Johnson Controls LSWU User Manual

JOHNSON CONTROLS
131
SECTION 5 – SEQUENCE OF OPERATION
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
5
Once the “ECONO SYS STATUS” is NORMAL - AC-
TIVE, the “ECONO SYS STATUS” is set to NOR-
MAL - INACTIVE if any of the following are met:
• The OUTSIDE AIR TEMP is 10.0°F or higher
than the “SUPPLY AIR TEMP ACTIVE SP”
• The OUTSIDE AIR ENTHALPY is greater than
or equal to the “OUTSIDE AIR ENTHALPY
SETPOINT” plus 1 BTU/LB
• The current UNIT MODE is not OCC COOLING
or UNOCCUPIED COOLING
Dual Enthalpy
When the “ECONO METHOD TO USE” is set to
“DUAL ENTHALPY,” the Unit Controller refer-
ences the OUTSIDE AIR TEMP, OUTSIDE AIR EN-
THALPY (derived from OUTSIDE AIR TEMP and
OUTSIDE AIR HUMIDITY), and RETURN AIR
ENTHALPY (derived from RETURN AIR TEMP
and RETURN AIR HUMIDITY) to determine the
“ECONO SYS STATUS.”
The “ECONO SYS STATUS” is NORMAL - ACTIVE
if all of the following conditions are met:
• The OUTSIDE AIR TEMP is less than or equal
to the “SUPPLY AIR TEMP ACTIVE SP” or up
to 8.0°F over the “SUPPLY AIR TEMP ACTIVE
SP”
• The OUTSIDE AIR ENTHALPY is less than or
equal to the RETURN AIR ENTHALPY minus
1 BTU/LB
• The current UNIT MODE is OCCUPIED COOL-
ING or UNOCCUPIED COOLING
Once the “ECONO SYS STATUS” is NORMAL - AC-
TIVE, the “ECONO SYS STATUS” is set to NOR-
MAL - INACTIVE if any of the following are met:
• The OUTSIDE AIR TEMP is 10.0°F or higher
than the “SUPPLY AIR TEMP ACTIVE SP”
• The OUTSIDE AIR ENTHALPY is greater than
or equal to the RETURN AIR ENTHALPY
• The current UNIT MODE is not OCCUPIED
COOLING or UNOCCUPIED COOLING
Best Available
When the “ECONO METHOD TO USE” is set to
BEST AVAILABLE, the Unit Controller determines
the “ECONO METHOD TO USE” based on the sensor
that is installed and reliable. The Dry Bulb method is
used if only the “OAT SENSOR RELIABLE” is true.
The Single Enthalpy method is used if both the “OAT
SENSOR RELIABLE” and the “OA HUMIDITY
SENSOR RELIABLE” are true. The Dual Enthalpy
method is used if the “OAT SENSOR RELIABLE,”
“RET SENSOR RELIABLE,” “OA HUMIDITY SEN-
SOR RELIABLE,” and the “RA HUMIDITY SEN-
SOR RELIABLE” are all true.
With this setting, all of the above logic for Dry Bulb,
Single Enthalpy, and Dual Enthalpy apply.
Compressor Control
Whenever a change in the unit cooling status is made—
compressor turned ON, compressor turned OFF, etc.
—a 3-1/2 minute Interstage Delay Timer is initiated.
During the countdown of the timer no compressor can
be staged ON or OFF until the timer has expired. The
only exception would be if the compressor protection
circuit experienced a fault.
On CONSTANT VOLUME and VARIABLE AIR
VOLUME, when the Unit Controller enters an active
COOLING mode, the Unit Controller sets the “COOL-
ING CONTROL OFFSET” to 2.0°F. The Unit Control-
ler compares the SUPPLY AIR TEMP CURRENT to
the “SUPPLY AIR TEMP ACTIVE SP” plus or minus
the “COOLING CONTROL OFFSET.” If the SUPPLY
AIR TEMP CURRENT is greater than the “SUPPLY
AIR TEMP ACTIVE SP” plus the “COOLING CON-
TROL OFFSET” and all the compressors are not ON,
the Unit Controller initiates a call for compressor or
additional compressor operation based on the “NEXT
STAGE TO ENABLE.”
If the SUPPLY AIR TEMP CURRENT is less than the
“SUPPLY AIR TEMP ACTIVE SP” minus the “COOL-
ING CONTROL OFFSET” and all the compressors are
not OFF, the Unit Controller turns a compressor OFF
based on the “NEXT STAGE TO DISABLE.”
Compressor Operation with Economizer
If the economizer is suitable, the Unit Controller sets
the “COOLING CONTROL OFFSET” to 4.5°F. As
long as the economizer remains active, the Unit Con-
troller does not recalculate the “COOLING CONTROL
OFFSET” and it remains at the 4.5°F setting.

Johnson Controls LSWU Specifications

General

Brand	Johnson Controls
Model	LSWU
Category	Chiller
Language	English