Finish Thompson BE-55C - Manual (Page 21)

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CAUTION: Disconnect electrical power to the BE unit before performing tests on
the temperature activated Switches (TAS)
Check TAS3. This is a “normally open” switch threaded into the front of the Process Tank behind the
access panel in the insulation. It is a 1/2” diameter white ceramic sensor with a brass hex base and
two wires (#13 and #14) connected to it; it will be the switch on the left hand side. This switch closes
when the process tank reaches 280ºF, which energizes the divert solenoid and upper heater dropout
relay (CR1).
 If TAS3 is closed (while the units temperature is above 280ºF), then proceed to Possible
Cause 3. The most accurate method of checking the temperature is to remove TAS3 from its
mount and insert a temperature probe in its place; the use of an infrared gun may also be used.
 If TAS3 is open (while the units temperature is above 280ºF), it is defective and needs replaced.
Possible Cause 3: Distillate Piping has overheated from improper cooling.
Refer to the “TAS4 keeps tripping due to cooling problems” on page 22 of this manual.
Possible Cause 4: Process Tank overheating.
CAUTION: Disconnect electrical power to the BE unit before performing tests on
the temperature activated Switches (TAS)
Check TAS2. This is a “normally closed” switch threaded into the front of the Process Tank behind the
access panel in the insulation. It is a 1/2” diameter white ceramic sensor with a brass hex base and
two wires (#1L1 and #10) connected to it. This switch opens if the Process Tank reaches 385
F. The
most accurate method of checking the Process Tanks temperature is to remove TAS2 from its mount
and insert a temperature probe in its place; the use of an infrared gun may also be used.
 If TAS2 is closed, the switch is O.K.
 If TAS2 is open, and the Process Tanks temperature is less than 385ºF, then TAS2 is too sensitive.
Replace TAS2.
 If TAS2 is open, and the Process Tanks temperature is greater than 385ºF, a possible cause may
be Residue build-up in the Process Tank, refer to heater plate pull out procedure on page 35.
Causes of Residue Build up
1. Improper maintenance. If the Process Tank is not drained after every run and the Residues are
slow to drain, most likely there is a Residue build-up. Proper maintenance is the key to preventing
a build-up in the Process Tank.
2. Large concentrations of solids in the waste coolant.
3. Oil or transmission fluid is present in the waste coolant. When this is the case, the residue is less
likely to be flushed away with the “Flush” procedure during maintenance.