JOHNSON CONTROLS
33
FORM 450.50-N1
ISSUE DATE: 08/19/2019
3
LED INDICATORS
There are 9 LEDs on the SC-EQ Comm Card to indi-
cate the operational status of the SC-EQ and the 3 com-
munication ports. The LEDs on the SC-EQ and related
communication LEDs on the chiller microboard should
be observed to help diagnose communication problems.
FIGURE 38 - SC-EQ LEDS AND USB
LD19992a
LEDs/
USB
Power
A Green LED that is ON whenever power is applied to
the SC-EQ Comm Card either by the 24 VAC (20.4 to
30 VAC) input or the +12 VDC (+12 VDC +or- 10%)
input. The Power LED should always be illuminated.
If not then a digital multimeter should be used to verify
the power source to the SC-EQ is present or not. If the
power source is present at the SC-EQ power terminals
(J9 +12 VDC (Red wire + Black wire - ) or J10 24 VAC
as applicable) and the Power LED is not illuminated
then the SC-EQ is faulty.
Connected Services Network
CS BUS - A Green LED that indicates the commu-
nication activity on the Connected Services commu-
nication port. It blinks ON and OFF every 500ms to
indicate that communications is established with the
SC-AP. The LED is ON solid when there are no com-
muncations established with the SC-AP and the SC-EQ
CS port is therfore polling for a Master. If the LED is
OFF continuously then the SC-EQ is waiting for the
SC-AP to start polling the SC-EQ.
BAS Network
BS BUS - A Green LED that indicates the communi-
cation activity on the BAS communication port. The
LED illumination has two variations depending upon
the protocol present on the BAS port.
BACnet MS/TP - The LED is OFF when there are no
active BACnet communications on the network. It is
also OFF when it is initially auto-bauding and waiting
for a master device to poll on the network. The LED
illuminates ON when the SC-EQ sees any communica-
tions on the network.
N2 and Modbus RTU - SC-EQ receives a request
from the Master to the SC-EQ network address. The
LED then illuminates while the SC-EQ is transmitting
the response message.
There are two additional LEDs on the BAS Port to aid
in diagnosing BAS Network Integration problems.
BRX - A Green LED that illuminates when the SC-EQ
is Receiving data on the BAS Network Port.
BTX - A Red LED that illuminates when the SC-EQ is
Transmitting data on the BAS Network Port.
Normal Sequence - The Green BRX LED illuminates
whenever there is a data packet sent on the BAS net-
work to Any address. If this LED illuminates for a
short period of time then it indicates that the BAS Port
RS-485 receive circuitry is functioning. If the BRX
illuminates solid, then the + and - RS-485 wires are
probably swapped and should be corrected. If the data
message address matches the SC-EQ address then the
SC-EQ responds with the requested data and the Red
BTX LED illuminates during the response. If the BAS
system is polling the SC-EQ but the SC-EQ is not re-
sponding then the MAC address should be checked to
see if it is set to the desired address.
SECTION 3 - TROUBLESHOOTING
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