CPEV Adjustment?

[boshuter]

I finally got my first chiller going. This was a comercial lab chiller and has a cpev (pretty sure thats what it is). When I got it it had a couple of cracked lines and no wiring. I repaired or replaced all the lines, added low and high side service ports, installed a new filter/drier, and leak tested it with nitrogen overnight. I vaccuumed it today for around 6hrs with an electric heater on it to help moisture removal. I charged it with propane and everything went pretty well, it reached a low evap temp of -28.5c and frosted to withing 2" of the compressor. I think I need to adjust the cpev, it mantains 12psi low side pressure and my high side ran 175psi. Would I get better temps if the low side was around 4psi? I've never messed with a cpev before so any advice will be appreciated.

http://img176.imageshack.us/img176/6852/759chiller72dx.jpg

http://img311.imageshack.us/img311/1235/cpev12hf.jpg
not a good pic of the cpev... may have to take one without the frost if you need it.

http://img404.imageshack.us/img404/2333/evapfrost14dr.jpg

[boshuter]

Well I reduced the charge a little and backed the screw out on the cpev and dropped my temps by 10c. I'm sitting at -37.7c right now. I think this is about all I'm going to be able to do until I get a load on it so I can tweak it. Not too bad for a 1/6th hp compressor :)

http://img302.imageshack.us/img302/8913/37c2fh.jpg

http://img302.imageshack.us/img302/6828/pressures5re.jpg

I have to drill and tap the top of the res for the liquid lines so I can hook the water system up, then I'll see what it will do with a load. I don't expect much capacity from it with this small compressor, but it should handle a gpu without much problem.

[wdrzal]

ITS A WONDER IT WORKS AT ALL WITH THE CONDENSOR MOUNTED WRONG,IT NEEDS ROTATED 90 DEGREES. tHE INLET FROM COMP. SHOULD GO IN THE TOP AND THE LIQUID LINE TO CPEV SHOULD COME OUT THE BOTTOM. The tubes in the condensor should run horazontal.

[boshuter]

ITS A WONDER IT WORKS AT ALL WITH THE CONDENSOR MOUNTED WRONG,IT NEEDS ROTATED 90 DEGREES. tHE INLET FROM COMP. SHOULD GO IN THE TOP AND THE LIQUID LINE TO CPEV SHOULD COME OUT THE BOTTOM. The tubes in the condensor should run horazontal.

Well you could lose the caps :rolleyes: ... Acutally I worried about that because I kept reading on here that they won't work that way; but this is a comercial lab chiller and was built that way, I never touched the condensor. I figured it wouldn't hurt to try it the way it was built and if it did work it would go a long way to figuring out the credibility of some of the posts I'd read saying that won't work. I'm not much good at just blindly following advice from the internet without a good explanation of "why". As you can see the tubes from the condensor are both on the same end, that's another reason I just didn't go ahead and rotate it. A lot of people say it won't work but I have yet to read a good explanation of "why" it won't work..... and it's hard to argue with results :)

[Blaster]

the correct way is to rotate it 90º, but that doesnt mean it will not work like ur results prove it :p

it just looses efficiency because liquid travels downward due to gravity and the heat travels upwards

[johann]

Good little chiller there, you would have to recharge/adjust charge when you put load on it. I dont charge without load as I always end up recharging.

With a 185 watt heatload I would guess evap temp around -20c to -15c and a liquid temp of -10c to -5c and a CPU temp of around 0c to 10c

[RussC]

The issue with the evap is efficiency and consitancy. You'll most likely get in-consistent temps because the liquid refrigerant will puddle in the lower loops. This will cause the supply of liquid refrigerant to vary to the cpev, causing temps to vary more than you want, which makes adjusting very hit and miss. You also loose effiensency due to the same condition I just explained, and that should be self evident.

Adjusting the cpev is a game of temps vs capacity. shrinking the orafice size will lower temps but lower capacity, larger orafice size will raise temps but will increase capacity. With a GPU, you may need to shrink orafice size, as the load is not large like a cpu, depending on what temps you want.

RussC

[wdrzal]

It will also start to surge, the only way to prevent that is to sevierly overcharge the condensor with liquid which causes a loss in capacity.

[gclg2000]

Well you could lose the caps :rolleyes: ...

:slapass:

[aussie_guy00000]

The issue with the evap is efficiency and consitancy. You'll most likely get in-consistent temps because the liquid refrigerant will puddle in the lower loops. RussC

I think you mean condensor :confused: . Having the condensor sideways won't stop it from working, but it won't work as well as if the condensor was mounted properly. It's funny that that's how it was originally mounted:slap: .