Ó
Warning:
Use National Electric (NEC)
or other country-specific
standard wiring and safety
practices when wiring and
connecting this controller to
a power source and to elec-
trical sensors or peripheral
devices . Failure to do so may
result in damage to equip-
ment and property, and/or
injury or loss of life .
NOTE: To prevent ground
loops, isolation needs to be
maintained from input to out-
put when using switched DC
or analog process outputs .
CAUTION: Always mount the
controller with the heat-sink
fins aligned vertically .
NOTE: Terminals L4 and
A1 on the limit connector
are jumpered at the factory
to complete the contactor
circuit . Additional switches
may be wired in series to the
terminals .
Ó
WARNING: If high voltage is
applied to a low-voltage con-
troller, irreversible damage
will occur .
Watlow EZ-ZONE
®
ST
•
24
•
Chapter 2 Install and Wire
Note: Excessive writes to
EEPROM over Modbus can
cause premature EEPROM
failure . The EEPROM is rated
for 1,000,000 writes . See
"Saving Settings to Nonvola-
tile Memory" in Chapter 2,
Install and Wire .
Standard Bus EIA-485 Communications
T-/R-
common
98
99
CF
CD
CE
B5
D6
D5
Slot C
T+/R+
• Wire T-/R- to the A terminal of
the EIA-485 port.
• Wire T+/R+ to the B terminal of
the EIA-485 port.
• Wire common to the common
terminal of the EIA-485 port.
• Do not route network wires
with power wires. Connect net-
work wires in daisy-chain fash-
ion when connecting multiple
devices in a network.
• Do not connect more than 16
controllers on a network.
• maximum network length:
1,200 meters (4,000 feet)
• 1/8th unit load on EIA-485 bus
ST _ _ - _ _
*
_ - _ _ _ _
*
All models include Standard Bus
communications
Modbus RTU or Standard Bus EIA-485 Communications
Modbus RTU or
Standard Bus EIA-485
T-/R-
common
98
99
CC
CA
CB
B5
D6
D5
Slot C
T+/R+
• Wire T-/R- to the A terminal of
the EIA-485 port.
• Wire T+/R+ to the B terminal of
the EIA-485 port.
• Wire common to the common
terminal of the EIA-485 port.
• Do not route network wires
with power wires. Connect net-
work wires in daisy-chain fash-
ion when connecting multiple
devices in a network.
• A termination resistor may be
required. Place a 120 Ω resistor
across T+/R+ and T-/R- of last
controller on network.
• Only one protocol per port is
available at a time: either Mod-
bus RTU or Standard Bus.
• Do not connect more than 16
controllers on a Standard Bus
network.
• Do not connect more than 247
controllers on a Modbus RTU
network.
• maximum network length:
1,200 meters (4,000 feet)
• 1/8th unit load on EIA-485 bus.
ST _ _ - _ _
M
_ - _ _ _ _ (Modbus
RTU or EIA-485)
Modbus-IDA
Terminal
EIA/TIA-485
Name
Watlow Termi-
nal Label
Function
DO
A
CA or CD
T-/R-
D1
B
CB or CE
T+/R+
common
common
CC or CF
common
