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7
Condition
Temperature fluctuations/rapid
cycling from hot to cold.
Unit does not heat properly/can
not achieve set point.
Unit does not heat.
Page 52
Possible cause
Undersized connectors/lines.
Long connecting lines between
unit and mold.
Serpentine flow through mold.
Blocked line in mold.
Quick disconnect fitting with
check valve.
Carbon build-up in unit piping or
fittings.
Faulty AEC TCU.
Reversed probes.
Loss of fluid in process.
Vent valve open.
Faulty/dirty solenoid valve;
usually detected when there is a
steady stream or trickle of water
out of the drain line.
Degraded fluid.
Defective heater contactor.
Defective immersion heater.
Heater burnout.
TDH-6 Series Hot Oil Large Temperature Control Units
Troubleshooting
Solution
Increase size of connectors/
water lines.
Move the unit closer to the mold
and shorten connecting lines.
Connect lines for parallel flow
instead of series flow.
Check mold for metal chips or
deposits. Clean mold.
Remove and replace fitting or
valve.
Clean or replace affected piping.
Replace fluid.
Check unit by opening the
manual bypass to determine if
the TCU controls the set point
temperature.
Switch Return and Delivery
probes.
Check all lines/connections/
fittings.
Allow vent timer to run out; or,
check valve operation when unit
is cold by opening the fill port.
Switch to Manual Cool mode
several times to flush valve. If
the leak continues, disconnect
the power to the unit, turn off the
water supply, and clean or
replace the solenoid.
Drain and replace fluid.
Visual inspection of coil and
contacts. Repair/replace
defective contactors.
Check resistance on all three (3)
legs of heater with an
ohmmeter. If not all equal,
contact factory for replacement
heater.
Check heater tank for scorched/
discolored paint. Check
resistance on all three (3) legs of
heater with an ohmmeter.
Replace heater as needed.
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