"DANGERS" of a Cascade System ????

[DaBit]

R410A does it's job fine. With compressors designed for it.

The Danfoss SC12 is NOT made for these high static pressures, and neither does it's design guarantee me that they will hold at 600psi+.

[chilly1]

Fugger's cascade system has no expansion tanks it's a baxter. It does have a reciever on the highside and an oilseperator on the low side. System charge is high enough so the low side has both liquid and gas present in the system (R503) simmilar pressures to 508b, therfore @ 85 degF the system will be @ 650psi. There is a 1000 psi pressure relief device that vents to atmosphere and a melt away slug in both circuits. O yeah the compressors for the baxter frige are one ton bristol compressors designed for r502.
This is pretty much standard for the entire industry, I don't think I have ever seen a compressor designed for R508b,R23,R114,R1150 ect...

[chilly1]

DaBit, I took a danfoss sc12 put it in a steel continer pressurized it to 2200 psi (nitrogen) let it stand at that pressure for two days. No leaks or explosions.... I would not recommend that anyone do this.....

[]JR[]

?

If you put the whole compressor in the 'steel container' surely it wouldnt have any real pressure exerted on it?

Youd have to seal the process, high and suction tubes and then pressurise to 2200psi, and im sorry no hermetic we use wouldnt blow its top at that pressure.

And 500gm of flying steel aint going to be pretty.

]JR[

[berkut]

chilly1 - could you do that with a A/C compressor ?

Do you guys know where to find specs of Sanyo A/C compressors ?

[Slickthellama]

can anyone tell me what a cascade is, simply? Like just a summary please. Thanks. im

[Gary Lloyd]

Stacked chase change systems. Just like stacking tecs.

[Poki]

Hmm... I was googling for a good pic of a low stage failure and this is what i found...
It looks pretty darned serious to me!!! Be careful guys!

[ellsworth]

has anyone ever seen one explode? im sure the weakest joint would start leaking before anything ever exploded or a pipe would crack, i cant imagine everything just failing at the same time and blowing up. btw the compressor shell in most compressors are rated at 500psi withstanding i think

[Poki]

When metal fatigues it tends to tear, i would expect a failure near an evaprator joint where theres a broader temperature variation.

[captaincascade]

Originally posted by chilly1
Fugger's cascade system has no expansion tanks it's a baxter. It does have a reciever on the highside and an oilseperator on the low side. System charge is high enough so the low side has both liquid and gas present in the system (R503) simmilar pressures to 508b, therfore @ 85 degF the system will be @ 650psi. There is a 1000 psi pressure relief device that vents to atmosphere and a melt away slug in both circuits. O yeah the compressors for the baxter frige are one ton bristol compressors designed for r502.
This is pretty much standard for the entire industry, I don't think I have ever seen a compressor designed for R508b,R23,R114,R1150 ect...

Wait are you saying the baxters (wich is a revco with a baxter sticker on it) static pressure is 650 psi?

Is it one of those where the charge is a code on the side where the serial number is?
If you give me the model and serial # i can tell you the exact charge and internal configuration.


Oh and it does have expansion tanks, you just cant see them, they're inside the walls.

[DaBit]

Originally posted by chilly1
DaBit, I took a danfoss sc12 put it in a steel continer pressurized it to 2200 psi (nitrogen) let it stand at that pressure for two days. No leaks or explosions.... I would not recommend that anyone do this.....

That one compressor handles this at one specific operating environment doesn't mean that all compressors do so under all conditions. If I watch the street and I see a red car passing, I cannot possibly say that all cars are red.

I agree: only one in many compressors will fail at 600psi pressure. And of the one failing, one one in thousand will produce high speed shrapnel; the rest will just rupture and release the gas. But still, *if* an accident happens you would be seriously in trouble here in NL.

I'd rather avoid the risk than thrusting on the built-in safety margins. Especially when it is so simple to avoid the risks. Connect an old large enough receiver with a piece of captube to the low side of the system, close the other port of the receiver, and you are done.

[berkut]

And a 2nd thing about what DaBit said- connect the compressors discharge line to the suction line so theres no pressure build up and start it so there are vibrations and a lil more "work conditions"

[chilly1]

The weakest point of any compressor is the terminal block. If you have brazed the discharge line and suction line properly as well as used components rated above the burst of the compressor and install a pressure relief device rated slightly below the burst of the systems lowest pressure device, keep the terminal covers on and shield them, all will be well. Remember that your system should be installed is a steel cabinet and any hoses,pipe or evaporator parts not in the cabinet need to be rated at three times burst pressure(my recommendation) and well shielded from damage.Here i the states teflon hosos with stainless braid rated at 300 psi are available at most refrigeration suppliers ($100 us). As for the burst of 600 psi you would need to install an isolated expansion tank on the suction side to keep the internal volume high enough so that when the system is fully charged your static pressure would not exceed the rating of your relief device. If you do use another expantion (Thermostatic Pressure, Hand ect.) device that requires a liquid column to operate properly you must use the smallest possiable charge in the system. To do this you either limit the capacity and don't install a reciever and have times when the evaporator under high loads will starve. Or you install a very small reciever (6-8 cuin) Keep in mind the larger the reciever you use the larger the internal volume required to keep the pressure below burst.

[|RickY|]

... i'm thinking that if the pressures are highest than some solding point can hold the sistem will have a leak, never think on a explosion :S i'm tkinking on trying to do a cascade system, but now.... i donk know :P this danger exist with all the freons?

[chilly1]

You braze all your joints the silfoss 15% is harder than copper. If you set it up right the high pressure gas charge in the system will be only a couple of ounces and this will be very hard to make dangerous

[runmc]

Originally posted by chilly1
You braze all your joints the silfoss 15% is harder than copper. If you set it up right the high pressure gas charge in the system will be only a couple of ounces and this will be very hard to make dangerous

No more dangerous than a 15 year of bottle wine?? How ya feelin??

[chilly1]

Your up?

[pythagoras]

slickthellama wrote:

can anyone tell me what a cascade is, simply? Like just a summary please

Does this work for you?:



A cascade condensing unit uses two refrigerating systems that we will refer to as system A and system B. The condenser of system A, called the "first" or "high" stage, is usually fan cooled by the ambient air. In some cases a water supply may be used but air-cooling is much more common. The evaporator of system A is used to cool the condenser of system B called the "second" or "low" stage. The unit that makes up the evaporator of system A and the condenser of system B is often referred to as the "inter-stage or cascade condenser". Cascade systems use two different refrigerants, one in each stage. One type is used for the low stage and a different one for the high stage. The reason that two refrigeration systems are used is that a single system cannot economically achieve the high compression ratios necessary to obtain the proper evaporating and condensing temperatures.


Regards

JOhn.

[runmc]

I started my low stage compressor before my first stage got cold enough. First stage temperature was right at 0F.

WRONG!!!!

I wasn't looking at my gauges until I heard my low stage compressor lugging down and then I heard a whistle coming from the compressor. I looked at my gauges and my low stage high side gauge was at 500psi. I freaked out and unplugged it real fast.

I only had my low stage pluged in for 15 to 20 seconds before this happened. It didn't take long at all for the pressure to build.

From what Gary and Chilly1 told me , the pressure release inside the compressor was bypassing the refrigerant. Lucky for me this compressor had one.

[DaBit]

Most hermetics have one afaik, but according to an engineer I talked to these are usually single-use devices. If they break: end of the compressor.

[runmc]

Originally posted by DaBit
Most hermetics have one afaik, but according to an engineer I talked to these are usually single-use devices. If they break: end of the compressor.

In my case, after the pressure release activated, I let my first stage cool down to -20F and started the low stage and it worked fine. Hopefully I didn't damage anything.

[DaBit]

You have had your portion of bad luck already, so I hope indeed that the compressor is still 100% OK

[HawainPanda]

thx for the picca pythagoras, u know...im getting the notioin, that the more stages=more danger, correct? so, perhaps, if maybe u had a 4 stage cascades and the first one...somehow doesn't provide enough cooling, maybe oil clog, then the rest are bound to get screwed up, so wouldn't it be better...to setup temp probs, or gauges, at each stage to make sure each is working, and then turning on each compressor one by one...maybe that's wat u guys are saying...but i understand maybe 1 out of 10 words from ur posts..so take pity