Comp; Chiller Data; Load Limiting Status - McQuay MicroTech II Operation Manual

Comp #

On dual centrifugal chillers, refrigerant pressure and saturated refrigerant temperature data is displayed one compressor at a
time. This is also the case for multiple circuit screw and scroll chillers. The Comp # variable tells you which compressor
(or circuit) is currently being displayed on the CSM. To change compressors (or circuits) right-click your mouse on the
box displaying the current number and then select the "Set" command of the dialog box that appears. Changing the
displayed Comp # for any chiller changes the Comp # variable for all chillers.

Chiller Data

%RLA (Chiller Load)
For any given chiller, the chiller load is the percent of available capacity currently being used. The way the chiller load is
calculated depends on the type of chiller. See below.
Load Calculation: Centrifugal Chillers
The chiller load for centrifugal chillers is the percent of rated load amps (%RLA).
Load Calculation: Screw and Scroll Chillers
The chiller load for screw and scroll chillers is the percent of total compressor stages that are active. As an example,
consider a two-circuit, four-stage scroll chiller. If the chiller is operating at stage 3, the chiller load is 75%.
Flow
The chiller's evaporator water flow status is displayed for each chiller using a circle with a triangle inside pointing in the
direction of flow. This status represents a signal sent from the chiller to the CSM indicating that the chiller has proven
evaporator flow. A green circle indicates evaporator flow has been proven and a red circle indicates no flow.
For water-cooled chillers the condenser water flow status is also displayed similar to the evaporator (see Chiller # 1 in
Figure 46).
Evaporator Water Temperatures
The leaving evaporator water temperature is displayed for all chillers. The entering evaporator water temperature is also
displayed for water-cooled centrifugal chillers (see Chiller # 1 in Figure 46).
Condenser Temperatures
The entering condenser water temperature is displayed for all water-cooled chillers. Leaving condenser water temperature
is displayed on all water-cooled centrifugal chillers (see Chiller # 1 in Figure 46).
The outside air temperature is displayed for all air-cooled chillers (see Chiller # 3 in Figure 46).
Refrigerant Pressures
The evaporator and condenser refrigerant pressures are displayed for all chillers. On dual centrifugal or multiple circuit
screw/scroll chillers, these pressures represent the compressor (or circuit) selected by the Comp # variable.
Saturated Refrigerant Temperatures
The saturated evaporator refrigerant temperature and the saturated condenser refrigerant temperature are tabled on the Misc
screen for all chillers. On dual centrifugal or multiple circuit screw/scroll chillers, these temperatures represent the
compressor (or circuit) selected by the Comp # variable.

Load Limiting Status

The CSM can perform three types of load limiting:
1. Demand Limiting
2. Soft Load
3. Load Balancing
For more information, see Load Limiting Control on page 45. The effects of these load-limiting functions are shown on the
Load Limit screen.
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