Watlow Series D8 - Manual (Page 184)

Chapter 7: Troubleshooting and Reconfiguring Series D8 User’s Guide
166 Watlow Anafaze Doc. 0600-3120-2000
NOTE! If the controller has failed, it is likely that it
was damaged by excessive voltage or noise.
Before replacing the controller, troubleshoot
for noise and ground loops.
Keys Do Not Work
If the D8 seems to function but one or more keys do not work,
check the following:
•
If the . key does not work, but other keys work, then the
keypad is probably locked. Unlock the keypad according
to the instructions in Keypad Lock on page 129.
• Check whether there is an unacknowledged alarm. The
keys will not work for anything else until all alarms are
acknowledged. To acknowledge an alarm, press x.
Checking Analog Inputs
1. If the process variable read via communications does not
agree with the process variable on the controller display,
verify that the controller is communicating. See Reading
the DeviceNet LEDs on page 148.
2. If the process variable indicated on the controller display
is incorrect:
a) Verify that you have selected the correct input type
for the affected loops.
b) Verify that sensors are properly connected.
3. If the sensors are correctly connected, with power on to
the heaters check for high common mode voltage:
a) Set a voltmeter to measure volts ac.
b) Connect the negative lead to a good earth ground.
c) One by one, check each input for ac voltage by con-
necting the positive lead on the voltmeter to the pos-
itive and negative sensor input connections. The
process variable should indicate ambient tempera-
ture. If it does not, contact your supplier to return
the unit for repair. See Returning a Unit on page
158.
NOTE! Noise in excess of 1 Vac should be eliminat-
ed by correctly grounding the D8. See Wiring
the Power Supply on page 23.
4. Verify the sensors: