OMM 1008-1
5
Definitions
Active Setpoint
The active setpoint is the parameter setting in effect at any given moment. This variation can occur 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 capacity 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.
Active-Amp-Limit
Active amp limit is the actual amp limit imposed by an outside signal such as the load limit function.
Condenser Recirc (Recirculation) Timer
A timing function, with a 30-second default, that holds off any reading of condenser water for the duration of
the timing setting. This delay allows the sensors to take a more accurate reading of the condenser water
temperature.
Dead Band
The dead band is a set of values associated with a setpoint such that a change in the variable occurring within
the dead band causes no action from the controller. For example, if a temperature setpoint is 44
°
F and it has
a dead band of
±
2.0 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.
Discharge Superheat
Discharge superheat is calculated using the following equation:
Discharge Superheat = Discharge Temperature – Condenser 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.
Evaporator Approach
The evaporator approach is calculated for each circuit. The equation is as follows:
Evaporator Approach = LWT – Evaporator Saturated Temperature
Evap Hold-loading
This is a setpoint that establishes the minimum evaporator pressure to which the chiller is allowed to go. It
signals that the unit is at full load so the no further loading will occur that would lower the pressure even
further.
Evap Recirc (Evaporation Recirculation) 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 to take a more accurate reading of the chilled
water temperature.
EXV
Electronic expansion valve, used to control the flow of refrigerant to the evaporator, controlled by the circuit
microprocessor.
