Heatcraft Refrigeration Products II - Manual (Page 27)

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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 finish 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.
Note: Maximum refrigerant charge for the cooler system should not exceed 20# (R-22).
Maximum refrigerant charge for the freezer systems should not to exceed 10# (R404A).
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 voltage taps on transformer. The transformer is shipped wired to 240 voltage tap/connection. If your
supply voltage is 208 volt systems, change to 208 voltage tap.
(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) On freezers only, check the low pressure switch setting. It must be set to 0 PSIG cut out, 10 PSIG cut in,
to allow start and operation, especially in cold ambients.
(e) Liquid line should always be insulated.
(f) Wiring diagrams, instruction bulletins, etc. attached to the condensing units should be read and filed for
future reference.
(g) 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.
(h) 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.
(i) Continue charging until system has sufficient 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.
(j) 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.
(k) At initial start-up, the system may cycle off at 2 minutes and display a low superheat error, then restart
itself. This cycle may be repeated a few times. Do not shut the system off. Let the system run, as it may take
a few cycles for the electric expansion valve to attain the correct setting for the desired superheat.
CAUTION : Extreme care must be taken in starting compressors for the first 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 beneficial in eliminating this condition which might never reoccur.