User`s manual

Watlow Series C ■ 12 ■ Troubleshooting
Indication Probable Cause(s) Corrective Action
Troubleshooting RTD inputs
Temperature reading is incor-
rect, showing a sensor error,
[Er;In] , or LOAD LED is
switching at the wrong tem-
perature.
• Sensor or controller may be bad. Sensor
connections may be bad.
• Ambient temperature in the control cab-
inet is over 70°C (158°F).
• Sensor connections may be bad. Exces-
sive lead wire resistance.
• Place a 110 ohm resistor across the sen-
sor input terminals. The display should
indicate 25°C (77°F). If it does, the con-
troller is OK. Sensor or connections may
be bad.
For controllers without the ability to view
process temperature:
- Decrease set point below ambient tem-
perature, LOAD LED should be off for
heating controllers and on for cooling con-
trollers.
- Increase set point above ambient tem-
perature. LOAD LED should be on for
heating controllers and off for cooling con-
trollers.
• Measure temperature in cabinet to en-
sure it is below 70°C (158°F). Vent cabi-
net or add fans if necessary.
• Check sensor connections. Measure lead
wire resistance. There will be a 2.6C
(4.7°F) error for every ohm of lead wire
resistance.
Troubleshooting controller outputs
Controller output signal is
not on when it should be.
Load LED is not on.
• Temperature reading is incorrect on dis-
play of indicating controls or limit. See in-
put troubleshooting.
• Set point is not set correctly.
• See input troubleshooting.
• Verify set point setting.
Controller output signal is
not on when it should be.
Load LED is on.
• Output wiring is incorrect • Verify wiring. Relay outputs act as a
switch, they do not source power.
For DC output controls, voltage should be
about 20VDC with no load. Greater than
5 volts with load of 500Ω or greater.
Control output signal is on
when it should not be on.
Load LED is on.
• Temperature reading is incorrect on dis-
play of indicating controls or limit. see
input troubleshooting.
• Set point is not set correctly.
• Control output is defective.
• See input troubleshooting.
• Verify set point setting.
• Repair or replace controller.
Load is on when it should
not be on. Load LED is off.
• Power switching device (SSR, HG relay,
mechanical relay) is shorted. Controller
outputs shorted.
• Output wiring is incorrect
• Remove wires from output of control to
input of power switching device. If load
is still on, replace power switching de-
vice. If load turns off, replace controller
or sensor. See input troubleshooting..
• Verify wiring.