Build advice

[rintintin78]

Hi, I would like to build a new custom liquid cooling loop, but I need some clarifications. My PC specs are an RTX 5090, a 9800X3D, and a Havn HS 420 case, with an Alphacool VPP Apex D5 pump. After doing some research, I have a doubt regarding the configuration. I have two options in mind:

1. Two 420mm x 30mm radiators: one on top and one on the back, equipped with 140mm T30 fans, both set as intake. Additionally, three 140mm T30 fans on the side as intake, and two 140mm T30 fans on the rear as exhaust.
2. Three 360mm x 30mm radiators: one on top as exhaust, one on the back as intake, and one on the side as intake (all radiators equipped with 120mm T30 fans). Plus, two 140mm T30 fans on the rear: the bottom one as intake and the top one as exhaust.

I checked the W/10°DeltaT values on the Xtremerigs website based on my specific needs (@1.0 GPM and fans at 750 RPM). The values are roughly 175W for the 360mm radiators and around 230W for the 420mm ones. According to my calculations to dissipate 700W, the coolant temperature difference between the two setups would only be a few degrees (2 to 3°C).
However, with the two-radiator setup, I will have more fresh air entering the case (via the 3x140mm side fans), meaning internal components (motherboard, RAM, and SSDs) should get lower temperatures. On the other hand, with the three-radiator configuration, even though the liquid temperature might be slightly lower, I would only have one fan bringing in fresh air (the bottom rear 140mm), while all the others would be blowing radiator-warmed air into the case.
Could you help me understand if my reasoning is correct? If not, what mistakes did I make? And would the internal case temperature with three radiators really be bad enough to justify giving up those 3 to 4 degrees on the coolant?
Thanks!

 

[Eddy]

There’s a simple saying in the field of water cooling: “Nothing beats radiator surface area.”

If you want maximum cooling performance, go with the 3x 360 mm radiators. If you care more about a clean-looking build, then choose the 2x 420 mm radiators. That said, the difference in cooling surface area is only about 10% in favor of the 3x 360 mm radiators.

The case has so many openings that you don’t really need to worry much about airflow. However, it would actually be better if the radiator fans pulled air in from the outside instead of pushing air from the inside to the outside. That would give you another boost in cooling performance.

But in the end, is your goal to have great temperatures so you can show them off somewhere, or is it to have a quiet system that looks good? Because whether the water temperature ends up being 5°C higher or lower shouldn’t really matter, as long as neither the CPU nor the GPU starts throttling. And with this kind of setup, that won’t happen either way.

Also, whether your RAM or SSD runs a few degrees warmer or cooler won’t kill them. They’ll fail for other reasons long before slightly higher temperatures could cause any damage.

 

[rintintin78]

There’s a simple saying in the field of water cooling: “Nothing beats radiator surface area.”

If you want maximum cooling performance, go with the 3x 360 mm radiators. If you care more about a clean-looking build, then choose the 2x 420 mm radiators. That said, the difference in cooling surface area is only about 10% in favor of the 3x 360 mm radiators.

The case has so many openings that you don’t really need to worry much about airflow. However, it would actually be better if the radiator fans pulled air in from the outside instead of pushing air from the inside to the outside. That would give you another boost in cooling performance.

But in the end, is your goal to have great temperatures so you can show them off somewhere, or is it to have a quiet system that looks good? Because whether the water temperature ends up being 5°C higher or lower shouldn’t really matter, as long as neither the CPU nor the GPU starts throttling. And with this kind of setup, that won’t happen either way.

Also, whether your RAM or SSD runs a few degrees warmer or cooler won’t kill them. They’ll fail for other reasons long before slightly higher temperatures could cause any damage.

Thank you very much for your reply.
Please excuse me, I’m new to this world, even though I’ve been planning my loop for several months now. My main goal is to have a silent PC—I’m not into showing off or anything like that; I just like to have things as optimized as possible. However, I have always built air-cooled PCs, so alongside silence, I used to focus on achieving good airflow inside the case. I definitely want positive pressure; for everything else, I need the advice of those more experienced than me.

I have decided to go with a dual 420mm radiator setup, so that if needed, I can add another radiator in the future (though I don't think it's necessary right now). I still have some doubts regarding two specific configurations:

1. Two 420mm x 30mm radiators: one on top and one on the back, equipped with 140mm T30 fans, both set as intake. Additionally, three 120mm T30 fans on the side as intake, and two 120mm T30 fans on the rear as exhaust. This is how I think you intended for me to proceed. My doubt is: at full load (600W) with an ambient temperature of 25°C, the water Delta T might be around 10-11°C. Therefore, I would be pulling in hot air at 37-38°C, which could be slightly mitigated by the side intake fans pulling in fresh air at 25°C. Making a rough average (excuse the low-level approximation), I would have an internal case temperature of around 34-35°C (clearly, I'm not considering the heat that components like RAM, motherboard, etc., contribute, so the temperature would be worse, not better).

2. Two 420mm x 30mm radiators: one mounted on the top as exhaust and one on the side as intake, both equipped with 140mm T30/G2 fans. Additionally, three 120mm T30 fans on the bottom as intake, one 120mm T30 top-rear exhaust fan, and one 120mm T30 bottom-rear intake fan. Clearly, with this configuration, I expect a slight worsening of the Delta T—let's say 12-13°C—but the internal case temperature would be significantly lower (I estimate 30-31°C, given the greater intake of fresh air and less hot air).

So, in conclusion, based on my estimates—though I’m not sure if they are correct, which is why I want to rely on you experts in the field—by sacrificing 1-2 degrees on the liquid temperature, I would gain 5-6 degrees on the case temperature, which seems like an excellent compromise. What do you think? Am I missing something?"

 

[Eddy]

I would leave out the 30 mm fans. We do not even offer mounting screws for our radiators for those. You would have to get extra screws with an M3 thread and a length of 35 mm. I am assuming here that you would mount the fans on top and not between the case and the radiator. If that is the case, you would need M3x38 mm screws.

I would still recommend using normal 25 mm fans. They are completely sufficient.

In general, you are simply overthinking this too much. The case is like Swiss cheese, with an almost completely open rear panel. There are so many slots that the interior will not heat up that much. You can also generally forget all those calculations. All of our industrial customers also come around the corner with wonderful calculations, which in the end have absolutely nothing to do with reality. Our long-standing customers do not do that anymore either; they test it directly themselves and rely on our experience.

A Delta T of 10–11 °C would be record-breaking. More realistic would be 15–20 °C, depending on fan speed. If you want to set it up ideally, then have the air come in from the bottom and go out through the top, or the other way around. That will give you the best results. With that case, however, I would not worry about it too much and would build it the way I personally like the look of best. In the end, whether your GPU reaches 55 or 65 °C under full load is completely irrelevant. It will not get much hotter than that anyway.

The CPU with the X3D cache will generally run very warm, even with water cooling. That is simply because the cache sits on the die, and the CPU heatspreader is extremely thick and transfers heat poorly. But the temperatures will still remain in the green range. I would estimate around 80–85 °C on the CPU, even if the ambient temperature is 30 °C.

Let me give you a practical tip: do not overthink it. Just build it the way you like it best. You have 700 W of waste heat; that is not a problem for water cooling. We have already cooled servers with 1500 W of waste heat using two 360 mm radiators in a sandwich setup. We used be quiet! Silent Wings fans that only ran at 1500 rpm. We had a water temperature of 50 °C at around 22 °C ambient temperature. And as mentioned, the radiators were in a sandwich setup because we used a 4U server chassis.

If your goal is not to keep the GPU below 50 °C under full load, which would theoretically be possible, then you will have absolutely no problems cooling 700 W with the two 420 mm radiators. In the end, it is not about 2, 3, or 5 degrees. That no longer plays any real role here. The internal temperature of your case is also relatively irrelevant as long as there is airflow. It will be lower than with air cooling either way.

Especially GPU air coolers distribute all the waste heat inside the case. Due to the ATX layout, that heat is very difficult to move out of the case. You do not have that problem with water cooling at all.

You will not have the critical temperature zones you would have with air cooling. That is out of the question.

 

[rintintin78]

I would leave out the 30 mm fans. We do not even offer mounting screws for our radiators for those. You would have to get extra screws with an M3 thread and a length of 35 mm. I am assuming here that you would mount the fans on top and not between the case and the radiator. If that is the case, you would need M3x38 mm screws.

I would still recommend using normal 25 mm fans. They are completely sufficient.

In general, you are simply overthinking this too much. The case is like Swiss cheese, with an almost completely open rear panel. There are so many slots that the interior will not heat up that much. You can also generally forget all those calculations. All of our industrial customers also come around the corner with wonderful calculations, which in the end have absolutely nothing to do with reality. Our long-standing customers do not do that anymore either; they test it directly themselves and rely on our experience.

A Delta T of 10–11 °C would be record-breaking. More realistic would be 15–20 °C, depending on fan speed. If you want to set it up ideally, then have the air come in from the bottom and go out through the top, or the other way around. That will give you the best results. With that case, however, I would not worry about it too much and would build it the way I personally like the look of best. In the end, whether your GPU reaches 55 or 65 °C under full load is completely irrelevant. It will not get much hotter than that anyway.

The CPU with the X3D cache will generally run very warm, even with water cooling. That is simply because the cache sits on the die, and the CPU heatspreader is extremely thick and transfers heat poorly. But the temperatures will still remain in the green range. I would estimate around 80–85 °C on the CPU, even if the ambient temperature is 30 °C.

Let me give you a practical tip: do not overthink it. Just build it the way you like it best. You have 700 W of waste heat; that is not a problem for water cooling. We have already cooled servers with 1500 W of waste heat using two 360 mm radiators in a sandwich setup. We used be quiet! Silent Wings fans that only ran at 1500 rpm. We had a water temperature of 50 °C at around 22 °C ambient temperature. And as mentioned, the radiators were in a sandwich setup because we used a 4U server chassis.

If your goal is not to keep the GPU below 50 °C under full load, which would theoretically be possible, then you will have absolutely no problems cooling 700 W with the two 420 mm radiators. In the end, it is not about 2, 3, or 5 degrees. That no longer plays any real role here. The internal temperature of your case is also relatively irrelevant as long as there is airflow. It will be lower than with air cooling either way.

Especially GPU air coolers distribute all the waste heat inside the case. Due to the ATX layout, that heat is very difficult to move out of the case. You do not have that problem with water cooling at all.

You will not have the critical temperature zones you would have with air cooling. That is out of the question.

So I miscalculated with two 420mm radiators—will my coolant have a delta T of 15/20 degrees? And if I added a third 360mm radiator, how much would the fluid temperature drop?

 

[Eddy]

I was assuming a very low fan speed of around 500–700 rpm here. That is the bigger deciding factor. With 3x 360 mm radiators, the difference would also only be around ~2 °C. To be honest, I do not know how you arrive at a Delta T of 10–11 °C.

 

[rintintin78]

I was assuming a very low fan speed of around 500–700 rpm here. That is the bigger deciding factor. With 3x 360 mm radiators, the difference would also only be around ~2 °C. To be honest, I do not know how you arrive at a Delta T of 10–11 °C.

Thanks! I had assumed a slightly higher fan speed and a PC power consumption of 600W while gaming.
So, are you confirming that even if I install 3 radiators, I won't have any temperature issues inside the case?

 

[Eddy]

You will not have that with either the 2x 420 mm or the 3x 360 mm radiators. As long as you exhaust enough air, there will be no problem here.
And as I said, 600–700 W is not an issue for either configuration.

 

[rintintin78]

You will not have that with either the 2x 420 mm or the 3x 360 mm radiators. As long as you exhaust enough air, there will be no problem here.
And as I said, 600–700 W is not an issue for either configuration.

Thank you for taking the time to meet with me