JOHNSON CONTROLS
18
FORM 160.79-PW2
ISSUE DATE: 01/31/2019
SECTION 2 - FIELD CONTROL MODIFICATIONS
The closure of a Momentary or Maintained N.O.
Switch or Relay Contacts will cause the unit to shut
down and display: SAFETY SHUTDOWN – MAN-
UAL RESTART and AUXILIARY SAFETY – CON-
TACTS CLOSED. The unit will not restart until the
contacts open and the keypad COMPRESSOR switch
is moved to the STOP-RESET position (“
O
”) and then
to the START (“
t
”) position.
EVAPORATOR FLOW SENSORS
The Thermal-type flow sensor interfaces with the
Microboard and Paddle/Differential Pressure type flow
sensor interfaces with the I/O board.
MICROBOARD
THERMAL-TYPE FLOW SENSOR
12
1
TB4
I/O BOARD
PADDLE-TYPE FLOW SENSOR
EVAPORATOR
J14-4
J14-5
+5V
FIGURE 23 -
EVAPORATOR FLOW SENSORS
LD20686
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 OPERATIONS Screen
using Service the Access Level. Enter "Analog" for
Thermal- type or "Digital" for paddle/DP type. Refer
to
Unit Operation Manual Form 160.79‑O1
.
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 "Leaving Chilled Liquid - Flow Switch
Open". The flow sensor status is bypassed for the first
25 seconds of "System Prelube".
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 applying >+4VDC to the microboard input
J14-4.
When no flow of liquid is sensed, the relay output is
turned off, this results in <1VDC to the microboard in-
put.
PADDLE/DP TYPE FLOW SENSOR
When Evaporator Water is flowing, the flow switch
contact will close. If the flow switch opens for 2 sec-
onds, the unit shuts down.
FIGURE 24 -
PADDLE/DP TYPE FLOW SENSOR
LD20688
DIGITAL-TYPE FLOW SENSORS
If desired, a digital type chilled water flow sensor can
be applied. Paddle type – JCI F261MAL-V01C, max.
150 psi (YORK Part No. 024-26116-000); McDonnel-
Miller FS7-4W, max. 300 psi (YORK Part No. 024-
12144-000); Differential pressure type – Potter 1382,
max. 300 psi (YORK Part No. 025-30919-000) avail-
able at additional cost.
