64 KOMAC00607-09EN
Appendix
Definitions
Active Setpoint
The active setpoint is the setting in effect at any given moment. This variation occurs on
setpoints that can be altered during normal operation. Resetting the chilled water
leaving temperature setpoint by one of several methods, such as return water
temperature, is an example.
Active Capacity Limit
The active setpoint is the setting in effect at any given moment. Any one of several
external inputs can limit a compressor’s capacity below its maximum value.
Condenser Saturated Temperature Target
The saturated condenser temperature target is calculated by first using the following
equation:
Sat condenser temp target raw = 0.833(evaporator sat temp) + 68.34
The “raw” value is the initial calculated value. This value is then limited to a range
defined by the Condenser Saturated Temperature Target minimum and maximum
setpoints. These setpoints simply cut off the value to a working range, and this range
can be limited to a single value if the two setpoints are set to the same value.
Dead Band
The dead band is a range of values surrounding a setpoint such that a change in the
variable occurring within the dead band range causes no action from the controller. For
example, if a temperature setpoint is 44°F and it has a dead band of ± 2 degrees F,
nothing will happen until the measured temperature is less than 42°F or more than 46°F.
DIN
Digital input, usually followed by a number designating the number of the input.
Error
In the context of this manual, “Error” is the difference between the actual value of a
variable and the target setting or setpoint.
Evaporator Approach
The evaporator approach is calculated for each circuit. The equation is as follows:
Evaporator Approach = LWT – Evaporator Saturated Temperature
See page 38 for more details
Evap Recirc Timer
A timing function, with a 30-second default, that holds off any reading of chilled water
for the duration of the timing setting. This delay allows the chilled water sensors
(especially water temperatures) to take a more accurate reading of the chilled water
system conditions.
EXV
Electronic expansion valve, used to control the flow of refrigerant to the evaporator,
controlled by the circuit microprocessor.
High Saturated Condenser – Hold Value
High Cond Hold Value = Max Saturated Condenser Value – 5 degrees F
This function prevents the compressor from loading whenever the pressure approaches
within 5 degrees of the maximum discharge pressure. The purpose is to keep the
compressor online during periods of possibly temporary elevated pressures.
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