Installation manual

IM 1029-2 Magnitude™ Frictionless Centrifugal Chillers – Model WMC 49
Operation
Operator Responsibilities
It is important that the operator become familiar with the equipment and the system before attempting operation.
During the initial startup of the chiller, the Daikin technician will be available to answer any questions and
instruct in the proper operating procedures.
I
t is recommended that the operator maintain an operating log for each individual chiller unit. In addition, a
separate maintenance log should be kept of the periodic maintenance and servicing activities.
Now that you have made an investment in modern, efficient Daikin equipment, its care and operation should
be a high priority. For training information on all Daikin HVAC products, please visit us at
www.DaikinApplied.com and click on
Training, or phone [phone] and ask for the Training
Department. These sessions are structured to provide basic classroom instruction and include hands-on
operating and troubleshooting
exercises.
Compressor Operation
The WMC compressors are two-stage. Suction gas enters the compressor through inlet guide vanes that can be
opened and closed to control refrigerant flow as the cooling load changes. The suction gas enters the first stage
impeller, is compressed, and travels through the vaned radial diffuser to the second stage impeller where
compression is completed. The gas travels to the condenser via the discharge volute, which converts any
remaining velocity pressure to static pressure.
Motor cooling is accomplished by utilizing the refrigerant effect of high-pressure liquid refrigerant from the
condenser expanded to a gas within the compressor. The refrigerant cools VFD heat sinks and the motor.
A five-axis magnetic bearing system supports the motor/compressor shaft, resisting radial and thrust forces. The
bearing control system uses shaft position feedback to continually adjust the bearing to keep the shaft in the
correct position. During coast down or in the event of a power failure, the compressor motor acts as a generator
and in conjunction with on-board capacitors powers the bearing support system. There is also a system to gently
de-levitate the shaft.
Many controls are mounted directly on the compressor where they monitor and control compressor operation.
These compressor controls are interfaced with the conventional MicroTech II controls to provide a complete
chiller control system.
System Water Volume
It is important to have adequate water volume in the system to provide an opportunity for the chiller to sense a
load change, adjust to the change, and stabilize. As the expected load change becomes more rapid, a greater
water volume is needed. The system water volume is the total amount of water in the evaporator, air handling
products and associated piping. If the water volume is too low, operational problems can occur including rapid
compressor cycling, rapid loading and unloading of compressors, erratic refrigerant flow in the chiller, improper
motor cooling, shortened equipment life and other undesirable consequences.
Some of the things the designer should consider when looking at water volume are the minimum cooling load,
the minimum chiller plant capacity during the low load period and the desired cycle time for the compressors.
Assuming that there are no sudden load changes and that the chiller plant has reasonable turndown, a rule of
thumb of “gallons of water volume equal to two to three times the chilled water gpm flow rate” is often used.
For process applications where the cooling load can change rapidly, additional system water volume is needed.
A process example would be a quenching tank. The load would be very stable until the hot material is immersed
in the water tank. Then, the load would increase drastically. For this type of application, system volume may
need to be increased.