Silver Cascade (2 x 1 HP) with bypass valve

[SiuL]

amazing work nice cascate

[piotres]

Hi

After first bypass tests I can say it's working just as I've thought - discharge is lower when bypass is open, suction is higher - it can't be another , so I trully don't know Patrick, from where You take this idea that discharge will be higher with valve opened ? I was able to hold sth like -91C@260W load with bypass very little opened (with more opened I seen -76C), while when bypass was off I have had sth like -97C@260W . Nevermind, that're just initial tests .

Regards
Peter

[tiborrr]

Hi

After first bypass tests I can say it's working just as I've thought - discharge is lower when bypass is open, suction is higher

That's how it supposed to be. When you open bypass from high side to low side you basically lower the compression ratio. On old sharp's cascade me & moonman currently use (until i charge mine with R1150a) with bypass (oil return basically) fully opened you get around -65°C (~ 7barg HP), with bypass closed around -105°C (~ 14barg HP) - all measurements on cpu idling in Windows.

Good work Peter, love your cascade builds!

[Patrickclouds]

what is lower? pressure or temperature?
i wrote a few postings ago: "the hotgas bypass will increase discharge and compressor temp"

and i would say, that this is the "normal" reaktion of the circuit.
you increase the suction gas temperature and after compressing it, it should be hotter, than compressing a gas that has a suction gas temperature of -50°C.

our discharge copper pipe was so hot, that you couldn´t realy touch it.
i don´t know the reason for that, but we used a hot gas bypass before desuperheater. and the regulation of the bypass was controlled by the sps that fully opens the mgv (which has a inner diameter of 3mm) so a lot of hotgas will flow through it at once.

you have only opened the valve a little bit and you are using gas at room temperature. so this amount of gas is also cooled by the suctin gas. so all at all your suction temp doesn´t rise a lot.

[piotres]

what is lower? pressure or temperature?
i wrote a few postings ago: "the hotgas bypass will increase discharge and compressor temp"

and i would say, that this is the "normal" reaktion of the circuit.
you increase the suction gas temperature and after compressing it, it should be hotter, than compressing a gas that has a suction gas temperature of -50°C.

our discharge copper pipe was so hot, that you couldn´t realy touch it.
i don´t know the reason for that, but we used a hot gas bypass before desuperheater. and the regulation of the bypass was controlled by the sps that fully opens the mgv (which has a inner diameter of 3mm) so a lot of hotgas will flow through it at once.

you have only opened the valve a little bit and you are using gas at room temperature. so this amount of gas is also cooled by the suctin gas. so all at all your suction temp doesn´t rise a lot.

ok sorry I didn't read well I thought You had been saying about discharge pressure .

[tiborrr]

Patrick -> correction here!

i wrote a few postings ago: "the hotgas bypass will increase discharge and compressor temp"

It will increase suction temp but it will lower discharge temperature hence lower HP. You should be using desuperheated gas after aux condensor (dshx).

At least from my experiences.

[Patrickclouds]

Patrick -> correction here!

It will increase suction temp but it will lower discharge temperature hence lower HP. You should be using desuperheated gas after aux condensor (dshx).

At least from my experiences.

yeah you are absolutly right

we were too lazy to braze a new shrader into the filled unit.
so we used the existing for our test. if you take a look at the picture on the previous page you can see, that discharge shrader is before desuperheater and that we used the service port on compressor. so there is no chance that the hot gas from the bypass is cooled by suction gas.

[piotres]

Hello

Long time no update here, because I met leak problem with this cascade (also I've had problems with 2nd stage compressor and now it's swaped for bit bigger one - Sanyo C-RN112H5A which is sth around 12000-13000 BTU).

"First time" cascade was ready in the end of December 2008, I made some load tests and left if stay in mine garage for leak testing (cascade have pressure gauges so static pressure can be checked). After some weeks of testing (test in the begining of February 2009) I notticed sth like 1 bara static pressure drop and problems with load holding. So I decided - that must be tiny leak somewhere and I MUST find it . That seems to be very hard work, becuase before put on insulation I test every connection at least 2 times with leak testing spray and all was fine . So again case umounting, removing insulation, ehhh .Again I made test with spray, I remember mine previous problems with leaking straight part of captube, so I sprayed EVERY pipe even staight parts with leak tester - again all seems to be OK :-O .
I decide to umount every part of cascade's 2nd stage and test it in water,under pressure. And I found it ! - leak was again on straight part of captube, after bypass valve, only test under 20+ bara in water bath show it, I test again leaked place with spray and spray didn't show even the smallest bubbles there even (I tried few sprays - Wigam, Wurth, Tectane) !

One is sure - I'll never buy those captubes in future -that's second time when I have leak of straight part of captube (another one was in blue cascade) . Fuxxx crap I just want to say about those captubes .

So I fixed leaked place, changed both driers on 2nd stage, cover pipes again with black pipe, make new insulation for 2nd stage and finally mount case .

Cascade is already packed .

Finaly -96*C @ 260W load after 1 hour test but warm but seems like it's the best which I can take from this setup . I tried 320+ cm of 0.9mm captube, and finaly it's 280cm of 0.9mm and same result .

Some photos from next part of work :






Making electric instalation (before leak find) .




Power consumtion of whole unit (when it loaded with 260W) .







And that's hell captube .






I use almost all pipes new in 2nd stage ...




so painting pipes again was a must .



Final unloaded temperature is around -106*C .



On 260W after more than 1h of test .




1st stage loaded by 260W load on evaporator .































Both units are going in one pack










I prefer to make 100% "idiot-proof" packing .



And here is 100% packed .


Best Regards,
Peter

[runmc]

Bravo mi amigo

[Moc]

Very good packing job!

[0cool]

Yes you had got the same leak's problem with my cascade

[Evil_AnAnAs]

I really need more money, I'd eat noodles for a year to afford this. XD

Great build.

[piotres]

Yes you had got the same leak's problem with my cascade

You're right 0cool . But with Your unit I have had more luck, because there spray leak detector show the leak, and here only water show the truth . That's why that was really hard way to find this .

Thanks Guys for all comments .

During incoming week I'll upload movie on Youtube showing bypass work . I'll paste link here .

Regards
Peter

[Duh]

even though I dont understand the technical part of the refrigeration unit I must say yout unit is gorgeous and you packing in very PRO

[tiborrr]

One of the best jobs I have ever seen lately - both cascade & single-stage aswell as packaging look very industrial like. Top notch!

P.S.: Who is the manufacturer of this cap tube? Is it a 2mm one? What batch (serial numbers) if you still have them?

[sjg0]

Holy Smokes great!

Customer requested shoes too? lol.

[piotres]

One of the best jobs I have ever seen lately - both cascade & single-stage aswell as packaging look very industrial like. Top notch!

P.S.: Who is the manufacturer of this cap tube? Is it a 2mm one? What batch (serial numbers) if you still have them?

Thanks

That captube was "no-name" (that was 1.5m captube with 1/4 nuts on both sides , I don't know what diam. it have but looks like much over 2.0mm) I bet it's chineese one .

[piotres]

Hi

MOVIE SHOWING BYPASS IN ACTION :

http://www.youtube.com/watch?v=NMo8BakJORk

Sorry for not working photos, I hope that Lycos server will be working again soon if not ....I have a problem .

Regards
Peter

[Diegis0n]

It has a fast reaction, really nice job there

You didn't "open" the valve fully i presume?

[sdumper]

How much does it fully drop? Did it stop at -96 and how many whats were you loading?
Amazing work!!!

[piotres]

How much does it fully drop? Did it stop at -96 and how many whats were you loading?
Amazing work!!!

Sure, on movie it's very light open, once I open it more and I get around -70C, but valve still wasn't fully opened . I test cascade during load with 260W .

[tiborrr]

Wanna see fast reaction? Old sharp's cascade with ball valve bypass (essentially an oil return valve).

http://www.youtube.com/watch?v=0TURqnM3kLw