Chapter 4 Page 6
CALIBRATED CHARGING CYLINDER
Because refrigeration systems using a capillary tube require a critical refrigerant charge, a calibrated charging cylinder is needed to ensure an accurate charge in the system. The calibrated charging cylinder is a tank equipped with a vertical sight glass for determining the liquid level in the cylinder. A plastic dial encircling the assembly is imprinted with graduation marks calibrated in ounces. The volume of refrigerant in the tank will change with a change in temperature. Temperature determines pressure, so note the pressure of the gauge on the tank. Then by rotating the calibrated dial until the proper refrigerant scale corresponding to the pressure is lined up with the sight glass, the liquid level can then be converted into ounces of refrigerant in the tank.
To fill the charging cylinder, attach a hose from the refrigerant supply drum to the valve at the bottom of the tank. (Always purge air from the hose by passing some refrigerant vapors through it before making the last fitting tight.) Invert the supply drum and open both the supply valve and the cylinder valve. The reason the supply drum is inverted is to be sure that liquid, not vapor, enters the cylinder. Watch the liquid level as it fills. If the refrigerant ceases toflow into the cylinder due to pressure inside, release the vapor pressure by operating the valve at the top of the charging cylinder. Replace the cap after bleeding. When the cylinder contains the correct charge, shut off the cylinder and supply drum valves, and place the supply drum upright.
flow into the cylinder due to pressure inside, release the vapor pressure by operating the valve at the top of the charging cylinder. Replace the cap after bleeding. When the cylinder contains the correct charge, shut off the cylinder and supply drum valves, and place the supply drum upright.
With the ever-changing technology service practices sometimes change to keep up with that technology. Charging scales were an easy way to measure an exact refrigerant charge in a refrigerator. Look at the model/serial number plate found on almost every refrigerator and you will see the type of refrigerant and amount to charge within the system.
Remove scale from case and place on a smooth flat surface.
Press the ON/OFF key to power the scale. The LCD should display 0.00/0.000.
Use the UNIT/SHIFT key to choose between Kilograms (Kg) or Pounds(Lbs).
When Charging refrigerant, place cylinder in the center of scale (DO NOT place a cylinder over
max weight which scale can measure as damage may occur to the scale) Attach your charging hose according to generally accepted HVAC practices, bleed air from your hose, and hit the TARE key to reset the scale to zero. Refrigerant charge will be displayed in negative numbers.
Using model and serial plate from the refrigerator you are trying to charge there is information on the plate specifying type of refrigerant and amount to charge the refrigerator.
Once Tare has been selected the scale will show 0.00 LB/Oz, as the refrigerant leaves the cylinder the scale will show a negative number. This is the amount of refrigerant that is entering the refrigerator once the amount on the scale matches the model number plate specitifcations you are done.
When Recovering refrigerant, place tank in the center of the scale. Scale will display gross weight of tank and recovered refrigerant.