Co2 as a refrigerant

[RoBoTeq]

They better size the condensers bigger in sacramento, ca. It gets to 110 degrees here in the summer sometimes. It will be interesting this next summer to hear some stories.

From what I understand, over 88 degrees ambient, CO2 systems go into some sort of hypermode that can take the pressures to 1,600-2,500 psi.

[Slatts]

From what I understand, over 88 degrees ambient, CO2 systems go into some sort of hypermode that can take the pressures to 1,600-2,500 psi.

That would be your supercritical fluid.

Above 31.1C and 7390Kpa (1071PSI)

Have a look at the youtube link at the bottom of jps post Robo.

It explains it pretty well.

Here's a link to an explanation as well.

[eng&tech]

I was scrolling though and found this thread. So I thought I would add my two cents. So here is my readers digest version. THIS IS ONLY AN OVERVIEW

First there are 3 type of systems
1. CO2 Secondary - normal operating pressure of 175 - 240 psig. There are about 50 in use in the US and Canada. You still have a primary refrigerant (an HFC) These are subcritical systems, there is no compression of the CO2 it cooled by the primary refrigerant then the CO2 is pump though out the low temperature cases and walkins
2. Cascade Systems - The Lower Cascade is CO2 and the normal operating pressure on the discharge side of the system about 400- 450 (20 degree condensing) normal operating pressure on the suction side is ~200psig or -20 SST. Both Bitzer and Copeland have CO2 compressors and have been selling them for a couple of years. This also is a subcritical system and will alway operate subcritically regradless of ambent.

These two types of systems are being used in many place all over the US and Canada. At last count there are about 70 or more.

The third is a Medium temperature booster system that is currently best suitied for lower ambints, that why you see them in use in Canada, there are more than 1000 of them in use in Europe. Unlike the first two systems, Booster systems are HFC free, only using CO2 as the refrigerant. There is one being installed in Brooklin NY as we speak.

All refrigerant have a critical temperature and pressure its just that CO2's critical temperature is lower than most 87 degrees. That means that when CO2 hits the critical temperature there is no Pressure/Temperature relationship. At 90 deg. you will have a pressure around 1200psig, but only on the high side and it is designed to handle those pressures. Once it enters the flash tank (receiver of sorts) the pressure is dropped below the critical pressure the operation is once again subcritical and again a pressure/temperature relationship. CO2 is now in the liquid state and is sent to the low and medium temperature case, were the refrigerant is metered into the case though an EEV like any other refrigerant. Suction on the low temp case is ~ 200psig (-20sst) and the medium temp suction is ~400 psig (+20 sst)

CO2 liquid will turn to dry ice at 60 psig, so when servicing these system slowly vent the liquid refrigerant until there is no more liquid only vapor then you can open the system up to do your repairs. Make sure you pull a vaccum before put it back into service.

To find out more contact Hill Phoenix they are teaching classes on these system.

[crackertech]

I was scrolling though and found this thread. So I thought I would add my two cents. So here is my readers digest version. THIS IS ONLY AN OVERVIEW

First there are 3 type of systems
1. CO2 Secondary - normal operating pressure of 175 - 240 psig. There are about 50 in use in the US and Canada. You still have a primary refrigerant (an HFC) These are subcritical systems, there is no compression of the CO2 it cooled by the primary refrigerant then the CO2 is pump though out the low temperature cases and walkins
2. Cascade Systems - The Lower Cascade is CO2 and the normal operating pressure on the discharge side of the system about 400- 450 (20 degree condensing) normal operating pressure on the suction side is ~200psig or -20 SST. Both Bitzer and Copeland have CO2 compressors and have been selling them for a couple of years. This also is a subcritical system and will alway operate subcritically regradless of ambent.

These two types of systems are being used in many place all over the US and Canada. At last count there are about 70 or more.

The third is a Medium temperature booster system that is currently best suitied for lower ambints, that why you see them in use in Canada, there are more than 1000 of them in use in Europe. Unlike the first two systems, Booster systems are HFC free, only using CO2 as the refrigerant. There is one being installed in Brooklin NY as we speak.

All refrigerant have a critical temperature and pressure its just that CO2's critical temperature is lower than most 87 degrees. That means that when CO2 hits the critical temperature there is no Pressure/Temperature relationship. At 90 deg. you will have a pressure around 1200psig, but only on the high side and it is designed to handle those pressures. Once it enters the flash tank (receiver of sorts) the pressure is dropped below the critical pressure the operation is once again subcritical and again a pressure/temperature relationship. CO2 is now in the liquid state and is sent to the low and medium temperature case, were the refrigerant is metered into the case though an EEV like any other refrigerant. Suction on the low temp case is ~ 200psig (-20sst) and the medium temp suction is ~400 psig (+20 sst)

CO2 liquid will turn to dry ice at 60 psig, so when servicing these system slowly vent the liquid refrigerant until there is no more liquid only vapor then you can open the system up to do your repairs. Make sure you pull a vaccum before put it back into service.

To find out more contact Hill Phoenix they are teaching classes on these system.

I hear that Conyers GA is getting a co2 store.

[eng&tech]

They are going to be two CO2 systems in conyers, both are going to be CO2 cascade

[crackertech]

They are going to be two CO2 systems in conyers, both are going to be CO2 cascade

I just might have to make a visit when their done.

[eng&tech]

Let me know and ill met ya there if i can

[crackertech]

Let me know and ill met ya there if i can

Will do.. We have a great Hill rep down here that keeps us informed.

[icemeister]

They are going to be two CO2 systems in conyers, both are going to be CO2 cascade

WOW!...Conyers must have grown a lot since my last time at H/P in 1990...when I doubt it could support two supermarkets.

Rusty...Is Glenn's Barbeque still there? I liked mine "Inside, Outside, Chopped & Sliced with a side of Brunswick Stew".

I may have to hitch a ride north with crackertech.

[MikeySq]

I work on a few CO2 systems, in the Toronto Canada area subcritical DX and subcritical secondary, I must say i Like it, it works well. I've got a lot of "face time"with those systems and and am getting the itch for some face time with a transcritical system! its only a matter of when now!

Micro Thermo is working a lot with CO2 and are doing a pretty good job with the control systems, and last fall HillPhoenix bought an european company Advansor, that has a lot of experience with CO2 in europe so I'm excited to see some of that stuff soon!, so transcritical CO2 with Gas defrost comming now we're gonna have some fun!!

A funny Quote I heard about it too in regards to technicians..... Like Darwins Natural Selection only the strong and adataptable will survive! haha

1. CO2 Secondary - normal operating pressure of 175 - 240 psig. There are about 50 in use in the US and Canada.

cant forget about a CO2 Secondary Medium temp application,pressures run 390 to 490psi(390/420 normal)

IMO, Glycol is better suited for MT Secondary, but CO2 works OK with some case temps as temperature control is more difficult!

Yes, you buy Coleman Grade Co2.

You CAN use the CO2 out of your truck, but you must run it through a drier first.

Using the CO2 in your van would not be a good idea, Moisture is not all that may be in there, gas companies often use a "cap Charge" of other gases(like Nitrogen) with CO2 to raise pressure in the cylinder so the gas may not be pure

Colman grade is dry and almost 100% pure

there is a higher grade of CO2 scientific grade or pharmaceutical grade i forget exactly, its more pure than Coleman but not necessary in refrig applications especially for the extra cost

Mike

[Phase Loss]

I work on a few CO2 systems, in the Toronto Canada

You're Canadian?......

[crackertech]

You're Canadian?......

[MikeySq]

Yep and up here I'd fall in the sub category of Newfie! haha