Co2 as a refrigerant

[Icefixer]

I was in the supply house and heard that Source had just started up a rack system that uses co2 as the refrigerant. Anyone work on this stuff? What are the pressures? High and low side. What leak detector do you use? What are the down sides?

[pherman]

Haven't worked with it yet. Here's some info on it. (pretty much sales info though)

http://www.hillphoenix.com/refrigera...second-nature/

[Swiss78]

I know it is only ok for cooler climates due to the high pressures. Not sure on the leak detector but I know that it supposed to be really good as long as you don't have a condensor issue or you will blow the reliefs on the receivers. I know they use this alot in Canada and this was I think a test store for Fresh and Easy, but not positive. I know it is 100% green and can be vented. Don't know if you could ever find a leak, as it is naturally in the atmosphere. See the pt chart by following the link below


http://www.coldsystemsllc.com/co2-refrigeration.html

[Phase Loss]

I've not "worked" on it, but been to a Fresh & Easy Co2 site a few times. Its a cascade system with 134a on the freon side cooling the C02.

Co2 suction runs 195-200# (-20 to -25*SST)
Co2 discharge 430# (right around 20*SCT)

They just built a Co2 Target in my neck of the woods too, but I've yet to go there.

[Icefixer]

Questions. Do you have to buy refrigerant quality co2 or just use the co2 that we blow out condensers with? Because we were taught to use nitrogen instead of co2 to pressurize systems due to the moisture in co2. And why can it be vented if California is so concerned with co2 emissions. Just some questions.

[jpsmith1cm]

Yes, you buy Coleman Grade Co2.

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

[prorefco]

Yes, you buy Coleman Grade Co2.

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

DO you have a reference for this information?

[icemeister]

For those who would like to learn all about CO2 as a refrigerant and CO2-based refrigeration systems, there's a FREE on-line couse available here:

http://www.r744.com/articles/2009-12...ble-online.php


How to access the CO2 online course

The e-learning module can be accessed after submitting the following information at marnik.lenaerts@khlim.be :

• First Name
• Last Name
• Country
• In which language do you want your course? Choose English or Dutch
• Company Name (optional)
• Reason why you are interested in this course (optional)

Upon receipt of the registration details you will receive an electronic confirmation notice containing your login details and note of acceptance into the module.

[Icefixer]

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.

[itsiceman]

What leak detector do you use?

This one is CO2 specific and is simple to use IMO



http://www.accutools.com/pages/servi...0%20Manual.pdf

[jpsmith1cm]

DO you have a reference for this information?

I have paper documentation, but I cannot locate an on-line source for that documentation.

http://hvac-talk.com/vbb/showthread....=Coleman+Grade

There is a good thread on CO2 use.

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.

You maybe need to study up on how CO2 is used as a refrigerant.

CO2 has a critical point of 88 degrees. This mean that, above that temperature, it cannot condense.

Here's a neat video from Danfoss on CO2.

[Slatts]

We've recently had a supermarket come online with a co2 system and will be taking on another 1in a few months when it comes online.

The present one uses an R134a rack for medium temp and for the co2 condenser (cascade system).

The medium temp rack has, if I recall correctly, 1 VSD compressor to maintain a very steady LP curve. This makes it a whole lot easier to maintain control of the co2 condensers.

We've just had a couple of weeks in the mid 30s (C) with no problems from the co2 rack so it seems to be a winning strategy.

In case of power failure, we've got a back up generator that runs a smallish 134a plant that chills the co2 racks receiver in order to stop it from venting the charge.

That said, there's a set of bottles in the plant room with a complete spare charge for the system. One of the advantages of using a dirt cheap refrigerant.

2 things about using CO2:
1: The CO2 is condensed out of the atmosphere, not manufactured so I guess you could call it carbon sequestration.

2: CO2 has a GWP of 1 and an ODP of 0 Follow the link and compare it to the refrigerant of your choice.

[barbar]

There are 2 types of CO2 installations, transcritical (normally deemed as stand alone system) and sub critical, which normally a cascade system (If you have a cold condensing source you can have a stand alone sub critical system.)
Sub critical systems act as just about any other refrigerant.
How ever, care does need to be taken during service, not just because of the high pressures, but also low pressures. CO2 drops below its triple point 75lb (ish)
So it can turn into a solid. If you are working on the low side, you must remove the CO2 out very slowly.(unlike a normal system which you pump down quickly). If do remove quickly you produce a plug of dry ice that blocks the flow through a pipe. You start to make your repairs, suddenly you may get a shot of dry ice, coming out at many 100s feet per second.