Quote:

Originally Posted by buildtoexcess

I am doing this to minimise thermal spiking/stressing of the expensive bits.

I don't really see any need for this really. Temps won't be spiking if the computer is off so whatever temp the parts are at when you shut the computer down will only go down until they eventually reach room temp - even without additional cooling post-shutdown.

 

Would it be easier to go off the pins that connect to the front panel power button instead? I would think the fan headers are worthless after the thing is shut off.

 

Actually the thermal interface of each water block will +deltaT when coolant flow stops/system shutdown occurs, for several minutes or longer, depending on final maxT of chip interface.

I have also looked into simply continuing case fan(s) operation after system shutdown, but not as effective.

 

You could always get a bay psu like this and connect the water cooling pump and fans to it. It wouldn't automatically shut off but I'm sure there's a way to rig that up.

 

gm88, yes this is another way, I was thinking that mobo fan header, can be used to hold 12vDC relay "open" during pc operation, followed by mobo header @ 0.0vDC resulting in "closed" relay contacts after pc shutdown.

thanks

 

s.e. thanks I'll look at this approach tonight - I prefer DC circuit timers inside pc - I will check whether bay pwr unit uses mains AC 110/240 input or has isolated external pwr brick

 

They usually have a cable that runs down from the 5.25" bay to one of the expansion bay (PCI) brackets with a cable to plug from the wall to that bracket.

 

what do u want to tern the pc of when its under full load??

as my system is idle for 5 to 8min the loop is back to room temp

so if u just let the system idle be for u shot down there ant any problem
as any heat that is in the block will disapait into the still water

 

Quote:

Originally Posted by buildtoexcess

Actually the thermal interface of each water block will +deltaT when coolant flow stops/system shutdown occurs, for several minutes or longer, depending on final maxT of chip interface.
I have also looked into simply continuing case fan(s) operation after system shutdown, but not as effective.

How do you know about this? It just seems very unlogical that chip temperature will increase after system shut-down. And i dont think heat matters much when there is no current flowing through your components.
I think it's a waste of money to let it run longer.

 

If you have a good water cooling setup what you are wanting to do is completely unnecessary unneeded and a wast of money extra wear on your water cooling parts.

 

Let's look at what happens at cpu heat spreader surface & water block - as long as there is coolant flow, the sb will run between mid-30's to mid-70's (or higher if aggressively oc'd) AND those "moderate temps" ONLY result from constant coolant flow/high latent heat capacity of water.

Now when we shutdown system & motherboard, immediately ending coolant flow, although sb cpu has powered down, the silicon is still v. hot and will immediately transfer thermal energy to the mass of the water block, and without coolant flow the water block rapidly warms up to 45+ (especially if you were previously oc'd and stressing the system).

Even final prolonged idle immediately before system shutdown will not prevent temp rise - ie: cpu waterblock mass will be slow to achieve eqilibrium with surrounding air inside case - additional coolant flow AFTER cpu shutdown is req'd.

 

No it isn't. The amount of watercoolers that there are and have had no problems should show you its not needed.

 

I'm sure all of you are wondering if this extra cost is justified and have largely decided it's not worth the money.

Equal goals of "Quiet" operation and "Max" performance, combined with "Max" reliability - I can adjust my budget if something looks promising.

It's interesting that Koolance a few years ago offered an external controller + pump + res w/thermal sensing that would continue coolant flow, after cpu shutdown, using temp profile set points. This product does not now appear in Koolance consumer catalogs.

 

I completely agree that no individual pc user is presently doing this, however in emergency shutdowns of large server arrays, coolant keeps flowing.

 

You'll be absolutely fine without having the pump run after shutdown. There's no reason to do what you're talking about whatsoever.
It'd be nice if you could set up your sig with your system's specs for us (located at the bottom of your profile page).

 

What about this.

http://www.frozencpu.com/products/14773/bus-296/Bitspower_Universal_Cooling_After_X-Station_-_Blue_LED_BP-XSUCAM-BL.html

I think this is what you are looking for.

 

spot-on, I buy from bp & even have friends fluent in charactors to read through the bp tw/hk on-line store & have not found this,
thank you!

 

this looks so convoluted and complex for hardly any benefit

the water will still circulate slightly as the body of water still has momentum and is still a continuous body of water so the heat will still get to the radiator and be passively removed

 

If I wanted to keep my pump powered up after motherboard/cpu/gpu shutdown I would be powering my pump off either the power supply in my pfsense router (always on) my WHS box (always on) or a small AC/DC power supply.You would not need any more that 12v 1.75 amps to power the pump (this would be a pretty cheap power supply.It is when you want variable voltage and over 3 amps out of your power supply they get a bit pricy.My local electronics store has a couple of used units.Not a terrible idea to keep the water running after shutdown.I really do not see too much need to keep the fans running.

 

You're refering to "thermo-syphons" which require rather low flow resistance to work correctly.

The only real world performance application was two-stroke single cylinder trials & road racing motorcycles of the 50's & 60's - true thermo-syphon cooling systems, but unable to maintain cylinder head operating temp if combustion temperature suddenly increased (lean burn condition).

Coolant flow rates in pc systems must be moderately high to quite high when aggressively oc'g or fans are simply blasting away - thermo-syphon flow rate (no pump / pc system) is low due to multiple water blocks & radiator design - coolant temp rise quite rapid even if fan(s) are run max rpm.

Actually the most successful application of the thermo-syphon principle is the present day "cross flow" automobile water radiator - water already cooled in radiator develops increased density and settles to "bottom" of radiator assisting water pump flow.

 

im sorry but it just wont matter..... if you properly shut down your chip will unload most if not all load before it turns off the fans/pump. To test this its easy just load your pc, then suddenly unload it to as small as possibly and watch how quickly it cools down.... you can also use an external temp probe to mesuare the temps after a shutdown. you may find that 1 or 2 degrees above ambient may hold true for a bit but its nothing to worry about... these chips can run at 85 with no worries im sure even if it holds in the mid 40's (very unlikely) its not an issue.

HOWEVER if you truely wish to waste your money away a simple 12v 2amp power supply woiuld work jsut fine.. like the kind you plug into the wall to charge your phone....

 

If I've been load testing and the CPU temps hit, say 60ºC, as soon as I stop load testing the temps drop down to a few degrees above the 'normal' idle temps in less than a second before gradually reaching 'normal' idle temps within a few minutes. Can't see the point of keeping the pump running.

 

I think I have a cheaper (though slightly less elegant) solution for you. Just hook your second PSU up to this and pop one of these in-line running from your main PSU to the 4-pin plug on the Add2PSU adapter. That should tell the adapter that the main PSU is on for about 5 minutes longer than it actually is, which will keep your second PSU running the pump and fans for an additional 5 minutes after you turn your computer off.

 

Chips are thrown in ovens to be soldered to boards. A tiny spike in temperature when they are not running isn't going to kill them. Even if the water isn't being pumped it will still move in the presence of heat (convection). If this was such a problem there would have been systems in place to keep fans power on, for years now. This keeping the computer cooling on after shutdown is the same gimmicky deal as turbo timers.

 

Thank you, Cory, this is interesting approach - my main psu is Corsair AX-850 (Seasonic production w/Corsair sourced cabling) and is v. quiet.

I would add Seasonic X-400 Fanless using Add2Psu adapter - all fans, all pumps, all system related cooling devices dedicated to X-400 psu.

The only thing missing is longer timeout - let me think about this approach.

To answer expected comments, X-400 is smallest quality build fanless psu available and "yes" it is larger than necessary for fans + pumps but is reliable psu.