10 ED 15121
Protocol Point Summary
The following section provides a summary of Modbus properties available from the MicroTech III Chiller Unit
Controller. Tables 4-8 contains the complete list of chiller, circuit, compressor, pump, and miscellaneous data points
respectively. The items shown in boldface represent the minimum integration properties (as identified previously in
Table 3.)
Register Mapping
The Modbus Communication Module supports zero-based addressing. For example, holding register 40002 is addressed
as 0001 in a Modbus message. The following tables assume 4xxxx addressing. For example, 1 will be holding register
40001.
Table 4. Chiller Data Points
Network Control Property Page
Holding
Register
(4xxxx)
Read/
Write
Description
Chiller Local/Remote 21 1 R 0=Remote, 1=Local
Chiller Enable Output 21 2 R 0=Disable, 1=Enable
Run Enabled 27 3 R 0=Off 1= RunAllowed
Chiller Capacity Limited 20
4
R 0=Not Limited, 1=Limited
Alarm Digital Output 19 5 R 0=No Alarm, 1=Alarm
Evaporator Flow Switch Status 25 6 R 0=No Flow, 1=Flow
Chiller On/Off 22 8 R 0=Off, 1=On
*Chiller Enable Setpoint (4) 21 9 R/W 0=Disable, 1=Enable, 2=Null
*Clear Alarms – Network (14) 22 10 R/W 0=Normal, 1=Clear Alarms, 2=Null
Chiller Mode Output 21 11 R 1=Ice, 2=Cool, 3=Heat, 4=Cool/Heat Recovery, 5=Defrost
Active Setpoint 19 12 R 15.08°F to 149.9°F (-9.4°C to 65.5°C)
*Actual Capacity (3) 19 13 R 0 - 100%
Active Capacity Limit Output 19 14 R 0 - 100%
*Chiller Status (Chiller Run Mode) (1) 22 15 R 1=Off, 2=Start, 3=Run, 4=Pre Shutdown, 5=Service
*Evaporator Entering Fluid Temperature (5) 25
16
R
-40-230°F (-40-110°C)
*Evaporator Leaving Fluid Temperature (6) 25 17 R
-40-230°F (-40-110°C)
Outdoor Air Temperature 26
24
R
-40-230°F (-40-110°C)
Chiller Current 20 25 R 0-10,000 Amps
Warning Alarm Index 27 28 R 0=No Alarms
5=Evaporator pump maintenance
7=Compressor maintenance Circuit #n
8=Bad setpoint override input
9=Bad demand limit input
11=Unit power restore
12=Circuit failed pumpdown
13=External Event
Problem Alarm Index 27 29 R 0=No Alarms
64=RESTART DELAYED-Power Loss While Running Circuit #n
65=START INHIBITED - Ambient Temperature Low
67=INHIBIT LOAD – Condenser Pressure High Circuit #n
69=UNLOAD – Condenser Pressure High Circuit #n
76=INHIBIT LOAD - Evaporator Pressure Low Circuit #n
78=UNLOAD - Evaporator Pressure Low Circuit #n
Fault Alarm Index 26 30 R 0=No Alarms
127=COMP SHUTDOWN–Low pressure ratio #n
128=COMP SHUTDOWN-Outside Air Temp Sensor Fault
135=COMP SHUTDOWN–Motor Temp High Circuit #n
136=COMP SHUTDOWN–Motor Temp Sensor Fault #n
142=COMP SHUTDOWN-Condenser Pressure Sensor Fault #n
145=COMP SHUTDOWN-Condenser Pressure High #n,
147=COMP SHUTDOWN-Discharge Temp Sensor Fault #n
148=COMP SHUTDOWN-Discharge Temp High #n
150=UNIT SHUTDOWN-Evaporator Water Flow Loss
151=UNIT SHUTDOWN–Evaporator Leaving Water Temp Low
(Freeze)
153=COMP SHUTDOWN-Evaporator Pressure Low #n,
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