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Refrigeration Charging
Refrigeration Charging
1. Install a liquid line drier in the refrigerant supply line between the service gauge and the liquid service port of the
receiver. This extra drier will insure that all refrigerant supplied to the system is clean and dry.
2. When initially charging a system that is in a vacuum, liquid refrigerant can be added directly into the receiver tank
to break the vacuum. Weighing in the charge is recommended with the initial charge
consisting of approximately 2 pounds per system compressor horsepower.
3. Remove the refrigerant drum and connect it to the suction side of the compressor to charge with refrigerant vapor
into the low side of the system until the pressure is above atmospheric.
4. Start the system and nish charging until the sight glass indicates a full charge and the proper amount has been
weighed in (a total of 4 to 5 pounds per system compressor horsepower).
5. If refrigerant must be added to the system through the suction side of the compressor, charge in vapor form only.
Liquid charging must be done in the high side only or with liquid metering devices to protect the compressor.
Check-Out & Start-Up
After the installation has been completed, the following points should be covered before the system is placed in
operation:
(a) Check all electrical and refrigerant connections. Be sure they are all correct and tight.
(b) Check setting of time delay relay for low pressure switch in condensing unit. It should be set at two minutes (the
third marker).
(c) Check high and low pressure controls, pressure regulating valves, oil pressure safety controls, and all other safety
controls and adjust them, if necessary.
(d) Liquid line should always be insulated.
(e) Wiring diagrams, instruction bulletins, etc. attached to the condensing units should be read and led for future
reference.
(f) All fan motors on air cooled condensers, evaporators, etc. should be checked for proper rotation. Fan motor
mounts should be carefully checked for tightness and proper alignment.
(g) Observe system pressures during charging and initial operation. Do not add oil while the system is short of
refrigerant unless oil level is dangerously low.
(h) Continue charging until system has sucient refrigerant for proper operation. Do not overcharge. Remember that
bubbles in a sight glass may be caused by a restriction as well as a shortage of refrigerant.
(i) Do not leave unit unattended until the system has reached normal operating conditions and the oil charge has
been properly adjusted to maintain the oil level at the center of the sight glass.
CAUTION: Extreme care must be taken in starting compressors for the rst time after system charging. At
this time, all of the oil and most of the refrigerant might be in the compressor creating a condition which
could cause compressor damage due to slugging. Activating the crankcase heater for 24 hours prior to
start-up is recommended. If no crankcase heater is present, then directing a 500 watt heat lamp or other
safe heat source on the lower shell of the compressor for approximately thirty minutes will be benecial in
eliminating this condition which might never reoccur.