inlet and outlet tubes from the pump. This is how quiet I am used to with my previous pumps. When I went into the BIOS, my pump was spinning at 1800RPM (Normal Speed). If I increased the pump speed to 4787RPM (Full Speed), I can replicate the loudness in the first video which sounds like a turbine. I also tried used a different inlet (top of my multi-port cap) on my reservoir and the water seems to be flowing well and not trickling or splashing back in.

View: https://youtu.be/lYzx9GVfms0


So all in all, it was indeed the pump speed/RPM. After modulating its speed, there are less air bubbles, less turbulence and the pump is much quiet now. I still did do a lot of tilting and rotating to bleed out the air bubbles as much as possible, but this looks and sounds much better than before. I’m more confident with my pump now and will reinstall it back in my system.
 

rubix_1011

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If the pump has a separate power adapter (SATA, MOLEX) you can use it to have it run at full speed and not have the PWM cable connected. This is how I run my D5.

Some D5's can be PWM controlled, some have a manual speed dial, I guess I assumed that pump speed had already been factored out, my fault.
 

turok_tt

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If the pump has a separate power adapter (SATA, MOLEX) you can use it to have it run at full speed and not have the PWM cable connected. This is how I run my D5.

Some D5's can be PWM controlled, some have a manual speed dial, I guess I assumed that pump speed had already been factored out, my fault.
No worries, I actually DON'T want to run the pump at full speed outside of my case because it creates a lot of air bubbles, I want to run it at a lower speed instead. My pump is not the Vario (manual 5-speed control at the bottom of the pump), mine is PWM controlled and requires it to be plugged into the mobo to control the speed. Hence, thats why i plugged it into a different computer in my video above.
 

rubix_1011

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That's another thing to consider - if it is introducing bubbles due to flow or cavitation, it might mean filling the reservoir to a fuller volume. You mention using the top inlet, which this will cause the most cavitation and introduction of bubbles whereas a bottom inlet will minimize turbulence.

With a filled reservoir and air purged from radiators, the air bubbles should begin to subside and no longer be reintroduced into the flow cycle. It might take a few days and coolant cycles to become apparent, but it should occur provided there are no leaks and air is removed.

You'll also see the best cooling potential of the loop with the pump running at full speed, but there is a diminishing curve at some point. I am firmly in the camp that pumps should be maintained at a consistent speed and not PWM managed as ramping pump RPM up and down based on monitored temps does very little in the short term due to the specific heat and thermal conductivity of water and water-based fluids. Radiator fans based on PWM and temp readings would be more effective, but even so, CPU core temps can bounce up and down many times in the course of seconds and it can easily take 15-30 seconds for coolant temp to change based on fan or pump speed changes. CPU temp readings are also not the same as coolant temp readings, which is why this concept is an important item to consider for watercooling temp management.
 

turok_tt

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That's another thing to consider - if it is introducing bubbles due to flow or cavitation, it might mean filling the reservoir to a fuller volume. You mention using the top inlet, which this will cause the most cavitation and introduction of bubbles whereas a bottom inlet will minimize turbulence.

With a filled reservoir and air purged from radiators, the air bubbles should begin to subside and no longer be reintroduced into the flow cycle. It might take a few days and coolant cycles to become apparent, but it should occur provided there are no leaks and air is removed.

You'll also see the best cooling potential of the loop with the pump running at full speed, but there is a diminishing curve at some point. I am firmly in the camp that pumps should be maintained at a consistent speed and not PWM managed as ramping pump RPM up and down based on monitored temps does very little in the short term due to the specific heat and thermal conductivity of water and water-based fluids. Radiator fans based on PWM and temp readings would be more effective, but even so, CPU core temps can bounce up and down many times in the course of seconds and it can easily take 15-30 seconds for coolant temp to change based on fan or pump speed changes. CPU temp readings are also not the same as coolant temp readings, which is why this concept is an important item to consider for watercooling temp management.
Using either the top inlet or bottom inlet of the reservoir both cause cavitation and introduces many bubbles when the pump is at max speed. When the inlet is at the top and if the filling tube is too short, it introduces a lot of splashing and air bubbles given the water returns with much force. When the inlet is at the bottom, the turbulence also produces a lot of air bubbles that are sucked right back into the pump before giving them a chance to bleed out. So in both cases, its not so much the location of the inlet, but moreso the speed/RPM of the pump affecting the turbulence of the water.

I normally don't even change the pump RPM fan speed when installed in my case, I tend to keep it as low as possible to minimize noise and extend the pump's life. I don't really see any performance difference when manipulating the pump speed according to CPU temps. I'm more inclined to adjust radiator fan speed like you as well.
 

rubix_1011

Contributing Writer
Moderator
I've had the same issue with the D5's I have used over the years in terms of air bubbles in a newly filled loop. Normally, these go away after a few days of operation. Most of the issue is fixed by maintaining a reservoir that is as full as possible while continuing to bleed air during the process.

This was less of an issue with older D5's where they did not have an integrated reservoir top like we see in most instances today, but mostly due to the separation and distance between each. Integrated reservoirs make life much simpler in terms of loop design and filling but do present a tendency for turbulence to exist.

Baffles and directional inserts can also help.
 

turok_tt

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Hi everyone, here is an update on my build. Pump and reservoir has been installed back into my rig and I’m just leak testing everything. So far, there are no leaks, however, I’m wondering if my pump flow is being restricted. As you can see from the picture below, I have a sharp 90 degree angle as the pump outlet, and sharp 90 degree angle as the pump inlet. I’ve seen other builds with these angled fittings, so I thought it would be okay. Would the 90 degrees outlet restrict the water coming out of the pump? The reason why im asking is because I have a flow meter right after the water leaves the pump and it is showing 10 revs/second and 0.4L/min which is really low, especially when the pump is on full speed at 4700 RPM. My flow meter works perfectly as I tested it out before on my other rigs. On my other rigs, when my D5 Vario was on setting 3-4, it would show 40 rev/sec and 1.8L/min. But now on my D5 PWM pump it is showing much less flow at max speed. I also included a video of this at the bottom too, along with my entire water loop. I have a CPU and GPU waterblock and two 360 rad.





Here is the video:
View: https://youtu.be/otqEArfF0vI
 

turok_tt

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Naaah, that wasn't the problem, the water level was high enough to prevent any cavitation. Anyways, I fixed the issue. The flow meter is much more accurate now and increasing the pump RPM doesn't create bubbles from the impeller. All the air bubbles are gone and the pump is inaudible even at high RPMs.
 

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