10TA Service Manual
SERVICE OPERATIONS
4/28/14
9-9
Sentronic Oil Pressure Safety Control (4D & 6D compressors before March 2011).
The Sentronic utilizes a pressure sensor and an electronic control module to precisely measure oil
pump differential pressure. The main advantage of Sentronic is the elimination of the traditional
capillary tubes, bellows, and pressure connections that mechanical pressure switches require to
measure differential oil pressure. These require careful handling and are known to be a source of
leaks in refrigeration systems.
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.
FIGURE 9-7A
Sentronic Oil Pressure Safety Control
Sentronic Sensor (2D, 3D, 4D & 6D compressors before March 2011). The same oil pressure
sensor is used for all Sentronic Oil Pressure Controls. It mounts directly into the oil pump. The
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 Oil Safety (Sensor Only)
Part #: 12A2117A0501
Sentronic Oil Safety Control
(Entire Unit)
Part #: 12A2117A05
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