Which design for Cascade

[godspeed]

Hi,

Im not going to build a Cascade yet, i need to learn a lot more yet. But i was wondering which design was better and could handle the higher heat load better. On both pic's that have a question on them as well if you could answer them please. Also which one do you think would be the easiest to do?

Picture\design was borrowed from Gclg2000 (hope you dont mind) and chilly1



Thanks a lot

[Tyrou]

on the first pic, you can relapce the pev by a tev or even by a cap tube :)

on the second, this is the HX ;)

[gclg2000]

Dont mind at all. Your welcome to use anything i've posted.

Actually you can't really use a TEV on the 2nd stage. The temperature range on the TEV's only go down to about -50 C. The 2nd stage gas will get the sense bulb to cold and cause it not to open up correctly and not meter enough freon.

There is not really an "easy" way to meter the gas on 2nd stage. That's why chilly uses a PEV on 2nd stage w/ some adjustment so you can tweak it and allow the gas to meter best. The store owner where i get my HVAC supplies from (including that PEV) said you can sorta think of the PEV as an automatic cap tube. Although it goes by pressure, you can still adjust it to a degree to help meter teh flow.

That, or you can cut the cap tube to an exact length for an exact load w/ a specific gas.

I'm not a total expert, but this is how i understand it. Chilly and other's would be the better one's to talk to. Hope i helped some. :toast:

[gclg2000]

Oh and one thing about my design...."generally" you should prob use a compressor bigger than 5200btu's for 1st stage. I'm going to try this out and see how it works out, i've got a large desuperheater on 2nd stage so i think it will work otu ok.

[godspeed]

Thanks for the quick reply guys. :D

So then if that is the HX then what are those other 2 things? take a look at pic.

Thanks again

[chilly1]

Thanks for the quick reply guys. :D

So then if that is the HX then what are those other 2 things? take a look at pic.

Thanks again
Well the othe to "things" are HX points wherer I solder the lines together for the heat transfer in the correct direction so that it adds capacity to the system.

[gclg2000]

The knob thing is an Expansion Valve. I can't totally speak for chilly, but i think that's his old design just putting it right on the block like that. He now just uses a long piece of 1/8" tubing from the expansion valve to the block instead. He just doesn't have a picture i think of how he is doing it now. THe knob is to adjust the flow of the device and/or as many say too, to adjust the superheat.

Once, again....chilly will be best to ask.

[godspeed]

haha o ok kool thanks a bunch.

i have just one or two more questions can you get TEV that can handle more than -50 so that you can put it on the second stage?

And


Well the othe to "things" are HX points wherer I solder the lines together for the heat transfer in the correct direction so that it adds capacity to the system.

do you need to have these HX points, and what do u mean by transfer heat in the right direction and add system capacity?

Thanks

[gclg2000]

haha o ok kool thanks a bunch.

i have just one or two more questions can you get TEV that can handle more than -50 so that you can put it on the second stage?

And

do you need to have these HX points, and what do u mean by transfer heat in the right direction and add system capacity?

Thanks

The goal of the 1st stage is to remove as much heat from parts of the 2nd stage (before 2nd stage condensor) so that the 2nd stage gas can condense (or condense easier). These "smaller" HX's chilly diagram's help draw out some of the heat b/f it goes into the condensor of the 2nd stage (after drier and metering device).

No they don't make TEV's that work at that low temp, or we would be using them. :slap: The metal start's contracting/expanding along w/ the spring and the gas that is used in the sensing bulbs will not work properly.

Maybe they will one day find a gas that's suitable for the sense bulbs and machine the valve and valve spring out of a more durable metal like titanium or something that won't suffer from the (already very cold) temps of -50 C or below. Some company may infact make one, but i bet its god awful expensive.

As far as you must have the smaller HX's....you don't HAVE TO, but its a good idea too. Either way you must remove enough of the heat b/f the interstage HX. The more heat you can remove from the gas on 2nd stage b/f it enters the interstage HX, the easier it is for the evaporator of the 1st stage "chill down" the liquid condensor line(s) of the 2nd stage.

Hope you understand man, we are here to help ya. :toast:

[godspeed]

Hay kool thanks for the quick reply

yea i understand, you explained it very well thank you very much :D
and thank you for letting me borrow your design it was really easy to understand.

Last question: on the picture that chilly1 designed, on the second stage is that winding of copper after the compressor on the dischage line there to stop vibrations from the compressor for when it starts up?

[gclg2000]

No its not....well not exactly...That represents the "desuperheater" for the 2nd stage. The desuperheater does just what it implies, removes some heat from the compression of the gas the motor puts off. It helps remove heat (acting as a Heat Exchanger) before it goes to the oil seperator. Now, in addition to that, you do need to have a "vibration loop" as you stated.

In my picture its a little easier to understand, only because i labeled most of it. Chilly has a drawing like his above w/ parts labeled somewhere on the board i think.

Here's two pic's below of the 2nd stage discharge--> vibration loop --> desuperheater --> filter --> oil sep in --> oil sep out --> the Interstage HX.

Hope this helps and i hope i was straight to the point....

This won't be your last questions btw... ;)

http://www.namike.com/albums/Cascade-Build/MVC_009F_003.jpg

http://www.namike.com/albums/Cascade-Build/MVC_011F.jpg

[hatemi]

Well actually there are TXVs designed for R23 atleast for the low temp range:)

[LostInSpace278]

I just looked that up. Seems it will go down to -55°C.

Something else I didn't know, Danfoss makes/made a TXV for co2.

[godspeed]

thanks gclg2000 for all the help much appreciated :toast:

and i havent come up with another question yet :rolleyes:...... well i could ask which refrigerant would be best for the first and second stage?

[gclg2000]

507 or 404 for 1st and 1150 (ethylene gas) for 2nd. Mix a little propane to help with oil return, but that's another question down the road.

lol hope i've helped, your starting to get to the end of what little i know about this stuff.

Good luck, keep reading. read read read read read for 2 month at least before you start.

[kayl]

I just looked that up. Seems it will go down to -55°C.

Something else I didn't know, Danfoss makes/made a TXV for co2.


do they know how to stop it forming ice
have you a link by any chance :confused:

[LostInSpace278]

not sure, but you can read it Here (http://www.airah.org.au/downloads/2002-06-02.pdf)

[godspeed]

hi opening this back up again....

Could someone tell me what those are in the picture?

Thanks a lot

[gclg2000]

They are accumulators and they keep liquid form returning to the compressor.

[prc8]

those are accumilators. they catch any liquid refrigerant so that the compressor doesnt compress liquid, which will ruin the compressor.

[godspeed]

ok kool thanks guys

hay gclg2000 do u have any on yours?

[gclg2000]

Yes i do. I used 2 rotaries (bad decision for 1st stage turned out). All* Rotaries have them.

My picture in the 1st post also show's them.

[esdee]

Yes i do. I used 2 rotaries (bad decision for 1st stage turned out)

sorry if you posted this on your thread, but why it was bad?

[Tyrou]

his first stage compressor died ;)

[gclg2000]

Yah, something mechanical happened to it. Plus it just wasn't big enough. I was barely holding enough load to condense 2nd stage gas.

[esdee]

Yah, something mechanical happened to it. Plus it just wasn't big enough. I was barely holding enough load to condense 2nd stage gas.


im going to use a 1Hp rotory on the a first stage + 1 1/2hp on the second and i got confused for a minute that rotories are not good (generaly) for the first stage ...

thanks, sorry for the oftopic :slapass:

[gclg2000]

first, you should use the bigger compressor for 1st stage. It has more heat load to manage.

And "generally" i'll say this about rotaries now. The put out a giant amount of heat, are loud and are cheap quality compressor's. The are used mainly for cheap A/C unit's you find in Home Depot or something.

**I know someone will prob disagree w/ me, but i'm making this statement after using one (too small, something messed up or w/e). I will never use a rotary again.**

I'm not saying to not use them, it's just i i will never use them again for an application like this. The oil got it messed up somehow i think.

All the best cascade's i've seen (i'm still newb too) have used piston. I'm going to swap out both compressor's on this unit and get some real load going on it.

Just today i got the hookup on a FREE year 2003 copeland 3/4 HP. It has some slight run time on it, but it will be fine. I'll be using it on the 2nd stage and a different 1 Horse copeland for the 1st stage.

Please excuse me...but I'm tired of F'ing around. I'll never make the mistake of using a wrong compressor again like this. I've learned my lesson...please :slapass: me.

http://www.namike.com/albums/Cascade-Build/DSCN0224.jpg

[esdee]

your opinion comes from your personal experience and i respect it.
i would like to hear an experts opinion into this

gclg2k thanksfor sharing

[godspeed]

hay gclg2000 what do u think about horizontal rotary compressors i was thinking of using them because there smaller and ment to be more energy efficient, and when i say smaller i mean its shorter.

[gclg2000]

Try it out if ya want. I will just personally never use them again. That's all i'm saying. Other's have made good units out of rotaries. And don't get me wrong, mine did work for a little while.

[chilly1]

I agree with glgc2000 I have never liked them due to the noise and the problems inherent in todays rotairies .. exceessive wear under low suction is another problem.

[godspeed]

hay gclg2000,

would this idea work, using the refrigerant thats left after cooling the CPU to cool the other parts such as GPU. the case will hopefully be air tight and filled with nitrogen, and with the help of the rad and fan it will keep the other parts of the system cool such as power supply and hard drives, if its a cascade i think i would have to have the HX and other stuff that gets cold in the case as well. so what do you think? I hope it will look something like this....

Thanks

[gclg2000]

Well, it could work. But would prob be better to use a dual evap instead of extending the suction line out like that. Plus, sounds like you want this to be on there for daily use...? Prob be alot better choice to go w/ 2 single stages for an application like that.

[godspeed]

o ok kool sweet as