16
Start-Up
Do not start the system while in a vacuum. Do not leave the system unattended until normal operating conditions
• Operate the system for a minimum of two hours and perform checks of the following:
o Check the compressor discharge and suction pressures to ensure they are in the normal operating range.
o Check the liquid line sight glass for proper refrigerant charge (based off of 105ºF condenser coil).
• Monitor the compressor oil level (semi-hermetic compressors), add oil as necessary to keep the level at ¾ sight glass
when idle and ½ sight glass when running.
• Check the voltage and amperage at the compressor terminals. Voltage must be within +10% or -5% of the rating
indicted on the condensing unit name plate. On three phase compressors, verify there is a balanced load.
• Check all fans on the evaporator coil and condensing unit to be sure they are operational and turning in the correct
direction.
• Check the piping and electrical connections for vibration. Add supports and strapping if needed.
• Check the crankcase heater operation (if equipped).
• Set the defrost control time and verify the defrost initiation settings. See pages 28-30 for additional details.
• Set temperature control to desired temperature range.
• Check the compressor and evaporator superheat (reference pages 21-23).
• After all system checks have been checked, properly adjusted, and verified, replace all Schrader caps, service valve
caps, electrical box covers, housings, etc. File a copy of this manual for future reference.
Failure to check and properly adjust compressor superheat can result in premature system failure.
Compressor Superheat
• Compressor superheat is a critical value that must be checked. Check the compressor superheat as follows:
o Determine the suction pressure at the suction service valve of the compressor.
o Determine the saturation temperature at the observed suction pressure using refrigeration pressure
temperature tables.
o Measure the suction line temperature 6 -10 inches away from the compressor.
o Subtract the saturation temperature (step 2) from the measured temperature (step 3). The difference is the
superheat of suction gas.
• A low suction superheat can cause liquid to return to the compressor. This will cause dilution of the oil and eventual
failure of the bearings, rings and valves.
• A high suction superheat will cause excessive discharge temperatures, which cause a breakdown of the oil. This
causes piston ring wear, and piston and cylinder wall damage.
• System capacity decreases as the suction superheat increases.
• For maximum system capacity, keep the suction superheat as low as practical. Copeland requires a minimum
compressor superheat of 20°F; however, to improve compressor life, 25°F to 40°F is preferred.
• Adjust the expansion valve at the evaporator when adjustments to the suction superheat are necessary.
• Refer to “Evaporator Superheat” on the next 2 pages for more information.
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