Co2 Systems in Supermarkets

[750 Valve]

Calling all carboneads , time to spill your guts! I was just wondering how the industry in general is going with R744 systems (mainly overseas, I'm in australia). Are there many systems going in? Are customers specifying Co2, or asking for price options? I know europe is installing quite a few but what about uk and us, are there any in tesco or walmart?
Is it costing more or less to install than standard racks?
How do you all approach the piping - sizing, load grouping - ring mains or individual stubs?
What setups are you guys seeing, just dx low temp? mt liquid overfeed? transcritical? One rack per store or split like a normal store over 2 or 3 racks?
What about temp and flow control - electronic or mech?
In aus both major chains are pretty interested, installing them where local councils require "green" initiatives. We have about 5 or 6 sites running to date, mostly all the same setup - each time fine tuning a little (sometimes going backwards - but hey ya gotta learn some how). Usually we run 2 cascade systems per store, all comps bitzer - low and hi stage, copper piping up to 7/8". Liquid recirc for mt and ht loads with akv valves expanding the r744 into dx coils in lt systems. Hi stage systems are standard 404a racks, some aircooled, some water cooled, controls are electronic as you can get (gotta love supermarkets ) but there isn't too much in the way of smaller gear rated to 40 bar, mainly all industrial gear - thats where you guys come in... What are you seeing/hearing in your neck of the woods?

Thanks in advance

[spr2003]

Calling all carboneads , time to spill your guts! I was just wondering how the industry in general is going with R744 systems (mainly overseas, I'm in australia). Are there many systems going in? Are customers specifying Co2, or asking for price options? I know europe is installing quite a few but what about uk and us, are there any in tesco or walmart?
Is it costing more or less to install than standard racks?
How do you all approach the piping - sizing, load grouping - ring mains or individual stubs?
What setups are you guys seeing, just dx low temp? mt liquid overfeed? transcritical? One rack per store or split like a normal store over 2 or 3 racks?
What about temp and flow control - electronic or mech?
In aus both major chains are pretty interested, installing them where local councils require "green" initiatives. We have about 5 or 6 sites running to date, mostly all the same setup - each time fine tuning a little (sometimes going backwards - but hey ya gotta learn some how). Usually we run 2 cascade systems per store, all comps bitzer - low and hi stage, copper piping up to 7/8". Liquid recirc for mt and ht loads with akv valves expanding the r744 into dx coils in lt systems. Hi stage systems are standard 404a racks, some aircooled, some water cooled, controls are electronic as you can get (gotta love supermarkets ) but there isn't too much in the way of smaller gear rated to 40 bar, mainly all industrial gear - thats where you guys come in... What are you seeing/hearing in your neck of the woods?

Thanks in advance

My company sells the same price R 404 and R 744 plants for medim wide super and hipermarket surfaces.
The plant is a bit more complicated, but pipes and compressors are smaller.
The normal temperature is with R404 machinery and piping, and it condenses the co2.
A good electronic control system is pretty required, and when the plant runs correctly, it gives a good energy saving.

[750 Valve]

Hi spr2003, how long have you been running these systems? What do you use for tempaerature control for both low and mediun temp systems?

[Dave the Fridge]

Hi,

We have a site in the uk which is using R717 and CO2 as a large industrial cascade system. It seems to work well, i only know of 2 or 3 sites at the moment. I am off to the Carbon dioxide conference in London tomorrow (28/03/07) to see what there is around the world and network etc. I went last year and it was a really good day and very interesting. I understand that in OZ you do have a good few units there?

Regards

[canmurt]

we want to use this system

is it hard to use ?

[Dave the Fridge]

I have just returned from a day in London at the CO2 conference and as like the 2006 conference there are alot of interest but this year tesco is looking like they are going to go all out on natural refrigerants like CO2 / Hydrocarbons etc. So i think it will happen very quickly but we in the UK are still behind europe as Denmark and the rest are really using CO2 and have been for sometime. I have not worked on 'Transcritical' plants yet only 'Sub-critical' plants in the UK and i am in contact with the other York offices in europe which use this refrigerant already on a large scale.

Sub-critical plants with R717 (on the high side) and CO2 (on the low side) for example is very good. But watch out for power cuts as the CO2 will expand and blow through the PRV's.

Transcritical applications are ok but they are operating in very high pressures like on the suction pressure you will be running at 40 Bar and the discharge pressure you will be running at 90 Bar (min).

But i do think it will happen sooner rather than later!!

What application are you thinking of using the plant for ' canmurt ' ??

Regards

[US Iceman]

But watch out for power cuts as the CO2 will expand and blow through the PRV's.

That's a heck of way to control the pressures. I wonder why they don't use an expansion tank to keep the pressure down.

[Rob S]

Can't see how one could use CO2 with out an expantion tank.. more in the line of tanks for that much refrigerant.
Going to have to assume its a gas charge only. And their are expantion tanks. But on both the high and low side of the system.
I mostly do Cascade systems. And all of which have tanks, but only on the low side. Because its only controlling one evaporator.
Would love to see one in operation..

[US Iceman]

Power outages on a CO2 system are major problem. An easy way of containing the CO2 charge is to just use a small refrigeration system to maintain the CO2 down to a reasonable pressure.

But, if you loose power then the whole affair is a problem as the small system will not run either. The only choices would be to:

A) Use a dedicated standby power system (small generator for the small refrigeration system), or
B) Let the CO2 blow off, or
C) Use expansion tanks (sometimes called a fade-out drum)

"C" gets to be expensive if the CO2 charge is large.

"B" would be a mess and cause a lot of excitement and frustration.

Therefore, I vote for "A" as a reasonable and cost effective method to solve this problem.

[750 Valve]

We do option A, small 1ph unit off store's backup generator - evaporator is a 1/2" pipe wrapped around co2 vessel keeping shell of vessel cool, have had power outages up to 9-10 hrs and only went off on low side pressure relief (25 bar lp, 40 bar hp - comps sumps only rated to 25) which is no big issue, mind you hp was touching on 40 bar (vessel holding 250 - 300kgs r744). Plant startups aren't exactly the same as a normal site. Gotta get vessel of co2 cold then start up circuits slowly, if racks fire up after big offtime the load on system too great for our hxchanger setups to cope. We run a thermosyphon setup off the top of a vessel, may be better pulldown with a dedicated return liquid/gas heat exchanger but right now we just dump back into the vessel and let vapour draw off the top.

[US Iceman]

We run a thermosyphon setup off the top of a vessel,...

Can you provide a sketch of the piping for this please. That sounds interesting.

Thanks.

[750 Valve]

Want to post a pic but can't!!! Why!!! trying to link to photobucket (gotta be easier than taking up RE server space) but it just times out when I submit reply.

I have put up photos here before, whats the go? Won't work with add image, insert link or with a copy/paste of url. Oh well too bad, maybe its my company's copyright kicking in!! Sorry iceman, no pic for now till I can sort this out (and I'm not wasting too much time). If you do a search for Co2 and supermarket on this site, I'm sure I've posted a photo of the racks about a year ago.

[750 Valve]

http://www.refrigeration-engineer.co...ead.php?t=4086

Thats the thread with some photos, the first one shows the h/x drains entering the vessel (traps are intrnal)

[Sledge]

I have never seen a system running CO2 as a refrigerant. I dont know if there are any in Canada.

I am wondering about those pressures. High pressure of 40 Bar=580psi. Wow. I havent worked on anything with that kind of pressure. Does that require the site to be manned? What pipe is used in this application?

[Rob S]

copper.org

[Peter_1]

We maintained some years the storage tanks for a huge halon fire extinguisher on a container boat.
I have somewhere the drawings, if interested, I can search them.

[Dan]

In the states Walmart has installed a Sam's club in Savannah, Georgia with glycol for medium temperature and C02 for low temperature each used as a secondary refrigerant, being pumped thoughout the system using circuit setters and solenoid valves for balancing flow and controlling temperatuer.

The CO2 operates at about 220 psig and is cooled via thermosiphon brazed plate heat exchangers with a strafication tank below the heat exchangers. The piping for the CO2 is copper and a back up compressor unit on a small generator is available to keep pressures down during power outages. The CO2 behaves both as a brine and a refrigerant so refrigeration piping practices such as reduced risers, traps etc are used to insure both the evaporated CO2 and the unevaporated CO2 are returned to the pumping station.

[spr2003]

Hi spr2003, how long have you been running these systems? What do you use for tempaerature control for both low and mediun temp systems?

We use Danfoss controls. AKC25 for racks and EKC414A1 for expansions. ETS valves with EKC312 controllers are used for CO2 condensers.

[spr2003]

Hi spr2003, how long have you been running these systems? What do you use for tempaerature control for both low and mediun temp systems?

Forgive me i answerd only half a question :-)

I'm at my fourth experience with CO2 plants. It works really great, but i think the bigger the better. I mean it works properly on big capacity plants.

[spr2003]

Power outages on a CO2 system are major problem. An easy way of containing the CO2 charge is to just use a small refrigeration system to maintain the CO2 down to a reasonable pressure.

But, if you loose power then the whole affair is a problem as the small system will not run either. The only choices would be to:

A) Use a dedicated standby power system (small generator for the small refrigeration system), or
B) Let the CO2 blow off, or
C) Use expansion tanks (sometimes called a fade-out drum)

"C" gets to be expensive if the CO2 charge is large.

"B" would be a mess and cause a lot of excitement and frustration.

Therefore, I vote for "A" as a reasonable and cost effective method to solve this problem.

All constructors opts for the "B" solution. R744 is really cheap.

[750 Valve]

All constructors opts for the "B" solution. R744 is really cheap.

But not easy to get on short notice yet. I don't want to try to find a tonne delivered in a tanker on a long weekend thats for sure and by the same token you wouldn't want to vapour charge that much from bottles... christmas will be here before you get that much in!


Just did a site on R134a/R744... what a nightmare! Works OK but plant shutdowns can be scary, R134a at 0psi is about -24C, I try to get the vessel below -20 on a shutdown... you do the math! Maybe some R717 will go better in the hi stage at the next site... They just keep getting GREENER

[Dan]

The availability of CO2 in large quantities is something that crossed my mind, too 750. I was assured that it was readily availble from those who supply soft drink CO2 supplies. In a flooded secondary situation, we are looking at a significant amount of CO2. But then, we have the same issues on supermarket racks with 1200 lbs charges of R507.

[spr2003]

Mimic screen of the CO2 plant.