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Hi to everyone,

I've used in the past R23 and R14 in a three stages cascade and I would highly recommend using R23 if you're not about getting the coldest possible temperature.

Compression...

There is no such thing as a " fully silent " 1/3 cv compressor, it's actually quiet a lot of power for a little SS system !

NL11F is a little noisy because it works at low pressure, every...

And what about oil egalization ? If there is a better way through one of the two compressors, there will be a lack of oil for the other.

It seems like it's hard to find little bottle in the US ... I'm in France and doesn't have any issue about ordering a twelve pack of pure R290 and R600a. I can also purchase some R600. Around 6 €...

For my 2 kg R14 bottle, I paid in France ~ 900? without taxes, with 4? per month for the bottle.

It's for 99,9995% purity. Price is very high :o

Supplier : Air Liquide Electronical.

@ Wdrzal : there's some rotaries designed to run in the horizontal position, Tecumseh for example.

Running hot isn't as critical as for piston type compressor. The crankcase is @ the HP pressure,...

Exactly.

I have to work around the cooling speed in the room, It's still too slow for me. I discovered that amount of gases is critical for a cascade, not enough = It won't condense, too much,...

Hi !

I'v managed to remove some extra R14 from the circuit. I think I've found the problem : I probably reached the MODP of the EEV, by removing some R14 I was able to lower the condensing...

Hey MoC.

You're right, except that it only remains a very little quantity of CO2 once air and moisture are pushed out of the room. It is not a continuous injection during cooling cycle !

I've...

I think it'll be okay, it costs a few € so worst case ...

But I have some difficulties to go down ~ -85C, so I put a watercooling hose, connected to a CO2 tank, and I'm trying to purge out of the...

http://www.youtube.com/watch?v=ibN1O5XD1o8

Hello !

First tests with 190 gr of R14. Pressures are a little high, I have to tune the TXV and R14's EEV, but got a nice -138C. Condensing at -73C, I have to lower that value :/
...

Yes, small atoms you're right. Hydrogen aside, there will be no leak if helium test showed no leak. My only fear is at low temperature, especially on the AKV, even if it has aluminum gasket. A french...

Hello !

All stages are done, with 10 bar of helium to check leaks. It remains some electrical stuff to do, but I hope to fire that beast up by the end of the year, it would be a nice gift for...

Okay thanks for the feedback.

I plan to use a solenoid valve as a hot gas bypass, to avoid excess oil in the evaporator by pushing some hot R14 just after the oil sep, directly to the evap. I hope...

No it's for the last stage, with R14.

I dit it because I have not access to AB oil. I wanted to use the same oil for the compressor, which is already POE.

Hi,

I've done some work today, with the room top, brazing liquid accumulator, filter, service valve and sight glass for first stage :)

http://imageshack.us/scaled/large/809/prxv.jpg...

Hi everyone !

Massive update today, I finished the copper part for the three stages ! It only remains the room piping work and some electrical stuff.

I also mounted together the condenser, fan...

Same price here in France, maybe even a little bit more. For ~ 150$ you have complete set of a danfoss AKV ( body + orifice + gasket + filter + coil ). But you'll have to get a PID controller to get...

You know I've a collegue who works with Sapratin, a german company, specialized in two-stage cascade for laboratory stuff ( freezer and climatic room ), they work with cap tube too. But there is...

Are you aware that CPEV's aren't designed to control a fluctuate load ( TXV's are, by adjusting the superheat ) but to keep the evaporation pressure @ a given value, regardless of the load, or almost...

Why ? because of leak-issues ? CPEV or EEV is way better than captube, getting that kind of stuff is without a doubt improving the second stage.

R404a/R507 is almost the same gas. what you can do is a R134A/R404A cascade.

R404a/R23 is a most common pattern though. The condenser @ the second stage can be removed for extra room.
Nice...

No TXV for such low heat load... But we don't have any idea about YOUR load. Danfoss TE-2 TXV series is usable for loads < 1 kW, even a few hundred watts.

Search for 0X orifice. That's what I use...

Isobutane is perfect for your range of temperature ( even R134A should do the job with tiny MBP compressor ).

With a chiller, a TXV instead of cap tube is way better to control fluctuant load,...