Vogt TUBE-ICE 05TA, Service Manual

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05TA Service Manual
SERVICE OPERATIONS
8/13/01
9-8
A second advantage of Sentronic is in the use of a precise electronic clock for the two minute time
out circuit. Traditional mechanical controls use resistance heaters to provide the time to trip in the
event of low oil pressure. 208 volt systems, low ambient temperatures or brown-out type conditions
cause the heater output to be reduced, thus increasing the time out period from two minutes to three
or four minutes when low oil pressure conditions exist. With the electronic clock, the time out will
always be the same.
As a result of the elimination of the capillary tube measuring system and a more precise timing circuit,
Sentronic will improve the overall reliability of the refrigeration system. As in the past, all new and
replacement Copelametic compressors equipped with oil pumps require the use of a Copeland
approved oil pressure safety switch. Failure to use an approved oil pressure safety switch will be
considered as misuse of the compressor, and can adversely affect warranty replacement of the
compressor should a lubrication connected failure occur.
Sentronic Sensor.
The same oil pressure sensor is used for all Sentronics. It mounts directly into
the oil pump. The Sentronic sensor measures oil pump differential pressure. It has an internal contact
that opens on low oil pressure and signals the Sentronic electronic control module to begin time out.
The same contact closes when proper oil pressure is present and stops the module time out. Should
oil pressure fall below 7-9 PSID for a period of two minutes, the Sentronic module will open the
control circuit, using its Normally-Closed (N) contact, and shut the compressor off.
Approximate oil pressure can be measured in the field. Oil pumps are furnished with a Schrader valve
mounted on the oil pump discharge port. To measure oil pressure, subtract crankcase pressure from
discharge oil pressure. Tripping of the oil pressure safety switch is a warning that the system has
been without proper lubrication for too long a time. Repeated trips of the oil pressure safety control
are a clear indication that something in the system requires immediate remedial action.
Sentronic Module. The Sentronic has in addition to the (N) contact, used for compressor shutdown,
a Normally Open (N.O.) contact that can be used in an alarm circuit (See Diagram 4A). The Single
Pole Double Throw (S.P.D.T.) contact of Sentronic can be electrically isolated from the control
circuit power supply, and used to control a circuit with a different voltage (See Figure 6-2).
Sentronic has a timing circuit that actually compares the amount of time with good oil pressure to
that with insufficient oil pressure and has a memory that will shut the compressor down after a period
of more than two minutes if the compressor has a "history" of oil pressure fluctuations with more
unacceptable than acceptable pressures.
Sentronic also has a memory that retains the compressor oil pressure "history" for up to one minute in
the event of a power loss. Sentronic uses a permanent magnet integral with the reset button to reset
its output control relay in the event of a trip. When the reset button is depressed, it magnetically pulls
the Sentronic relay's armature to its original, reset position. Sentronic needs no voltage present to
reset.