JOHNSON CONTROLS
126
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
SECTION 5 – SEQUENCE OF OPERATION
TRANSITION FROM STATE 3 TO 2 (COMP
TURNED OFF): Demand for mechanical cooling is
less.
• 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 3 TO 5 (ECONO-
MIZER GOING ACTIVE): At this point there’s still
a demand for cooling, but the condenser water is cold
enough for the WATERSIDE ECONOMIZER to assist
in cooling the space by the parameters that are pro-
grammed into the User Interface.
Once the “ECONO SYS STATUS” is “NORMAL
- ACTIVE,” the Unit Controller uses the “ECONO-
MIZER CONTROL OUTPUT” to control the valve
operation on the condenser water inlet for the water
economizer coil to maintain the “SUPPLY AIR TEMP
ACTIVE SP.” One compressor is turned OFF.
If turning OFF one compressor leaves no compressors
ON, the unit is in full waterside economizing.
• The CONDENSER WATER VALVE is held at its
current position for 60 seconds and set to 10VDC
(0%)
• The ECONOMIZER VALVE analog output is
controlled by the ECONOMIZER PI
If turning OFF one compressor still leaves compres-
sors ON:
• The CONDENSER WATER VALVE is held at its
current position for 60 seconds and set to 10VDC
(0%)
• The ECONOMIZER VALVE analog output is
controlled by either the ECONOMIZER PI or the
CONDENSER PI, whichever is the lowest
STATE 4 OPERATION: “CURRENT OPER MODE”
is UNOCCUPIED or OCCUPIED COOLING, econo-
mizer is active, and no compressors are ON.
• The CONDENSER WATER VALVE analog out-
put is set to 10VDC (0%)
• The ECONOMIZER VALVE analog output is-
controlled by the ECONOMIZER PI
TRANSITION FROM STATE 4 TO 2 (ECONO-
MIZER INACTIVE):
• 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 4 TO 5 (COMPRES-
SOR TURNED ON):
• The CONDENSER WATER VALVE remains set
to 10VDC (0%)
• The ECONOMIZER VALVE analog output is-
controlled by either the ECONOMIZER PI or the
CONDENSER PRESSURE PI, whichever is the
lowest
STATE 5 OPERATION: “CURRENT OPER MODE”
is UNOCCUPIED or OCCUPIED COOLING, Econo-
mizer is active, and one or more compressors are ON.
• The ECONOMIZER PI is DISABLED
• The CONDENSER PI is ENABLED
• The COND VALVE analog output is set to closed
10 VDC (0%)
• The ECONOMIZER VALVE AO is coupled to
the CONDENSER PRESSURE PI output
TRANSITION FROM STATE 5 TO 4 (All COM-
PRESSORS TURNED OFF):
• The ECONOMIZER PI is ENABLED
• The CONDENSER PRESSURE PI is DISABLED
• The ECONOMIZER VALVE analog output is
coupled to the ECONOMIZER CONTROL OUT-
PUT
TRANSITION FROM STATE 5 TO 3 (ECONO-
MIZER INACTIVE):
• The CONDENSER WATER VALVE analog out-
put is controlled by the COND PRESSURE PI
• The ECONOMIZER VALVE analog output is
held at its current position for 60 seconds and is
closed 2VDC (0%)
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