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Liquid Charging
Because R-404A is a near-azeotrope, only liquid
refrigerant can be used to recharge the
refrigeration system. To do that may take some
special techniques:
1. Use an electronic scale to measure the charge.
2. Place a drum or cylinder of R-404A on the
scale, valve side up (most R-404A disposable
cylinders have an internal dip tube and dispense
liquid refrigerant from the valve when it is upright -
check yours).
3. A refrigeration manifold should be attached to
the service access valves. Attach the charging
hose to the cylinder of R-404A. Open the
cylinder’s valve and purge the hose to the
manifold.
4. Close the low side service access valve.
5. Open the discharge side manifold valve and
weigh in the name plate charge. After the charge is
weighed in, wait a few minutes and re-check the
scale.
6. If all of the refrigerant charge has not been
weighed into the discharge side, it must be
carefully added thru the low side. Close the
discharge service access valve.
7. With a sight glass or charge faster in the hose to
the low side port, start the ice machine.
8. Open the low side service access valve.
9. Crack open the low side manifold valve and
watch the scale and sight glass. Open and close
the low side manifold valve to flow liquid into the
manifold but flash off to vapor before it enters the
suction side of the refrigeration system. This
should only be a few ounces at most.
10. After the scale = the correct charge, shut off
the valve on the refrigerant cylinder.
11. With the ice machine running and the
discharge access valve closed, open both manifold
valves to allow the refrigerant in the hoses to enter
the system.
12. Shut the suction service access valve.
13. Remove the refrigeration manifold gages.
14. Replace and tighten all caps.
CME1356R and CME1656R
March 2003
Page 44