6 OMM 1008-1
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.
Load Balance
Load balance is a technique that equally distributes the total unit load between two or more running
compressors.
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.
LWT
Evaporator leaving water temperature. The “water” is any fluid used in the chiller circuit.
LWT Error
Error in the controller context is the difference between the value of a variable and the setpoint. For
example, if the LWT setpoint is 44°F and the actual temperature of the water at a given moment is 46°F,
the LWT error is +2 degrees.
LWT Slope
The LWT slope is an indication of the trend of the chilled water temperature. It is calculated by taking
readings of the temperature every few seconds and subtracting them from the previous value over a
rolling one-minute interval.
ms
Milli-second
Maximum Saturated Condenser Temperature
The maximum saturated condenser temperature allowed is calculated based on the compressor
operational envelope.
OAT
Outside ambient air temperature
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.
pLAN
Peco Local Area Network is the proprietary name of the network connecting the control elements.
Refrigerant Saturated Temperature
Refrigerant saturated temperature is calculated from the pressure sensor readings. The pressure is fitted
to an R-134a temperature/pressure curve to determine the saturated temperature.
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).
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