JOHNSON CONTROLS
14
FORM 155.21-W2 (1209)
EVAPORATOR FLOW SENSORS
The Thermal‑type flow sensor interfaces with the
Microboard and Paddle-type flow sensor interfaces
with the I/O board.
FIG. 23 ‑
EVAPORATOR FLOW SENSORS
Flash Memory Card Version C.OPT.15.01.XXX and
later allows the use of either the Thermal-type or Paddle-
type flow sensors on the Style D and later chillers.
For the program to read the appropriate inputs for the
flow sensor status, the actual flow sensor type used must
be entered at the keypad SALES ORDER/CONFIG
Screen using
SERVICE access level. Enter "ANALOG"
for Thermal-type or "DIGITAL" for Paddle-type.
When flow is sensed, the flow sensor contacts are
closed. Opening of the flow sensor contacts (no flow)
for 2 continuous seconds causes a cycling shutdown
displaying "CHILLED LIQUID FLOW SWITCH
OPENED".
THERMAL TYPE FLOW SENSOR
When the Thermal-type flow switch is used, the flow
switch uses the cooling effect of liquid to sense flow.
When the flow of liquid is sensed, the relay output is
turned on conducting current through the microboard
load resistor to the +5VDC applying greater than
+4VDC to the microboard input J14-5.
When no flow of liquid is sensed, the relay output is
turned off, this results in less than 1VDC to the micro
‑
board input.
LD09134
J7-
MICROBOARD
THERMAL-TYPE FLOW SENSOR
12
1
TB4
I/O BOARD
PADDLE-TYPE FLOW SENSOR
EVAPORATOR
PADDLE TYPE FLOW SENSOR
When Evaporator Water is flowing, the flow switch con-
tact will close. If the flow switch opens for 2 seconds, the
unit shuts down.
GENERATOR BACKUP TRANSFER
During a prolonged power failure the unit will shutdown
without going through a dilution cycle. This could cause
the unit to crystallize depending on the duration of
power failure. By adding a small standby AC 3-phase
power supply, the solution pump can perform a limited
dilution cycle.
During a power failure a subsequent limited dilution
cycle, the system will NOT be able to produce chilled
water.
If unit experiences a power failure, the input (95) on
the I/O board is checked for a closed contact (indicating
that a standby power supply is online). No matter what
the solution concentration is at the time of the power
failure or what the dilution cycle to last NO longer than
4 hours. The generator will supply power to the unit
mounted power panel, which will supply OptiView
control panel and solution pump for the dilution period.
During this period, the unit will continue to monitor if
the fault condition has been cleared to switch to a normal
dilution cycle. If condenser flow is sensed through the
flow switch during the limited dilution cycle, the dilu
‑
tion cycle will cease.
Refer to 155.21-O1 for additional details on the limited
dilution cycle.
Refer to 155.21-EG1 for minimum power requirements
for standby power supply.
FIG. 24 –
PADDLE TYPE FLOW SENSOR
FIG. 25 –
GENERATOR BACK-UP TRANSFER
LD04400
95
BACKUP GENERATOR TRANSFER
CONTACT CLOSES ON POWER FAILURE
(SUPPLIED BY OTHERS)
LD14446
I/O BOARD
PADDLE-TYPE FLOW SENSOR
(DIGITAL)
MICROBOARD
THERMAL-TYPE FLOW SENSOR
(ANALOG)
