Zarathustra[H]
Extremely [H]
- Joined
- Oct 29, 2000
- Messages
- 38,877
Oh, you're using delta-t across the blocks? That's interesting... And the oscillating makes sense. Every time I've seen the "delta-t" figure used in reference to controlling a watercooled loop, it's always the delta between coolant and ambient temperature.
Yeah, you are right, that's how the term is usually used.
I did some thinking about it and decided to try to use that as my pump speed control. The reason being is, the goal is to have the water flowing fast enough that you approximate a steady state where the water in the loop is mostly the same temperature. So, I figured the delta T across the blocks would be the most appropriate way to control this If there is a high delta T across the blocks, that means you need more flow.
What I hadn't counted on was temperature sensors wouldn't be accurate enough to really do this delta, even the fancy, self calibrating Aquabus Calitetemp ones. They claim to be accurate to 0.01C, but that is a joke. They are no very linear, disagree with eachother, and drift all over the place relative to each other as the temperature changes, making the delta T across the block figure rather unreliable.
My setup uses two coolant temperature sensors - one at the hottest and one at the coolest parts of the loop - averaged together for an overall coolant temp. Then I have three ambient air sensors - one each set on the fan frame behind my three 140mm "intake" fans - also averaged together. I did an initial one point offset calibration of the sensors during my leak test when they theoretically all should be at the same temp, but this really doesn't help much.
As you can see, right now - for instance - I recently powered my system on, and it's getting up to a steady idle temp. the CPU temperature delta is behaving as expected, but for some reason the GPU temperature sensors have drifted to a 0.3C delta, which is what I would have expected to see during a ~50% GPU load. This is keeping the pump at a higher speed than I would have liked (ignore the 1 gal/min over the chart, for some reason it rounds to whole numbers only, so it only ever displays 1 gal/min or 0 gal/min depending on rounding. The chart is accurate though)
Yesterday it was doing the opposite, with the CPU having drifted out of control, and the GPU behaving as expected.
The good news is that at least it errs in the right direction. I get full pump speed at load no matter what. It's just that I often get higher than desired pump speed also at idle, but sometimes not. So it's not the end of the world.
The virtual sensor that controls my fans is the absolute value between those two averages. The closer my coolant is to ambient, the slower the fans turn.
Ahh, I have decided to control my fans based on absolute loop temp. I want to keep the water at or below 35C, because I now my GPU at full load tends to run 4C to 5C hotter than the loop temp, and I like to keep the GPU at or below 40C, because that's when I see the best boost clocks in my overclock.
This used to be a huge problem with my old cheap linear eBay special Chinese fan controller. It worked well during the winter, but during the summer, the fans would spin like crazy even at idle, trying to - in some cases - bring the loop temp below ambient
I got my Aquaero in December, so I ahve not yet experienced Summer with it yet, but I am hoping that since I have a curve that is long and flat in the beginning, but ramps up aggressively as I get closer to my target temp, I'll have reasonable fan speeds at idle, even during the summer.
I don't modulate my pump at all. As has been said, the pump seems to be the same volume all the time, just a different pitch - so I set mine to the highest speed that isn't occupying the resonant frequency of my case or desk and leave it be.
This used to be my philosophy as well. My old pump was louder than I would have liked, but it was so across the range, only the pitch changed, so I left it permanently at full speed.
With my new EK D5 G2 PWM, I can barely hear it at any speed, even in a quiet room. I decided it would be good to control pump speed anyway though, because both the pump and the friction through the loop dumps heat into the loop, so I figured if I could run the pump slower when it is not needed, I will have less of that pump/friction heat, which will means my fans (in theory) can run slower.