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Thread: Metering Device

  1. #1
    Join Date
    Apr 2010
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    Richmond, Virginia
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    Metering Device

    I was working on a small hp Tecumseh R134a cond. unit today. It was hooked up to a co2 tank and has some sort of a metering device I have never seen! I was hoping that somebody out there has seen this and explain how it works and how to properly set it up. It looks like a regular constant pressure valve but has an adjustment on the top of it like what would be on a cro or ori valve. It had like an aluminum cover screwed on top. The liquid line comes from the receiver into the side and the suction goes down into the tank to the evap. (shell within a shell). There are no sensing bulbs or sensors coming to or from it. The tank is called (Cardox) Md# 1-048-0915 Sn# T132. All I could find out was that it was made in Germany. When I put my gauges on the suction was 20 vac and head was 100psig. I figured there was a leak so I started putting in some 134a and my suction would not come up out of a vacuum and the head pressure would go up to 300psig then drop back down. I front seated the suction and the compressor pulled down to 22 vac. I disconnected power and she held there for 15 min. So I opened up everything and had bubbles in the S/G 10psig suction and 325psig head. I adjusted the valve till my suction was at 25psig and head was at 130psig. At these pressures I still had some flashing in the S/G I cleared it up and it ran like this for about 5 min. and went back into a vacuum? I am conviced that this metering device is bad but cannot find any info on it! Thought about installing a SQE and matching the cartridge to the btu rating of the compressor but not sure it this would work? Any help would be much appreciated!!

  2. #2
    Join Date
    Jan 2010
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    151
    sounds like an Automatic expansion valve

  3. #3
    Join Date
    Oct 2009
    Location
    Atlanta,Ga.
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    198
    Pretty sure that you have an automatic expansion valve.You don't see many around any more.You adjust the suction pressure by adjusting the screw on top of the valve(usually under a cap on top of the valve) you want a clear sight glass to valve,then adjust the valve to maintain the suction pressure to keep the coil at the temp you want.Sction pressure will remain constant.Does sound like you have a bad one.i ran across a brand new valve like that in my warehouse last weekend .Been there for years.It is yours,If you want it!!!!!

  4. #4
    Join Date
    Sep 2003
    Location
    North-Central Ohio
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    22
    The trade name "Cardox" is usually associated with co2 and fire suppression systems. What type of unit are you working on and how is co2 related to the 134a system -is it a cascade unit? Do you know if it an original factory set-up or has it been tampered with? It does sound a little like a flooded evap. system with an auto exp. valve (like batch freezers/ soft-serve units) but I don't understand how the co2 fits in the mix. Can you post pics?

  5. #5
    Join Date
    Oct 2003
    Location
    las vegas
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    1,505
    Quote Originally Posted by cool_tech_llc View Post
    The trade name "Cardox" is usually associated with co2 and fire suppression systems. What type of unit are you working on and how is co2 related to the 134a system -is it a cascade unit? Do you know if it an original factory set-up or has it been tampered with? It does sound a little like a flooded evap. system with an auto exp. valve (like batch freezers/ soft-serve units) but I don't understand how the co2 fits in the mix. Can you post pics?
    this thread needs pics. why the co2 tank?
    does sound like an old axv & these are readilly available.

  6. #6
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    311
    Thanks guys for the info. I found the valve and have it on order! I remember way back when in tech. school they talked about the (Automatic) Expansion valve as a metering device but never run into any. I probly missed that test question when asked "name all the different type metering devices" This was before all the new electronics! 1.) Thermostatic Expasion Valve. 2.) Capilary Tube 3.) Highside Float 4.) Low Side Float 5.) Fixed Orvice.

  7. #7
    Join Date
    Sep 2002
    Posts
    12,280

    Cardox has been using that same valve since the 1950's

    You want to get the subcooling to about 4-6-8 and then adjust that valve (it adjusts opposite to a TXV) to control the suction pressure to hold the CO2 at about zero degrees F. With that Cardox system you can run lean on the subcooling because the load and valve's control is pretty much dead constant. Might same you some head pressure costs too.

    It's a standard automatic expansion valve you're looking at. Parker makes the ones I always use. They are sometimes also called a Constant Suction Pressure valve.

    An AEV controls based only on downstream pressure. When you adjust it you are just setting the suction pressure at which it will control.

    PHM
    --------





    Quote Originally Posted by NANOTECH View Post
    I was working on a small hp Tecumseh R134a cond. unit today. It was hooked up to a co2 tank and has some sort of a metering device I have never seen! I was hoping that somebody out there has seen this and explain how it works and how to properly set it up. It looks like a regular constant pressure valve but has an adjustment on the top of it like what would be on a cro or ori valve. It had like an aluminum cover screwed on top. The liquid line comes from the receiver into the side and the suction goes down into the tank to the evap. (shell within a shell). There are no sensing bulbs or sensors coming to or from it. The tank is called (Cardox) Md# 1-048-0915 Sn# T132. All I could find out was that it was made in Germany. When I put my gauges on the suction was 20 vac and head was 100psig. I figured there was a leak so I started putting in some 134a and my suction would not come up out of a vacuum and the head pressure would go up to 300psig then drop back down. I front seated the suction and the compressor pulled down to 22 vac. I disconnected power and she held there for 15 min. So I opened up everything and had bubbles in the S/G 10psig suction and 325psig head. I adjusted the valve till my suction was at 25psig and head was at 130psig. At these pressures I still had some flashing in the S/G I cleared it up and it ran like this for about 5 min. and went back into a vacuum? I am conviced that this metering device is bad but cannot find any info on it! Thought about installing a SQE and matching the cartridge to the btu rating of the compressor but not sure it this would work? Any help would be much appreciated!!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  8. #8
    Join Date
    Sep 2002
    Posts
    12,280

    Marvin -

    The CO2 is either being stored for sale for soda carbonating systems and the like - or is being kept ready to use for a fire supression system.

    At zero degrees F. CO2 is about 300 lbs pressure. This makes the tank to store it in much less expensive than one for ambient temperature storage - which would have to contain more like 1500-2000 psi instead of 300 psi.

    This guy's refrigeration system is keeping the CO2 at about zero degrees. The tank relief valves blow off at about 325 lbs. That will also keep the tank cold - but you have to keep buying more CO2. <g>

    PHM
    --------.

    one
    Quote Originally Posted by marvin View Post
    this thread needs pics. why the co2 tank?
    does sound like an old axv & these are readilly available.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  9. #9
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    311
    This the replacement valve our cost was 75.00 installed worked perfect!
    Attached Images Attached Images    

  10. #10
    Join Date
    Sep 2002
    Posts
    12,280

    Did you install a large new liquid line drier ?

    Because your first post makes it seem a lot like there was moisture in the system.

    PHM
    -------




    Quote Originally Posted by NANOTECH View Post
    This the replacement valve our cost was 75.00 installed worked perfect!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    311

    Smile

    Thank you Poodle Head Mickey You were right on the money with this cardox system!!

  12. #12
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    311
    Yes, installed a new large hh f/d!!

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