Daikin Magnitude - Chiller Operation Basics; Operator Responsibilities Overview; Chiller Unit Operation Sequence

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IOM 1210-7 • MAGNITUDE
®
MODEL WMC CHILLERS 28 www.DaikinApplied.com
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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 Applied technician will
be available to answer any questions and instruct the proper
operating procedures. It 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.
Operator Schools
Training courses for Magnitude
®
Centrifugal Maintenance and
Operation are held through the year at the Daikin Learning
Institute in Verona, Virginia. The school duration is three and
one-half days and includes instruction on basic refrigeration,
MicroTech
®
II controllers, enhancing chiller efciency and
reliability, MicroTech
®
II troubleshooting, system components,
and other related subjects. For more information, visit us
at www.DaikinApplied.com and click on Training or call the
Training Department. Refer to the back cover of this document
for contact information.
Sequence of Unit Operation
A general chiller sequence of operation is outlined below
for Magnitude
®
Model WMC chillers. A separate sequence
is provided for single and dual compressor units. Certain
conditions and chiller alarms may alter this sequence, but the
chiller’s objective is to achieve the target temperature of the
leaving water.
Single Compressor Units
The following sequence of operation applies to Magnitude®
Model WMC chillers with a single compressor.
1. Chiller enabled
With the chiller enabled via its onboard interlocks
and selected external control source, it will start the
evaporator pump and check for ow and chiller load.
2. Water ow and load proven
Once evaporator ow has been conrmed and the chiller
load proven, the sequence for starting the compressor
will begin.
3. Compressor shaft levitation and start
The magnetic bearings are activated and shaft rotation
begins, as fault monitoring continues. The compressor
moves into run state and ramps its speed, which is
dened by the load. The compressor maintains its speed
between the calculated minimum and maximum speed,
while the Inlet Guide Vanes (IGV) modulate to full open.
4. Condenser pump start
As positive Lift is developed, the condenser pump is
commanded to start and water ow is conrmed.
5. Compressor loading
As building load increases, the compressor will load
up maximizing the Inlet Guide Vane (IGV) position and
impeller speed. Maximum capacity at a given operating
condition can be found either when the compressors
have reached their maximum speed limit (Mechanical
limitation) or when the compressors have reached the
chiller’s Rated Load Amperage (Electrical limitation).
6. Compressor unloading
As load decreases, the compressor will unload to sustain
the water temperature setpoint by reducing speed until
the minimum speed limit has been reached. If further
unloading is required, the IGV assemblies will close as
required to maintain stable compressor operation.
7. Chiller shutdown
The compressor will adjust capacity to manage the chiller
load and will shut off when the stop delta temperature is
acquired. Anytime the chiller is disabled, it will perform an
orderly unload and compressor shutdown.
Dual Compressor Units
The following sequence of operation applies to Magnitude®
Model WMC chillers with dual compressors.
1. Chiller enabled
With the chiller enabled via its onboard interlocks
and selected external control source, it will start the
evaporator pump and check for ow and chiller load.
2. Water ow and load proven
Once evaporator ow has been conrmed and the chiller
load proven, auto lead-lag logic will determine which
compressor to start as the Lead.
3. Compressor shaft levitation and start
The magnetic bearings are activated and shaft rotation
begins, as fault monitoring continues. The compressor
moves into run state and ramps its speed, which is
dened by the load. The compressor maintains its speed
between the calculated minimum and maximum speed,
while the Inlet Guide Vanes (IGV) modulate to full open.
4. Condenser pump start
As positive Lift is developed, the condenser pump is
commanded to start and water ow is conrmed.
5. Lead compressor operation
The Lead compressor will adjust capacity to manage
the chiller load. As the Lead compressor approaches its
maximum capacity it will assess the need for the Lag
compressor. If the Lag compressor is needed, the Lead
compressor will signal the Lag compressor to start, and
may adjust its capacity to assist the Lag compressor
from start to vanes fully open.
6. Lag compressor start
Once started and the vanes have fully opened, the Lag
compressor will quickly ramp up to balance the chiller
load between the two compressors.