JOHNSON CONTROLS
125
SECTION 5 – SEQUENCE OF OPERATION
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
5
Control of Compressors with Economizer
Enabled
Whenever the WATERSIDE ECONOMIZER is suit-
able and has been enabled, and the conditions are such
that the building's water supply to the units alone are
not sufficiently cold enough to maintain the “SUPPLY
AIR TEMP~ACTIVE SP” (indicated by a saturated
ECONOMIZER CONTROL OUTPUT), the compres-
sors is turned ON. The same COOLING CONTROL
OFFSET logic (deciding when to turn compressors
on and off but not the actual calculation) is used when
starting and stopping compressors with the additional
conditions that the ECONOMIZER CONTROL OUT-
PUT must be saturated and the COOLING CONTROL
OFFSET is set held at 4.5°F.
Compressors are turned ON based on the NEXT
STAGE TO ENABLE, when all of the following are
satisfied:
• The ECONOMIZER CONTROL OUTPUT is >
95% for 30 seconds
• The SUPPLY AIR TEMP CURRENT is great-
er than or equal to the current “SUPPLY AIR
TEMP~ACTIVE SP” plus the “COOLING CON-
TROL OFFSET”
• The Interstage Delay Timer has expired
Compressors are turned OFF based on the NEXT
STAGE TO DISABLE, when all of the following are
satisfied:
• The ECONOMIZER CONTROL OUTPUT is <
5% for 30 seconds
• The SUPPLY AIR TEMP CURRENT is less
than or equal to the current “SUPPLY AIR
TEMP~ACTIVE SP” minus the “COOLING
CONTROL OFFSET”
• The Interstage Delay Timer has expired
Sequence of Operation
Five different operating states can exist when both
CONDENSER WATER CONTROL and WATERSIDE
ECONOMIZER are enabled. These scenarios are in ef-
fect when the front rock switch is in the ON or AUTO
position and the unit is ready to operate.
STATE 1 OPERATION: Press STATUS key, and
use the UP▲ or DOWN▼ to navigate to “CURRENT
OPER MODE;” the unit display is either OCCUPIED
STANDBY or UNOCCUPIED STANDBY.
No Cooling Needed:
• The CONDENSER WATER VALVE analog out-
put is 10VDC (0%)
• The ECONOMIZER VALVE analog output is
2VDC (0%)
STATE 2 OPERATION: Press STATUS key, and
use the UP▲ or DOWN▼ to navigate to “CURRENT
OPER MODE.” The unit display is either OCCUPIED
STANDBY or UNOCCUPIED STANDBY, Econo-
mizer is not active, and no compressors are ON.
When Cooling Operation is active:
• The CONDENSER WATER VALVE analog out-
put is set to the “COND VALVE MIN POS”
• The ECONOMIZER VALVE analog output is
2VDC (0%)
TRANSITION FROM STATE 2 TO 3 (COMP
OPERATION ACTIVE): The “ENTERING WA-
TER TEMP” is less than or equal to the “MIXED AIR
TEMP” minus the “WATER ECONO DELTA.” The
current UNIT MODE is OCC COOLING or UNOC
COOLING.
• The CONDENSER WATER VALVE analog out-
put is controlled by the COND PRESSURE PI
• The ECONOMIZER VALVE analog output is
2VDC (0%)
TRANSITION FROM STATE 2 TO 4 (ECONO-
MIZER ACTIVE):
• The CONDENSER WATER VALVE analog out-
put is held at COND VALVE MIN POS for 60
seconds and is set to 10VDC (0%)
• The ECONOMIZER VALVE analog output is
controlled by the ECONOMIZER PI
STATE 3 OPERATION: Press STATUS key, and
use the UP▲ or DOWN▼ to navigate to “CURRENT
OPER MODE.” The unit display is either UNOCCU-
PIED COOLING or OCCUPIED COOLING, Econo-
mizer is not active, and compressors are ON, or Econo-
mizer is not active, and one or more compressors have
or will be staging ON.
• The CONDENSER WATER VALVE analog out-
put is controlled by the COND PRESSURE PI
• The ECONOMIZER VALVE analog output is
2VDC (0%)
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