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TROUBLESHOOTING
SYMPTOM
Heaters do not heat up
Heaters on one leg are on all
the time, others 25- 50%
Heaters are on full all the time
Process will not stabilize,
control signal oscillates
POSSIBLE CAUSE
no power to 110-Z3
blown fuses in 110-Z3
no control signal to 110-Z3
defective heaters
defective source
short to ground, sneak path
in between lines
incorrect source signal
shorted SCR's in controller
incorrect temperature
control tuning, slow
temperature sensing
POSSIBLE SOLUTION
verify correct input voltage between the
three "LINE" lugs on 110-Z3.
check for heater and wiring shorts, check
current rating on heaters and replace fuses
as necessary. will blow fuses on tungsten
lamps or transformers
verify 4-20mA signal is hooked up
correctly (positive to "+" and negative to
"-") on the source and 110-Z3.
check for output voltage between the
three "HTR" lugs. If voltage is present,
check
wiring to the heaters and the actual
heaters
measure the output of the source
(temperature controller, PLC, etc.) by
placing a milliamp meter in SERIES
with the signal wires.
Heater or power wires are shorted to
ground. Third leg (uncontrolled) is
conducting. Use amp probe to find were
current draw is going. Use meg-ohm
meter to find short to ground or in
between lines.
verify 4-20mA signal varies from 4-
20mA
with power applied, measure voltage drop
across "LINE 1" and "HTR 1", if voltage
reading is less than one volt, the
associated SCR is bad. Perform same
test on "LINE 2" to "HTR 2"
re-tune temperature control, use faster
sensor, place sensor closer to process
Page 8
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