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SECTION 17 - REFRIGERANT LEVEL CONTROL
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
17
When transitioning from Zone 2 to Zone 1, ZONE 2
TO ZONE 1 is displayed and the ZONE CONTROL
TIME REMAINING status box displays the amount
of time remaining in the 60-second countdown timer.
The following are the control thresholds:
Zone 1
Zone 2
Proportion Limit Open (fixed)
50%
52%
Proportion Limit Close (fixed)
45%
45%
Rate Limit* (setpoint)
3%-15%
3%-15%
Default
7%
5%
Period (setpoint) (seconds)
8-22
2.5-10
Default
15
2.5
Zone 1 and Zone 2
Level Setpoint
20% to 80%;
default 30%
Valve Preset Time (setpoint)
(seconds)
0 to 100; default 50
Ramp Up Time (setpoint)
(minutes)
3 to 15; default 8
Proportion Error Deadband -
+0%
Rate Error Deadband –
+0%
* This Rate Limit setpoint sets the Rate Limit threshold
for refrigerant levels both above (open) and below
(close) the Refrigerant Level setpoint.
The entire chiller run time is divided into Level Control
Periods. They occur consecutively and continuously.
The first one begins upon entering System run and when
it ends the next one begins, etc. This repeats until the
chiller is shutdown. The duration of these periods are
programmed as the Level Control Period
setpoint. At
the completion of each Level Control Period, the actual
level is compared to the Level setpoint. The result is the
Proportion Error.
The Proportion Error is compared to setpoints Proportion
Limit Open (if level is above setpoint) and Proportion
Limit Close (if level is below setpoint). If the Proportion
Error exceeds the Limit, the Proportion Error influence
in the response will be large. If the Proportion Error is
less than the Limit, the Proportion error influence in the
response is determined by how close the Proportion Er-
ror is to the Limit; close yields larger influence, further
yields smaller influence. To establish the response to the
rate of change, the amount of change in the Level within
the Level Control Period is compared to the Rate Limit
Close (if level less than setpoint) and Rate Limit Open
(if level greater than setpoint). If the result exceeds the
setpoint, the rate influence in the response will be large;
if less than the setpoint, the rate influence is determined
by how close the result is to the setpoint; close yields
larger influence, further yields smaller influence.
Therefore, per the above, the values programmed for
Proportion Limit Open/Close and Rate Limit Open/
Close determine the sensitivity of the level control.
Smaller values generally yield greater response for
the same level change in the Level Control Period.
Also, the smaller the value programmed for the Level
Control Period, the more often an output signal is ap-
plied to the Variable Orifice Actuator. The orifice valve
movement is animated on the REFRIGERANT LEV-
EL CONTROL Screen as follows:
• When 0 to 20% open, shown fully closed
• When 20 to 40% open, shown as 20% open
• When 40 to 60% open, shown as 40% open
• When 60 to 80% open, shown as 80% open
• When 80 to 100% open, shown as 100% open
MANUAL OPERATION
The Orifice Actuator can be manually controlled from
the keypad using the REFRIGERANT LEVEL CON-
TROL Screen after logging in at SERVICE access level.
Open, Close, Hold and AUTO keys are used to control
the Variable Orifice. Using the Open, Close and Hold
keys, the Variable Orifice can be placed in a fixed posi-
tion. Pressing the AUTO key returns Level Control to
Automatic operation.
ACTUATORS
New production units use a Belimo actuator that operates
from 24 VAC. If the OptiView Control Center is retrofit
to an existing chiller, the chiller could be equipped with
a Barber-Coleman actuator that operates from 115 VAC.
The interface for both actuators is shown in
The description of the operation of both actua-
of this manual.
