[eng&tech]

Hey, I'm new to this website and happen to be looking though some of the older posting. I would like to clear up a couple of things on the SAMS CO2 store.
1. The store is using 35% propelyene gylcol at +20F fluid temp as the secondary fluid w/404a as the pirmary refrigerant.

2. The low temp system has 404a as the primary refrigerant and CO2 as a secondary fluid w/a supply fluid temp of about -20F. The chillers are standard braze plate heat exchanger and all the components are standard refrigeration componets. CO2 at -20F is around 198psig. Using it as a sencondary fluid you dont have the high pressure of a transcritical system. As long as the DX portion of the system is working your pressure will vary between 198-250PSIG. If you have a DX failure a small aux. heat exchanger with it own condensing unit and eneratogr will kick in until repairs to the DX system are made.

3. CO2 is .50 a pound compared to ~$7.00 a pound for most refrigerants. Also, the thermal properties of CO2 are so much better you only need a 3/8" liquid line to feed a line up of glass doors, but they are using 1/2" for rigidity. With the small refrig line you save money on install (copper only)

4. CO2 has an ODP number of 1 with no global warming portential

5. Since its a secondary fluid there is no concern with oil return.

This is our future they are doing in all over Europe, if they can make it work I'm sure we can do it also.
I enjoy reading all of the other posting it just show we still have some really good talent out there.

 

[eng&tech]

The pumps are not cycled, the compressors are cycled based on co2 fluid temp leaving the liquid/vapor seperator. There are pop offs on ever circuit just in case. Pressure of co2 at 70F is about 800# (dont have r-744 pt chart at home)

 

[eng&tech]

Dynalene helped push the industrey to CO2 and still cause me nightmares.

The key to defrost is clear the coil of CO2 before the heaters come on . You do see a small increase of pressure in the circuit being defrosted because of the added heat, but since the circiut is open to the return line the increse is minimized.

 

[eng&tech]

gerryboy00, nice diagram did you find it on the HP websites? The only thing I would say is that when defrosting the coils the heaters are on the same amount of time as a typical DX system, but your pump down and drip time are longer than a DX system. And with CO2 the defrost termination temp is the same as with DX.
To answer nesc522 you can use a hand held leak dectors (there is a nice one made by D-Teck that sell for about $500)that can pick up CO2. And I belive that there is a leak dector in the machine house that lets you know when theres a leak in the house.

 

[eng&tech]

Temperature in the case is controlled by a temp sensor in the discharge air, when the case air temp is at set point the rack controller shuts off the case's liquid line solenoild, as the temp raise the LLS is opened. The pump is a liquid pump simular to the pump used on a regular secondary system.

You dont have to travel to Georiga to see one, one started up in VA about a month ago at a Food Lion. With the price of refrigerant at $7-$8 a pound we are all going to see one sooner or later.

 

[eng&tech]

Discharge pressure on the HP rack will run about 400-420psig, regardless of ambient. These system are not trans-crittical system. Condensing is done at about 20^F. Pressure on the CO2 racks in the USA will be simular to those of 410A. I think by the end of the year Food Lion will have 4 CO2 systems running. What's really kool is the Kysor rack and the Hill rack that is being installed right now are both med temp and low temp CO2@ .50 cent a pound!!!

 

[eng&tech]

The HP will have heat recalim both potable water and air reclaim

 

[eng&tech]

Co2 is cheaper than glycol, CO2 has better heat trasfer capacity than glycol.
The flow rates with CO2 are very low so the pipe size get smaller and samaller pump sizes with less energy. Remember the system that Kysor and Hill are putting into Food Lion right now are Low Temperature CO2 using CO2 compressors, the mediuim temp is using CO2 as a secondary fluid and it being moved though the system with a centrifical pump.

Dont get me wrong gylcol is a great system easy to start up and very little maintanace.

 

[eng&tech]

for documentation on gylcol system go to the technical info section on the Hill website. http:////www.hillphoenix.com/techInfo/handbooks/installIndex.html

I hope that link works.

The only differant tool you'll need for CO2 is a set of 410A gauges, and a CO2 leak detector ( Detec has one)

If you lose power and the system shuts down you have two options. Some store will put in a small generator that will trun on a small condensing unit that will supply just enough refrigeration to keep the CO2 below 400#. But most store's do nothing speacal. If the sytem is off long enough the pressure will rise once the system hits 425# the pressure relief will release CO2. Once CO2 is released it evaporates and cools itself and lowers the pressure and the relief vavle is reset then if the pressure goes back up the vavle opens back up and we repeat until power has been restroed. So if you are off for 10 hours you lose only a small protion of the CO2 (appx 5-8% as test in the lab and in the field). Then once the system power is restored we cool the CO2 and start all over again. remember that CO2 is about 60 cents a pound with a GWP of 1.

 

[eng&tech]

Hill and Kysor and anyone else doing CO2 requires coleman grade CO2. If you are paying
$30/pound your getting ripped off up there in the Great White North. We in the USA pay on average 50 cents a pound US. Not only are we paying about .50/lb it is relativly easy to get. Plus in an emergency Hill has approved industrail grade which is the same stuff used at any McDonalds, Buger King or Wal-mart anyone that use's foutain drinks. At $30/lb even canadan money is alot. To use industrail grade just run it though a sprolan filter-dryer.

 

[eng&tech]

Ive called a couple of my friends in Canada and they tell me you can get it at Air Liquid (I believe that was the name) and the price was ~.60/lb. and was not hard to get. Hill has a CO2 cascade system going in at a store right outside of Toronto should start up sometime early next year. This one has CO2 low temp and CO2 on the mediuim temp. I believe it has 404a on the primary. It just like the system goning in at Food Lion

 

[eng&tech]

mspanky,
If you have a job coming up in 6 weeks you may want to have someone at your company attend the Hill Phoenix training class coming up in September in Chicago. It would explain how to install and startup a CO2 system. They also talk about CO2 in general. Their instructor's email is rusty.walker@hillphoenix.com I took the class and thought it was pretty good, very service friendly I hope that helps

 

[eng&tech]

huumm dealer in Canada tell Steve and Sim I said Hey!!