Appendix; Definitions - Daikin Magnitude WME Series Installation, Operation And Maintenance Manual

Active LWT Setpoint
The active LWT (leaving water temperature) setpoint is the
actual target value for leaving water temperature in effect at
any given time. It is the Leaving Water Temp - Cool setpoint as
modified by any active LWT reset input.
Amp Limit
Active amp limit is the actual amp limit in effect at any given
time. It is the lowest value of any active external inputs and
internal setpoints.
Deadband
The deadband is a range of values for a controlled variable
over which no action is taken by the controller.
Demand Limit
A signal from the User Interface or the BAS that limits the
compressor loading to a designated percent of full load. This
function limits the % RLA value.
Discharge Superheat
Discharge superheat is calculated using the following equation:
Discharge Superheat = Discharge Line Temperature –
Discharge Saturated Temperature
Error
In the context of this manual, "Error" is the difference between
the actual value of a variable and the target setting or setpoint.
For example, if the ELWT setpoint is 44°F and the actual
temperature of the water at a given moment is 46°F, the ELWT
error is +2 degrees.
Evaporator/Condenser Approach
The evaporator/condenser approach is calculated as follows:
Evap Approach = LWT – Saturated Temperature
Cond Approach = Saturated Temperature – LWT
Load Balance
Load balance is a technique that equally distributes the total
unit load between two or more running compressors. On the
WME, this function uses compressor power.
Low Pressure Delta Setpoint
Chiller logic attempts to prevent low pressure shutdowns
by keeping evaporator pressure above the shutdown limit.
The target low pressure limit is the Low Evap Pressure Stop
setpoint plus the Low Evap Pressure Delta setpoint.
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Definitions

Maximum Compressor Speed
The maximum compressor speed is a fixed value based on the
impeller size.
Minimum Compressor Speed
The minimum compressor speed is a dynamically calculated
value based on operating conditions that is further limited on
the low side by the VFD Minimum Speed setpoint.
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.
RapidRestore
This capability uses an optional power supply running from a
facility's uninterruptable power source that keeps the unit and
compressor controllers powered during a power interruption.
This option allows the chiller to restart quickly when power
returns.
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. The WME uses sealed gage transducers so that
barometric pressure compensation is not required.
Stage Delay
The time delay from the start of the first compressor to the start
of the second or from the start of the second until the time it
can shut down.
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.
Suction Superheat
Suction superheat is calculated using the following equation:
Suction Superheat = Suction Temperature – Suction
Saturated Temperature
VDC
Volts, Direct Current.
57 IOM 1266-2 • MAGNITUDE
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