6 WGS 130A to 190A OM WGS-5
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 44F and the actual temperature of the water
at a given moment is 46F, the LWT error is +2 degrees.
LWT Slope
The LWT slope is an indication of the trend of the 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.
NC
Normally closed - usually refers to a contactor or valve.
NO
Normally open - usually refers to a contactor. or valve.
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. See
notes on page 33 for explanation of sensor off set.
pLAN
Peco Local Area Network is the proprietary name of the network connecting the control
elements.
Rapid Stop
A compressor stop process that circumvents the normal pumpdown cycle.
Refrigerant Saturated Temperature
Refrigerant saturated temperature is calculated from the pressure sensor readings for each
circuit. 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).
SP
Setpoint
SSS
Solid state starter as used on McQuay screw compressors.
Suction Superheat
Suction superheat is calculated for each circuit using the following equation:
Suction Superheat = Suction Temperature – Evaporator Saturated Temperature
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