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FORM 160.54-M1
ISSUE DATE: 10/25/2019
Bits, Parity and Stop Bits must be programmed on the
COMMS Screen. Other printer setup is performed on
the Printer Screen. Refer to OptiView Control Panel -
Operation (Form 160.54-O1) for details of available
printers and printer setup instructions.
SC-EQ Communication Interface
An optional SC-Equiptment printed circuit board can
be connected to the COM 4B RS-232 serial data port
(J2). TX data to the SC-EQ is at J2-7. RX data from
the E-Link Gateway is at J2-6. Signal levels are stan-
dard RS-232. The SC-EQ Communication Interface
polls sys-tem pressures, temperatures and status from
the mi-croboard. It holds it for retrieval by third-party
devices. See SECTION 19 - COMMUNICATIONS of
this manual.
Digital Inputs
The I/O Board converts the 115 VAC inputs to logic
level inputs for the microboard at J19. A 115 VAC in-
put to the I/O Board is converted to a logic low (less
than 1 VDC). A 0 VAC input to the I/O Board is con-
verted to a logic high (greater than 4 VDC). See SEC-
TION 6 - I/O BOARD of this manual for details of the
I/O Board.
Digital Outputs
The microboard controls 115 VAC relays and so-
lenoids via the I/O Board (via J19). The I/O Board
contains +12 VDC relays that isolate the microboard
low voltage circuits from the 115 VAC device coils.
Solid state switching devices are used to control the
relays. The microboard energizes the +12 VDC re-
lays by applying a ground to the coil input. They are
de-energized by opening the ground path. The con-
tacts of these relays switch 115 VAC to system relays
and solenoids. The outputs that control the chilled
liquid pump and compressor motor starter have anti-
chatter (anti-recycle) timers associated with them.
The output that controls relay K0 is not allowed to
change at a rate greater than once every 10 seconds.
The output that controls relay K13 is not allowed to
change at a rate greater than once every 20 seconds.
The microboard controls actuator motors via Triacs on
the I/O Board. Each actuator has an open winding and
a close winding. Current flowing through a winding
causes the actuator to rotate in the respective direction.
Each winding is controlled by a Triac. The Triac is
turned ON to allow current to flow through a winding.
The microboard turns on the Triac by applying a logic
low (less than 1 VDC) to the Triac driver on the I/O
JOHNSON CONTROLS
Board. It turns it OFF by applying a logic high (greater
than 4 VDC). See SECTION 6 - I/O BOARD of this
manual for details of the I/O Board.
Analog Inputs
System pressures, in the form of analog DC voltages,
are input from Pressure Transducers. See SECTION 20
- PRESSURE TRANSDUCERS of this manual. Formu-
las and graphs are included to calculate the expected
transducer output voltage for a given pressure input.
System temperatures, in the form of analog DC volt-
ages, are input from thermistors. See SECTION 21
- TEMPERATURE THERMISTORS of this manual.
Included are tables to convert the expected output volt-
age for any temperature applied to the thermistor.
Flow Switch
Style "F" (and later) chillers are supplied with factory-
mounted Flow Sensors on the evaporator and condens-
er. These are electronic thermal-type sensors. The op-
erating principle of the sensor is thermal conductivity.
It uses the cooling effect of a flowing liquid to sense
flow. The temperature of the heated sensor tip is sensed
by a thermistor located in the tip. A second thermistor,
located higher in the tip in a non-heated area, is only
affected by changes in liquid temperature. The temper-
atures sensed by the thermistors are compared. Flow-
ing liquid carries heat away from the heated sensor tip,
lowering its temperature. The higher the flow rate, the
lower the tip temperature and therefore a lower differ-
ential between thermistors. Lower flow rates remove
less heat from the tip allowing a higher tip temperature.
The lower the flow, the greater the differential between
thermistors. The sensor is vendor-calibrated to turn ON
its output at a flow rate of 20cm (0.6 ft.)/second. This
is the setpoint.
The sensor operates from a 24 VAC power source and
has a solid state relay output. On each sensor, one side
of the solid state relay (pin 4) is connected to +5 VDC
on the microboard and the other side (pin 2) is con-
nected to an Analog Input of the microboard (See Fig-
ure 24 on page 72 and Figure 30 on page 94).
After power is applied, there is a thermal warm-up pe-
riod of up to 20 seconds. During this time, the output
could be unstable. When the setpoint (or greater) flow
rate is sensed, the solid state relay output is turned ON
causing it to conduct current through the 7.5K ohm
Microboard load resistor to the +5 VDC. This applies
greater than +4 VDC to the microboard input. When a
flow rate less than the setpoint is sensed, the solid state
JCI COMPANY CONFIDENTIAL
SECTION 5 - MICROBOARD 031-03630-001
5
81
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