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ARCTIC EAGLE ORIGINS  |  TECHNICIAN RESOURCES

 

R-744 (CO2) 20 lb Cylinder

Technician Instruction Manual: Vapor and Liquid Charging

 

One cylinder, both phases. Upright for vapor. Inverted for liquid. One CGA 320 valve, no dip tube, no second cylinder.

1. About This Cylinder

Refrigerant grade R-744 has traditionally been sold as two separate cylinders: a vapor cylinder and a dip tube cylinder for liquid. This cylinder replaces both. At roughly 45.5 lb full, it is light enough for one technician to invert safely, so the same cylinder delivers vapor when upright and liquid when turned upside down, through the same valve.

  • Cylinder: DOT-3AL aluminum, 20 lb refrigerant grade R-744

  • Full weight: Approximately 45.5 lb

  • Valve: CGA 320, the standard US CO2 connection

  • Internal construction: No dip tube

  • Vapor withdrawal: Cylinder upright, valve on top

  • Liquid withdrawal: Cylinder inverted, valve down, resting on the valve guard

  • Cylinder pressure: Above 800 psi at room temperature; approaches 1,000 psi on a hot day

 

2. Safety

Required personal protective equipment

  • Insulated gloves. Liquid CO2 and the dry ice it forms on release can cause cold burns on contact.

  • Safety glasses.

  • Steel toe boots. The cylinder is lifted and inverted during the procedure.

Hazards to know before you start

  • High pressure. Every hose, gauge and fitting must be rated for CO2 pressure. Standard HFC equipment is not.

  • Dry ice formation. Liquid CO2 introduced into a system below the triple point (about 60 psig) turns to dry ice and can plug lines, valves and strainers. This is why the system is always pressurized with vapor first.

  • Relief valves. Cylinder pressure is higher than the relief settings on the low temperature and intermediate sides of most transcritical and cascade systems. Charge at a controlled rate and watch vessel pressures.

  • Trapped liquid. Never leave liquid CO2 trapped in a hose or line between two closed valves. Pressure rises rapidly as it warms.

  • Heat. Keep the cylinder away from heat sources. Pressure rises quickly with temperature.

 

3. Equipment Required

  • Cylinder fitting: CGA 320 connection with a flat washer in good condition. Replace a worn or cracked washer. Never use an HFC adaptor.

  • Charging hoses: Reverse threaded CO2 hoses are generally used. Any hose rated for CO2 pressure is acceptable.

  • Bleed and shutoff: A bleed valve on a tee behind the CGA 320 fitting, and a shutoff valve before the hose, as shown in Step 2.

  • Gauges: Rated for CO2 system and cylinder pressures.

  • PPE: Insulated gloves, safety glasses, steel toe boots.

No pump needed. The cylinder's own pressure moves the CO2 into the system, in both vapor and liquid. The technician controls the rate with the cylinder valve.

 

4. Charging Procedure

Follow the steps in order. The rack or equipment manufacturer's charging procedure governs wherever it differs from these instructions, including target pressures.

Step 1 – Inspect and position the cylinder

Confirm the cylinder is Arctic Eagle Origins R-744 and within its requalification date. Inspect the valve and CGA 320 threads for damage or debris. Stand the cylinder upright with the valve closed.

Step 2 – Attach the CGA 320 fitting

With the cylinder upright and valve closed, thread the CGA 320 fitting onto the valve outlet with the washer seated and tighten securely. The charging assembly has a tee with a bleed valve directly behind the CGA 320 fitting and a shutoff ball valve before the hose, so the line can be bled and isolated at the cylinder.

Step 3 – Bleed the line

Crack the cylinder valve and bleed the hose at the system end to purge all non-condensable gases (NCGs) from the line. Close the bleed once only CO2 is escaping.

Step 4 – Pressurize the high side with vapor

With the cylinder still upright, open the valve and charge vapor into the high side of the system. Continue until the system is above the triple point and at the pressure specified by the equipment manufacturer. Confirm on the gauges before moving on.

Step 5 – Close the cylinder valve

Once the high side is pressurized with vapor, close the cylinder valve fully before moving the cylinder.

Step 6 – Flip the cylinder

Lift the cylinder and turn it upside down so it rests on the valve guard, valve down. Set it on a firm, level surface and confirm it is stable.

Step 7 – Bleed the NCGs again

With the cylinder inverted, bleed the line a second time to purge any non-condensable gases before liquid enters the system.

Step 8 – Fill the system with liquid

Open the cylinder valve and fill the system with liquid. Charge at a controlled rate and watch vessel pressures so no relief valve lifts. Stop when the system reaches the manufacturer's specified charge.

Step 9 – Finish and disconnect

Close the cylinder valve. Return the cylinder upright. Clear the charge line per site procedure so no liquid is trapped in the hose, then disconnect the fitting.

 

5. Why Vapor Comes First

CO2 has a triple point of about 60 psig, the pressure at which it can exist as a solid, liquid and gas at once. If liquid enters a system sitting below that pressure, part of it instantly turns to dry ice inside the piping. Pressurizing the high side with vapor first puts the system safely above the triple point, so the liquid that follows stays liquid.

 

6. Handling, Storage and Return

  • Store and transport the cylinder upright with the valve closed.

  • Keep cylinders out of direct heat and secured against tipping.

  • Return empty cylinders with the valve closed. FluoroFusion handles all testing and requalification.

  • General CO2 handling and hazard guidance follows CGA G-6 (Carbon Dioxide) and CGA G-6.9 (Dry Ice).

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