Watlow EZ-ZONE
®
ST
•
81
•
Appendix
Indication
Description
Possible Cause(s)
Corrective Action
Process doesn’t con-
trol to set point
Process is unstable or never
reaches set point
• Controller not tuned correctly
• Perform autotune or manually tune
system.
• Control mode is incorrectly set
• Set control mode appropriately (Open
vs Closed Loop).
• Control set point is incorrect
• Set control set point in appropriate
control mode and check source of set
point: remote, idle, profile, closed loop,
open loop.
Temperature runway Process value continues to
increase or decrease past set
point.
• Controller output incorrectly pro-
grammed
• Verify output function is correct (heat
or cool).
• Thermocouple reverse wired
• Correct sensor wiring (red wire nega-
tive).
• Controller output wired incorrectly
• Verify and correct wiring.
• Short in heater
• Replace heater.
• Power controller connection to con-
troller defective
• Replace or repair power controller.
• Controller output defective
• Replace or repair controller.
[`100]
Device Error
[rEtn]
Controller displays internal
malfunction message at
power up.
• Controller defective
• Replace or repair controller.
[`h;Er]
Heater Error Heater Error
• Current through load is above current
trip set point
• Check that the load current is proper.
Correct cause of overcurrent and/or en-
sure current trip set point is correct.
• Current through load is below current
trip set point
• Check that the load current is proper.
Correct cause of undercurrent and/or
ensure current trip set point is correct.
[`C;Er]
Current Error
Load current incorrect.
• Shorted solid-state or mechanical
relay
• Replace relay.
• Open solid-state or mechanical relay • Replace relay.
• Defective current transformer or con-
troller
• Replace or repair sensor or controller.
• Noisy electrical lines
• Route wires appropriately, check for
loose connections, add line filters.
Menus inaccessible
Unable to access
[`SEt]
,
[oPEr]
,
[FCty]
or
[ProF]
menus or particular prompts
in Home Page
• Security set to incorrect level
• Check lockout setting in Factory Page.
• Digital input set to lockout keypad
• Change state of digital input.
• Custom parameters incorrect
• Change custom parameters in Factory
Page.
EZ-Key doesn’t work EZ-Key does not activate re-
quired function
• EZ-Key function incorrect
• Verify EZ-Key function in Setup
Menu.
• EZ-Key function instance not correct • Check that the function instance is
correct.
• Keypad malfunction
• Replace or repair controller.
[``no]
upper display
[`dEu]
lower display
The RUI (Remote User Inter-
face) will not communicate
with the controller at the
selected zone.
• Communications wired incorrectly
• Communications wires routed with
power wires
• Zone address set out of range
• RUI or controller defective
• Check and correct wiring.
• Check and correct wiring.
• Check zone range and address.
• Replace or repair RUI or controller.
[uALU]
Value cannot be displayed
• Scaling is out of range
• Check scaling.
• Call technical support.
