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Filter Driers
Multistack modules contain very short piping runs to the major components. Only a micro refrigerant charge (0.6 lbs. per ton) is used, and all circuits are
evacuated to 150 microns. For this reason a liquid line lter drier is not factory installed in the unit. When changing a major component in the system,
a replaceable core suction line lter kit can be added to reduce contamination. The suction lter kit can be purchased from Multistack through your local
representative.
Superheat/Subcooling
Subcooling is necessary in the system to prevent ash gas as the refrigerant enters the expansion valve. Multistack uses a mechanical-type expansion valve
on all modules. Clockwise adjustment of the valve increases superheat. On water-cooled modules, superheat is set at 10°-12°F during the factory run test.
Multistack condensers are sized so that liquid refrigerant subcooling occurs without a separate subcooler. The general range of subcooling is 10°-20°F.
Daily Log Sheet
Log sheets foud at the back of this manual can be used daily, weekly or as desired to record operation characteristics of the chiller. The information recorded
on the log sheet can also help diagnose potential system problems.
Annual Maintenance
DANGER: To avoid the risk of electrical shock, personal injury or death, disconnect all electrical power to the unit before performing any maintenance
or service. The unit may have more than one electrical power supply. Assume all electrical wires are live, energized wires. Use lockout/tagouts.
Annual maintenance requirements for Multistack Chillers involve proper shut-down of the machine and cleaning of the heat exchangers. The Preventative
Maintenance bulletin (MAINT-002-0416) and Heat Exchanger Cleaning bulletin (MAINT-003-0416) describe the recommended procedures for both
processes. Multistack makes available the 151A Cleaning Kit to assist with this process. Refer to the 151A Cleaning Kit bulletin for more details.
Also check annually:
• All electrical components (contactors, fuses, relays, etc.) to identify any signs of excessive wear. Check for tight connections.
• Superheat, pressure gauges, oil levels, Master Controller condition, and sensor accuracy should also be checked.
• Exercise all isolation valves, manual or power operated.
Compressors
In the event of a compressor failure, determine the cause. A motor burn due to a fault in the motor insulation is quite rare. Most burnouts are actually
caused by a mechanical condition or lubrication problem. In the event of a burnout, proper clean up procedures should be followed.
1. Check all electrical components of the circuit (contactors, fuses, wires, etc.)
2. If necessary do a system clean up. Nu-Calgon RX-11 ush, or Sporlan System Cleaner work well.
3. Install a suction lter drier with burnout core.
4. Evacuate the system to a minimum of 500 microns and hold for 20 minutes.
5. Charge the circuit with virgin refrigerant. Charge with liquid into the discharge side. See proper refrigerant charge on nameplate data of unit.
6. Run the system 2-3 weeks with burnout lter core. Replace with standard core drier
Heat Exchanger Cleaning
Multistack publication MAINT-003-0416 provides procedures for cleaning heat exchangers. Contact your Multistack representative for more information.
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