SS performance

[DonNiger]

The WC cooled SS of mine has a strange habbit.

I'm useing chiller to cool the SS. If I run the SS first time chiller cooled down to ~+2c, the SS can not handle loads at all. E8600 @ 5Ghz, and the EVAP temps will go up to -40c under load. Also, the chiller can not handle the load of the SS, with just an hour, the coolant temp will go up to +10c.

But, if I shut down the SS for 3-5 minutes and run it again, the EVAP temp will stay around -50c with E8600 @ 5,6Ghz without any problems. Also, the load for chiller is significatly lower, the temp will go from +10c to -5c without any problems.

[sdumper]

Can you please reword and explain how your setup is laid out and then list numerically what is happening and the temps.

Example:
Intro: I have a SS system with a water chiller cooling my condenser. The SS is a rotary SS with a 3/4hp 8K btu compressor using cap-tube, my condenser is <????> and is cooled by an external water chiller???? which is powered by a 1/2 hp reciprocating compressor and air cooled condenser??
My normal temps on both are????


Now list your starting sequence and temps...

1)
2)
3)

[[XC] Oj101]

I THINK what he's trying to say is that if the rig is powered on with the head at -40'c it can't hold load at all but if at -50'c it somehow holds load properly? I'm going to go on a limb and guess that the last 10'c takes long enough for the water to drop temperature enough to hold load for his benching session or whatever he's doing.

Or I really don't understand his post

[sdumper]

I THINK what he's trying to say is that if the rig is powered on with the head at -40'c it can't hold load at all but if at -50'c it somehow holds load properly? I'm going to go on a limb and guess that the last 10'c takes long enough for the water to drop temperature enough to hold load for his benching session or whatever he's doing.

Or I really don't understand his post

Ok that makes sense so hes starting his system before hes reached stability pressure assuming hes using captube.

But then again I really have no idea what sort of setup he is using...

[[XC] Oj101]

And I have no idea whether I'm translating it correctly or not, so don't help him based purely on what I've said so far

[[XC] gomeler]

It could also be that running the condenser at such low temperatures is dropping the high-side pressure of the unit and killing the massflow through the evaporator, thereby making it crash under the load of the CPU.

Another stab at this is that he is saying when he turns on the chiller and then turns on the single-stage the system crashes but if he turns off the single-stage and lets the chiller pull-down the system holds.

A final stab at this is that he is indeed providing the Ultimate Question to which the answer is precisely 42.

[[XC] Oj101]

YES! Well done man, according to his question something happens between -40'c and -50'c, so if we take the exact figure and multiply by -1 we get 42

[DonNiger]

Sorry, but you all missed.

Lets say, I have an regular SS. I power it up, wait until the temp goes down to -50c. I start the PC, the temp goes up to -40c under load. Doesn't matter how long I run it, it just cann't handle the load (idle -50c, load -40c).
But if I shut down the SS for ~5 minutes and start it again (evap still -20c), I have much better temps. Idle -56c, load -50c.
The question is: why my SS handles better loads after shuting it down for couple of minutes? Why does it produce more heat (chiller cann't handle it) and has less load capacity if I do not shut it down?

Telling you the speeds and voltages wount give you anything because I can not tell you the actual heat produced by CPU.
But if you insist...
1st startup: E8600@5Ghz, 1,69v. Orthos fails after couple of minutes (CPU temp +20c)
2nd startup: E8600@5,6Ghz 1,69v. Orthos 1h (CPU temp +10c)

SS itself: http://www.xtremesystems.org/forums/...d.php?t=233163

[Stewie007]

This seems to have a bit to do with your chiller. What kind of charge is in your chiller? What kind of Evap pressure are we talking about? (In your chiller)

I'm guessing you're going all in and trying to make your condenser water as COLD as possible without considering the overall capacity that your chiller needs to have. Undercharging your chiller could be your problem. You may not have enough refrigerant in the evaporator to absorb the necessary heat load that your SS condenser is putting out.

If this is the case, its like putting a car radiator fan on an residential A/C unit.... Not enough. Consider running your chiller at a higher pressure. It might not get as cold, but with better refrigerant pressure you will absorb more of that heat and give your condenser water a better delta T.

[DonNiger]

Chiller does not have anything to do with it. Instead of chiller, I can connect a bit bigger WC, put the rad outside (-3c at this moment) and I have the same issue. I have to restart SS to run it normaly.

[Stewie007]

How long does the WC/Chiller loop run before you turn on the SS

[DonNiger]

The coolant temp between 0 - +10c does not have any impact to the SS holds, mayby just 2-3 degrees. I am not restarting chiller, it can run for days (temp controlled). I am restarting SS because before restart it can handle less load and it produces more heat than after restart. I have to restart it before the pressure in high and low side has not been balanced yet. If I wait too long, I still have to make 2 startups.

[Stewie007]

Just asking a question.

That's okay though. I'll leave myself out of this.

[Dualist]

Rip out and throw away the HX and use a proper sized condensor and have done with it.

[lowfat]

It could also be that running the condenser at such low temperatures is dropping the high-side pressure of the unit and killing the massflow through the evaporator, thereby making it crash under the load of the CPU.

Well I am a phase n00b, but you can actually have too big of a condenser? The condenser on my single stage is big enough for 3 120mm fans and all of them are insanely high speeds. This could be a reason why it can't hold much of a load?

[blinker0]

What is your High and low side pressures on your first SS startup , and then on your restart ?

[blinker0]

Well I am a phase n00b, but you can actually have too big of a condenser? The condenser on my single stage is big enough for 3 120mm fans and all of them are insanely high speeds. This could be a reason why it can't hold much of a load?

Not actualy It will effect the amount of charge needed, As the intenal Volume is larger.
A larger condenser will affect the seer rating.( Run a bit more effecient) And your compressor will not have to work as hard. "It is no substitude for a compressor that is to small for the load".

So As Long as you have the correct Compressor for the heat load I.E BTU/ Watt rating. And your Subcooling and superheat is correct. With proper minimal Kw rating condensor . The problem will Be some where else in your setup. Bad Evap contact, Evap not designed to handle the Load. Partialy blocked Cap tube ECT...

But initial Question at a certian point a condenser that is too large will not be of any benefit. A condenser 4 times larger than what is needed Will need a compressor that can push the volume of refrigerant needed for Correct Sub cooling

[DonNiger]

What is your High and low side pressures on your first SS startup , and then on your restart ?

I'm not a phase builder, so I do not have those useful toys.

[tiborrr]

It's simple - too cold and the condensing pressure drops too much. R-507 should be condensed somewhere in the range of 10-35°C, any lower and you may experience load handling ability to flutter.

[DonNiger]

Made some tests and some corrections to the compressor (actual torque). Finally got the compressor temp down from 70c to 40c, high side gas temp from 65c to 38c.
So it is not 1HP any more but my temps are much better.
For my big surprize, the active cooling for compressor have a very small impact to it's temp (44 versus 40 after 1 hour CPU full load test).
Although I have a Manifold, I do not have any R507 (to connect). Local market is pretty sad, CO2 is the only one I could get