JOHNSON CONTROLS
119
SECTION 5 – SEQUENCE OF OPERATION
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
5
Water Flow Switch (Factory Installed
Option)
When units are equipped with this option, the Unit
Controller monitors the status of the binary input from
the condenser water flow switch. The 24VAC input is
found at the connector J13 – terminal 10. A 24VAC
input at this input indicates adequate condenser water
flow.
The following parameter must be programmed through
the User Interface:
• OPTIONS key, CONDENSER subsection:
“WATER FLOW SWITCH” must be set to “IN-
STALLED”
Sequence of Operation
If the UNIT MODE is OCCUPIED or UNOCCUPIED
COOLING and the 24VAC input is lost for 10 seconds
a “WRN-LOW WATER FLOW” is declared and all ac-
tive compressors are turned OFF.
After a “WRN-LOW WATER FLOW” is declared, the
24VAC input must be reestablished for 30 seconds be-
fore compressor operation is reinstated.
When “WRN-LOW WATER FLOW” is active, the
compressors are not able to run and each compressor
status reads “INHIBITED.”
Do not apply power to unit with factory
installed flow switch if condenser piping
has no fluid in it for heat transfer.
WATER COOLED CONDENSER
OPERATIONS
The LSWU unit can be ordered with no condenser wa-
ter valves installed from the factory if regulating re-
frigerant discharge pressure for proper compressor op-
eration is needed. A water flow sequence requires set
up on site using third party controls, such as binary or
analog controls or BAS (building automation system).
Otherwise, no recommendations are made for this ex-
cept for having the factory ordered controls.
This section describes the different control and opera-
tion scenarios the LSWU unit could have depending
on what is factory installed and how the unit is set up
through the OPTIONS, PROGRAM, and SETTINGS
keys on the Unit Interface.
The following types of valve and piping options are
available from the factory:
• No Valve installed
• Condenser Valve only
• Condenser Valve with Bypass
• Condenser Valve with Waterside Economizer
It is recommended that the technician verify what type
of condenser piping is used in the LSWU unit and ver-
ify how it is programed for operation under the previ-
ously mentioned keys on the unit's User Interface. The
technician needs to verify if the unit is using an econo-
mizer for cooling operation, and this requires set up in
the User Interface of the unit.
Condenser Water Control
This setting indicates what type of water system the
unit is connected to. It is used to determine what posi-
tion the water valves should be in when the unit is on
but not in an active COOLING mode.
No Valve
WATER-COOLED
CONDENSER
WATER
SUPPLY
WATER
RETURN
No Valves
LD21630
FIGURE 72 -
CONDENSER ONLY PIPING DIAGRAM
WITH NO VALVES FROM THE FACTORY