JOHNSON CONTROLS
70
FORM 160.69-O1
ISSUE DATE: 9/30/2012
SECTION 2 – OPTIVIEW CONTROL CENTER
Lead Compressor
Identifies the compressor that has been assigned as the
lead compressor.
High Head Lag Start (LED)
(Software version C.MLM.11.02.xxx (and later) or
C.OPT.11.02.300 (and later)).
Illuminates when a High Head Lag Start condition
exists. Service technicians refer to Service Manual
160.69-M1.
Lag Compressor Control
Displays the control state of the lag compressor as fol-
lows. Normally, the lag compressor progresses through
the following states in the order presented.
“Stopped”
The lag compressor is in this state when locked out,
in anti-recycle, its vane motor switch is open or shut-
down by the Surge Protection feature.
“Inhibited”
The lag compressor is prevented from running because
the Chiller Pulldown Demand Limit Setpoint is less
than or equal to 50% (during the Chiller Pulldown Pe-
riod) or the Chiller Current Limit Setpoint is less than
or equal to 50% (during the Chiller Steady State Pe-
riod), but is otherwise able to run.
“Waiting For Pulldown Delay”
Displayed during the first 8 minutes of the Chiller
Pulldown Period. Delay consists of a 3 minute bypass
when the chiller first enters the run state followed by a
5 minute evaluation period to establish the first 5-point
rolling average of the Delta T Rate.
“Checking Minimum Rate” and “Waiting Mini-
mum Rate Time”
When the 8 minute Pulldown Delay is finished, the
Chiller Pulldown Period continues until the Leaving
Chilled Liquid Temperature is within 2ºF of the Leav-
ing Chilled Liquid Temperature Setpoint. During this
period, the Delta T Rate is compared to the Minimum
Rate Setpoint and the Minimum Rate Time Setpoint to
determine if the lead compressor is meeting the load
requirement. If the Delta T Rate is less than the pro-
grammed Minimum Rate Setpoint for a period equal to
the Minimum Rate Time Setpoint and the Chiller Pull-
down Limit Setpoint is above 50%, the lag compres-
sor is brought on line. “Checking Minimum Rate” is
displayed after the Pulldown Delay is finished and until
either the Delta T Rate is less than the Minimum Rate
Setpoint (whereupon “Waiting Minimum Rate Time”
is displayed), the Chiller Pulldown Period is no longer
in effect (whereupon “Checking Maximum Delta T” is
displayed) or the Chiller Pulldown Limit Setpoint is set
to 50% or less. When “Waiting Minimum Rate Time”
is displayed, it will be displayed until the Chiller Pull-
down Period has ended (whereupon “Checking Maxi-
mum Delta T” is displayed), the Delta T Rate is less
than the Minimum Rate Setpoint (whereupon “Check-
ing Minimum rate” is again displayed), the Minimum
Rate Time has expired (whereupon the lag compressor
is brought on line and “Preparing Chiller for Lag Run”
is displayed) or the Chiller Pulldown Demand Limit is
set to 50% or less.
“Checking Maximum Delta T” and “Waiting Maxi-
mum Delta T Time”
When the Leaving Chilled Liquid Temperature is
within 2ºF of the Leaving Chilled Liquid Tempera-
ture Setpoint, the Chiller Pulldown Period ends and
the Chiller Steady State Period begins. During this pe-
riod, the Temperature Differential is compared to the
Maximum Delta T Setpoint and the Maximum Delta
T Time Setpoint to determine if the lead compressor is
meeting the load requirement. If the Temperature Dif-
ferential exceeds the Maximum Delta T Setpoint for
a period equal to the Maximum Delta T Time and the
Chiller Current Limit is above 50%, the lag compressor
is brought on line. “Checking Maximum Delta T” is
displayed after the Chiller Pulldown Period is no longer
in effect and until the Temperature Differential exceeds
the Maximum Delta T Setpoint (whereupon “Waiting
Maximum Delta T Time” is displayed) or the Chiller
Current Limit is set to 50% or less. When “Waiting
Maximum Delta T Time” is displayed, it is displayed
until the Temperature Differential does not exceed the
Maximum Delta T Setpoint (whereupon “Checking
Maximum Delta T” is displayed), the Maximum Delta
T Time has expired (whereupon “Preparing Chiller for
Lag Run’ is displayed and the lag chiller is brought on
line) or the Chiller Current Limit Setpoint is set to 50%
or less.
“Preparing Chiller for Lag Run”
Displayed while bringing the lag compressor on line.
Displayed during the prelube period and until the Dis-
charge Valve has fully opened (whereupon “Waiting
Minimum Run Time” is displayed). When bringing the
lag compressor on line, a normal prelube is performed.
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