Watlow ez-zone pm - Page 233

Watlow EZ-ZONE
®
PMI Controller • 229 • Chapter 11 Appendix
Indication Description Possible Cause(s) Corrective Action
No Serial Com-
munication
Cannot establish se-
rial communications
with the controller
• Address parameter incor-
rect
• Incorrect protocol se-
lected
• Baud rate incorrect
• Parity incorrect
• Wiring error
• EIA-485 converter issue
• Incorrect computer or
PLC communications port
• Incorrect software setup
• Wires routed with power
cables
• Termination resistor may
be required
• Set unique addresses on
network
• Match protocol between
devices
• Match baud rate between
devices
• Match parity between de-
vices
• Correct wiring issue
• Check settings or replace
converter
• Set correct communica-
tion port
• Correct software setup to
match controller
• Route communications
wires away from power
wires
• Place 120 Ω resistor
across EIA-485 on last
controller
Process
doesn’t con-
trol to set
point
Process is unstable
or never reaches
set point
• Controller not tuned cor-
rectly
• Control mode is incor-
rectly set
• Control set point is incor-
rect
• Perform autotune or
manually tune system
• Set control mode appro-
priately (Open vs Closed
Loop)
• Set control set point in
appropriate control mode
and check source of set
point: remote, idle, pro-
file, closed loop, open
loop
Temperature
runway
Process value con-
tinues to increase
or decrease past set
point.
• Controller output incor-
rectly programmed
• Thermocouple reverse
wired
• Controller output wired
incorrectly
• Short in heater
• Power controller connec-
tion to controller defec-
tive
• Controller output defec-
tive
• Verify output function is
correct (heat or cool)
• Correct sensor wiring
(red wire negative)
• Verify and correct wiring
• Replace heater
• Replace or repair power
controller
• Replace or repair control-
ler