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Not trying to hi-jack
I made this a few months ago and tried to get it stickied
its a step by step guide to posting images.

http://hvac-talk.com/vbb/showthread....s-the-EASY-way

Simplest of terms moving, the heat from here to there or we could get into all the physics of the refigeration cycle plotted out on that damn diagram.
I have sat in seminars and passed the RSES test but when you don't use it, and when would you for most refrigeration most of us do today, you lose it.

Here is another point to ponder:

The high side system creates the same conditions that It runs under - for the low side compressor.

Look at a P/T chart for say; R404 and for R503. I don't have those charts in front of me but let's pick a 10 lb. suction pressure and a 200 lb. head pressure for both.

Can you see what I mean yet?

Both compressors can be the same - they don't know What they are pumping - the compressors are only aware of the pressures and volumes that they have to deal with.

PHM
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Originally Posted by Want to Learn

Well, now that makes a lot of sense to me. What are the low side compressors that are used ? I had a bunch of other stuff written in a Word doc. but that's not what this threads about. Thanks I have been interested in the cascade stuff but have never done any more than I wrote about.

Any 404a low temp compressor seems to do pretty well as a low stage compressor with R508b. I've seen all brands used. You just have to keep them cool, which is never a problem in the self-contained ULT freezers that are 80-90% of this side of the trade. With the rest of the equipment (freeze drivers, environmental chambers, etc) all you need to keep that R404a low temp compressor happily pumping R508b is a de-superheat TXV or demand cooling module. Sometimes you need a crankcase pressure regulator...

Well, now that makes a lot of sense to me. What are the low side compressors that are used ? I had a bunch of other stuff written in a Word doc. but that's not what this threads about. Thanks I have been interested in the cascade stuff but have never done any more than I wrote about.

No and the system volume versus refrigerant charge is specifically calculated to prevent any liquid refrigerant during non-operation. This is done so that containment doesn't require other than standard materials.

Picture how the construction of the cylinder the low temp refrigerants come in differs from the construction of the system.

PHM
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Originally Posted by cmclifton

Your low stage refrigerant (508, 23, 13, 503) is never liquid when your cascade system is sitting off at room temp, in 99% of these systems. These things are charged to a static pressure with vapor. They would need to be piped like a CO2 system to contain liquid refrigerant at room temperature.

There may be a few cascade systems that contain liquid refrigerant in the low stage when they're not running (aside from the additive to help return oil) but I've never seen or heard of one in 16 years.

Your low stage refrigerant (508, 23, 13, 503) is never liquid when your cascade system is sitting off at room temp, in 99% of these systems. These things are charged to a static pressure with vapor. They would need to be piped like a CO2 system to contain liquid refrigerant at room temperature.

There may be a few cascade systems that contain liquid refrigerant in the low stage when they're not running (aside from the additive to help return oil) but I've never seen or heard of one in 16 years.

Okay I need input, later, this is interesting

Or perhaps that the temperature of the liquid refrigerant in the system has changed?

PHM
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Originally Posted by Want to Learn

What ?
R-508B has a boiling point -126 degrees

R-508B at 75 degrees would have a pressure of ...well my chart stopped at 285.4 and I’m not smart enough to calculate it out.

=================================
A change of 10 pounds of static pressure in any refrigeration system will only tell you that there is no liquid in that system.
=================================

What am I missing here aside from the fact is does not have anything more than a leak in the low side ?

I am by no means any kind of an expert with cascade systems. I did maintain some Ice Wagon chillers though that used a two stage Copeland compressor. These units were water cooled so I could maintain consistent head pressure. They had a desuperheater; the purpose of this was to remove all of the sensible heat from the refrigerant before it reached the primary TXV so that it worked harder at cooling the medium glycol. The refrigerant was well below 32 degrees as the sight glass was always ice covered. The set point we were attempting to maintain was -40 degrees I say attempting as the only time we could was with no load on it, normal low side pressure was -6”hg. When we did get down to -40 the hot gas bypass would open so that the unit never shutdown. In the shop with the on board tank it had it took less than an hour I believe to come down to temp.

Sorry didn't mean to totally hi-jack the thread just question the begining

What ?
R-508B has a boiling point -126 degrees

R-508B at 75 degrees would have a pressure of ...well my chart stopped at 285.4 and I’m not smart enough to calculate it out .

A change of 10 pounds of static pressure in any refrigeration system will only tell you that there is no liquid in that system.
What am I missing here aside from the fact is does not have anything more than a leak in the low side ?

I am by no means any kind of an expert with cascade systems. I did maintain some Ice Wagon chillers though that used a two stage Copeland compressor. These units were water cooled so I could maintain consistent head pressure. They had a desuperheater; the purpose of this was to remove all of the sensible heat from the refrigerant before it reached the primary TXV so that it worked harder at cooling the medium glycol. The refrigerant was well below 32 degrees as the sight glass was always ice covered. The set point we were attempting to maintain was -40 degrees I say attempting as the only time we could was with no load on it, normal low side pressure was -6”hg. When we did get down to -40 the hot gas bypass would open so that the unit never shutdown. In the shop with the on board tank it had it took less than an hour I believe to come down to temp.
Sorry didn't mean to totally hi-jack the thread just question the begining

There is no such thing on the screen I see. Nothing which says: Managed Attachments. But there is an 'attachment' thing I can click on. I think it looks like a paperclip. And from that a pic-file-selection area to drag-&-drop files into some provided box.

Then I think I had to put a check in some more boxes on the pics.

I guess that seems useless - I'm not sure I could follow it myself. <g>

PHM
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Originally Posted by joebuck585

I still can't find the manage attachments

Originally Posted by Poodle Head Mikey

...

You're lucky, all my roofs are white this time of year.

I still can't find the manage attachments

Wow; that is the first time I've ever managed to have an actual pic appear in any post I've ever made here. <g>

here's some piping I did

...

Originally Posted by pecmsg

In the reply section hit the “go advanced” button then “Managed Attachments”

When moisture is introduced into the system it's best to flush it out. I worked with a tech from thermofisher scientific and he told me the best thing to do at this point is to flush the sytem

Im still confused
Oil is always in the system, the last thing i'd want is the flushing agent in a ULT.

In the reply section hit the “go advanced” button then “Managed Attachments”

I am using RX-11 flush kit. Wish I knew how to send pics cause I have a detailed picture with my idea how to do this.

I want to flush it because there is oil that I would like to get out of the system. I would like some literature just to verify I am correct. I am going to take out the filter drier, eliminate the oil separator and the compressor of course. I am working on a stand up ultra low. I have made several repairs and charged the system. Just first time flushing.
Thanks,
Joe DuBois