Daikin WMC Installation, Operation And Maintenance Manual page 64

and the condenser flow loss is adjustable from 20 to 3s (default
20s).
Load Balance
Load balance is a technique that equally distributes the total
unit load between two or more running compressors.
Load Limit
An external signal from the keypad, the BAS, or a 4-20 ma
signal that limits the compressor loading to a designated
percent of full load. Used to limit unit power input.
Low Pressure Hold (Inhibit) Setpoint
The psi evaporator pressure setting at which the controller will
not allow further compressor loading. "Hold" and "Inhibit" are
used interchangeably.
Low Pressure Unload Setpoint
The psi evaporator pressure setting at which the controller will
unload the compressor in an effort to maintain the minimum
setting.
LRA
Locked rotor amps.
Minimum and Maximum Compressor
Speeds
The (respective) Surge and Choke speeds, determined by the
compressor software, are based on suction and discharge
pressures.
Offset
Offset is the difference between the actual value of a variable
(such as temperature or pressure) and the reading shown on
the microprocessor as a result of the sensor signal.
OITS
Operator Interface Touch Screen, one screen per unit provides
operating data visually and accommodates setpoint entry.
Part Load Balance Valves
These valves open before compressor start, to allow gas flow
through the compressor, which stabilizes the impeller as it
ramps up in speed.
pLAN
Pico Local Area Network is the proprietary name of the network
connecting the control elements.
RapidRestore Function
®
This logic has been introduced to reduce the time the chiller
needs to recover from a power loss event. The chiller's run
status is continuously stored in battery backed RAM. When
IOM 1210-1 • MAGNITUDE MODEL WMC CHILLERS
®
power is returned to the compressors it checks the status of
this function, and if enabled it then checks if the chiller was
running when power was lost. If so, it clears timers, enables the
pumps, and clears power loss alarms. Evaporator water flow
must be detected before the compressor is allowed to start,
the re-circulation timer will be cleared. As the compressors
start in quick session the maximum pull down rate is relaxed to
promote a fast return to set point. The function ends when the
ELWT has dropped below the Stage-Delta temperature, or a
compressor shuts down (for any reason).
If other alarms are pending (such as a bearing fault) the
RapidRestore ® function will be canceled.
Refrigerant Saturated Temperature
Refrigerant saturated temperature is calculated from the
pressure sensor readings. The pressure is fitted to an HFC-
134a temperature/pressure curve to determine the saturated
temperature.
RLA
Run load amps.
Soft Load
Soft Load is a control sub-routine that allows the chiller to load
up gradually. It requires setpoint inputs of selecting it by Yes or
No inputs by selecting the percent load to start ramping up and
by selecting the time to ramp up to full load (up to 60 minutes).
SP
Setpoint
Stageup Delay
The time delay from the start of the first compressor to the start
of the second.
Stageup/Stagedown Delta-T
Staging is the act of starting or stopping a compressor or fan
when another is still operating. Startup and Stop is the act
of starting the first compressor or fan and stopping the last
compressor or fan. The Delta-T is the "dead band" on either
side the setpoint in which no action is taken.
Startup Delta-T
Number of degrees above the LWT setpoint required to start
the first compressor.
Stop Delta-T
Number of degrees below the LWT setpoint required for the
last compressor to stop.
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